avcodec/utils: document allocation requirement of extradata

[ffmpeg] / libavcodec / avcodec.h

/*
 * copyright (c) 2001 Fabrice Bellard
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef AVCODEC_AVCODEC_H
#define AVCODEC_AVCODEC_H

/**
 * @file
 * @ingroup libavc
 * Libavcodec external API header
 */

#include <errno.h>
#include "libavutil/samplefmt.h"
#include "libavutil/attributes.h"
#include "libavutil/avutil.h"
#include "libavutil/buffer.h"
#include "libavutil/cpu.h"
#include "libavutil/channel_layout.h"
#include "libavutil/dict.h"
#include "libavutil/frame.h"
#include "libavutil/hwcontext.h"
#include "libavutil/log.h"
#include "libavutil/pixfmt.h"
#include "libavutil/rational.h"

#include "version.h"

/**
 * @defgroup libavc libavcodec
 * Encoding/Decoding Library
 *
 * @{
 *
 * @defgroup lavc_decoding Decoding
 * @{
 * @}
 *
 * @defgroup lavc_encoding Encoding
 * @{
 * @}
 *
 * @defgroup lavc_codec Codecs
 * @{
 * @defgroup lavc_codec_native Native Codecs
 * @{
 * @}
 * @defgroup lavc_codec_wrappers External library wrappers
 * @{
 * @}
 * @defgroup lavc_codec_hwaccel Hardware Accelerators bridge
 * @{
 * @}
 * @}
 * @defgroup lavc_internal Internal
 * @{
 * @}
 * @}
 */

/**
 * @ingroup libavc
 * @defgroup lavc_encdec send/receive encoding and decoding API overview
 * @{
 *
 * The avcodec_send_packet()/avcodec_receive_frame()/avcodec_send_frame()/
 * avcodec_receive_packet() functions provide an encode/decode API, which
 * decouples input and output.
 *
 * The API is very similar for encoding/decoding and audio/video, and works as
 * follows:
 * - Set up and open the AVCodecContext as usual.
 * - Send valid input:
 *   - For decoding, call avcodec_send_packet() to give the decoder raw
 *     compressed data in an AVPacket.
 *   - For encoding, call avcodec_send_frame() to give the encoder an AVFrame
 *     containing uncompressed audio or video.
 *   In both cases, it is recommended that AVPackets and AVFrames are
 *   refcounted, or libavcodec might have to copy the input data. (libavformat
 *   always returns refcounted AVPackets, and av_frame_get_buffer() allocates
 *   refcounted AVFrames.)
 * - Receive output in a loop. Periodically call one of the avcodec_receive_*()
 *   functions and process their output:
 *   - For decoding, call avcodec_receive_frame(). On success, it will return
 *     an AVFrame containing uncompressed audio or video data.
 *   - For encoding, call avcodec_receive_packet(). On success, it will return
 *     an AVPacket with a compressed frame.
 *   Repeat this call until it returns AVERROR(EAGAIN) or an error. The
 *   AVERROR(EAGAIN) return value means that new input data is required to
 *   return new output. In this case, continue with sending input. For each
 *   input frame/packet, the codec will typically return 1 output frame/packet,
 *   but it can also be 0 or more than 1.
 *
 * At the beginning of decoding or encoding, the codec might accept multiple
 * input frames/packets without returning a frame, until its internal buffers
 * are filled. This situation is handled transparently if you follow the steps
 * outlined above.
 *
 * In theory, sending input can result in EAGAIN - this should happen only if
 * not all output was received. You can use this to structure alternative decode
 * or encode loops other than the one suggested above. For example, you could
 * try sending new input on each iteration, and try to receive output if that
 * returns EAGAIN.
 *
 * End of stream situations. These require "flushing" (aka draining) the codec,
 * as the codec might buffer multiple frames or packets internally for
 * performance or out of necessity (consider B-frames).
 * This is handled as follows:
 * - Instead of valid input, send NULL to the avcodec_send_packet() (decoding)
 *   or avcodec_send_frame() (encoding) functions. This will enter draining
 *   mode.
 * - Call avcodec_receive_frame() (decoding) or avcodec_receive_packet()
 *   (encoding) in a loop until AVERROR_EOF is returned. The functions will
 *   not return AVERROR(EAGAIN), unless you forgot to enter draining mode.
 * - Before decoding can be resumed again, the codec has to be reset with
 *   avcodec_flush_buffers().
 *
 * Using the API as outlined above is highly recommended. But it is also
 * possible to call functions outside of this rigid schema. For example, you can
 * call avcodec_send_packet() repeatedly without calling
 * avcodec_receive_frame(). In this case, avcodec_send_packet() will succeed
 * until the codec's internal buffer has been filled up (which is typically of
 * size 1 per output frame, after initial input), and then reject input with
 * AVERROR(EAGAIN). Once it starts rejecting input, you have no choice but to
 * read at least some output.
 *
 * Not all codecs will follow a rigid and predictable dataflow; the only
 * guarantee is that an AVERROR(EAGAIN) return value on a send/receive call on
 * one end implies that a receive/send call on the other end will succeed, or
 * at least will not fail with AVERROR(EAGAIN). In general, no codec will
 * permit unlimited buffering of input or output.
 *
 * This API replaces the following legacy functions:
 * - avcodec_decode_video2() and avcodec_decode_audio4():
 *   Use avcodec_send_packet() to feed input to the decoder, then use
 *   avcodec_receive_frame() to receive decoded frames after each packet.
 *   Unlike with the old video decoding API, multiple frames might result from
 *   a packet. For audio, splitting the input packet into frames by partially
 *   decoding packets becomes transparent to the API user. You never need to
 *   feed an AVPacket to the API twice (unless it is rejected with AVERROR(EAGAIN) - then
 *   no data was read from the packet).
 *   Additionally, sending a flush/draining packet is required only once.
 * - avcodec_encode_video2()/avcodec_encode_audio2():
 *   Use avcodec_send_frame() to feed input to the encoder, then use
 *   avcodec_receive_packet() to receive encoded packets.
 *   Providing user-allocated buffers for avcodec_receive_packet() is not
 *   possible.
 * - The new API does not handle subtitles yet.
 *
 * Mixing new and old function calls on the same AVCodecContext is not allowed,
 * and will result in undefined behavior.
 *
 * Some codecs might require using the new API; using the old API will return
 * an error when calling it. All codecs support the new API.
 *
 * A codec is not allowed to return AVERROR(EAGAIN) for both sending and receiving. This
 * would be an invalid state, which could put the codec user into an endless
 * loop. The API has no concept of time either: it cannot happen that trying to
 * do avcodec_send_packet() results in AVERROR(EAGAIN), but a repeated call 1 second
 * later accepts the packet (with no other receive/flush API calls involved).
 * The API is a strict state machine, and the passage of time is not supposed
 * to influence it. Some timing-dependent behavior might still be deemed
 * acceptable in certain cases. But it must never result in both send/receive
 * returning EAGAIN at the same time at any point. It must also absolutely be
 * avoided that the current state is "unstable" and can "flip-flop" between
 * the send/receive APIs allowing progress. For example, it's not allowed that
 * the codec randomly decides that it actually wants to consume a packet now
 * instead of returning a frame, after it just returned AVERROR(EAGAIN) on an
 * avcodec_send_packet() call.
 * @}
 */

/**
 * @defgroup lavc_core Core functions/structures.
 * @ingroup libavc
 *
 * Basic definitions, functions for querying libavcodec capabilities,
 * allocating core structures, etc.
 * @{
 */


/**
 * Identify the syntax and semantics of the bitstream.
 * The principle is roughly:
 * Two decoders with the same ID can decode the same streams.
 * Two encoders with the same ID can encode compatible streams.
 * There may be slight deviations from the principle due to implementation
 * details.
 *
 * If you add a codec ID to this list, add it so that
 * 1. no value of an existing codec ID changes (that would break ABI),
 * 2. it is as close as possible to similar codecs
 *
 * After adding new codec IDs, do not forget to add an entry to the codec
 * descriptor list and bump libavcodec minor version.
 */
enum AVCodecID {
    AV_CODEC_ID_NONE,

    /* video codecs */
    AV_CODEC_ID_MPEG1VIDEO,
    AV_CODEC_ID_MPEG2VIDEO, ///< preferred ID for MPEG-1/2 video decoding
    AV_CODEC_ID_H261,
    AV_CODEC_ID_H263,
    AV_CODEC_ID_RV10,
    AV_CODEC_ID_RV20,
    AV_CODEC_ID_MJPEG,
    AV_CODEC_ID_MJPEGB,
    AV_CODEC_ID_LJPEG,
    AV_CODEC_ID_SP5X,
    AV_CODEC_ID_JPEGLS,
    AV_CODEC_ID_MPEG4,
    AV_CODEC_ID_RAWVIDEO,
    AV_CODEC_ID_MSMPEG4V1,
    AV_CODEC_ID_MSMPEG4V2,
    AV_CODEC_ID_MSMPEG4V3,
    AV_CODEC_ID_WMV1,
    AV_CODEC_ID_WMV2,
    AV_CODEC_ID_H263P,
    AV_CODEC_ID_H263I,
    AV_CODEC_ID_FLV1,
    AV_CODEC_ID_SVQ1,
    AV_CODEC_ID_SVQ3,
    AV_CODEC_ID_DVVIDEO,
    AV_CODEC_ID_HUFFYUV,
    AV_CODEC_ID_CYUV,
    AV_CODEC_ID_H264,
    AV_CODEC_ID_INDEO3,
    AV_CODEC_ID_VP3,
    AV_CODEC_ID_THEORA,
    AV_CODEC_ID_ASV1,
    AV_CODEC_ID_ASV2,
    AV_CODEC_ID_FFV1,
    AV_CODEC_ID_4XM,
    AV_CODEC_ID_VCR1,
    AV_CODEC_ID_CLJR,
    AV_CODEC_ID_MDEC,
    AV_CODEC_ID_ROQ,
    AV_CODEC_ID_INTERPLAY_VIDEO,
    AV_CODEC_ID_XAN_WC3,
    AV_CODEC_ID_XAN_WC4,
    AV_CODEC_ID_RPZA,
    AV_CODEC_ID_CINEPAK,
    AV_CODEC_ID_WS_VQA,
    AV_CODEC_ID_MSRLE,
    AV_CODEC_ID_MSVIDEO1,
    AV_CODEC_ID_IDCIN,
    AV_CODEC_ID_8BPS,
    AV_CODEC_ID_SMC,
    AV_CODEC_ID_FLIC,
    AV_CODEC_ID_TRUEMOTION1,
    AV_CODEC_ID_VMDVIDEO,
    AV_CODEC_ID_MSZH,
    AV_CODEC_ID_ZLIB,
    AV_CODEC_ID_QTRLE,
    AV_CODEC_ID_TSCC,
    AV_CODEC_ID_ULTI,
    AV_CODEC_ID_QDRAW,
    AV_CODEC_ID_VIXL,
    AV_CODEC_ID_QPEG,
    AV_CODEC_ID_PNG,
    AV_CODEC_ID_PPM,
    AV_CODEC_ID_PBM,
    AV_CODEC_ID_PGM,
    AV_CODEC_ID_PGMYUV,
    AV_CODEC_ID_PAM,
    AV_CODEC_ID_FFVHUFF,
    AV_CODEC_ID_RV30,
    AV_CODEC_ID_RV40,
    AV_CODEC_ID_VC1,
    AV_CODEC_ID_WMV3,
    AV_CODEC_ID_LOCO,
    AV_CODEC_ID_WNV1,
    AV_CODEC_ID_AASC,
    AV_CODEC_ID_INDEO2,
    AV_CODEC_ID_FRAPS,
    AV_CODEC_ID_TRUEMOTION2,
    AV_CODEC_ID_BMP,
    AV_CODEC_ID_CSCD,
    AV_CODEC_ID_MMVIDEO,
    AV_CODEC_ID_ZMBV,
    AV_CODEC_ID_AVS,
    AV_CODEC_ID_SMACKVIDEO,
    AV_CODEC_ID_NUV,
    AV_CODEC_ID_KMVC,
    AV_CODEC_ID_FLASHSV,
    AV_CODEC_ID_CAVS,
    AV_CODEC_ID_JPEG2000,
    AV_CODEC_ID_VMNC,
    AV_CODEC_ID_VP5,
    AV_CODEC_ID_VP6,
    AV_CODEC_ID_VP6F,
    AV_CODEC_ID_TARGA,
    AV_CODEC_ID_DSICINVIDEO,
    AV_CODEC_ID_TIERTEXSEQVIDEO,
    AV_CODEC_ID_TIFF,
    AV_CODEC_ID_GIF,
    AV_CODEC_ID_DXA,
    AV_CODEC_ID_DNXHD,
    AV_CODEC_ID_THP,
    AV_CODEC_ID_SGI,
    AV_CODEC_ID_C93,
    AV_CODEC_ID_BETHSOFTVID,
    AV_CODEC_ID_PTX,
    AV_CODEC_ID_TXD,
    AV_CODEC_ID_VP6A,
    AV_CODEC_ID_AMV,
    AV_CODEC_ID_VB,
    AV_CODEC_ID_PCX,
    AV_CODEC_ID_SUNRAST,
    AV_CODEC_ID_INDEO4,
    AV_CODEC_ID_INDEO5,
    AV_CODEC_ID_MIMIC,
    AV_CODEC_ID_RL2,
    AV_CODEC_ID_ESCAPE124,
    AV_CODEC_ID_DIRAC,
    AV_CODEC_ID_BFI,
    AV_CODEC_ID_CMV,
    AV_CODEC_ID_MOTIONPIXELS,
    AV_CODEC_ID_TGV,
    AV_CODEC_ID_TGQ,
    AV_CODEC_ID_TQI,
    AV_CODEC_ID_AURA,
    AV_CODEC_ID_AURA2,
    AV_CODEC_ID_V210X,
    AV_CODEC_ID_TMV,
    AV_CODEC_ID_V210,
    AV_CODEC_ID_DPX,
    AV_CODEC_ID_MAD,
    AV_CODEC_ID_FRWU,
    AV_CODEC_ID_FLASHSV2,
    AV_CODEC_ID_CDGRAPHICS,
    AV_CODEC_ID_R210,
    AV_CODEC_ID_ANM,
    AV_CODEC_ID_BINKVIDEO,
    AV_CODEC_ID_IFF_ILBM,
#define AV_CODEC_ID_IFF_BYTERUN1 AV_CODEC_ID_IFF_ILBM
    AV_CODEC_ID_KGV1,
    AV_CODEC_ID_YOP,
    AV_CODEC_ID_VP8,
    AV_CODEC_ID_PICTOR,
    AV_CODEC_ID_ANSI,
    AV_CODEC_ID_A64_MULTI,
    AV_CODEC_ID_A64_MULTI5,
    AV_CODEC_ID_R10K,
    AV_CODEC_ID_MXPEG,
    AV_CODEC_ID_LAGARITH,
    AV_CODEC_ID_PRORES,
    AV_CODEC_ID_JV,
    AV_CODEC_ID_DFA,
    AV_CODEC_ID_WMV3IMAGE,
    AV_CODEC_ID_VC1IMAGE,
    AV_CODEC_ID_UTVIDEO,
    AV_CODEC_ID_BMV_VIDEO,
    AV_CODEC_ID_VBLE,
    AV_CODEC_ID_DXTORY,
    AV_CODEC_ID_V410,
    AV_CODEC_ID_XWD,
    AV_CODEC_ID_CDXL,
    AV_CODEC_ID_XBM,
    AV_CODEC_ID_ZEROCODEC,
    AV_CODEC_ID_MSS1,
    AV_CODEC_ID_MSA1,
    AV_CODEC_ID_TSCC2,
    AV_CODEC_ID_MTS2,
    AV_CODEC_ID_CLLC,
    AV_CODEC_ID_MSS2,
    AV_CODEC_ID_VP9,
    AV_CODEC_ID_AIC,
    AV_CODEC_ID_ESCAPE130,
    AV_CODEC_ID_G2M,
    AV_CODEC_ID_WEBP,
    AV_CODEC_ID_HNM4_VIDEO,
    AV_CODEC_ID_HEVC,
#define AV_CODEC_ID_H265 AV_CODEC_ID_HEVC
    AV_CODEC_ID_FIC,
    AV_CODEC_ID_ALIAS_PIX,
    AV_CODEC_ID_BRENDER_PIX,
    AV_CODEC_ID_PAF_VIDEO,
    AV_CODEC_ID_EXR,
    AV_CODEC_ID_VP7,
    AV_CODEC_ID_SANM,
    AV_CODEC_ID_SGIRLE,
    AV_CODEC_ID_MVC1,
    AV_CODEC_ID_MVC2,
    AV_CODEC_ID_HQX,
    AV_CODEC_ID_TDSC,
    AV_CODEC_ID_HQ_HQA,
    AV_CODEC_ID_HAP,
    AV_CODEC_ID_DDS,
    AV_CODEC_ID_DXV,
    AV_CODEC_ID_SCREENPRESSO,
    AV_CODEC_ID_RSCC,
    AV_CODEC_ID_AVS2,

    AV_CODEC_ID_Y41P = 0x8000,
    AV_CODEC_ID_AVRP,
    AV_CODEC_ID_012V,
    AV_CODEC_ID_AVUI,
    AV_CODEC_ID_AYUV,
    AV_CODEC_ID_TARGA_Y216,
    AV_CODEC_ID_V308,
    AV_CODEC_ID_V408,
    AV_CODEC_ID_YUV4,
    AV_CODEC_ID_AVRN,
    AV_CODEC_ID_CPIA,
    AV_CODEC_ID_XFACE,
    AV_CODEC_ID_SNOW,
    AV_CODEC_ID_SMVJPEG,
    AV_CODEC_ID_APNG,
    AV_CODEC_ID_DAALA,
    AV_CODEC_ID_CFHD,
    AV_CODEC_ID_TRUEMOTION2RT,
    AV_CODEC_ID_M101,
    AV_CODEC_ID_MAGICYUV,
    AV_CODEC_ID_SHEERVIDEO,
    AV_CODEC_ID_YLC,
    AV_CODEC_ID_PSD,
    AV_CODEC_ID_PIXLET,
    AV_CODEC_ID_SPEEDHQ,
    AV_CODEC_ID_FMVC,
    AV_CODEC_ID_SCPR,
    AV_CODEC_ID_CLEARVIDEO,
    AV_CODEC_ID_XPM,
    AV_CODEC_ID_AV1,
    AV_CODEC_ID_BITPACKED,
    AV_CODEC_ID_MSCC,
    AV_CODEC_ID_SRGC,
    AV_CODEC_ID_SVG,
    AV_CODEC_ID_GDV,
    AV_CODEC_ID_FITS,
    AV_CODEC_ID_IMM4,
    AV_CODEC_ID_PROSUMER,

    /* various PCM "codecs" */
    AV_CODEC_ID_FIRST_AUDIO = 0x10000,     ///< A dummy id pointing at the start of audio codecs
    AV_CODEC_ID_PCM_S16LE = 0x10000,
    AV_CODEC_ID_PCM_S16BE,
    AV_CODEC_ID_PCM_U16LE,
    AV_CODEC_ID_PCM_U16BE,
    AV_CODEC_ID_PCM_S8,
    AV_CODEC_ID_PCM_U8,
    AV_CODEC_ID_PCM_MULAW,
    AV_CODEC_ID_PCM_ALAW,
    AV_CODEC_ID_PCM_S32LE,
    AV_CODEC_ID_PCM_S32BE,
    AV_CODEC_ID_PCM_U32LE,
    AV_CODEC_ID_PCM_U32BE,
    AV_CODEC_ID_PCM_S24LE,
    AV_CODEC_ID_PCM_S24BE,
    AV_CODEC_ID_PCM_U24LE,
    AV_CODEC_ID_PCM_U24BE,
    AV_CODEC_ID_PCM_S24DAUD,
    AV_CODEC_ID_PCM_ZORK,
    AV_CODEC_ID_PCM_S16LE_PLANAR,
    AV_CODEC_ID_PCM_DVD,
    AV_CODEC_ID_PCM_F32BE,
    AV_CODEC_ID_PCM_F32LE,
    AV_CODEC_ID_PCM_F64BE,
    AV_CODEC_ID_PCM_F64LE,
    AV_CODEC_ID_PCM_BLURAY,
    AV_CODEC_ID_PCM_LXF,
    AV_CODEC_ID_S302M,
    AV_CODEC_ID_PCM_S8_PLANAR,
    AV_CODEC_ID_PCM_S24LE_PLANAR,
    AV_CODEC_ID_PCM_S32LE_PLANAR,
    AV_CODEC_ID_PCM_S16BE_PLANAR,

    AV_CODEC_ID_PCM_S64LE = 0x10800,
    AV_CODEC_ID_PCM_S64BE,
    AV_CODEC_ID_PCM_F16LE,
    AV_CODEC_ID_PCM_F24LE,

    /* various ADPCM codecs */
    AV_CODEC_ID_ADPCM_IMA_QT = 0x11000,
    AV_CODEC_ID_ADPCM_IMA_WAV,
    AV_CODEC_ID_ADPCM_IMA_DK3,
    AV_CODEC_ID_ADPCM_IMA_DK4,
    AV_CODEC_ID_ADPCM_IMA_WS,
    AV_CODEC_ID_ADPCM_IMA_SMJPEG,
    AV_CODEC_ID_ADPCM_MS,
    AV_CODEC_ID_ADPCM_4XM,
    AV_CODEC_ID_ADPCM_XA,
    AV_CODEC_ID_ADPCM_ADX,
    AV_CODEC_ID_ADPCM_EA,
    AV_CODEC_ID_ADPCM_G726,
    AV_CODEC_ID_ADPCM_CT,
    AV_CODEC_ID_ADPCM_SWF,
    AV_CODEC_ID_ADPCM_YAMAHA,
    AV_CODEC_ID_ADPCM_SBPRO_4,
    AV_CODEC_ID_ADPCM_SBPRO_3,
    AV_CODEC_ID_ADPCM_SBPRO_2,
    AV_CODEC_ID_ADPCM_THP,
    AV_CODEC_ID_ADPCM_IMA_AMV,
    AV_CODEC_ID_ADPCM_EA_R1,
    AV_CODEC_ID_ADPCM_EA_R3,
    AV_CODEC_ID_ADPCM_EA_R2,
    AV_CODEC_ID_ADPCM_IMA_EA_SEAD,
    AV_CODEC_ID_ADPCM_IMA_EA_EACS,
    AV_CODEC_ID_ADPCM_EA_XAS,
    AV_CODEC_ID_ADPCM_EA_MAXIS_XA,
    AV_CODEC_ID_ADPCM_IMA_ISS,
    AV_CODEC_ID_ADPCM_G722,
    AV_CODEC_ID_ADPCM_IMA_APC,
    AV_CODEC_ID_ADPCM_VIMA,

    AV_CODEC_ID_ADPCM_AFC = 0x11800,
    AV_CODEC_ID_ADPCM_IMA_OKI,
    AV_CODEC_ID_ADPCM_DTK,
    AV_CODEC_ID_ADPCM_IMA_RAD,
    AV_CODEC_ID_ADPCM_G726LE,
    AV_CODEC_ID_ADPCM_THP_LE,
    AV_CODEC_ID_ADPCM_PSX,
    AV_CODEC_ID_ADPCM_AICA,
    AV_CODEC_ID_ADPCM_IMA_DAT4,
    AV_CODEC_ID_ADPCM_MTAF,

    /* AMR */
    AV_CODEC_ID_AMR_NB = 0x12000,
    AV_CODEC_ID_AMR_WB,

    /* RealAudio codecs*/
    AV_CODEC_ID_RA_144 = 0x13000,
    AV_CODEC_ID_RA_288,

    /* various DPCM codecs */
    AV_CODEC_ID_ROQ_DPCM = 0x14000,
    AV_CODEC_ID_INTERPLAY_DPCM,
    AV_CODEC_ID_XAN_DPCM,
    AV_CODEC_ID_SOL_DPCM,

    AV_CODEC_ID_SDX2_DPCM = 0x14800,
    AV_CODEC_ID_GREMLIN_DPCM,

    /* audio codecs */
    AV_CODEC_ID_MP2 = 0x15000,
    AV_CODEC_ID_MP3, ///< preferred ID for decoding MPEG audio layer 1, 2 or 3
    AV_CODEC_ID_AAC,
    AV_CODEC_ID_AC3,
    AV_CODEC_ID_DTS,
    AV_CODEC_ID_VORBIS,
    AV_CODEC_ID_DVAUDIO,
    AV_CODEC_ID_WMAV1,
    AV_CODEC_ID_WMAV2,
    AV_CODEC_ID_MACE3,
    AV_CODEC_ID_MACE6,
    AV_CODEC_ID_VMDAUDIO,
    AV_CODEC_ID_FLAC,
    AV_CODEC_ID_MP3ADU,
    AV_CODEC_ID_MP3ON4,
    AV_CODEC_ID_SHORTEN,
    AV_CODEC_ID_ALAC,
    AV_CODEC_ID_WESTWOOD_SND1,
    AV_CODEC_ID_GSM, ///< as in Berlin toast format
    AV_CODEC_ID_QDM2,
    AV_CODEC_ID_COOK,
    AV_CODEC_ID_TRUESPEECH,
    AV_CODEC_ID_TTA,
    AV_CODEC_ID_SMACKAUDIO,
    AV_CODEC_ID_QCELP,
    AV_CODEC_ID_WAVPACK,
    AV_CODEC_ID_DSICINAUDIO,
    AV_CODEC_ID_IMC,
    AV_CODEC_ID_MUSEPACK7,
    AV_CODEC_ID_MLP,
    AV_CODEC_ID_GSM_MS, /* as found in WAV */
    AV_CODEC_ID_ATRAC3,
    AV_CODEC_ID_APE,
    AV_CODEC_ID_NELLYMOSER,
    AV_CODEC_ID_MUSEPACK8,
    AV_CODEC_ID_SPEEX,
    AV_CODEC_ID_WMAVOICE,
    AV_CODEC_ID_WMAPRO,
    AV_CODEC_ID_WMALOSSLESS,
    AV_CODEC_ID_ATRAC3P,
    AV_CODEC_ID_EAC3,
    AV_CODEC_ID_SIPR,
    AV_CODEC_ID_MP1,
    AV_CODEC_ID_TWINVQ,
    AV_CODEC_ID_TRUEHD,
    AV_CODEC_ID_MP4ALS,
    AV_CODEC_ID_ATRAC1,
    AV_CODEC_ID_BINKAUDIO_RDFT,
    AV_CODEC_ID_BINKAUDIO_DCT,
    AV_CODEC_ID_AAC_LATM,
    AV_CODEC_ID_QDMC,
    AV_CODEC_ID_CELT,
    AV_CODEC_ID_G723_1,
    AV_CODEC_ID_G729,
    AV_CODEC_ID_8SVX_EXP,
    AV_CODEC_ID_8SVX_FIB,
    AV_CODEC_ID_BMV_AUDIO,
    AV_CODEC_ID_RALF,
    AV_CODEC_ID_IAC,
    AV_CODEC_ID_ILBC,
    AV_CODEC_ID_OPUS,
    AV_CODEC_ID_COMFORT_NOISE,
    AV_CODEC_ID_TAK,
    AV_CODEC_ID_METASOUND,
    AV_CODEC_ID_PAF_AUDIO,
    AV_CODEC_ID_ON2AVC,
    AV_CODEC_ID_DSS_SP,
    AV_CODEC_ID_CODEC2,

    AV_CODEC_ID_FFWAVESYNTH = 0x15800,
    AV_CODEC_ID_SONIC,
    AV_CODEC_ID_SONIC_LS,
    AV_CODEC_ID_EVRC,
    AV_CODEC_ID_SMV,
    AV_CODEC_ID_DSD_LSBF,
    AV_CODEC_ID_DSD_MSBF,
    AV_CODEC_ID_DSD_LSBF_PLANAR,
    AV_CODEC_ID_DSD_MSBF_PLANAR,
    AV_CODEC_ID_4GV,
    AV_CODEC_ID_INTERPLAY_ACM,
    AV_CODEC_ID_XMA1,
    AV_CODEC_ID_XMA2,
    AV_CODEC_ID_DST,
    AV_CODEC_ID_ATRAC3AL,
    AV_CODEC_ID_ATRAC3PAL,
    AV_CODEC_ID_DOLBY_E,
    AV_CODEC_ID_APTX,
    AV_CODEC_ID_APTX_HD,
    AV_CODEC_ID_SBC,
    AV_CODEC_ID_ATRAC9,

    /* subtitle codecs */
    AV_CODEC_ID_FIRST_SUBTITLE = 0x17000,          ///< A dummy ID pointing at the start of subtitle codecs.
    AV_CODEC_ID_DVD_SUBTITLE = 0x17000,
    AV_CODEC_ID_DVB_SUBTITLE,
    AV_CODEC_ID_TEXT,  ///< raw UTF-8 text
    AV_CODEC_ID_XSUB,
    AV_CODEC_ID_SSA,
    AV_CODEC_ID_MOV_TEXT,
    AV_CODEC_ID_HDMV_PGS_SUBTITLE,
    AV_CODEC_ID_DVB_TELETEXT,
    AV_CODEC_ID_SRT,

    AV_CODEC_ID_MICRODVD   = 0x17800,
    AV_CODEC_ID_EIA_608,
    AV_CODEC_ID_JACOSUB,
    AV_CODEC_ID_SAMI,
    AV_CODEC_ID_REALTEXT,
    AV_CODEC_ID_STL,
    AV_CODEC_ID_SUBVIEWER1,
    AV_CODEC_ID_SUBVIEWER,
    AV_CODEC_ID_SUBRIP,
    AV_CODEC_ID_WEBVTT,
    AV_CODEC_ID_MPL2,
    AV_CODEC_ID_VPLAYER,
    AV_CODEC_ID_PJS,
    AV_CODEC_ID_ASS,
    AV_CODEC_ID_HDMV_TEXT_SUBTITLE,
    AV_CODEC_ID_TTML,

    /* other specific kind of codecs (generally used for attachments) */
    AV_CODEC_ID_FIRST_UNKNOWN = 0x18000,           ///< A dummy ID pointing at the start of various fake codecs.
    AV_CODEC_ID_TTF = 0x18000,

    AV_CODEC_ID_SCTE_35, ///< Contain timestamp estimated through PCR of program stream.
    AV_CODEC_ID_BINTEXT    = 0x18800,
    AV_CODEC_ID_XBIN,
    AV_CODEC_ID_IDF,
    AV_CODEC_ID_OTF,
    AV_CODEC_ID_SMPTE_KLV,
    AV_CODEC_ID_DVD_NAV,
    AV_CODEC_ID_TIMED_ID3,
    AV_CODEC_ID_BIN_DATA,


    AV_CODEC_ID_PROBE = 0x19000, ///< codec_id is not known (like AV_CODEC_ID_NONE) but lavf should attempt to identify it

    AV_CODEC_ID_MPEG2TS = 0x20000, /**< _FAKE_ codec to indicate a raw MPEG-2 TS
                                * stream (only used by libavformat) */
    AV_CODEC_ID_MPEG4SYSTEMS = 0x20001, /**< _FAKE_ codec to indicate a MPEG-4 Systems
                                * stream (only used by libavformat) */
    AV_CODEC_ID_FFMETADATA = 0x21000,   ///< Dummy codec for streams containing only metadata information.
    AV_CODEC_ID_WRAPPED_AVFRAME = 0x21001, ///< Passthrough codec, AVFrames wrapped in AVPacket
};

/**
 * This struct describes the properties of a single codec described by an
 * AVCodecID.
 * @see avcodec_descriptor_get()
 */
typedef struct AVCodecDescriptor {
    enum AVCodecID     id;
    enum AVMediaType type;
    /**
     * Name of the codec described by this descriptor. It is non-empty and
     * unique for each codec descriptor. It should contain alphanumeric
     * characters and '_' only.
     */
    const char      *name;
    /**
     * A more descriptive name for this codec. May be NULL.
     */
    const char *long_name;
    /**
     * Codec properties, a combination of AV_CODEC_PROP_* flags.
     */
    int             props;
    /**
     * MIME type(s) associated with the codec.
     * May be NULL; if not, a NULL-terminated array of MIME types.
     * The first item is always non-NULL and is the preferred MIME type.
     */
    const char *const *mime_types;
    /**
     * If non-NULL, an array of profiles recognized for this codec.
     * Terminated with FF_PROFILE_UNKNOWN.
     */
    const struct AVProfile *profiles;
} AVCodecDescriptor;

/**
 * Codec uses only intra compression.
 * Video and audio codecs only.
 */
#define AV_CODEC_PROP_INTRA_ONLY    (1 << 0)
/**
 * Codec supports lossy compression. Audio and video codecs only.
 * @note a codec may support both lossy and lossless
 * compression modes
 */
#define AV_CODEC_PROP_LOSSY         (1 << 1)
/**
 * Codec supports lossless compression. Audio and video codecs only.
 */
#define AV_CODEC_PROP_LOSSLESS      (1 << 2)
/**
 * Codec supports frame reordering. That is, the coded order (the order in which
 * the encoded packets are output by the encoders / stored / input to the
 * decoders) may be different from the presentation order of the corresponding
 * frames.
 *
 * For codecs that do not have this property set, PTS and DTS should always be
 * equal.
 */
#define AV_CODEC_PROP_REORDER       (1 << 3)
/**
 * Subtitle codec is bitmap based
 * Decoded AVSubtitle data can be read from the AVSubtitleRect->pict field.
 */
#define AV_CODEC_PROP_BITMAP_SUB    (1 << 16)
/**
 * Subtitle codec is text based.
 * Decoded AVSubtitle data can be read from the AVSubtitleRect->ass field.
 */
#define AV_CODEC_PROP_TEXT_SUB      (1 << 17)

/**
 * @ingroup lavc_decoding
 * Required number of additionally allocated bytes at the end of the input bitstream for decoding.
 * This is mainly needed because some optimized bitstream readers read
 * 32 or 64 bit at once and could read over the end.<br>
 * Note: If the first 23 bits of the additional bytes are not 0, then damaged
 * MPEG bitstreams could cause overread and segfault.
 */
#define AV_INPUT_BUFFER_PADDING_SIZE 64

/**
 * @ingroup lavc_encoding
 * minimum encoding buffer size
 * Used to avoid some checks during header writing.
 */
#define AV_INPUT_BUFFER_MIN_SIZE 16384

/**
 * @ingroup lavc_decoding
 */
enum AVDiscard{
    /* We leave some space between them for extensions (drop some
     * keyframes for intra-only or drop just some bidir frames). */
    AVDISCARD_NONE    =-16, ///< discard nothing
    AVDISCARD_DEFAULT =  0, ///< discard useless packets like 0 size packets in avi
    AVDISCARD_NONREF  =  8, ///< discard all non reference
    AVDISCARD_BIDIR   = 16, ///< discard all bidirectional frames
    AVDISCARD_NONINTRA= 24, ///< discard all non intra frames
    AVDISCARD_NONKEY  = 32, ///< discard all frames except keyframes
    AVDISCARD_ALL     = 48, ///< discard all
};

enum AVAudioServiceType {
    AV_AUDIO_SERVICE_TYPE_MAIN              = 0,
    AV_AUDIO_SERVICE_TYPE_EFFECTS           = 1,
    AV_AUDIO_SERVICE_TYPE_VISUALLY_IMPAIRED = 2,
    AV_AUDIO_SERVICE_TYPE_HEARING_IMPAIRED  = 3,
    AV_AUDIO_SERVICE_TYPE_DIALOGUE          = 4,
    AV_AUDIO_SERVICE_TYPE_COMMENTARY        = 5,
    AV_AUDIO_SERVICE_TYPE_EMERGENCY         = 6,
    AV_AUDIO_SERVICE_TYPE_VOICE_OVER        = 7,
    AV_AUDIO_SERVICE_TYPE_KARAOKE           = 8,
    AV_AUDIO_SERVICE_TYPE_NB                   , ///< Not part of ABI
};

/**
 * @ingroup lavc_encoding
 */
typedef struct RcOverride{
    int start_frame;
    int end_frame;
    int qscale; // If this is 0 then quality_factor will be used instead.
    float quality_factor;
} RcOverride;

/* encoding support
   These flags can be passed in AVCodecContext.flags before initialization.
   Note: Not everything is supported yet.
*/

/**
 * Allow decoders to produce frames with data planes that are not aligned
 * to CPU requirements (e.g. due to cropping).
 */
#define AV_CODEC_FLAG_UNALIGNED       (1 <<  0)
/**
 * Use fixed qscale.
 */
#define AV_CODEC_FLAG_QSCALE          (1 <<  1)
/**
 * 4 MV per MB allowed / advanced prediction for H.263.
 */
#define AV_CODEC_FLAG_4MV             (1 <<  2)
/**
 * Output even those frames that might be corrupted.
 */
#define AV_CODEC_FLAG_OUTPUT_CORRUPT  (1 <<  3)
/**
 * Use qpel MC.
 */
#define AV_CODEC_FLAG_QPEL            (1 <<  4)
/**
 * Use internal 2pass ratecontrol in first pass mode.
 */
#define AV_CODEC_FLAG_PASS1           (1 <<  9)
/**
 * Use internal 2pass ratecontrol in second pass mode.
 */
#define AV_CODEC_FLAG_PASS2           (1 << 10)
/**
 * loop filter.
 */
#define AV_CODEC_FLAG_LOOP_FILTER     (1 << 11)
/**
 * Only decode/encode grayscale.
 */
#define AV_CODEC_FLAG_GRAY            (1 << 13)
/**
 * error[?] variables will be set during encoding.
 */
#define AV_CODEC_FLAG_PSNR            (1 << 15)
/**
 * Input bitstream might be truncated at a random location
 * instead of only at frame boundaries.
 */
#define AV_CODEC_FLAG_TRUNCATED       (1 << 16)
/**
 * Use interlaced DCT.
 */
#define AV_CODEC_FLAG_INTERLACED_DCT  (1 << 18)
/**
 * Force low delay.
 */
#define AV_CODEC_FLAG_LOW_DELAY       (1 << 19)
/**
 * Place global headers in extradata instead of every keyframe.
 */
#define AV_CODEC_FLAG_GLOBAL_HEADER   (1 << 22)
/**
 * Use only bitexact stuff (except (I)DCT).
 */
#define AV_CODEC_FLAG_BITEXACT        (1 << 23)
/* Fx : Flag for H.263+ extra options */
/**
 * H.263 advanced intra coding / MPEG-4 AC prediction
 */
#define AV_CODEC_FLAG_AC_PRED         (1 << 24)
/**
 * interlaced motion estimation
 */
#define AV_CODEC_FLAG_INTERLACED_ME   (1 << 29)
#define AV_CODEC_FLAG_CLOSED_GOP      (1U << 31)

/**
 * Allow non spec compliant speedup tricks.
 */
#define AV_CODEC_FLAG2_FAST           (1 <<  0)
/**
 * Skip bitstream encoding.
 */
#define AV_CODEC_FLAG2_NO_OUTPUT      (1 <<  2)
/**
 * Place global headers at every keyframe instead of in extradata.
 */
#define AV_CODEC_FLAG2_LOCAL_HEADER   (1 <<  3)

/**
 * timecode is in drop frame format. DEPRECATED!!!!
 */
#define AV_CODEC_FLAG2_DROP_FRAME_TIMECODE (1 << 13)

/**
 * Input bitstream might be truncated at a packet boundaries
 * instead of only at frame boundaries.
 */
#define AV_CODEC_FLAG2_CHUNKS         (1 << 15)
/**
 * Discard cropping information from SPS.
 */
#define AV_CODEC_FLAG2_IGNORE_CROP    (1 << 16)

/**
 * Show all frames before the first keyframe
 */
#define AV_CODEC_FLAG2_SHOW_ALL       (1 << 22)
/**
 * Export motion vectors through frame side data
 */
#define AV_CODEC_FLAG2_EXPORT_MVS     (1 << 28)
/**
 * Do not skip samples and export skip information as frame side data
 */
#define AV_CODEC_FLAG2_SKIP_MANUAL    (1 << 29)
/**
 * Do not reset ASS ReadOrder field on flush (subtitles decoding)
 */
#define AV_CODEC_FLAG2_RO_FLUSH_NOOP  (1 << 30)

/* Unsupported options :
 *              Syntax Arithmetic coding (SAC)
 *              Reference Picture Selection
 *              Independent Segment Decoding */
/* /Fx */
/* codec capabilities */

/**
 * Decoder can use draw_horiz_band callback.
 */
#define AV_CODEC_CAP_DRAW_HORIZ_BAND     (1 <<  0)
/**
 * Codec uses get_buffer() for allocating buffers and supports custom allocators.
 * If not set, it might not use get_buffer() at all or use operations that
 * assume the buffer was allocated by avcodec_default_get_buffer.
 */
#define AV_CODEC_CAP_DR1                 (1 <<  1)
#define AV_CODEC_CAP_TRUNCATED           (1 <<  3)
/**
 * Encoder or decoder requires flushing with NULL input at the end in order to
 * give the complete and correct output.
 *
 * NOTE: If this flag is not set, the codec is guaranteed to never be fed with
 *       with NULL data. The user can still send NULL data to the public encode
 *       or decode function, but libavcodec will not pass it along to the codec
 *       unless this flag is set.
 *
 * Decoders:
 * The decoder has a non-zero delay and needs to be fed with avpkt->data=NULL,
 * avpkt->size=0 at the end to get the delayed data until the decoder no longer
 * returns frames.
 *
 * Encoders:
 * The encoder needs to be fed with NULL data at the end of encoding until the
 * encoder no longer returns data.
 *
 * NOTE: For encoders implementing the AVCodec.encode2() function, setting this
 *       flag also means that the encoder must set the pts and duration for
 *       each output packet. If this flag is not set, the pts and duration will
 *       be determined by libavcodec from the input frame.
 */
#define AV_CODEC_CAP_DELAY               (1 <<  5)
/**
 * Codec can be fed a final frame with a smaller size.
 * This can be used to prevent truncation of the last audio samples.
 */
#define AV_CODEC_CAP_SMALL_LAST_FRAME    (1 <<  6)

/**
 * Codec can output multiple frames per AVPacket
 * Normally demuxers return one frame at a time, demuxers which do not do
 * are connected to a parser to split what they return into proper frames.
 * This flag is reserved to the very rare category of codecs which have a
 * bitstream that cannot be split into frames without timeconsuming
 * operations like full decoding. Demuxers carrying such bitstreams thus
 * may return multiple frames in a packet. This has many disadvantages like
 * prohibiting stream copy in many cases thus it should only be considered
 * as a last resort.
 */
#define AV_CODEC_CAP_SUBFRAMES           (1 <<  8)
/**
 * Codec is experimental and is thus avoided in favor of non experimental
 * encoders
 */
#define AV_CODEC_CAP_EXPERIMENTAL        (1 <<  9)
/**
 * Codec should fill in channel configuration and samplerate instead of container
 */
#define AV_CODEC_CAP_CHANNEL_CONF        (1 << 10)
/**
 * Codec supports frame-level multithreading.
 */
#define AV_CODEC_CAP_FRAME_THREADS       (1 << 12)
/**
 * Codec supports slice-based (or partition-based) multithreading.
 */
#define AV_CODEC_CAP_SLICE_THREADS       (1 << 13)
/**
 * Codec supports changed parameters at any point.
 */
#define AV_CODEC_CAP_PARAM_CHANGE        (1 << 14)
/**
 * Codec supports avctx->thread_count == 0 (auto).
 */
#define AV_CODEC_CAP_AUTO_THREADS        (1 << 15)
/**
 * Audio encoder supports receiving a different number of samples in each call.
 */
#define AV_CODEC_CAP_VARIABLE_FRAME_SIZE (1 << 16)
/**
 * Decoder is not a preferred choice for probing.
 * This indicates that the decoder is not a good choice for probing.
 * It could for example be an expensive to spin up hardware decoder,
 * or it could simply not provide a lot of useful information about
 * the stream.
 * A decoder marked with this flag should only be used as last resort
 * choice for probing.
 */
#define AV_CODEC_CAP_AVOID_PROBING       (1 << 17)
/**
 * Codec is intra only.
 */
#define AV_CODEC_CAP_INTRA_ONLY       0x40000000
/**
 * Codec is lossless.
 */
#define AV_CODEC_CAP_LOSSLESS         0x80000000

/**
 * Codec is backed by a hardware implementation. Typically used to
 * identify a non-hwaccel hardware decoder. For information about hwaccels, use
 * avcodec_get_hw_config() instead.
 */
#define AV_CODEC_CAP_HARDWARE            (1 << 18)

/**
 * Codec is potentially backed by a hardware implementation, but not
 * necessarily. This is used instead of AV_CODEC_CAP_HARDWARE, if the
 * implementation provides some sort of internal fallback.
 */
#define AV_CODEC_CAP_HYBRID              (1 << 19)

/**
 * Pan Scan area.
 * This specifies the area which should be displayed.
 * Note there may be multiple such areas for one frame.
 */
typedef struct AVPanScan {
    /**
     * id
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
    int id;

    /**
     * width and height in 1/16 pel
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
    int width;
    int height;

    /**
     * position of the top left corner in 1/16 pel for up to 3 fields/frames
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
    int16_t position[3][2];
} AVPanScan;

/**
 * This structure describes the bitrate properties of an encoded bitstream. It
 * roughly corresponds to a subset the VBV parameters for MPEG-2 or HRD
 * parameters for H.264/HEVC.
 */
typedef struct AVCPBProperties {
    /**
     * Maximum bitrate of the stream, in bits per second.
     * Zero if unknown or unspecified.
     */
    int max_bitrate;
    /**
     * Minimum bitrate of the stream, in bits per second.
     * Zero if unknown or unspecified.
     */
    int min_bitrate;
    /**
     * Average bitrate of the stream, in bits per second.
     * Zero if unknown or unspecified.
     */
    int avg_bitrate;

    /**
     * The size of the buffer to which the ratecontrol is applied, in bits.
     * Zero if unknown or unspecified.
     */
    int buffer_size;

    /**
     * The delay between the time the packet this structure is associated with
     * is received and the time when it should be decoded, in periods of a 27MHz
     * clock.
     *
     * UINT64_MAX when unknown or unspecified.
     */
    uint64_t vbv_delay;
} AVCPBProperties;

/**
 * The decoder will keep a reference to the frame and may reuse it later.
 */
#define AV_GET_BUFFER_FLAG_REF (1 << 0)

/**
 * @defgroup lavc_packet AVPacket
 *
 * Types and functions for working with AVPacket.
 * @{
 */
enum AVPacketSideDataType {
    /**
     * An AV_PKT_DATA_PALETTE side data packet contains exactly AVPALETTE_SIZE
     * bytes worth of palette. This side data signals that a new palette is
     * present.
     */
    AV_PKT_DATA_PALETTE,

    /**
     * The AV_PKT_DATA_NEW_EXTRADATA is used to notify the codec or the format
     * that the extradata buffer was changed and the receiving side should
     * act upon it appropriately. The new extradata is embedded in the side
     * data buffer and should be immediately used for processing the current
     * frame or packet.
     */
    AV_PKT_DATA_NEW_EXTRADATA,

    /**
     * An AV_PKT_DATA_PARAM_CHANGE side data packet is laid out as follows:
     * @code
     * u32le param_flags
     * if (param_flags & AV_SIDE_DATA_PARAM_CHANGE_CHANNEL_COUNT)
     *     s32le channel_count
     * if (param_flags & AV_SIDE_DATA_PARAM_CHANGE_CHANNEL_LAYOUT)
     *     u64le channel_layout
     * if (param_flags & AV_SIDE_DATA_PARAM_CHANGE_SAMPLE_RATE)
     *     s32le sample_rate
     * if (param_flags & AV_SIDE_DATA_PARAM_CHANGE_DIMENSIONS)
     *     s32le width
     *     s32le height
     * @endcode
     */
    AV_PKT_DATA_PARAM_CHANGE,

    /**
     * An AV_PKT_DATA_H263_MB_INFO side data packet contains a number of
     * structures with info about macroblocks relevant to splitting the
     * packet into smaller packets on macroblock edges (e.g. as for RFC 2190).
     * That is, it does not necessarily contain info about all macroblocks,
     * as long as the distance between macroblocks in the info is smaller
     * than the target payload size.
     * Each MB info structure is 12 bytes, and is laid out as follows:
     * @code
     * u32le bit offset from the start of the packet
     * u8    current quantizer at the start of the macroblock
     * u8    GOB number
     * u16le macroblock address within the GOB
     * u8    horizontal MV predictor
     * u8    vertical MV predictor
     * u8    horizontal MV predictor for block number 3
     * u8    vertical MV predictor for block number 3
     * @endcode
     */
    AV_PKT_DATA_H263_MB_INFO,

    /**
     * This side data should be associated with an audio stream and contains
     * ReplayGain information in form of the AVReplayGain struct.
     */
    AV_PKT_DATA_REPLAYGAIN,

    /**
     * This side data contains a 3x3 transformation matrix describing an affine
     * transformation that needs to be applied to the decoded video frames for
     * correct presentation.
     *
     * See libavutil/display.h for a detailed description of the data.
     */
    AV_PKT_DATA_DISPLAYMATRIX,

    /**
     * This side data should be associated with a video stream and contains
     * Stereoscopic 3D information in form of the AVStereo3D struct.
     */
    AV_PKT_DATA_STEREO3D,

    /**
     * This side data should be associated with an audio stream and corresponds
     * to enum AVAudioServiceType.
     */
    AV_PKT_DATA_AUDIO_SERVICE_TYPE,

    /**
     * This side data contains quality related information from the encoder.
     * @code
     * u32le quality factor of the compressed frame. Allowed range is between 1 (good) and FF_LAMBDA_MAX (bad).
     * u8    picture type
     * u8    error count
     * u16   reserved
     * u64le[error count] sum of squared differences between encoder in and output
     * @endcode
     */
    AV_PKT_DATA_QUALITY_STATS,

    /**
     * This side data contains an integer value representing the stream index
     * of a "fallback" track.  A fallback track indicates an alternate
     * track to use when the current track can not be decoded for some reason.
     * e.g. no decoder available for codec.
     */
    AV_PKT_DATA_FALLBACK_TRACK,

    /**
     * This side data corresponds to the AVCPBProperties struct.
     */
    AV_PKT_DATA_CPB_PROPERTIES,

    /**
     * Recommmends skipping the specified number of samples
     * @code
     * u32le number of samples to skip from start of this packet
     * u32le number of samples to skip from end of this packet
     * u8    reason for start skip
     * u8    reason for end   skip (0=padding silence, 1=convergence)
     * @endcode
     */
    AV_PKT_DATA_SKIP_SAMPLES,

    /**
     * An AV_PKT_DATA_JP_DUALMONO side data packet indicates that
     * the packet may contain "dual mono" audio specific to Japanese DTV
     * and if it is true, recommends only the selected channel to be used.
     * @code
     * u8    selected channels (0=mail/left, 1=sub/right, 2=both)
     * @endcode
     */
    AV_PKT_DATA_JP_DUALMONO,

    /**
     * A list of zero terminated key/value strings. There is no end marker for
     * the list, so it is required to rely on the side data size to stop.
     */
    AV_PKT_DATA_STRINGS_METADATA,

    /**
     * Subtitle event position
     * @code
     * u32le x1
     * u32le y1
     * u32le x2
     * u32le y2
     * @endcode
     */
    AV_PKT_DATA_SUBTITLE_POSITION,

    /**
     * Data found in BlockAdditional element of matroska container. There is
     * no end marker for the data, so it is required to rely on the side data
     * size to recognize the end. 8 byte id (as found in BlockAddId) followed
     * by data.
     */
    AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL,

    /**
     * The optional first identifier line of a WebVTT cue.
     */
    AV_PKT_DATA_WEBVTT_IDENTIFIER,

    /**
     * The optional settings (rendering instructions) that immediately
     * follow the timestamp specifier of a WebVTT cue.
     */
    AV_PKT_DATA_WEBVTT_SETTINGS,

    /**
     * A list of zero terminated key/value strings. There is no end marker for
     * the list, so it is required to rely on the side data size to stop. This
     * side data includes updated metadata which appeared in the stream.
     */
    AV_PKT_DATA_METADATA_UPDATE,

    /**
     * MPEGTS stream ID, this is required to pass the stream ID
     * information from the demuxer to the corresponding muxer.
     */
    AV_PKT_DATA_MPEGTS_STREAM_ID,

    /**
     * Mastering display metadata (based on SMPTE-2086:2014). This metadata
     * should be associated with a video stream and contains data in the form
     * of the AVMasteringDisplayMetadata struct.
     */
    AV_PKT_DATA_MASTERING_DISPLAY_METADATA,

    /**
     * This side data should be associated with a video stream and corresponds
     * to the AVSphericalMapping structure.
     */
    AV_PKT_DATA_SPHERICAL,

    /**
     * Content light level (based on CTA-861.3). This metadata should be
     * associated with a video stream and contains data in the form of the
     * AVContentLightMetadata struct.
     */
    AV_PKT_DATA_CONTENT_LIGHT_LEVEL,

    /**
     * ATSC A53 Part 4 Closed Captions. This metadata should be associated with
     * a video stream. A53 CC bitstream is stored as uint8_t in AVPacketSideData.data.
     * The number of bytes of CC data is AVPacketSideData.size.
     */
    AV_PKT_DATA_A53_CC,

    /**
     * This side data is encryption initialization data.
     * The format is not part of ABI, use av_encryption_init_info_* methods to
     * access.
     */
    AV_PKT_DATA_ENCRYPTION_INIT_INFO,

    /**
     * This side data contains encryption info for how to decrypt the packet.
     * The format is not part of ABI, use av_encryption_info_* methods to access.
     */
    AV_PKT_DATA_ENCRYPTION_INFO,

    /**
     * The number of side data types.
     * This is not part of the public API/ABI in the sense that it may
     * change when new side data types are added.
     * This must stay the last enum value.
     * If its value becomes huge, some code using it
     * needs to be updated as it assumes it to be smaller than other limits.
     */
    AV_PKT_DATA_NB
};

#define AV_PKT_DATA_QUALITY_FACTOR AV_PKT_DATA_QUALITY_STATS //DEPRECATED

typedef struct AVPacketSideData {
    uint8_t *data;
    int      size;
    enum AVPacketSideDataType type;
} AVPacketSideData;

/**
 * This structure stores compressed data. It is typically exported by demuxers
 * and then passed as input to decoders, or received as output from encoders and
 * then passed to muxers.
 *
 * For video, it should typically contain one compressed frame. For audio it may
 * contain several compressed frames. Encoders are allowed to output empty
 * packets, with no compressed data, containing only side data
 * (e.g. to update some stream parameters at the end of encoding).
 *
 * AVPacket is one of the few structs in FFmpeg, whose size is a part of public
 * ABI. Thus it may be allocated on stack and no new fields can be added to it
 * without libavcodec and libavformat major bump.
 *
 * The semantics of data ownership depends on the buf field.
 * If it is set, the packet data is dynamically allocated and is
 * valid indefinitely until a call to av_packet_unref() reduces the
 * reference count to 0.
 *
 * If the buf field is not set av_packet_ref() would make a copy instead
 * of increasing the reference count.
 *
 * The side data is always allocated with av_malloc(), copied by
 * av_packet_ref() and freed by av_packet_unref().
 *
 * @see av_packet_ref
 * @see av_packet_unref
 */
typedef struct AVPacket {
    /**
     * A reference to the reference-counted buffer where the packet data is
     * stored.
     * May be NULL, then the packet data is not reference-counted.
     */
    AVBufferRef *buf;
    /**
     * Presentation timestamp in AVStream->time_base units; the time at which
     * the decompressed packet will be presented to the user.
     * Can be AV_NOPTS_VALUE if it is not stored in the file.
     * pts MUST be larger or equal to dts as presentation cannot happen before
     * decompression, unless one wants to view hex dumps. Some formats misuse
     * the terms dts and pts/cts to mean something different. Such timestamps
     * must be converted to true pts/dts before they are stored in AVPacket.
     */
    int64_t pts;
    /**
     * Decompression timestamp in AVStream->time_base units; the time at which
     * the packet is decompressed.
     * Can be AV_NOPTS_VALUE if it is not stored in the file.
     */
    int64_t dts;
    uint8_t *data;
    int   size;
    int   stream_index;
    /**
     * A combination of AV_PKT_FLAG values
     */
    int   flags;
    /**
     * Additional packet data that can be provided by the container.
     * Packet can contain several types of side information.
     */
    AVPacketSideData *side_data;
    int side_data_elems;

    /**
     * Duration of this packet in AVStream->time_base units, 0 if unknown.
     * Equals next_pts - this_pts in presentation order.
     */
    int64_t duration;

    int64_t pos;                            ///< byte position in stream, -1 if unknown

#if FF_API_CONVERGENCE_DURATION
    /**
     * @deprecated Same as the duration field, but as int64_t. This was required
     * for Matroska subtitles, whose duration values could overflow when the
     * duration field was still an int.
     */
    attribute_deprecated
    int64_t convergence_duration;
#endif
} AVPacket;
#define AV_PKT_FLAG_KEY     0x0001 ///< The packet contains a keyframe
#define AV_PKT_FLAG_CORRUPT 0x0002 ///< The packet content is corrupted
/**
 * Flag is used to discard packets which are required to maintain valid
 * decoder state but are not required for output and should be dropped
 * after decoding.
 **/
#define AV_PKT_FLAG_DISCARD   0x0004
/**
 * The packet comes from a trusted source.
 *
 * Otherwise-unsafe constructs such as arbitrary pointers to data
 * outside the packet may be followed.
 */
#define AV_PKT_FLAG_TRUSTED   0x0008
/**
 * Flag is used to indicate packets that contain frames that can
 * be discarded by the decoder.  I.e. Non-reference frames.
 */
#define AV_PKT_FLAG_DISPOSABLE 0x0010


enum AVSideDataParamChangeFlags {
    AV_SIDE_DATA_PARAM_CHANGE_CHANNEL_COUNT  = 0x0001,
    AV_SIDE_DATA_PARAM_CHANGE_CHANNEL_LAYOUT = 0x0002,
    AV_SIDE_DATA_PARAM_CHANGE_SAMPLE_RATE    = 0x0004,
    AV_SIDE_DATA_PARAM_CHANGE_DIMENSIONS     = 0x0008,
};
/**
 * @}
 */

struct AVCodecInternal;

enum AVFieldOrder {
    AV_FIELD_UNKNOWN,
    AV_FIELD_PROGRESSIVE,
    AV_FIELD_TT,          //< Top coded_first, top displayed first
    AV_FIELD_BB,          //< Bottom coded first, bottom displayed first
    AV_FIELD_TB,          //< Top coded first, bottom displayed first
    AV_FIELD_BT,          //< Bottom coded first, top displayed first
};

/**
 * main external API structure.
 * New fields can be added to the end with minor version bumps.
 * Removal, reordering and changes to existing fields require a major
 * version bump.
 * You can use AVOptions (av_opt* / av_set/get*()) to access these fields from user
 * applications.
 * The name string for AVOptions options matches the associated command line
 * parameter name and can be found in libavcodec/options_table.h
 * The AVOption/command line parameter names differ in some cases from the C
 * structure field names for historic reasons or brevity.
 * sizeof(AVCodecContext) must not be used outside libav*.
 */
typedef struct AVCodecContext {
    /**
     * information on struct for av_log
     * - set by avcodec_alloc_context3
     */
    const AVClass *av_class;
    int log_level_offset;

    enum AVMediaType codec_type; /* see AVMEDIA_TYPE_xxx */
    const struct AVCodec  *codec;
    enum AVCodecID     codec_id; /* see AV_CODEC_ID_xxx */

    /**
     * fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
     * This is used to work around some encoder bugs.
     * A demuxer should set this to what is stored in the field used to identify the codec.
     * If there are multiple such fields in a container then the demuxer should choose the one
     * which maximizes the information about the used codec.
     * If the codec tag field in a container is larger than 32 bits then the demuxer should
     * remap the longer ID to 32 bits with a table or other structure. Alternatively a new
     * extra_codec_tag + size could be added but for this a clear advantage must be demonstrated
     * first.
     * - encoding: Set by user, if not then the default based on codec_id will be used.
     * - decoding: Set by user, will be converted to uppercase by libavcodec during init.
     */
    unsigned int codec_tag;

    void *priv_data;

    /**
     * Private context used for internal data.
     *
     * Unlike priv_data, this is not codec-specific. It is used in general
     * libavcodec functions.
     */
    struct AVCodecInternal *internal;

    /**
     * Private data of the user, can be used to carry app specific stuff.
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    void *opaque;

    /**
     * the average bitrate
     * - encoding: Set by user; unused for constant quantizer encoding.
     * - decoding: Set by user, may be overwritten by libavcodec
     *             if this info is available in the stream
     */
    int64_t bit_rate;

    /**
     * number of bits the bitstream is allowed to diverge from the reference.
     *           the reference can be CBR (for CBR pass1) or VBR (for pass2)
     * - encoding: Set by user; unused for constant quantizer encoding.
     * - decoding: unused
     */
    int bit_rate_tolerance;

    /**
     * Global quality for codecs which cannot change it per frame.
     * This should be proportional to MPEG-1/2/4 qscale.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int global_quality;

    /**
     * - encoding: Set by user.
     * - decoding: unused
     */
    int compression_level;
#define FF_COMPRESSION_DEFAULT -1

    /**
     * AV_CODEC_FLAG_*.
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int flags;

    /**
     * AV_CODEC_FLAG2_*
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int flags2;

    /**
     * some codecs need / can use extradata like Huffman tables.
     * MJPEG: Huffman tables
     * rv10: additional flags
     * MPEG-4: global headers (they can be in the bitstream or here)
     * The allocated memory should be AV_INPUT_BUFFER_PADDING_SIZE bytes larger
     * than extradata_size to avoid problems if it is read with the bitstream reader.
     * The bytewise contents of extradata must not depend on the architecture or CPU endianness.
     * Must be allocated with the av_malloc() family of functions.
     * - encoding: Set/allocated/freed by libavcodec.
     * - decoding: Set/allocated/freed by user.
     */
    uint8_t *extradata;
    int extradata_size;

    /**
     * This is the fundamental unit of time (in seconds) in terms
     * of which frame timestamps are represented. For fixed-fps content,
     * timebase should be 1/framerate and timestamp increments should be
     * identically 1.
     * This often, but not always is the inverse of the frame rate or field rate
     * for video. 1/time_base is not the average frame rate if the frame rate is not
     * constant.
     *
     * Like containers, elementary streams also can store timestamps, 1/time_base
     * is the unit in which these timestamps are specified.
     * As example of such codec time base see ISO/IEC 14496-2:2001(E)
     * vop_time_increment_resolution and fixed_vop_rate
     * (fixed_vop_rate == 0 implies that it is different from the framerate)
     *
     * - encoding: MUST be set by user.
     * - decoding: the use of this field for decoding is deprecated.
     *             Use framerate instead.
     */
    AVRational time_base;

    /**
     * For some codecs, the time base is closer to the field rate than the frame rate.
     * Most notably, H.264 and MPEG-2 specify time_base as half of frame duration
     * if no telecine is used ...
     *
     * Set to time_base ticks per frame. Default 1, e.g., H.264/MPEG-2 set it to 2.
     */
    int ticks_per_frame;

    /**
     * Codec delay.
     *
     * Encoding: Number of frames delay there will be from the encoder input to
     *           the decoder output. (we assume the decoder matches the spec)
     * Decoding: Number of frames delay in addition to what a standard decoder
     *           as specified in the spec would produce.
     *
     * Video:
     *   Number of frames the decoded output will be delayed relative to the
     *   encoded input.
     *
     * Audio:
     *   For encoding, this field is unused (see initial_padding).
     *
     *   For decoding, this is the number of samples the decoder needs to
     *   output before the decoder's output is valid. When seeking, you should
     *   start decoding this many samples prior to your desired seek point.
     *
     * - encoding: Set by libavcodec.
     * - decoding: Set by libavcodec.
     */
    int delay;


    /* video only */
    /**
     * picture width / height.
     *
     * @note Those fields may not match the values of the last
     * AVFrame output by avcodec_decode_video2 due frame
     * reordering.
     *
     * - encoding: MUST be set by user.
     * - decoding: May be set by the user before opening the decoder if known e.g.
     *             from the container. Some decoders will require the dimensions
     *             to be set by the caller. During decoding, the decoder may
     *             overwrite those values as required while parsing the data.
     */
    int width, height;

    /**
     * Bitstream width / height, may be different from width/height e.g. when
     * the decoded frame is cropped before being output or lowres is enabled.
     *
     * @note Those field may not match the value of the last
     * AVFrame output by avcodec_receive_frame() due frame
     * reordering.
     *
     * - encoding: unused
     * - decoding: May be set by the user before opening the decoder if known
     *             e.g. from the container. During decoding, the decoder may
     *             overwrite those values as required while parsing the data.
     */
    int coded_width, coded_height;

    /**
     * the number of pictures in a group of pictures, or 0 for intra_only
     * - encoding: Set by user.
     * - decoding: unused
     */
    int gop_size;

    /**
     * Pixel format, see AV_PIX_FMT_xxx.
     * May be set by the demuxer if known from headers.
     * May be overridden by the decoder if it knows better.
     *
     * @note This field may not match the value of the last
     * AVFrame output by avcodec_receive_frame() due frame
     * reordering.
     *
     * - encoding: Set by user.
     * - decoding: Set by user if known, overridden by libavcodec while
     *             parsing the data.
     */
    enum AVPixelFormat pix_fmt;

    /**
     * If non NULL, 'draw_horiz_band' is called by the libavcodec
     * decoder to draw a horizontal band. It improves cache usage. Not
     * all codecs can do that. You must check the codec capabilities
     * beforehand.
     * When multithreading is used, it may be called from multiple threads
     * at the same time; threads might draw different parts of the same AVFrame,
     * or multiple AVFrames, and there is no guarantee that slices will be drawn
     * in order.
     * The function is also used by hardware acceleration APIs.
     * It is called at least once during frame decoding to pass
     * the data needed for hardware render.
     * In that mode instead of pixel data, AVFrame points to
     * a structure specific to the acceleration API. The application
     * reads the structure and can change some fields to indicate progress
     * or mark state.
     * - encoding: unused
     * - decoding: Set by user.
     * @param height the height of the slice
     * @param y the y position of the slice
     * @param type 1->top field, 2->bottom field, 3->frame
     * @param offset offset into the AVFrame.data from which the slice should be read
     */
    void (*draw_horiz_band)(struct AVCodecContext *s,
                            const AVFrame *src, int offset[AV_NUM_DATA_POINTERS],
                            int y, int type, int height);

    /**
     * callback to negotiate the pixelFormat
     * @param fmt is the list of formats which are supported by the codec,
     * it is terminated by -1 as 0 is a valid format, the formats are ordered by quality.
     * The first is always the native one.
     * @note The callback may be called again immediately if initialization for
     * the selected (hardware-accelerated) pixel format failed.
     * @warning Behavior is undefined if the callback returns a value not
     * in the fmt list of formats.
     * @return the chosen format
     * - encoding: unused
     * - decoding: Set by user, if not set the native format will be chosen.
     */
    enum AVPixelFormat (*get_format)(struct AVCodecContext *s, const enum AVPixelFormat * fmt);

    /**
     * maximum number of B-frames between non-B-frames
     * Note: The output will be delayed by max_b_frames+1 relative to the input.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int max_b_frames;

    /**
     * qscale factor between IP and B-frames
     * If > 0 then the last P-frame quantizer will be used (q= lastp_q*factor+offset).
     * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
     * - encoding: Set by user.
     * - decoding: unused
     */
    float b_quant_factor;

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int b_frame_strategy;
#endif

    /**
     * qscale offset between IP and B-frames
     * - encoding: Set by user.
     * - decoding: unused
     */
    float b_quant_offset;

    /**
     * Size of the frame reordering buffer in the decoder.
     * For MPEG-2 it is 1 IPB or 0 low delay IP.
     * - encoding: Set by libavcodec.
     * - decoding: Set by libavcodec.
     */
    int has_b_frames;

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int mpeg_quant;
#endif

    /**
     * qscale factor between P- and I-frames
     * If > 0 then the last P-frame quantizer will be used (q = lastp_q * factor + offset).
     * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
     * - encoding: Set by user.
     * - decoding: unused
     */
    float i_quant_factor;

    /**
     * qscale offset between P and I-frames
     * - encoding: Set by user.
     * - decoding: unused
     */
    float i_quant_offset;

    /**
     * luminance masking (0-> disabled)
     * - encoding: Set by user.
     * - decoding: unused
     */
    float lumi_masking;

    /**
     * temporary complexity masking (0-> disabled)
     * - encoding: Set by user.
     * - decoding: unused
     */
    float temporal_cplx_masking;

    /**
     * spatial complexity masking (0-> disabled)
     * - encoding: Set by user.
     * - decoding: unused
     */
    float spatial_cplx_masking;

    /**
     * p block masking (0-> disabled)
     * - encoding: Set by user.
     * - decoding: unused
     */
    float p_masking;

    /**
     * darkness masking (0-> disabled)
     * - encoding: Set by user.
     * - decoding: unused
     */
    float dark_masking;

    /**
     * slice count
     * - encoding: Set by libavcodec.
     * - decoding: Set by user (or 0).
     */
    int slice_count;

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
     int prediction_method;
#define FF_PRED_LEFT   0
#define FF_PRED_PLANE  1
#define FF_PRED_MEDIAN 2
#endif

    /**
     * slice offsets in the frame in bytes
     * - encoding: Set/allocated by libavcodec.
     * - decoding: Set/allocated by user (or NULL).
     */
    int *slice_offset;

    /**
     * sample aspect ratio (0 if unknown)
     * That is the width of a pixel divided by the height of the pixel.
     * Numerator and denominator must be relatively prime and smaller than 256 for some video standards.
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
    AVRational sample_aspect_ratio;

    /**
     * motion estimation comparison function
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_cmp;
    /**
     * subpixel motion estimation comparison function
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_sub_cmp;
    /**
     * macroblock comparison function (not supported yet)
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mb_cmp;
    /**
     * interlaced DCT comparison function
     * - encoding: Set by user.
     * - decoding: unused
     */
    int ildct_cmp;
#define FF_CMP_SAD          0
#define FF_CMP_SSE          1
#define FF_CMP_SATD         2
#define FF_CMP_DCT          3
#define FF_CMP_PSNR         4
#define FF_CMP_BIT          5
#define FF_CMP_RD           6
#define FF_CMP_ZERO         7
#define FF_CMP_VSAD         8
#define FF_CMP_VSSE         9
#define FF_CMP_NSSE         10
#define FF_CMP_W53          11
#define FF_CMP_W97          12
#define FF_CMP_DCTMAX       13
#define FF_CMP_DCT264       14
#define FF_CMP_MEDIAN_SAD   15
#define FF_CMP_CHROMA       256

    /**
     * ME diamond size & shape
     * - encoding: Set by user.
     * - decoding: unused
     */
    int dia_size;

    /**
     * amount of previous MV predictors (2a+1 x 2a+1 square)
     * - encoding: Set by user.
     * - decoding: unused
     */
    int last_predictor_count;

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int pre_me;
#endif

    /**
     * motion estimation prepass comparison function
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_pre_cmp;

    /**
     * ME prepass diamond size & shape
     * - encoding: Set by user.
     * - decoding: unused
     */
    int pre_dia_size;

    /**
     * subpel ME quality
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_subpel_quality;

    /**
     * maximum motion estimation search range in subpel units
     * If 0 then no limit.
     *
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_range;

    /**
     * slice flags
     * - encoding: unused
     * - decoding: Set by user.
     */
    int slice_flags;
#define SLICE_FLAG_CODED_ORDER    0x0001 ///< draw_horiz_band() is called in coded order instead of display
#define SLICE_FLAG_ALLOW_FIELD    0x0002 ///< allow draw_horiz_band() with field slices (MPEG-2 field pics)
#define SLICE_FLAG_ALLOW_PLANE    0x0004 ///< allow draw_horiz_band() with 1 component at a time (SVQ1)

    /**
     * macroblock decision mode
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mb_decision;
#define FF_MB_DECISION_SIMPLE 0        ///< uses mb_cmp
#define FF_MB_DECISION_BITS   1        ///< chooses the one which needs the fewest bits
#define FF_MB_DECISION_RD     2        ///< rate distortion

    /**
     * custom intra quantization matrix
     * - encoding: Set by user, can be NULL.
     * - decoding: Set by libavcodec.
     */
    uint16_t *intra_matrix;

    /**
     * custom inter quantization matrix
     * - encoding: Set by user, can be NULL.
     * - decoding: Set by libavcodec.
     */
    uint16_t *inter_matrix;

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int scenechange_threshold;

    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int noise_reduction;
#endif

    /**
     * precision of the intra DC coefficient - 8
     * - encoding: Set by user.
     * - decoding: Set by libavcodec
     */
    int intra_dc_precision;

    /**
     * Number of macroblock rows at the top which are skipped.
     * - encoding: unused
     * - decoding: Set by user.
     */
    int skip_top;

    /**
     * Number of macroblock rows at the bottom which are skipped.
     * - encoding: unused
     * - decoding: Set by user.
     */
    int skip_bottom;

    /**
     * minimum MB Lagrange multiplier
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mb_lmin;

    /**
     * maximum MB Lagrange multiplier
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mb_lmax;

#if FF_API_PRIVATE_OPT
    /**
     * @deprecated use encoder private options instead
     */
    attribute_deprecated
    int me_penalty_compensation;
#endif

    /**
     * - encoding: Set by user.
     * - decoding: unused
     */
    int bidir_refine;

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int brd_scale;
#endif

    /**
     * minimum GOP size
     * - encoding: Set by user.
     * - decoding: unused
     */
    int keyint_min;

    /**
     * number of reference frames
     * - encoding: Set by user.
     * - decoding: Set by lavc.
     */
    int refs;

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int chromaoffset;
#endif

    /**
     * Note: Value depends upon the compare function used for fullpel ME.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mv0_threshold;

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int b_sensitivity;
#endif

    /**
     * Chromaticity coordinates of the source primaries.
     * - encoding: Set by user
     * - decoding: Set by libavcodec
     */
    enum AVColorPrimaries color_primaries;

    /**
     * Color Transfer Characteristic.
     * - encoding: Set by user
     * - decoding: Set by libavcodec
     */
    enum AVColorTransferCharacteristic color_trc;

    /**
     * YUV colorspace type.
     * - encoding: Set by user
     * - decoding: Set by libavcodec
     */
    enum AVColorSpace colorspace;

    /**
     * MPEG vs JPEG YUV range.
     * - encoding: Set by user
     * - decoding: Set by libavcodec
     */
    enum AVColorRange color_range;

    /**
     * This defines the location of chroma samples.
     * - encoding: Set by user
     * - decoding: Set by libavcodec
     */
    enum AVChromaLocation chroma_sample_location;

    /**
     * Number of slices.
     * Indicates number of picture subdivisions. Used for parallelized
     * decoding.
     * - encoding: Set by user
     * - decoding: unused
     */
    int slices;

    /** Field order
     * - encoding: set by libavcodec
     * - decoding: Set by user.
     */
    enum AVFieldOrder field_order;

    /* audio only */
    int sample_rate; ///< samples per second
    int channels;    ///< number of audio channels

    /**
     * audio sample format
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
    enum AVSampleFormat sample_fmt;  ///< sample format

    /* The following data should not be initialized. */
    /**
     * Number of samples per channel in an audio frame.
     *
     * - encoding: set by libavcodec in avcodec_open2(). Each submitted frame
     *   except the last must contain exactly frame_size samples per channel.
     *   May be 0 when the codec has AV_CODEC_CAP_VARIABLE_FRAME_SIZE set, then the
     *   frame size is not restricted.
     * - decoding: may be set by some decoders to indicate constant frame size
     */
    int frame_size;

    /**
     * Frame counter, set by libavcodec.
     *
     * - decoding: total number of frames returned from the decoder so far.
     * - encoding: total number of frames passed to the encoder so far.
     *
     *   @note the counter is not incremented if encoding/decoding resulted in
     *   an error.
     */
    int frame_number;

    /**
     * number of bytes per packet if constant and known or 0
     * Used by some WAV based audio codecs.
     */
    int block_align;

    /**
     * Audio cutoff bandwidth (0 means "automatic")
     * - encoding: Set by user.
     * - decoding: unused
     */
    int cutoff;

    /**
     * Audio channel layout.
     * - encoding: set by user.
     * - decoding: set by user, may be overwritten by libavcodec.
     */
    uint64_t channel_layout;

    /**
     * Request decoder to use this channel layout if it can (0 for default)
     * - encoding: unused
     * - decoding: Set by user.
     */
    uint64_t request_channel_layout;

    /**
     * Type of service that the audio stream conveys.
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
    enum AVAudioServiceType audio_service_type;

    /**
     * desired sample format
     * - encoding: Not used.
     * - decoding: Set by user.
     * Decoder will decode to this format if it can.
     */
    enum AVSampleFormat request_sample_fmt;

    /**
     * This callback is called at the beginning of each frame to get data
     * buffer(s) for it. There may be one contiguous buffer for all the data or
     * there may be a buffer per each data plane or anything in between. What
     * this means is, you may set however many entries in buf[] you feel necessary.
     * Each buffer must be reference-counted using the AVBuffer API (see description
     * of buf[] below).
     *
     * The following fields will be set in the frame before this callback is
     * called:
     * - format
     * - width, height (video only)
     * - sample_rate, channel_layout, nb_samples (audio only)
     * Their values may differ from the corresponding values in
     * AVCodecContext. This callback must use the frame values, not the codec
     * context values, to calculate the required buffer size.
     *
     * This callback must fill the following fields in the frame:
     * - data[]
     * - linesize[]
     * - extended_data:
     *   * if the data is planar audio with more than 8 channels, then this
     *     callback must allocate and fill extended_data to contain all pointers
     *     to all data planes. data[] must hold as many pointers as it can.
     *     extended_data must be allocated with av_malloc() and will be freed in
     *     av_frame_unref().
     *   * otherwise extended_data must point to data
     * - buf[] must contain one or more pointers to AVBufferRef structures. Each of
     *   the frame's data and extended_data pointers must be contained in these. That
     *   is, one AVBufferRef for each allocated chunk of memory, not necessarily one
     *   AVBufferRef per data[] entry. See: av_buffer_create(), av_buffer_alloc(),
     *   and av_buffer_ref().
     * - extended_buf and nb_extended_buf must be allocated with av_malloc() by
     *   this callback and filled with the extra buffers if there are more
     *   buffers than buf[] can hold. extended_buf will be freed in
     *   av_frame_unref().
     *
     * If AV_CODEC_CAP_DR1 is not set then get_buffer2() must call
     * avcodec_default_get_buffer2() instead of providing buffers allocated by
     * some other means.
     *
     * Each data plane must be aligned to the maximum required by the target
     * CPU.
     *
     * @see avcodec_default_get_buffer2()
     *
     * Video:
     *
     * If AV_GET_BUFFER_FLAG_REF is set in flags then the frame may be reused
     * (read and/or written to if it is writable) later by libavcodec.
     *
     * avcodec_align_dimensions2() should be used to find the required width and
     * height, as they normally need to be rounded up to the next multiple of 16.
     *
     * Some decoders do not support linesizes changing between frames.
     *
     * If frame multithreading is used and thread_safe_callbacks is set,
     * this callback may be called from a different thread, but not from more
     * than one at once. Does not need to be reentrant.
     *
     * @see avcodec_align_dimensions2()
     *
     * Audio:
     *
     * Decoders request a buffer of a particular size by setting
     * AVFrame.nb_samples prior to calling get_buffer2(). The decoder may,
     * however, utilize only part of the buffer by setting AVFrame.nb_samples
     * to a smaller value in the output frame.
     *
     * As a convenience, av_samples_get_buffer_size() and
     * av_samples_fill_arrays() in libavutil may be used by custom get_buffer2()
     * functions to find the required data size and to fill data pointers and
     * linesize. In AVFrame.linesize, only linesize[0] may be set for audio
     * since all planes must be the same size.
     *
     * @see av_samples_get_buffer_size(), av_samples_fill_arrays()
     *
     * - encoding: unused
     * - decoding: Set by libavcodec, user can override.
     */
    int (*get_buffer2)(struct AVCodecContext *s, AVFrame *frame, int flags);

    /**
     * If non-zero, the decoded audio and video frames returned from
     * avcodec_decode_video2() and avcodec_decode_audio4() are reference-counted
     * and are valid indefinitely. The caller must free them with
     * av_frame_unref() when they are not needed anymore.
     * Otherwise, the decoded frames must not be freed by the caller and are
     * only valid until the next decode call.
     *
     * This is always automatically enabled if avcodec_receive_frame() is used.
     *
     * - encoding: unused
     * - decoding: set by the caller before avcodec_open2().
     */
    attribute_deprecated
    int refcounted_frames;

    /* - encoding parameters */
    float qcompress;  ///< amount of qscale change between easy & hard scenes (0.0-1.0)
    float qblur;      ///< amount of qscale smoothing over time (0.0-1.0)

    /**
     * minimum quantizer
     * - encoding: Set by user.
     * - decoding: unused
     */
    int qmin;

    /**
     * maximum quantizer
     * - encoding: Set by user.
     * - decoding: unused
     */
    int qmax;

    /**
     * maximum quantizer difference between frames
     * - encoding: Set by user.
     * - decoding: unused
     */
    int max_qdiff;

    /**
     * decoder bitstream buffer size
     * - encoding: Set by user.
     * - decoding: unused
     */
    int rc_buffer_size;

    /**
     * ratecontrol override, see RcOverride
     * - encoding: Allocated/set/freed by user.
     * - decoding: unused
     */
    int rc_override_count;
    RcOverride *rc_override;

    /**
     * maximum bitrate
     * - encoding: Set by user.
     * - decoding: Set by user, may be overwritten by libavcodec.
     */
    int64_t rc_max_rate;

    /**
     * minimum bitrate
     * - encoding: Set by user.
     * - decoding: unused
     */
    int64_t rc_min_rate;

    /**
     * Ratecontrol attempt to use, at maximum, <value> of what can be used without an underflow.
     * - encoding: Set by user.
     * - decoding: unused.
     */
    float rc_max_available_vbv_use;

    /**
     * Ratecontrol attempt to use, at least, <value> times the amount needed to prevent a vbv overflow.
     * - encoding: Set by user.
     * - decoding: unused.
     */
    float rc_min_vbv_overflow_use;

    /**
     * Number of bits which should be loaded into the rc buffer before decoding starts.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int rc_initial_buffer_occupancy;

#if FF_API_CODER_TYPE
#define FF_CODER_TYPE_VLC       0
#define FF_CODER_TYPE_AC        1
#define FF_CODER_TYPE_RAW       2
#define FF_CODER_TYPE_RLE       3
    /**
     * @deprecated use encoder private options instead
     */
    attribute_deprecated
    int coder_type;
#endif /* FF_API_CODER_TYPE */

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int context_model;
#endif

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int frame_skip_threshold;

    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int frame_skip_factor;

    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int frame_skip_exp;

    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int frame_skip_cmp;
#endif /* FF_API_PRIVATE_OPT */

    /**
     * trellis RD quantization
     * - encoding: Set by user.
     * - decoding: unused
     */
    int trellis;

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int min_prediction_order;

    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int max_prediction_order;

    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int64_t timecode_frame_start;
#endif

#if FF_API_RTP_CALLBACK
    /**
     * @deprecated unused
     */
    /* The RTP callback: This function is called    */
    /* every time the encoder has a packet to send. */
    /* It depends on the encoder if the data starts */
    /* with a Start Code (it should). H.263 does.   */
    /* mb_nb contains the number of macroblocks     */
    /* encoded in the RTP payload.                  */
    attribute_deprecated
    void (*rtp_callback)(struct AVCodecContext *avctx, void *data, int size, int mb_nb);
#endif

#if FF_API_PRIVATE_OPT
    /** @deprecated use encoder private options instead */
    attribute_deprecated
    int rtp_payload_size;   /* The size of the RTP payload: the coder will  */
                            /* do its best to deliver a chunk with size     */
                            /* below rtp_payload_size, the chunk will start */
                            /* with a start code on some codecs like H.263. */
                            /* This doesn't take account of any particular  */
                            /* headers inside the transmitted RTP payload.  */
#endif

#if FF_API_STAT_BITS
    /* statistics, used for 2-pass encoding */
    attribute_deprecated
    int mv_bits;
    attribute_deprecated
    int header_bits;
    attribute_deprecated
    int i_tex_bits;
    attribute_deprecated
    int p_tex_bits;
    attribute_deprecated
    int i_count;
    attribute_deprecated
    int p_count;
    attribute_deprecated
    int skip_count;
    attribute_deprecated
    int misc_bits;

    /** @deprecated this field is unused */
    attribute_deprecated
    int frame_bits;
#endif

    /**
     * pass1 encoding statistics output buffer
     * - encoding: Set by libavcodec.
     * - decoding: unused
     */
    char *stats_out;

    /**
     * pass2 encoding statistics input buffer
     * Concatenated stuff from stats_out of pass1 should be placed here.
     * - encoding: Allocated/set/freed by user.
     * - decoding: unused
     */
    char *stats_in;

    /**
     * Work around bugs in encoders which sometimes cannot be detected automatically.
     * - encoding: Set by user
     * - decoding: Set by user
     */
    int workaround_bugs;
#define FF_BUG_AUTODETECT       1  ///< autodetection
#define FF_BUG_XVID_ILACE       4
#define FF_BUG_UMP4             8
#define FF_BUG_NO_PADDING       16
#define FF_BUG_AMV              32
#define FF_BUG_QPEL_CHROMA      64
#define FF_BUG_STD_QPEL         128
#define FF_BUG_QPEL_CHROMA2     256
#define FF_BUG_DIRECT_BLOCKSIZE 512
#define FF_BUG_EDGE             1024
#define FF_BUG_HPEL_CHROMA      2048
#define FF_BUG_DC_CLIP          4096
#define FF_BUG_MS               8192 ///< Work around various bugs in Microsoft's broken decoders.
#define FF_BUG_TRUNCATED       16384
#define FF_BUG_IEDGE           32768

    /**
     * strictly follow the standard (MPEG-4, ...).
     * - encoding: Set by user.
     * - decoding: Set by user.
     * Setting this to STRICT or higher means the encoder and decoder will
     * generally do stupid things, whereas setting it to unofficial or lower
     * will mean the encoder might produce output that is not supported by all
     * spec-compliant decoders. Decoders don't differentiate between normal,
     * unofficial and experimental (that is, they always try to decode things
     * when they can) unless they are explicitly asked to behave stupidly
     * (=strictly conform to the specs)
     */
    int strict_std_compliance;
#define FF_COMPLIANCE_VERY_STRICT   2 ///< Strictly conform to an older more strict version of the spec or reference software.
#define FF_COMPLIANCE_STRICT        1 ///< Strictly conform to all the things in the spec no matter what consequences.
#define FF_COMPLIANCE_NORMAL        0
#define FF_COMPLIANCE_UNOFFICIAL   -1 ///< Allow unofficial extensions
#define FF_COMPLIANCE_EXPERIMENTAL -2 ///< Allow nonstandardized experimental things.

    /**
     * error concealment flags
     * - encoding: unused
     * - decoding: Set by user.
     */
    int error_concealment;
#define FF_EC_GUESS_MVS   1
#define FF_EC_DEBLOCK     2
#define FF_EC_FAVOR_INTER 256

    /**
     * debug
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int debug;
#define FF_DEBUG_PICT_INFO   1
#define FF_DEBUG_RC          2
#define FF_DEBUG_BITSTREAM   4
#define FF_DEBUG_MB_TYPE     8
#define FF_DEBUG_QP          16
#if FF_API_DEBUG_MV
/**
 * @deprecated this option does nothing
 */
#define FF_DEBUG_MV          32
#endif
#define FF_DEBUG_DCT_COEFF   0x00000040
#define FF_DEBUG_SKIP        0x00000080
#define FF_DEBUG_STARTCODE   0x00000100
#define FF_DEBUG_ER          0x00000400
#define FF_DEBUG_MMCO        0x00000800
#define FF_DEBUG_BUGS        0x00001000
#if FF_API_DEBUG_MV
#define FF_DEBUG_VIS_QP      0x00002000
#define FF_DEBUG_VIS_MB_TYPE 0x00004000
#endif
#define FF_DEBUG_BUFFERS     0x00008000
#define FF_DEBUG_THREADS     0x00010000
#define FF_DEBUG_GREEN_MD    0x00800000
#define FF_DEBUG_NOMC        0x01000000

#if FF_API_DEBUG_MV
    /**
     * debug
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int debug_mv;
#define FF_DEBUG_VIS_MV_P_FOR  0x00000001 // visualize forward predicted MVs of P-frames
#define FF_DEBUG_VIS_MV_B_FOR  0x00000002 // visualize forward predicted MVs of B-frames
#define FF_DEBUG_VIS_MV_B_BACK 0x00000004 // visualize backward predicted MVs of B-frames
#endif

    /**
     * Error recognition; may misdetect some more or less valid parts as errors.
     * - encoding: unused
     * - decoding: Set by user.
     */
    int err_recognition;

/**
 * Verify checksums embedded in the bitstream (could be of either encoded or
 * decoded data, depending on the codec) and print an error message on mismatch.
 * If AV_EF_EXPLODE is also set, a mismatching checksum will result in the
 * decoder returning an error.
 */
#define AV_EF_CRCCHECK  (1<<0)
#define AV_EF_BITSTREAM (1<<1)          ///< detect bitstream specification deviations
#define AV_EF_BUFFER    (1<<2)          ///< detect improper bitstream length
#define AV_EF_EXPLODE   (1<<3)          ///< abort decoding on minor error detection

#define AV_EF_IGNORE_ERR (1<<15)        ///< ignore errors and continue
#define AV_EF_CAREFUL    (1<<16)        ///< consider things that violate the spec, are fast to calculate and have not been seen in the wild as errors
#define AV_EF_COMPLIANT  (1<<17)        ///< consider all spec non compliances as errors
#define AV_EF_AGGRESSIVE (1<<18)        ///< consider things that a sane encoder should not do as an error


    /**
     * opaque 64-bit number (generally a PTS) that will be reordered and
     * output in AVFrame.reordered_opaque
     * - encoding: unused
     * - decoding: Set by user.
     */
    int64_t reordered_opaque;

    /**
     * Hardware accelerator in use
     * - encoding: unused.
     * - decoding: Set by libavcodec
     */
    const struct AVHWAccel *hwaccel;

    /**
     * Hardware accelerator context.
     * For some hardware accelerators, a global context needs to be
     * provided by the user. In that case, this holds display-dependent
     * data FFmpeg cannot instantiate itself. Please refer to the
     * FFmpeg HW accelerator documentation to know how to fill this
     * is. e.g. for VA API, this is a struct vaapi_context.
     * - encoding: unused
     * - decoding: Set by user
     */
    void *hwaccel_context;

    /**
     * error
     * - encoding: Set by libavcodec if flags & AV_CODEC_FLAG_PSNR.
     * - decoding: unused
     */
    uint64_t error[AV_NUM_DATA_POINTERS];

    /**
     * DCT algorithm, see FF_DCT_* below
     * - encoding: Set by user.
     * - decoding: unused
     */
    int dct_algo;
#define FF_DCT_AUTO    0
#define FF_DCT_FASTINT 1
#define FF_DCT_INT     2
#define FF_DCT_MMX     3
#define FF_DCT_ALTIVEC 5
#define FF_DCT_FAAN    6

    /**
     * IDCT algorithm, see FF_IDCT_* below.
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int idct_algo;
#define FF_IDCT_AUTO          0
#define FF_IDCT_INT           1
#define FF_IDCT_SIMPLE        2
#define FF_IDCT_SIMPLEMMX     3
#define FF_IDCT_ARM           7
#define FF_IDCT_ALTIVEC       8
#define FF_IDCT_SIMPLEARM     10
#define FF_IDCT_XVID          14
#define FF_IDCT_SIMPLEARMV5TE 16
#define FF_IDCT_SIMPLEARMV6   17
#define FF_IDCT_FAAN          20
#define FF_IDCT_SIMPLENEON    22
#define FF_IDCT_NONE          24 /* Used by XvMC to extract IDCT coefficients with FF_IDCT_PERM_NONE */
#define FF_IDCT_SIMPLEAUTO    128

    /**
     * bits per sample/pixel from the demuxer (needed for huffyuv).
     * - encoding: Set by libavcodec.
     * - decoding: Set by user.
     */
     int bits_per_coded_sample;

    /**
     * Bits per sample/pixel of internal libavcodec pixel/sample format.
     * - encoding: set by user.
     * - decoding: set by libavcodec.
     */
    int bits_per_raw_sample;

#if FF_API_LOWRES
    /**
     * low resolution decoding, 1-> 1/2 size, 2->1/4 size
     * - encoding: unused
     * - decoding: Set by user.
     */
     int lowres;
#endif

#if FF_API_CODED_FRAME
    /**
     * the picture in the bitstream
     * - encoding: Set by libavcodec.
     * - decoding: unused
     *
     * @deprecated use the quality factor packet side data instead
     */
    attribute_deprecated AVFrame *coded_frame;
#endif

    /**
     * thread count
     * is used to decide how many independent tasks should be passed to execute()
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int thread_count;

    /**
     * Which multithreading methods to use.
     * Use of FF_THREAD_FRAME will increase decoding delay by one frame per thread,
     * so clients which cannot provide future frames should not use it.
     *
     * - encoding: Set by user, otherwise the default is used.
     * - decoding: Set by user, otherwise the default is used.
     */
    int thread_type;
#define FF_THREAD_FRAME   1 ///< Decode more than one frame at once
#define FF_THREAD_SLICE   2 ///< Decode more than one part of a single frame at once

    /**
     * Which multithreading methods are in use by the codec.
     * - encoding: Set by libavcodec.
     * - decoding: Set by libavcodec.
     */
    int active_thread_type;

    /**
     * Set by the client if its custom get_buffer() callback can be called
     * synchronously from another thread, which allows faster multithreaded decoding.
     * draw_horiz_band() will be called from other threads regardless of this setting.
     * Ignored if the default get_buffer() is used.
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int thread_safe_callbacks;

    /**
     * The codec may call this to execute several independent things.
     * It will return only after finishing all tasks.
     * The user may replace this with some multithreaded implementation,
     * the default implementation will execute the parts serially.
     * @param count the number of things to execute
     * - encoding: Set by libavcodec, user can override.
     * - decoding: Set by libavcodec, user can override.
     */
    int (*execute)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg), void *arg2, int *ret, int count, int size);

    /**
     * The codec may call this to execute several independent things.
     * It will return only after finishing all tasks.
     * The user may replace this with some multithreaded implementation,
     * the default implementation will execute the parts serially.
     * Also see avcodec_thread_init and e.g. the --enable-pthread configure option.
     * @param c context passed also to func
     * @param count the number of things to execute
     * @param arg2 argument passed unchanged to func
     * @param ret return values of executed functions, must have space for "count" values. May be NULL.
     * @param func function that will be called count times, with jobnr from 0 to count-1.
     *             threadnr will be in the range 0 to c->thread_count-1 < MAX_THREADS and so that no
     *             two instances of func executing at the same time will have the same threadnr.
     * @return always 0 currently, but code should handle a future improvement where when any call to func
     *         returns < 0 no further calls to func may be done and < 0 is returned.
     * - encoding: Set by libavcodec, user can override.
     * - decoding: Set by libavcodec, user can override.
     */
    int (*execute2)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg, int jobnr, int threadnr), void *arg2, int *ret, int count);

    /**
     * noise vs. sse weight for the nsse comparison function
     * - encoding: Set by user.
     * - decoding: unused
     */
     int nsse_weight;

    /**
     * profile
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
     int profile;
#define FF_PROFILE_UNKNOWN -99
#define FF_PROFILE_RESERVED -100

#define FF_PROFILE_AAC_MAIN 0
#define FF_PROFILE_AAC_LOW  1
#define FF_PROFILE_AAC_SSR  2
#define FF_PROFILE_AAC_LTP  3
#define FF_PROFILE_AAC_HE   4
#define FF_PROFILE_AAC_HE_V2 28
#define FF_PROFILE_AAC_LD   22
#define FF_PROFILE_AAC_ELD  38
#define FF_PROFILE_MPEG2_AAC_LOW 128
#define FF_PROFILE_MPEG2_AAC_HE  131

#define FF_PROFILE_DNXHD         0
#define FF_PROFILE_DNXHR_LB      1
#define FF_PROFILE_DNXHR_SQ      2
#define FF_PROFILE_DNXHR_HQ      3
#define FF_PROFILE_DNXHR_HQX     4
#define FF_PROFILE_DNXHR_444     5

#define FF_PROFILE_DTS         20
#define FF_PROFILE_DTS_ES      30
#define FF_PROFILE_DTS_96_24   40
#define FF_PROFILE_DTS_HD_HRA  50
#define FF_PROFILE_DTS_HD_MA   60
#define FF_PROFILE_DTS_EXPRESS 70

#define FF_PROFILE_MPEG2_422    0
#define FF_PROFILE_MPEG2_HIGH   1
#define FF_PROFILE_MPEG2_SS     2
#define FF_PROFILE_MPEG2_SNR_SCALABLE  3
#define FF_PROFILE_MPEG2_MAIN   4
#define FF_PROFILE_MPEG2_SIMPLE 5

#define FF_PROFILE_H264_CONSTRAINED  (1<<9)  // 8+1; constraint_set1_flag
#define FF_PROFILE_H264_INTRA        (1<<11) // 8+3; constraint_set3_flag

#define FF_PROFILE_H264_BASELINE             66
#define FF_PROFILE_H264_CONSTRAINED_BASELINE (66|FF_PROFILE_H264_CONSTRAINED)
#define FF_PROFILE_H264_MAIN                 77
#define FF_PROFILE_H264_EXTENDED             88
#define FF_PROFILE_H264_HIGH                 100
#define FF_PROFILE_H264_HIGH_10              110
#define FF_PROFILE_H264_HIGH_10_INTRA        (110|FF_PROFILE_H264_INTRA)
#define FF_PROFILE_H264_MULTIVIEW_HIGH       118
#define FF_PROFILE_H264_HIGH_422             122
#define FF_PROFILE_H264_HIGH_422_INTRA       (122|FF_PROFILE_H264_INTRA)
#define FF_PROFILE_H264_STEREO_HIGH          128
#define FF_PROFILE_H264_HIGH_444             144
#define FF_PROFILE_H264_HIGH_444_PREDICTIVE  244
#define FF_PROFILE_H264_HIGH_444_INTRA       (244|FF_PROFILE_H264_INTRA)
#define FF_PROFILE_H264_CAVLC_444            44

#define FF_PROFILE_VC1_SIMPLE   0
#define FF_PROFILE_VC1_MAIN     1
#define FF_PROFILE_VC1_COMPLEX  2
#define FF_PROFILE_VC1_ADVANCED 3

#define FF_PROFILE_MPEG4_SIMPLE                     0
#define FF_PROFILE_MPEG4_SIMPLE_SCALABLE            1
#define FF_PROFILE_MPEG4_CORE                       2
#define FF_PROFILE_MPEG4_MAIN                       3
#define FF_PROFILE_MPEG4_N_BIT                      4
#define FF_PROFILE_MPEG4_SCALABLE_TEXTURE           5
#define FF_PROFILE_MPEG4_SIMPLE_FACE_ANIMATION      6
#define FF_PROFILE_MPEG4_BASIC_ANIMATED_TEXTURE     7
#define FF_PROFILE_MPEG4_HYBRID                     8
#define FF_PROFILE_MPEG4_ADVANCED_REAL_TIME         9
#define FF_PROFILE_MPEG4_CORE_SCALABLE             10
#define FF_PROFILE_MPEG4_ADVANCED_CODING           11
#define FF_PROFILE_MPEG4_ADVANCED_CORE             12
#define FF_PROFILE_MPEG4_ADVANCED_SCALABLE_TEXTURE 13
#define FF_PROFILE_MPEG4_SIMPLE_STUDIO             14
#define FF_PROFILE_MPEG4_ADVANCED_SIMPLE           15

#define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_0   1
#define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_1   2
#define FF_PROFILE_JPEG2000_CSTREAM_NO_RESTRICTION  32768
#define FF_PROFILE_JPEG2000_DCINEMA_2K              3
#define FF_PROFILE_JPEG2000_DCINEMA_4K              4

#define FF_PROFILE_VP9_0                            0
#define FF_PROFILE_VP9_1                            1
#define FF_PROFILE_VP9_2                            2
#define FF_PROFILE_VP9_3                            3

#define FF_PROFILE_HEVC_MAIN                        1
#define FF_PROFILE_HEVC_MAIN_10                     2
#define FF_PROFILE_HEVC_MAIN_STILL_PICTURE          3
#define FF_PROFILE_HEVC_REXT                        4

#define FF_PROFILE_AV1_MAIN                         0
#define FF_PROFILE_AV1_HIGH                         1
#define FF_PROFILE_AV1_PROFESSIONAL                 2

#define FF_PROFILE_MJPEG_HUFFMAN_BASELINE_DCT            0xc0
#define FF_PROFILE_MJPEG_HUFFMAN_EXTENDED_SEQUENTIAL_DCT 0xc1
#define FF_PROFILE_MJPEG_HUFFMAN_PROGRESSIVE_DCT         0xc2
#define FF_PROFILE_MJPEG_HUFFMAN_LOSSLESS                0xc3
#define FF_PROFILE_MJPEG_JPEG_LS                         0xf7

#define FF_PROFILE_SBC_MSBC                         1

    /**
     * level
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
     int level;
#define FF_LEVEL_UNKNOWN -99

    /**
     * Skip loop filtering for selected frames.
     * - encoding: unused
     * - decoding: Set by user.
     */
    enum AVDiscard skip_loop_filter;

    /**
     * Skip IDCT/dequantization for selected frames.
     * - encoding: unused
     * - decoding: Set by user.
     */
    enum AVDiscard skip_idct;

    /**
     * Skip decoding for selected frames.
     * - encoding: unused
     * - decoding: Set by user.
     */
    enum AVDiscard skip_frame;

    /**
     * Header containing style information for text subtitles.
     * For SUBTITLE_ASS subtitle type, it should contain the whole ASS
     * [Script Info] and [V4+ Styles] section, plus the [Events] line and
     * the Format line following. It shouldn't include any Dialogue line.
     * - encoding: Set/allocated/freed by user (before avcodec_open2())
     * - decoding: Set/allocated/freed by libavcodec (by avcodec_open2())
     */
    uint8_t *subtitle_header;
    int subtitle_header_size;

#if FF_API_VBV_DELAY
    /**
     * VBV delay coded in the last frame (in periods of a 27 MHz clock).
     * Used for compliant TS muxing.
     * - encoding: Set by libavcodec.
     * - decoding: unused.
     * @deprecated this value is now exported as a part of
     * AV_PKT_DATA_CPB_PROPERTIES packet side data
     */
    attribute_deprecated
    uint64_t vbv_delay;
#endif

#if FF_API_SIDEDATA_ONLY_PKT
    /**
     * Encoding only and set by default. Allow encoders to output packets
     * that do not contain any encoded data, only side data.
     *
     * Some encoders need to output such packets, e.g. to update some stream
     * parameters at the end of encoding.
     *
     * @deprecated this field disables the default behaviour and
     *             it is kept only for compatibility.
     */
    attribute_deprecated
    int side_data_only_packets;
#endif

    /**
     * Audio only. The number of "priming" samples (padding) inserted by the
     * encoder at the beginning of the audio. I.e. this number of leading
     * decoded samples must be discarded by the caller to get the original audio
     * without leading padding.
     *
     * - decoding: unused
     * - encoding: Set by libavcodec. The timestamps on the output packets are
     *             adjusted by the encoder so that they always refer to the
     *             first sample of the data actually contained in the packet,
     *             including any added padding.  E.g. if the timebase is
     *             1/samplerate and the timestamp of the first input sample is
     *             0, the timestamp of the first output packet will be
     *             -initial_padding.
     */
    int initial_padding;

    /**
     * - decoding: For codecs that store a framerate value in the compressed
     *             bitstream, the decoder may export it here. { 0, 1} when
     *             unknown.
     * - encoding: May be used to signal the framerate of CFR content to an
     *             encoder.
     */
    AVRational framerate;

    /**
     * Nominal unaccelerated pixel format, see AV_PIX_FMT_xxx.
     * - encoding: unused.
     * - decoding: Set by libavcodec before calling get_format()
     */
    enum AVPixelFormat sw_pix_fmt;

    /**
     * Timebase in which pkt_dts/pts and AVPacket.dts/pts are.
     * - encoding unused.
     * - decoding set by user.
     */
    AVRational pkt_timebase;

    /**
     * AVCodecDescriptor
     * - encoding: unused.
     * - decoding: set by libavcodec.
     */
    const AVCodecDescriptor *codec_descriptor;

#if !FF_API_LOWRES
    /**
     * low resolution decoding, 1-> 1/2 size, 2->1/4 size
     * - encoding: unused
     * - decoding: Set by user.
     */
     int lowres;
#endif

    /**
     * Current statistics for PTS correction.
     * - decoding: maintained and used by libavcodec, not intended to be used by user apps
     * - encoding: unused
     */
    int64_t pts_correction_num_faulty_pts; /// Number of incorrect PTS values so far
    int64_t pts_correction_num_faulty_dts; /// Number of incorrect DTS values so far
    int64_t pts_correction_last_pts;       /// PTS of the last frame
    int64_t pts_correction_last_dts;       /// DTS of the last frame

    /**
     * Character encoding of the input subtitles file.
     * - decoding: set by user
     * - encoding: unused
     */
    char *sub_charenc;

    /**
     * Subtitles character encoding mode. Formats or codecs might be adjusting
     * this setting (if they are doing the conversion themselves for instance).
     * - decoding: set by libavcodec
     * - encoding: unused
     */
    int sub_charenc_mode;
#define FF_SUB_CHARENC_MODE_DO_NOTHING  -1  ///< do nothing (demuxer outputs a stream supposed to be already in UTF-8, or the codec is bitmap for instance)
#define FF_SUB_CHARENC_MODE_AUTOMATIC    0  ///< libavcodec will select the mode itself
#define FF_SUB_CHARENC_MODE_PRE_DECODER  1  ///< the AVPacket data needs to be recoded to UTF-8 before being fed to the decoder, requires iconv
#define FF_SUB_CHARENC_MODE_IGNORE       2  ///< neither convert the subtitles, nor check them for valid UTF-8

    /**
     * Skip processing alpha if supported by codec.
     * Note that if the format uses pre-multiplied alpha (common with VP6,
     * and recommended due to better video quality/compression)
     * the image will look as if alpha-blended onto a black background.
     * However for formats that do not use pre-multiplied alpha
     * there might be serious artefacts (though e.g. libswscale currently
     * assumes pre-multiplied alpha anyway).
     *
     * - decoding: set by user
     * - encoding: unused
     */
    int skip_alpha;

    /**
     * Number of samples to skip after a discontinuity
     * - decoding: unused
     * - encoding: set by libavcodec
     */
    int seek_preroll;

#if !FF_API_DEBUG_MV
    /**
     * debug motion vectors
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int debug_mv;
#define FF_DEBUG_VIS_MV_P_FOR  0x00000001 //visualize forward predicted MVs of P frames
#define FF_DEBUG_VIS_MV_B_FOR  0x00000002 //visualize forward predicted MVs of B frames
#define FF_DEBUG_VIS_MV_B_BACK 0x00000004 //visualize backward predicted MVs of B frames
#endif

    /**
     * custom intra quantization matrix
     * - encoding: Set by user, can be NULL.
     * - decoding: unused.
     */
    uint16_t *chroma_intra_matrix;

    /**
     * dump format separator.
     * can be ", " or "\n      " or anything else
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    uint8_t *dump_separator;

    /**
     * ',' separated list of allowed decoders.
     * If NULL then all are allowed
     * - encoding: unused
     * - decoding: set by user
     */
    char *codec_whitelist;

    /**
     * Properties of the stream that gets decoded
     * - encoding: unused
     * - decoding: set by libavcodec
     */
    unsigned properties;
#define FF_CODEC_PROPERTY_LOSSLESS        0x00000001
#define FF_CODEC_PROPERTY_CLOSED_CAPTIONS 0x00000002

    /**
     * Additional data associated with the entire coded stream.
     *
     * - decoding: unused
     * - encoding: may be set by libavcodec after avcodec_open2().
     */
    AVPacketSideData *coded_side_data;
    int            nb_coded_side_data;

    /**
     * A reference to the AVHWFramesContext describing the input (for encoding)
     * or output (decoding) frames. The reference is set by the caller and
     * afterwards owned (and freed) by libavcodec - it should never be read by
     * the caller after being set.
     *
     * - decoding: This field should be set by the caller from the get_format()
     *             callback. The previous reference (if any) will always be
     *             unreffed by libavcodec before the get_format() call.
     *
     *             If the default get_buffer2() is used with a hwaccel pixel
     *             format, then this AVHWFramesContext will be used for
     *             allocating the frame buffers.
     *
     * - encoding: For hardware encoders configured to use a hwaccel pixel
     *             format, this field should be set by the caller to a reference
     *             to the AVHWFramesContext describing input frames.
     *             AVHWFramesContext.format must be equal to
     *             AVCodecContext.pix_fmt.
     *
     *             This field should be set before avcodec_open2() is called.
     */
    AVBufferRef *hw_frames_ctx;

    /**
     * Control the form of AVSubtitle.rects[N]->ass
     * - decoding: set by user
     * - encoding: unused
     */
    int sub_text_format;
#define FF_SUB_TEXT_FMT_ASS              0
#if FF_API_ASS_TIMING
#define FF_SUB_TEXT_FMT_ASS_WITH_TIMINGS 1
#endif

    /**
     * Audio only. The amount of padding (in samples) appended by the encoder to
     * the end of the audio. I.e. this number of decoded samples must be
     * discarded by the caller from the end of the stream to get the original
     * audio without any trailing padding.
     *
     * - decoding: unused
     * - encoding: unused
     */
    int trailing_padding;

    /**
     * The number of pixels per image to maximally accept.
     *
     * - decoding: set by user
     * - encoding: set by user
     */
    int64_t max_pixels;

    /**
     * A reference to the AVHWDeviceContext describing the device which will
     * be used by a hardware encoder/decoder.  The reference is set by the
     * caller and afterwards owned (and freed) by libavcodec.
     *
     * This should be used if either the codec device does not require
     * hardware frames or any that are used are to be allocated internally by
     * libavcodec.  If the user wishes to supply any of the frames used as
     * encoder input or decoder output then hw_frames_ctx should be used
     * instead.  When hw_frames_ctx is set in get_format() for a decoder, this
     * field will be ignored while decoding the associated stream segment, but
     * may again be used on a following one after another get_format() call.
     *
     * For both encoders and decoders this field should be set before
     * avcodec_open2() is called and must not be written to thereafter.
     *
     * Note that some decoders may require this field to be set initially in
     * order to support hw_frames_ctx at all - in that case, all frames
     * contexts used must be created on the same device.
     */
    AVBufferRef *hw_device_ctx;

    /**
     * Bit set of AV_HWACCEL_FLAG_* flags, which affect hardware accelerated
     * decoding (if active).
     * - encoding: unused
     * - decoding: Set by user (either before avcodec_open2(), or in the
     *             AVCodecContext.get_format callback)
     */
    int hwaccel_flags;

    /**
     * Video decoding only. Certain video codecs support cropping, meaning that
     * only a sub-rectangle of the decoded frame is intended for display.  This
     * option controls how cropping is handled by libavcodec.
     *
     * When set to 1 (the default), libavcodec will apply cropping internally.
     * I.e. it will modify the output frame width/height fields and offset the
     * data pointers (only by as much as possible while preserving alignment, or
     * by the full amount if the AV_CODEC_FLAG_UNALIGNED flag is set) so that
     * the frames output by the decoder refer only to the cropped area. The
     * crop_* fields of the output frames will be zero.
     *
     * When set to 0, the width/height fields of the output frames will be set
     * to the coded dimensions and the crop_* fields will describe the cropping
     * rectangle. Applying the cropping is left to the caller.
     *
     * @warning When hardware acceleration with opaque output frames is used,
     * libavcodec is unable to apply cropping from the top/left border.
     *
     * @note when this option is set to zero, the width/height fields of the
     * AVCodecContext and output AVFrames have different meanings. The codec
     * context fields store display dimensions (with the coded dimensions in
     * coded_width/height), while the frame fields store the coded dimensions
     * (with the display dimensions being determined by the crop_* fields).
     */
    int apply_cropping;

    /*
     * Video decoding only.  Sets the number of extra hardware frames which
     * the decoder will allocate for use by the caller.  This must be set
     * before avcodec_open2() is called.
     *
     * Some hardware decoders require all frames that they will use for
     * output to be defined in advance before decoding starts.  For such
     * decoders, the hardware frame pool must therefore be of a fixed size.
     * The extra frames set here are on top of any number that the decoder
     * needs internally in order to operate normally (for example, frames
     * used as reference pictures).
     */
    int extra_hw_frames;
} AVCodecContext;

#if FF_API_CODEC_GET_SET
/**
 * Accessors for some AVCodecContext fields. These used to be provided for ABI
 * compatibility, and do not need to be used anymore.
 */
attribute_deprecated
AVRational av_codec_get_pkt_timebase         (const AVCodecContext *avctx);
attribute_deprecated
void       av_codec_set_pkt_timebase         (AVCodecContext *avctx, AVRational val);

attribute_deprecated
const AVCodecDescriptor *av_codec_get_codec_descriptor(const AVCodecContext *avctx);
attribute_deprecated
void                     av_codec_set_codec_descriptor(AVCodecContext *avctx, const AVCodecDescriptor *desc);

attribute_deprecated
unsigned av_codec_get_codec_properties(const AVCodecContext *avctx);

#if FF_API_LOWRES
attribute_deprecated
int  av_codec_get_lowres(const AVCodecContext *avctx);
attribute_deprecated
void av_codec_set_lowres(AVCodecContext *avctx, int val);
#endif

attribute_deprecated
int  av_codec_get_seek_preroll(const AVCodecContext *avctx);
attribute_deprecated
void av_codec_set_seek_preroll(AVCodecContext *avctx, int val);

attribute_deprecated
uint16_t *av_codec_get_chroma_intra_matrix(const AVCodecContext *avctx);
attribute_deprecated
void av_codec_set_chroma_intra_matrix(AVCodecContext *avctx, uint16_t *val);
#endif

/**
 * AVProfile.
 */
typedef struct AVProfile {
    int profile;
    const char *name; ///< short name for the profile
} AVProfile;

enum {
    /**
     * The codec supports this format via the hw_device_ctx interface.
     *
     * When selecting this format, AVCodecContext.hw_device_ctx should
     * have been set to a device of the specified type before calling
     * avcodec_open2().
     */
    AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX = 0x01,
    /**
     * The codec supports this format via the hw_frames_ctx interface.
     *
     * When selecting this format for a decoder,
     * AVCodecContext.hw_frames_ctx should be set to a suitable frames
     * context inside the get_format() callback.  The frames context
     * must have been created on a device of the specified type.
     */
    AV_CODEC_HW_CONFIG_METHOD_HW_FRAMES_CTX = 0x02,
    /**
     * The codec supports this format by some internal method.
     *
     * This format can be selected without any additional configuration -
     * no device or frames context is required.
     */
    AV_CODEC_HW_CONFIG_METHOD_INTERNAL      = 0x04,
    /**
     * The codec supports this format by some ad-hoc method.
     *
     * Additional settings and/or function calls are required.  See the
     * codec-specific documentation for details.  (Methods requiring
     * this sort of configuration are deprecated and others should be
     * used in preference.)
     */
    AV_CODEC_HW_CONFIG_METHOD_AD_HOC        = 0x08,
};

typedef struct AVCodecHWConfig {
    /**
     * A hardware pixel format which the codec can use.
     */
    enum AVPixelFormat pix_fmt;
    /**
     * Bit set of AV_CODEC_HW_CONFIG_METHOD_* flags, describing the possible
     * setup methods which can be used with this configuration.
     */
    int methods;
    /**
     * The device type associated with the configuration.
     *
     * Must be set for AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX and
     * AV_CODEC_HW_CONFIG_METHOD_HW_FRAMES_CTX, otherwise unused.
     */
    enum AVHWDeviceType device_type;
} AVCodecHWConfig;

typedef struct AVCodecDefault AVCodecDefault;

struct AVSubtitle;

/**
 * AVCodec.
 */
typedef struct AVCodec {
    /**
     * Name of the codec implementation.
     * The name is globally unique among encoders and among decoders (but an
     * encoder and a decoder can share the same name).
     * This is the primary way to find a codec from the user perspective.
     */
    const char *name;
    /**
     * Descriptive name for the codec, meant to be more human readable than name.
     * You should use the NULL_IF_CONFIG_SMALL() macro to define it.
     */
    const char *long_name;
    enum AVMediaType type;
    enum AVCodecID id;
    /**
     * Codec capabilities.
     * see AV_CODEC_CAP_*
     */
    int capabilities;
    const AVRational *supported_framerates; ///< array of supported framerates, or NULL if any, array is terminated by {0,0}
    const enum AVPixelFormat *pix_fmts;     ///< array of supported pixel formats, or NULL if unknown, array is terminated by -1
    const int *supported_samplerates;       ///< array of supported audio samplerates, or NULL if unknown, array is terminated by 0
    const enum AVSampleFormat *sample_fmts; ///< array of supported sample formats, or NULL if unknown, array is terminated by -1
    const uint64_t *channel_layouts;         ///< array of support channel layouts, or NULL if unknown. array is terminated by 0
    uint8_t max_lowres;                     ///< maximum value for lowres supported by the decoder
    const AVClass *priv_class;              ///< AVClass for the private context
    const AVProfile *profiles;              ///< array of recognized profiles, or NULL if unknown, array is terminated by {FF_PROFILE_UNKNOWN}

    /**
     * Group name of the codec implementation.
     * This is a short symbolic name of the wrapper backing this codec. A
     * wrapper uses some kind of external implementation for the codec, such
     * as an external library, or a codec implementation provided by the OS or
     * the hardware.
     * If this field is NULL, this is a builtin, libavcodec native codec.
     * If non-NULL, this will be the suffix in AVCodec.name in most cases
     * (usually AVCodec.name will be of the form "<codec_name>_<wrapper_name>").
     */
    const char *wrapper_name;

    /*****************************************************************
     * No fields below this line are part of the public API. They
     * may not be used outside of libavcodec and can be changed and
     * removed at will.
     * New public fields should be added right above.
     *****************************************************************
     */
    int priv_data_size;
    struct AVCodec *next;
    /**
     * @name Frame-level threading support functions
     * @{
     */
    /**
     * If defined, called on thread contexts when they are created.
     * If the codec allocates writable tables in init(), re-allocate them here.
     * priv_data will be set to a copy of the original.
     */
    int (*init_thread_copy)(AVCodecContext *);
    /**
     * Copy necessary context variables from a previous thread context to the current one.
     * If not defined, the next thread will start automatically; otherwise, the codec
     * must call ff_thread_finish_setup().
     *
     * dst and src will (rarely) point to the same context, in which case memcpy should be skipped.
     */
    int (*update_thread_context)(AVCodecContext *dst, const AVCodecContext *src);
    /** @} */

    /**
     * Private codec-specific defaults.
     */
    const AVCodecDefault *defaults;

    /**
     * Initialize codec static data, called from avcodec_register().
     *
     * This is not intended for time consuming operations as it is
     * run for every codec regardless of that codec being used.
     */
    void (*init_static_data)(struct AVCodec *codec);

    int (*init)(AVCodecContext *);
    int (*encode_sub)(AVCodecContext *, uint8_t *buf, int buf_size,
                      const struct AVSubtitle *sub);
    /**
     * Encode data to an AVPacket.
     *
     * @param      avctx          codec context
     * @param      avpkt          output AVPacket (may contain a user-provided buffer)
     * @param[in]  frame          AVFrame containing the raw data to be encoded
     * @param[out] got_packet_ptr encoder sets to 0 or 1 to indicate that a
     *                            non-empty packet was returned in avpkt.
     * @return 0 on success, negative error code on failure
     */
    int (*encode2)(AVCodecContext *avctx, AVPacket *avpkt, const AVFrame *frame,
                   int *got_packet_ptr);
    int (*decode)(AVCodecContext *, void *outdata, int *outdata_size, AVPacket *avpkt);
    int (*close)(AVCodecContext *);
    /**
     * Encode API with decoupled packet/frame dataflow. The API is the
     * same as the avcodec_ prefixed APIs (avcodec_send_frame() etc.), except
     * that:
     * - never called if the codec is closed or the wrong type,
     * - if AV_CODEC_CAP_DELAY is not set, drain frames are never sent,
     * - only one drain frame is ever passed down,
     */
    int (*send_frame)(AVCodecContext *avctx, const AVFrame *frame);
    int (*receive_packet)(AVCodecContext *avctx, AVPacket *avpkt);

    /**
     * Decode API with decoupled packet/frame dataflow. This function is called
     * to get one output frame. It should call ff_decode_get_packet() to obtain
     * input data.
     */
    int (*receive_frame)(AVCodecContext *avctx, AVFrame *frame);
    /**
     * Flush buffers.
     * Will be called when seeking
     */
    void (*flush)(AVCodecContext *);
    /**
     * Internal codec capabilities.
     * See FF_CODEC_CAP_* in internal.h
     */
    int caps_internal;

    /**
     * Decoding only, a comma-separated list of bitstream filters to apply to
     * packets before decoding.
     */
    const char *bsfs;

    /**
     * Array of pointers to hardware configurations supported by the codec,
     * or NULL if no hardware supported.  The array is terminated by a NULL
     * pointer.
     *
     * The user can only access this field via avcodec_get_hw_config().
     */
    const struct AVCodecHWConfigInternal **hw_configs;
} AVCodec;

#if FF_API_CODEC_GET_SET
attribute_deprecated
int av_codec_get_max_lowres(const AVCodec *codec);
#endif

struct MpegEncContext;

/**
 * Retrieve supported hardware configurations for a codec.
 *
 * Values of index from zero to some maximum return the indexed configuration
 * descriptor; all other values return NULL.  If the codec does not support
 * any hardware configurations then it will always return NULL.
 */
const AVCodecHWConfig *avcodec_get_hw_config(const AVCodec *codec, int index);

/**
 * @defgroup lavc_hwaccel AVHWAccel
 *
 * @note  Nothing in this structure should be accessed by the user.  At some
 *        point in future it will not be externally visible at all.
 *
 * @{
 */
typedef struct AVHWAccel {
    /**
     * Name of the hardware accelerated codec.
     * The name is globally unique among encoders and among decoders (but an
     * encoder and a decoder can share the same name).
     */
    const char *name;

    /**
     * Type of codec implemented by the hardware accelerator.
     *
     * See AVMEDIA_TYPE_xxx
     */
    enum AVMediaType type;

    /**
     * Codec implemented by the hardware accelerator.
     *
     * See AV_CODEC_ID_xxx
     */
    enum AVCodecID id;

    /**
     * Supported pixel format.
     *
     * Only hardware accelerated formats are supported here.
     */
    enum AVPixelFormat pix_fmt;

    /**
     * Hardware accelerated codec capabilities.
     * see AV_HWACCEL_CODEC_CAP_*
     */
    int capabilities;

    /*****************************************************************
     * No fields below this line are part of the public API. They
     * may not be used outside of libavcodec and can be changed and
     * removed at will.
     * New public fields should be added right above.
     *****************************************************************
     */

    /**
     * Allocate a custom buffer
     */
    int (*alloc_frame)(AVCodecContext *avctx, AVFrame *frame);

    /**
     * Called at the beginning of each frame or field picture.
     *
     * Meaningful frame information (codec specific) is guaranteed to
     * be parsed at this point. This function is mandatory.
     *
     * Note that buf can be NULL along with buf_size set to 0.
     * Otherwise, this means the whole frame is available at this point.
     *
     * @param avctx the codec context
     * @param buf the frame data buffer base
     * @param buf_size the size of the frame in bytes
     * @return zero if successful, a negative value otherwise
     */
    int (*start_frame)(AVCodecContext *avctx, const uint8_t *buf, uint32_t buf_size);

    /**
     * Callback for parameter data (SPS/PPS/VPS etc).
     *
     * Useful for hardware decoders which keep persistent state about the
     * video parameters, and need to receive any changes to update that state.
     *
     * @param avctx the codec context
     * @param type the nal unit type
     * @param buf the nal unit data buffer
     * @param buf_size the size of the nal unit in bytes
     * @return zero if successful, a negative value otherwise
     */
    int (*decode_params)(AVCodecContext *avctx, int type, const uint8_t *buf, uint32_t buf_size);

    /**
     * Callback for each slice.
     *
     * Meaningful slice information (codec specific) is guaranteed to
     * be parsed at this point. This function is mandatory.
     * The only exception is XvMC, that works on MB level.
     *
     * @param avctx the codec context
     * @param buf the slice data buffer base
     * @param buf_size the size of the slice in bytes
     * @return zero if successful, a negative value otherwise
     */
    int (*decode_slice)(AVCodecContext *avctx, const uint8_t *buf, uint32_t buf_size);

    /**
     * Called at the end of each frame or field picture.
     *
     * The whole picture is parsed at this point and can now be sent
     * to the hardware accelerator. This function is mandatory.
     *
     * @param avctx the codec context
     * @return zero if successful, a negative value otherwise
     */
    int (*end_frame)(AVCodecContext *avctx);

    /**
     * Size of per-frame hardware accelerator private data.
     *
     * Private data is allocated with av_mallocz() before
     * AVCodecContext.get_buffer() and deallocated after
     * AVCodecContext.release_buffer().
     */
    int frame_priv_data_size;

    /**
     * Called for every Macroblock in a slice.
     *
     * XvMC uses it to replace the ff_mpv_reconstruct_mb().
     * Instead of decoding to raw picture, MB parameters are
     * stored in an array provided by the video driver.
     *
     * @param s the mpeg context
     */
    void (*decode_mb)(struct MpegEncContext *s);

    /**
     * Initialize the hwaccel private data.
     *
     * This will be called from ff_get_format(), after hwaccel and
     * hwaccel_context are set and the hwaccel private data in AVCodecInternal
     * is allocated.
     */
    int (*init)(AVCodecContext *avctx);

    /**
     * Uninitialize the hwaccel private data.
     *
     * This will be called from get_format() or avcodec_close(), after hwaccel
     * and hwaccel_context are already uninitialized.
     */
    int (*uninit)(AVCodecContext *avctx);

    /**
     * Size of the private data to allocate in
     * AVCodecInternal.hwaccel_priv_data.
     */
    int priv_data_size;

    /**
     * Internal hwaccel capabilities.
     */
    int caps_internal;

    /**
     * Fill the given hw_frames context with current codec parameters. Called
     * from get_format. Refer to avcodec_get_hw_frames_parameters() for
     * details.
     *
     * This CAN be called before AVHWAccel.init is called, and you must assume
     * that avctx->hwaccel_priv_data is invalid.
     */
    int (*frame_params)(AVCodecContext *avctx, AVBufferRef *hw_frames_ctx);
} AVHWAccel;

/**
 * HWAccel is experimental and is thus avoided in favor of non experimental
 * codecs
 */
#define AV_HWACCEL_CODEC_CAP_EXPERIMENTAL 0x0200

/**
 * Hardware acceleration should be used for decoding even if the codec level
 * used is unknown or higher than the maximum supported level reported by the
 * hardware driver.
 *
 * It's generally a good idea to pass this flag unless you have a specific
 * reason not to, as hardware tends to under-report supported levels.
 */
#define AV_HWACCEL_FLAG_IGNORE_LEVEL (1 << 0)

/**
 * Hardware acceleration can output YUV pixel formats with a different chroma
 * sampling than 4:2:0 and/or other than 8 bits per component.
 */
#define AV_HWACCEL_FLAG_ALLOW_HIGH_DEPTH (1 << 1)

/**
 * Hardware acceleration should still be attempted for decoding when the
 * codec profile does not match the reported capabilities of the hardware.
 *
 * For example, this can be used to try to decode baseline profile H.264
 * streams in hardware - it will often succeed, because many streams marked
 * as baseline profile actually conform to constrained baseline profile.
 *
 * @warning If the stream is actually not supported then the behaviour is
 *          undefined, and may include returning entirely incorrect output
 *          while indicating success.
 */
#define AV_HWACCEL_FLAG_ALLOW_PROFILE_MISMATCH (1 << 2)

/**
 * @}
 */

#if FF_API_AVPICTURE
/**
 * @defgroup lavc_picture AVPicture
 *
 * Functions for working with AVPicture
 * @{
 */

/**
 * Picture data structure.
 *
 * Up to four components can be stored into it, the last component is
 * alpha.
 * @deprecated use AVFrame or imgutils functions instead
 */
typedef struct AVPicture {
    attribute_deprecated
    uint8_t *data[AV_NUM_DATA_POINTERS];    ///< pointers to the image data planes
    attribute_deprecated
    int linesize[AV_NUM_DATA_POINTERS];     ///< number of bytes per line
} AVPicture;

/**
 * @}
 */
#endif

enum AVSubtitleType {
    SUBTITLE_NONE,

    SUBTITLE_BITMAP,                ///< A bitmap, pict will be set

    /**
     * Plain text, the text field must be set by the decoder and is
     * authoritative. ass and pict fields may contain approximations.
     */
    SUBTITLE_TEXT,

    /**
     * Formatted text, the ass field must be set by the decoder and is
     * authoritative. pict and text fields may contain approximations.
     */
    SUBTITLE_ASS,
};

#define AV_SUBTITLE_FLAG_FORCED 0x00000001

typedef struct AVSubtitleRect {
    int x;         ///< top left corner  of pict, undefined when pict is not set
    int y;         ///< top left corner  of pict, undefined when pict is not set
    int w;         ///< width            of pict, undefined when pict is not set
    int h;         ///< height           of pict, undefined when pict is not set
    int nb_colors; ///< number of colors in pict, undefined when pict is not set

#if FF_API_AVPICTURE
    /**
     * @deprecated unused
     */
    attribute_deprecated
    AVPicture pict;
#endif
    /**
     * data+linesize for the bitmap of this subtitle.
     * Can be set for text/ass as well once they are rendered.
     */
    uint8_t *data[4];
    int linesize[4];

    enum AVSubtitleType type;

    char *text;                     ///< 0 terminated plain UTF-8 text

    /**
     * 0 terminated ASS/SSA compatible event line.
     * The presentation of this is unaffected by the other values in this
     * struct.
     */
    char *ass;

    int flags;
} AVSubtitleRect;

typedef struct AVSubtitle {
    uint16_t format; /* 0 = graphics */
    uint32_t start_display_time; /* relative to packet pts, in ms */
    uint32_t end_display_time; /* relative to packet pts, in ms */
    unsigned num_rects;
    AVSubtitleRect **rects;
    int64_t pts;    ///< Same as packet pts, in AV_TIME_BASE
} AVSubtitle;

/**
 * This struct describes the properties of an encoded stream.
 *
 * sizeof(AVCodecParameters) is not a part of the public ABI, this struct must
 * be allocated with avcodec_parameters_alloc() and freed with
 * avcodec_parameters_free().
 */
typedef struct AVCodecParameters {
    /**
     * General type of the encoded data.
     */
    enum AVMediaType codec_type;
    /**
     * Specific type of the encoded data (the codec used).
     */
    enum AVCodecID   codec_id;
    /**
     * Additional information about the codec (corresponds to the AVI FOURCC).
     */
    uint32_t         codec_tag;

    /**
     * Extra binary data needed for initializing the decoder, codec-dependent.
     *
     * Must be allocated with av_malloc() and will be freed by
     * avcodec_parameters_free(). The allocated size of extradata must be at
     * least extradata_size + AV_INPUT_BUFFER_PADDING_SIZE, with the padding
     * bytes zeroed.
     */
    uint8_t *extradata;
    /**
     * Size of the extradata content in bytes.
     */
    int      extradata_size;

    /**
     * - video: the pixel format, the value corresponds to enum AVPixelFormat.
     * - audio: the sample format, the value corresponds to enum AVSampleFormat.
     */
    int format;

    /**
     * The average bitrate of the encoded data (in bits per second).
     */
    int64_t bit_rate;

    /**
     * The number of bits per sample in the codedwords.
     *
     * This is basically the bitrate per sample. It is mandatory for a bunch of
     * formats to actually decode them. It's the number of bits for one sample in
     * the actual coded bitstream.
     *
     * This could be for example 4 for ADPCM
     * For PCM formats this matches bits_per_raw_sample
     * Can be 0
     */
    int bits_per_coded_sample;

    /**
     * This is the number of valid bits in each output sample. If the
     * sample format has more bits, the least significant bits are additional
     * padding bits, which are always 0. Use right shifts to reduce the sample
     * to its actual size. For example, audio formats with 24 bit samples will
     * have bits_per_raw_sample set to 24, and format set to AV_SAMPLE_FMT_S32.
     * To get the original sample use "(int32_t)sample >> 8"."
     *
     * For ADPCM this might be 12 or 16 or similar
     * Can be 0
     */
    int bits_per_raw_sample;

    /**
     * Codec-specific bitstream restrictions that the stream conforms to.
     */
    int profile;
    int level;

    /**
     * Video only. The dimensions of the video frame in pixels.
     */
    int width;
    int height;

    /**
     * Video only. The aspect ratio (width / height) which a single pixel
     * should have when displayed.
     *
     * When the aspect ratio is unknown / undefined, the numerator should be
     * set to 0 (the denominator may have any value).
     */
    AVRational sample_aspect_ratio;

    /**
     * Video only. The order of the fields in interlaced video.
     */
    enum AVFieldOrder                  field_order;

    /**
     * Video only. Additional colorspace characteristics.
     */
    enum AVColorRange                  color_range;
    enum AVColorPrimaries              color_primaries;
    enum AVColorTransferCharacteristic color_trc;
    enum AVColorSpace                  color_space;
    enum AVChromaLocation              chroma_location;

    /**
     * Video only. Number of delayed frames.
     */
    int video_delay;

    /**
     * Audio only. The channel layout bitmask. May be 0 if the channel layout is
     * unknown or unspecified, otherwise the number of bits set must be equal to
     * the channels field.
     */
    uint64_t channel_layout;
    /**
     * Audio only. The number of audio channels.
     */
    int      channels;
    /**
     * Audio only. The number of audio samples per second.
     */
    int      sample_rate;
    /**
     * Audio only. The number of bytes per coded audio frame, required by some
     * formats.
     *
     * Corresponds to nBlockAlign in WAVEFORMATEX.
     */
    int      block_align;
    /**
     * Audio only. Audio frame size, if known. Required by some formats to be static.
     */
    int      frame_size;

    /**
     * Audio only. The amount of padding (in samples) inserted by the encoder at
     * the beginning of the audio. I.e. this number of leading decoded samples
     * must be discarded by the caller to get the original audio without leading
     * padding.
     */
    int initial_padding;
    /**
     * Audio only. The amount of padding (in samples) appended by the encoder to
     * the end of the audio. I.e. this number of decoded samples must be
     * discarded by the caller from the end of the stream to get the original
     * audio without any trailing padding.
     */
    int trailing_padding;
    /**
     * Audio only. Number of samples to skip after a discontinuity.
     */
    int seek_preroll;
} AVCodecParameters;

/**
 * Iterate over all registered codecs.
 *
 * @param opaque a pointer where libavcodec will store the iteration state. Must
 *               point to NULL to start the iteration.
 *
 * @return the next registered codec or NULL when the iteration is
 *         finished
 */
const AVCodec *av_codec_iterate(void **opaque);

#if FF_API_NEXT
/**
 * If c is NULL, returns the first registered codec,
 * if c is non-NULL, returns the next registered codec after c,
 * or NULL if c is the last one.
 */
attribute_deprecated
AVCodec *av_codec_next(const AVCodec *c);
#endif

/**
 * Return the LIBAVCODEC_VERSION_INT constant.
 */
unsigned avcodec_version(void);

/**
 * Return the libavcodec build-time configuration.
 */
const char *avcodec_configuration(void);

/**
 * Return the libavcodec license.
 */
const char *avcodec_license(void);

#if FF_API_NEXT
/**
 * Register the codec codec and initialize libavcodec.
 *
 * @warning either this function or avcodec_register_all() must be called
 * before any other libavcodec functions.
 *
 * @see avcodec_register_all()
 */
attribute_deprecated
void avcodec_register(AVCodec *codec);

/**
 * Register all the codecs, parsers and bitstream filters which were enabled at
 * configuration time. If you do not call this function you can select exactly
 * which formats you want to support, by using the individual registration
 * functions.
 *
 * @see avcodec_register
 * @see av_register_codec_parser
 * @see av_register_bitstream_filter
 */
attribute_deprecated
void avcodec_register_all(void);
#endif

/**
 * Allocate an AVCodecContext and set its fields to default values. The
 * resulting struct should be freed with avcodec_free_context().
 *
 * @param codec if non-NULL, allocate private data and initialize defaults
 *              for the given codec. It is illegal to then call avcodec_open2()
 *              with a different codec.
 *              If NULL, then the codec-specific defaults won't be initialized,
 *              which may result in suboptimal default settings (this is
 *              important mainly for encoders, e.g. libx264).
 *
 * @return An AVCodecContext filled with default values or NULL on failure.
 */
AVCodecContext *avcodec_alloc_context3(const AVCodec *codec);

/**
 * Free the codec context and everything associated with it and write NULL to
 * the provided pointer.
 */
void avcodec_free_context(AVCodecContext **avctx);

#if FF_API_GET_CONTEXT_DEFAULTS
/**
 * @deprecated This function should not be used, as closing and opening a codec
 * context multiple time is not supported. A new codec context should be
 * allocated for each new use.
 */
int avcodec_get_context_defaults3(AVCodecContext *s, const AVCodec *codec);
#endif

/**
 * Get the AVClass for AVCodecContext. It can be used in combination with
 * AV_OPT_SEARCH_FAKE_OBJ for examining options.
 *
 * @see av_opt_find().
 */
const AVClass *avcodec_get_class(void);

#if FF_API_COPY_CONTEXT
/**
 * Get the AVClass for AVFrame. It can be used in combination with
 * AV_OPT_SEARCH_FAKE_OBJ for examining options.
 *
 * @see av_opt_find().
 */
const AVClass *avcodec_get_frame_class(void);

/**
 * Get the AVClass for AVSubtitleRect. It can be used in combination with
 * AV_OPT_SEARCH_FAKE_OBJ for examining options.
 *
 * @see av_opt_find().
 */
const AVClass *avcodec_get_subtitle_rect_class(void);

/**
 * Copy the settings of the source AVCodecContext into the destination
 * AVCodecContext. The resulting destination codec context will be
 * unopened, i.e. you are required to call avcodec_open2() before you
 * can use this AVCodecContext to decode/encode video/audio data.
 *
 * @param dest target codec context, should be initialized with
 *             avcodec_alloc_context3(NULL), but otherwise uninitialized
 * @param src source codec context
 * @return AVERROR() on error (e.g. memory allocation error), 0 on success
 *
 * @deprecated The semantics of this function are ill-defined and it should not
 * be used. If you need to transfer the stream parameters from one codec context
 * to another, use an intermediate AVCodecParameters instance and the
 * avcodec_parameters_from_context() / avcodec_parameters_to_context()
 * functions.
 */
attribute_deprecated
int avcodec_copy_context(AVCodecContext *dest, const AVCodecContext *src);
#endif

/**
 * Allocate a new AVCodecParameters and set its fields to default values
 * (unknown/invalid/0). The returned struct must be freed with
 * avcodec_parameters_free().
 */
AVCodecParameters *avcodec_parameters_alloc(void);

/**
 * Free an AVCodecParameters instance and everything associated with it and
 * write NULL to the supplied pointer.
 */
void avcodec_parameters_free(AVCodecParameters **par);

/**
 * Copy the contents of src to dst. Any allocated fields in dst are freed and
 * replaced with newly allocated duplicates of the corresponding fields in src.
 *
 * @return >= 0 on success, a negative AVERROR code on failure.
 */
int avcodec_parameters_copy(AVCodecParameters *dst, const AVCodecParameters *src);

/**
 * Fill the parameters struct based on the values from the supplied codec
 * context. Any allocated fields in par are freed and replaced with duplicates
 * of the corresponding fields in codec.
 *
 * @return >= 0 on success, a negative AVERROR code on failure
 */
int avcodec_parameters_from_context(AVCodecParameters *par,
                                    const AVCodecContext *codec);

/**
 * Fill the codec context based on the values from the supplied codec
 * parameters. Any allocated fields in codec that have a corresponding field in
 * par are freed and replaced with duplicates of the corresponding field in par.
 * Fields in codec that do not have a counterpart in par are not touched.
 *
 * @return >= 0 on success, a negative AVERROR code on failure.
 */
int avcodec_parameters_to_context(AVCodecContext *codec,
                                  const AVCodecParameters *par);

/**
 * Initialize the AVCodecContext to use the given AVCodec. Prior to using this
 * function the context has to be allocated with avcodec_alloc_context3().
 *
 * The functions avcodec_find_decoder_by_name(), avcodec_find_encoder_by_name(),
 * avcodec_find_decoder() and avcodec_find_encoder() provide an easy way for
 * retrieving a codec.
 *
 * @warning This function is not thread safe!
 *
 * @note Always call this function before using decoding routines (such as
 * @ref avcodec_receive_frame()).
 *
 * @code
 * avcodec_register_all();
 * av_dict_set(&opts, "b", "2.5M", 0);
 * codec = avcodec_find_decoder(AV_CODEC_ID_H264);
 * if (!codec)
 *     exit(1);
 *
 * context = avcodec_alloc_context3(codec);
 *
 * if (avcodec_open2(context, codec, opts) < 0)
 *     exit(1);
 * @endcode
 *
 * @param avctx The context to initialize.
 * @param codec The codec to open this context for. If a non-NULL codec has been
 *              previously passed to avcodec_alloc_context3() or
 *              for this context, then this parameter MUST be either NULL or
 *              equal to the previously passed codec.
 * @param options A dictionary filled with AVCodecContext and codec-private options.
 *                On return this object will be filled with options that were not found.
 *
 * @return zero on success, a negative value on error
 * @see avcodec_alloc_context3(), avcodec_find_decoder(), avcodec_find_encoder(),
 *      av_dict_set(), av_opt_find().
 */
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options);

/**
 * Close a given AVCodecContext and free all the data associated with it
 * (but not the AVCodecContext itself).
 *
 * Calling this function on an AVCodecContext that hasn't been opened will free
 * the codec-specific data allocated in avcodec_alloc_context3() with a non-NULL
 * codec. Subsequent calls will do nothing.
 *
 * @note Do not use this function. Use avcodec_free_context() to destroy a
 * codec context (either open or closed). Opening and closing a codec context
 * multiple times is not supported anymore -- use multiple codec contexts
 * instead.
 */
int avcodec_close(AVCodecContext *avctx);

/**
 * Free all allocated data in the given subtitle struct.
 *
 * @param sub AVSubtitle to free.
 */
void avsubtitle_free(AVSubtitle *sub);

/**
 * @}
 */

/**
 * @addtogroup lavc_packet
 * @{
 */

/**
 * Allocate an AVPacket and set its fields to default values.  The resulting
 * struct must be freed using av_packet_free().
 *
 * @return An AVPacket filled with default values or NULL on failure.
 *
 * @note this only allocates the AVPacket itself, not the data buffers. Those
 * must be allocated through other means such as av_new_packet.
 *
 * @see av_new_packet
 */
AVPacket *av_packet_alloc(void);

/**
 * Create a new packet that references the same data as src.
 *
 * This is a shortcut for av_packet_alloc()+av_packet_ref().
 *
 * @return newly created AVPacket on success, NULL on error.
 *
 * @see av_packet_alloc
 * @see av_packet_ref
 */
AVPacket *av_packet_clone(const AVPacket *src);

/**
 * Free the packet, if the packet is reference counted, it will be
 * unreferenced first.
 *
 * @param pkt packet to be freed. The pointer will be set to NULL.
 * @note passing NULL is a no-op.
 */
void av_packet_free(AVPacket **pkt);

/**
 * Initialize optional fields of a packet with default values.
 *
 * Note, this does not touch the data and size members, which have to be
 * initialized separately.
 *
 * @param pkt packet
 */
void av_init_packet(AVPacket *pkt);

/**
 * Allocate the payload of a packet and initialize its fields with
 * default values.
 *
 * @param pkt packet
 * @param size wanted payload size
 * @return 0 if OK, AVERROR_xxx otherwise
 */
int av_new_packet(AVPacket *pkt, int size);

/**
 * Reduce packet size, correctly zeroing padding
 *
 * @param pkt packet
 * @param size new size
 */
void av_shrink_packet(AVPacket *pkt, int size);

/**
 * Increase packet size, correctly zeroing padding
 *
 * @param pkt packet
 * @param grow_by number of bytes by which to increase the size of the packet
 */
int av_grow_packet(AVPacket *pkt, int grow_by);

/**
 * Initialize a reference-counted packet from av_malloc()ed data.
 *
 * @param pkt packet to be initialized. This function will set the data, size,
 *        buf and destruct fields, all others are left untouched.
 * @param data Data allocated by av_malloc() to be used as packet data. If this
 *        function returns successfully, the data is owned by the underlying AVBuffer.
 *        The caller may not access the data through other means.
 * @param size size of data in bytes, without the padding. I.e. the full buffer
 *        size is assumed to be size + AV_INPUT_BUFFER_PADDING_SIZE.
 *
 * @return 0 on success, a negative AVERROR on error
 */
int av_packet_from_data(AVPacket *pkt, uint8_t *data, int size);

#if FF_API_AVPACKET_OLD_API
/**
 * @warning This is a hack - the packet memory allocation stuff is broken. The
 * packet is allocated if it was not really allocated.
 *
 * @deprecated Use av_packet_ref or av_packet_make_refcounted
 */
attribute_deprecated
int av_dup_packet(AVPacket *pkt);
/**
 * Copy packet, including contents
 *
 * @return 0 on success, negative AVERROR on fail
 *
 * @deprecated Use av_packet_ref
 */
attribute_deprecated
int av_copy_packet(AVPacket *dst, const AVPacket *src);

/**
 * Copy packet side data
 *
 * @return 0 on success, negative AVERROR on fail
 *
 * @deprecated Use av_packet_copy_props
 */
attribute_deprecated
int av_copy_packet_side_data(AVPacket *dst, const AVPacket *src);

/**
 * Free a packet.
 *
 * @deprecated Use av_packet_unref
 *
 * @param pkt packet to free
 */
attribute_deprecated
void av_free_packet(AVPacket *pkt);
#endif
/**
 * Allocate new information of a packet.
 *
 * @param pkt packet
 * @param type side information type
 * @param size side information size
 * @return pointer to fresh allocated data or NULL otherwise
 */
uint8_t* av_packet_new_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
                                 int size);

/**
 * Wrap an existing array as a packet side data.
 *
 * @param pkt packet
 * @param type side information type
 * @param data the side data array. It must be allocated with the av_malloc()
 *             family of functions. The ownership of the data is transferred to
 *             pkt.
 * @param size side information size
 * @return a non-negative number on success, a negative AVERROR code on
 *         failure. On failure, the packet is unchanged and the data remains
 *         owned by the caller.
 */
int av_packet_add_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
                            uint8_t *data, size_t size);

/**
 * Shrink the already allocated side data buffer
 *
 * @param pkt packet
 * @param type side information type
 * @param size new side information size
 * @return 0 on success, < 0 on failure
 */
int av_packet_shrink_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
                               int size);

/**
 * Get side information from packet.
 *
 * @param pkt packet
 * @param type desired side information type
 * @param size pointer for side information size to store (optional)
 * @return pointer to data if present or NULL otherwise
 */
uint8_t* av_packet_get_side_data(const AVPacket *pkt, enum AVPacketSideDataType type,
                                 int *size);

#if FF_API_MERGE_SD_API
attribute_deprecated
int av_packet_merge_side_data(AVPacket *pkt);

attribute_deprecated
int av_packet_split_side_data(AVPacket *pkt);
#endif

const char *av_packet_side_data_name(enum AVPacketSideDataType type);

/**
 * Pack a dictionary for use in side_data.
 *
 * @param dict The dictionary to pack.
 * @param size pointer to store the size of the returned data
 * @return pointer to data if successful, NULL otherwise
 */
uint8_t *av_packet_pack_dictionary(AVDictionary *dict, int *size);
/**
 * Unpack a dictionary from side_data.
 *
 * @param data data from side_data
 * @param size size of the data
 * @param dict the metadata storage dictionary
 * @return 0 on success, < 0 on failure
 */
int av_packet_unpack_dictionary(const uint8_t *data, int size, AVDictionary **dict);


/**
 * Convenience function to free all the side data stored.
 * All the other fields stay untouched.
 *
 * @param pkt packet
 */
void av_packet_free_side_data(AVPacket *pkt);

/**
 * Setup a new reference to the data described by a given packet
 *
 * If src is reference-counted, setup dst as a new reference to the
 * buffer in src. Otherwise allocate a new buffer in dst and copy the
 * data from src into it.
 *
 * All the other fields are copied from src.
 *
 * @see av_packet_unref
 *
 * @param dst Destination packet
 * @param src Source packet
 *
 * @return 0 on success, a negative AVERROR on error.
 */
int av_packet_ref(AVPacket *dst, const AVPacket *src);

/**
 * Wipe the packet.
 *
 * Unreference the buffer referenced by the packet and reset the
 * remaining packet fields to their default values.
 *
 * @param pkt The packet to be unreferenced.
 */
void av_packet_unref(AVPacket *pkt);

/**
 * Move every field in src to dst and reset src.
 *
 * @see av_packet_unref
 *
 * @param src Source packet, will be reset
 * @param dst Destination packet
 */
void av_packet_move_ref(AVPacket *dst, AVPacket *src);

/**
 * Copy only "properties" fields from src to dst.
 *
 * Properties for the purpose of this function are all the fields
 * beside those related to the packet data (buf, data, size)
 *
 * @param dst Destination packet
 * @param src Source packet
 *
 * @return 0 on success AVERROR on failure.
 */
int av_packet_copy_props(AVPacket *dst, const AVPacket *src);

/**
 * Ensure the data described by a given packet is reference counted.
 *
 * @note This function does not ensure that the reference will be writable.
 *       Use av_packet_make_writable instead for that purpose.
 *
 * @see av_packet_ref
 * @see av_packet_make_writable
 *
 * @param pkt packet whose data should be made reference counted.
 *
 * @return 0 on success, a negative AVERROR on error. On failure, the
 *         packet is unchanged.
 */
int av_packet_make_refcounted(AVPacket *pkt);

/**
 * Create a writable reference for the data described by a given packet,
 * avoiding data copy if possible.
 *
 * @param pkt Packet whose data should be made writable.
 *
 * @return 0 on success, a negative AVERROR on failure. On failure, the
 *         packet is unchanged.
 */
int av_packet_make_writable(AVPacket *pkt);

/**
 * Convert valid timing fields (timestamps / durations) in a packet from one
 * timebase to another. Timestamps with unknown values (AV_NOPTS_VALUE) will be
 * ignored.
 *
 * @param pkt packet on which the conversion will be performed
 * @param tb_src source timebase, in which the timing fields in pkt are
 *               expressed
 * @param tb_dst destination timebase, to which the timing fields will be
 *               converted
 */
void av_packet_rescale_ts(AVPacket *pkt, AVRational tb_src, AVRational tb_dst);

/**
 * @}
 */

/**
 * @addtogroup lavc_decoding
 * @{
 */

/**
 * Find a registered decoder with a matching codec ID.
 *
 * @param id AVCodecID of the requested decoder
 * @return A decoder if one was found, NULL otherwise.
 */
AVCodec *avcodec_find_decoder(enum AVCodecID id);

/**
 * Find a registered decoder with the specified name.
 *
 * @param name name of the requested decoder
 * @return A decoder if one was found, NULL otherwise.
 */
AVCodec *avcodec_find_decoder_by_name(const char *name);

/**
 * The default callback for AVCodecContext.get_buffer2(). It is made public so
 * it can be called by custom get_buffer2() implementations for decoders without
 * AV_CODEC_CAP_DR1 set.
 */
int avcodec_default_get_buffer2(AVCodecContext *s, AVFrame *frame, int flags);

/**
 * Modify width and height values so that they will result in a memory
 * buffer that is acceptable for the codec if you do not use any horizontal
 * padding.
 *
 * May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
 */
void avcodec_align_dimensions(AVCodecContext *s, int *width, int *height);

/**
 * Modify width and height values so that they will result in a memory
 * buffer that is acceptable for the codec if you also ensure that all
 * line sizes are a multiple of the respective linesize_align[i].
 *
 * May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
 */
void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
                               int linesize_align[AV_NUM_DATA_POINTERS]);

/**
 * Converts AVChromaLocation to swscale x/y chroma position.
 *
 * The positions represent the chroma (0,0) position in a coordinates system
 * with luma (0,0) representing the origin and luma(1,1) representing 256,256
 *
 * @param xpos  horizontal chroma sample position
 * @param ypos  vertical   chroma sample position
 */
int avcodec_enum_to_chroma_pos(int *xpos, int *ypos, enum AVChromaLocation pos);

/**
 * Converts swscale x/y chroma position to AVChromaLocation.
 *
 * The positions represent the chroma (0,0) position in a coordinates system
 * with luma (0,0) representing the origin and luma(1,1) representing 256,256
 *
 * @param xpos  horizontal chroma sample position
 * @param ypos  vertical   chroma sample position
 */
enum AVChromaLocation avcodec_chroma_pos_to_enum(int xpos, int ypos);

/**
 * Decode the audio frame of size avpkt->size from avpkt->data into frame.
 *
 * Some decoders may support multiple frames in a single AVPacket. Such
 * decoders would then just decode the first frame and the return value would be
 * less than the packet size. In this case, avcodec_decode_audio4 has to be
 * called again with an AVPacket containing the remaining data in order to
 * decode the second frame, etc...  Even if no frames are returned, the packet
 * needs to be fed to the decoder with remaining data until it is completely
 * consumed or an error occurs.
 *
 * Some decoders (those marked with AV_CODEC_CAP_DELAY) have a delay between input
 * and output. This means that for some packets they will not immediately
 * produce decoded output and need to be flushed at the end of decoding to get
 * all the decoded data. Flushing is done by calling this function with packets
 * with avpkt->data set to NULL and avpkt->size set to 0 until it stops
 * returning samples. It is safe to flush even those decoders that are not
 * marked with AV_CODEC_CAP_DELAY, then no samples will be returned.
 *
 * @warning The input buffer, avpkt->data must be AV_INPUT_BUFFER_PADDING_SIZE
 *          larger than the actual read bytes because some optimized bitstream
 *          readers read 32 or 64 bits at once and could read over the end.
 *
 * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
 * before packets may be fed to the decoder.
 *
 * @param      avctx the codec context
 * @param[out] frame The AVFrame in which to store decoded audio samples.
 *                   The decoder will allocate a buffer for the decoded frame by
 *                   calling the AVCodecContext.get_buffer2() callback.
 *                   When AVCodecContext.refcounted_frames is set to 1, the frame is
 *                   reference counted and the returned reference belongs to the
 *                   caller. The caller must release the frame using av_frame_unref()
 *                   when the frame is no longer needed. The caller may safely write
 *                   to the frame if av_frame_is_writable() returns 1.
 *                   When AVCodecContext.refcounted_frames is set to 0, the returned
 *                   reference belongs to the decoder and is valid only until the
 *                   next call to this function or until closing or flushing the
 *                   decoder. The caller may not write to it.
 * @param[out] got_frame_ptr Zero if no frame could be decoded, otherwise it is
 *                           non-zero. Note that this field being set to zero
 *                           does not mean that an error has occurred. For
 *                           decoders with AV_CODEC_CAP_DELAY set, no given decode
 *                           call is guaranteed to produce a frame.
 * @param[in]  avpkt The input AVPacket containing the input buffer.
 *                   At least avpkt->data and avpkt->size should be set. Some
 *                   decoders might also require additional fields to be set.
 * @return A negative error code is returned if an error occurred during
 *         decoding, otherwise the number of bytes consumed from the input
 *         AVPacket is returned.
 *
* @deprecated Use avcodec_send_packet() and avcodec_receive_frame().
 */
attribute_deprecated
int avcodec_decode_audio4(AVCodecContext *avctx, AVFrame *frame,
                          int *got_frame_ptr, const AVPacket *avpkt);

/**
 * Decode the video frame of size avpkt->size from avpkt->data into picture.
 * Some decoders may support multiple frames in a single AVPacket, such
 * decoders would then just decode the first frame.
 *
 * @warning The input buffer must be AV_INPUT_BUFFER_PADDING_SIZE larger than
 * the actual read bytes because some optimized bitstream readers read 32 or 64
 * bits at once and could read over the end.
 *
 * @warning The end of the input buffer buf should be set to 0 to ensure that
 * no overreading happens for damaged MPEG streams.
 *
 * @note Codecs which have the AV_CODEC_CAP_DELAY capability set have a delay
 * between input and output, these need to be fed with avpkt->data=NULL,
 * avpkt->size=0 at the end to return the remaining frames.
 *
 * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
 * before packets may be fed to the decoder.
 *
 * @param avctx the codec context
 * @param[out] picture The AVFrame in which the decoded video frame will be stored.
 *             Use av_frame_alloc() to get an AVFrame. The codec will
 *             allocate memory for the actual bitmap by calling the
 *             AVCodecContext.get_buffer2() callback.
 *             When AVCodecContext.refcounted_frames is set to 1, the frame is
 *             reference counted and the returned reference belongs to the
 *             caller. The caller must release the frame using av_frame_unref()
 *             when the frame is no longer needed. The caller may safely write
 *             to the frame if av_frame_is_writable() returns 1.
 *             When AVCodecContext.refcounted_frames is set to 0, the returned
 *             reference belongs to the decoder and is valid only until the
 *             next call to this function or until closing or flushing the
 *             decoder. The caller may not write to it.
 *
 * @param[in] avpkt The input AVPacket containing the input buffer.
 *            You can create such packet with av_init_packet() and by then setting
 *            data and size, some decoders might in addition need other fields like
 *            flags&AV_PKT_FLAG_KEY. All decoders are designed to use the least
 *            fields possible.
 * @param[in,out] got_picture_ptr Zero if no frame could be decompressed, otherwise, it is nonzero.
 * @return On error a negative value is returned, otherwise the number of bytes
 * used or zero if no frame could be decompressed.
 *
 * @deprecated Use avcodec_send_packet() and avcodec_receive_frame().
 */
attribute_deprecated
int avcodec_decode_video2(AVCodecContext *avctx, AVFrame *picture,
                         int *got_picture_ptr,
                         const AVPacket *avpkt);

/**
 * Decode a subtitle message.
 * Return a negative value on error, otherwise return the number of bytes used.
 * If no subtitle could be decompressed, got_sub_ptr is zero.
 * Otherwise, the subtitle is stored in *sub.
 * Note that AV_CODEC_CAP_DR1 is not available for subtitle codecs. This is for
 * simplicity, because the performance difference is expect to be negligible
 * and reusing a get_buffer written for video codecs would probably perform badly
 * due to a potentially very different allocation pattern.
 *
 * Some decoders (those marked with AV_CODEC_CAP_DELAY) have a delay between input
 * and output. This means that for some packets they will not immediately
 * produce decoded output and need to be flushed at the end of decoding to get
 * all the decoded data. Flushing is done by calling this function with packets
 * with avpkt->data set to NULL and avpkt->size set to 0 until it stops
 * returning subtitles. It is safe to flush even those decoders that are not
 * marked with AV_CODEC_CAP_DELAY, then no subtitles will be returned.
 *
 * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
 * before packets may be fed to the decoder.
 *
 * @param avctx the codec context
 * @param[out] sub The Preallocated AVSubtitle in which the decoded subtitle will be stored,
 *                 must be freed with avsubtitle_free if *got_sub_ptr is set.
 * @param[in,out] got_sub_ptr Zero if no subtitle could be decompressed, otherwise, it is nonzero.
 * @param[in] avpkt The input AVPacket containing the input buffer.
 */
int avcodec_decode_subtitle2(AVCodecContext *avctx, AVSubtitle *sub,
                            int *got_sub_ptr,
                            AVPacket *avpkt);

/**
 * Supply raw packet data as input to a decoder.
 *
 * Internally, this call will copy relevant AVCodecContext fields, which can
 * influence decoding per-packet, and apply them when the packet is actually
 * decoded. (For example AVCodecContext.skip_frame, which might direct the
 * decoder to drop the frame contained by the packet sent with this function.)
 *
 * @warning The input buffer, avpkt->data must be AV_INPUT_BUFFER_PADDING_SIZE
 *          larger than the actual read bytes because some optimized bitstream
 *          readers read 32 or 64 bits at once and could read over the end.
 *
 * @warning Do not mix this API with the legacy API (like avcodec_decode_video2())
 *          on the same AVCodecContext. It will return unexpected results now
 *          or in future libavcodec versions.
 *
 * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
 *       before packets may be fed to the decoder.
 *
 * @param avctx codec context
 * @param[in] avpkt The input AVPacket. Usually, this will be a single video
 *                  frame, or several complete audio frames.
 *                  Ownership of the packet remains with the caller, and the
 *                  decoder will not write to the packet. The decoder may create
 *                  a reference to the packet data (or copy it if the packet is
 *                  not reference-counted).
 *                  Unlike with older APIs, the packet is always fully consumed,
 *                  and if it contains multiple frames (e.g. some audio codecs),
 *                  will require you to call avcodec_receive_frame() multiple
 *                  times afterwards before you can send a new packet.
 *                  It can be NULL (or an AVPacket with data set to NULL and
 *                  size set to 0); in this case, it is considered a flush
 *                  packet, which signals the end of the stream. Sending the
 *                  first flush packet will return success. Subsequent ones are
 *                  unnecessary and will return AVERROR_EOF. If the decoder
 *                  still has frames buffered, it will return them after sending
 *                  a flush packet.
 *
 * @return 0 on success, otherwise negative error code:
 *      AVERROR(EAGAIN):   input is not accepted in the current state - user
 *                         must read output with avcodec_receive_frame() (once
 *                         all output is read, the packet should be resent, and
 *                         the call will not fail with EAGAIN).
 *      AVERROR_EOF:       the decoder has been flushed, and no new packets can
 *                         be sent to it (also returned if more than 1 flush
 *                         packet is sent)
 *      AVERROR(EINVAL):   codec not opened, it is an encoder, or requires flush
 *      AVERROR(ENOMEM):   failed to add packet to internal queue, or similar
 *      other errors: legitimate decoding errors
 */
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt);

/**
 * Return decoded output data from a decoder.
 *
 * @param avctx codec context
 * @param frame This will be set to a reference-counted video or audio
 *              frame (depending on the decoder type) allocated by the
 *              decoder. Note that the function will always call
 *              av_frame_unref(frame) before doing anything else.
 *
 * @return
 *      0:                 success, a frame was returned
 *      AVERROR(EAGAIN):   output is not available in this state - user must try
 *                         to send new input
 *      AVERROR_EOF:       the decoder has been fully flushed, and there will be
 *                         no more output frames
 *      AVERROR(EINVAL):   codec not opened, or it is an encoder
 *      other negative values: legitimate decoding errors
 */
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame);

/**
 * Supply a raw video or audio frame to the encoder. Use avcodec_receive_packet()
 * to retrieve buffered output packets.
 *
 * @param avctx     codec context
 * @param[in] frame AVFrame containing the raw audio or video frame to be encoded.
 *                  Ownership of the frame remains with the caller, and the
 *                  encoder will not write to the frame. The encoder may create
 *                  a reference to the frame data (or copy it if the frame is
 *                  not reference-counted).
 *                  It can be NULL, in which case it is considered a flush
 *                  packet.  This signals the end of the stream. If the encoder
 *                  still has packets buffered, it will return them after this
 *                  call. Once flushing mode has been entered, additional flush
 *                  packets are ignored, and sending frames will return
 *                  AVERROR_EOF.
 *
 *                  For audio:
 *                  If AV_CODEC_CAP_VARIABLE_FRAME_SIZE is set, then each frame
 *                  can have any number of samples.
 *                  If it is not set, frame->nb_samples must be equal to
 *                  avctx->frame_size for all frames except the last.
 *                  The final frame may be smaller than avctx->frame_size.
 * @return 0 on success, otherwise negative error code:
 *      AVERROR(EAGAIN):   input is not accepted in the current state - user
 *                         must read output with avcodec_receive_packet() (once
 *                         all output is read, the packet should be resent, and
 *                         the call will not fail with EAGAIN).
 *      AVERROR_EOF:       the encoder has been flushed, and no new frames can
 *                         be sent to it
 *      AVERROR(EINVAL):   codec not opened, refcounted_frames not set, it is a
 *                         decoder, or requires flush
 *      AVERROR(ENOMEM):   failed to add packet to internal queue, or similar
 *      other errors: legitimate decoding errors
 */
int avcodec_send_frame(AVCodecContext *avctx, const AVFrame *frame);

/**
 * Read encoded data from the encoder.
 *
 * @param avctx codec context
 * @param avpkt This will be set to a reference-counted packet allocated by the
 *              encoder. Note that the function will always call
 *              av_frame_unref(frame) before doing anything else.
 * @return 0 on success, otherwise negative error code:
 *      AVERROR(EAGAIN):   output is not available in the current state - user
 *                         must try to send input
 *      AVERROR_EOF:       the encoder has been fully flushed, and there will be
 *                         no more output packets
 *      AVERROR(EINVAL):   codec not opened, or it is an encoder
 *      other errors: legitimate decoding errors
 */
int avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt);

/**
 * Create and return a AVHWFramesContext with values adequate for hardware
 * decoding. This is meant to get called from the get_format callback, and is
 * a helper for preparing a AVHWFramesContext for AVCodecContext.hw_frames_ctx.
 * This API is for decoding with certain hardware acceleration modes/APIs only.
 *
 * The returned AVHWFramesContext is not initialized. The caller must do this
 * with av_hwframe_ctx_init().
 *
 * Calling this function is not a requirement, but makes it simpler to avoid
 * codec or hardware API specific details when manually allocating frames.
 *
 * Alternatively to this, an API user can set AVCodecContext.hw_device_ctx,
 * which sets up AVCodecContext.hw_frames_ctx fully automatically, and makes
 * it unnecessary to call this function or having to care about
 * AVHWFramesContext initialization at all.
 *
 * There are a number of requirements for calling this function:
 *
 * - It must be called from get_format with the same avctx parameter that was
 *   passed to get_format. Calling it outside of get_format is not allowed, and
 *   can trigger undefined behavior.
 * - The function is not always supported (see description of return values).
 *   Even if this function returns successfully, hwaccel initialization could
 *   fail later. (The degree to which implementations check whether the stream
 *   is actually supported varies. Some do this check only after the user's
 *   get_format callback returns.)
 * - The hw_pix_fmt must be one of the choices suggested by get_format. If the
 *   user decides to use a AVHWFramesContext prepared with this API function,
 *   the user must return the same hw_pix_fmt from get_format.
 * - The device_ref passed to this function must support the given hw_pix_fmt.
 * - After calling this API function, it is the user's responsibility to
 *   initialize the AVHWFramesContext (returned by the out_frames_ref parameter),
 *   and to set AVCodecContext.hw_frames_ctx to it. If done, this must be done
 *   before returning from get_format (this is implied by the normal
 *   AVCodecContext.hw_frames_ctx API rules).
 * - The AVHWFramesContext parameters may change every time time get_format is
 *   called. Also, AVCodecContext.hw_frames_ctx is reset before get_format. So
 *   you are inherently required to go through this process again on every
 *   get_format call.
 * - It is perfectly possible to call this function without actually using
 *   the resulting AVHWFramesContext. One use-case might be trying to reuse a
 *   previously initialized AVHWFramesContext, and calling this API function
 *   only to test whether the required frame parameters have changed.
 * - Fields that use dynamically allocated values of any kind must not be set
 *   by the user unless setting them is explicitly allowed by the documentation.
 *   If the user sets AVHWFramesContext.free and AVHWFramesContext.user_opaque,
 *   the new free callback must call the potentially set previous free callback.
 *   This API call may set any dynamically allocated fields, including the free
 *   callback.
 *
 * The function will set at least the following fields on AVHWFramesContext
 * (potentially more, depending on hwaccel API):
 *
 * - All fields set by av_hwframe_ctx_alloc().
 * - Set the format field to hw_pix_fmt.
 * - Set the sw_format field to the most suited and most versatile format. (An
 *   implication is that this will prefer generic formats over opaque formats
 *   with arbitrary restrictions, if possible.)
 * - Set the width/height fields to the coded frame size, rounded up to the
 *   API-specific minimum alignment.
 * - Only _if_ the hwaccel requires a pre-allocated pool: set the initial_pool_size
 *   field to the number of maximum reference surfaces possible with the codec,
 *   plus 1 surface for the user to work (meaning the user can safely reference
 *   at most 1 decoded surface at a time), plus additional buffering introduced
 *   by frame threading. If the hwaccel does not require pre-allocation, the
 *   field is left to 0, and the decoder will allocate new surfaces on demand
 *   during decoding.
 * - Possibly AVHWFramesContext.hwctx fields, depending on the underlying
 *   hardware API.
 *
 * Essentially, out_frames_ref returns the same as av_hwframe_ctx_alloc(), but
 * with basic frame parameters set.
 *
 * The function is stateless, and does not change the AVCodecContext or the
 * device_ref AVHWDeviceContext.
 *
 * @param avctx The context which is currently calling get_format, and which
 *              implicitly contains all state needed for filling the returned
 *              AVHWFramesContext properly.
 * @param device_ref A reference to the AVHWDeviceContext describing the device
 *                   which will be used by the hardware decoder.
 * @param hw_pix_fmt The hwaccel format you are going to return from get_format.
 * @param out_frames_ref On success, set to a reference to an _uninitialized_
 *                       AVHWFramesContext, created from the given device_ref.
 *                       Fields will be set to values required for decoding.
 *                       Not changed if an error is returned.
 * @return zero on success, a negative value on error. The following error codes
 *         have special semantics:
 *      AVERROR(ENOENT): the decoder does not support this functionality. Setup
 *                       is always manual, or it is a decoder which does not
 *                       support setting AVCodecContext.hw_frames_ctx at all,
 *                       or it is a software format.
 *      AVERROR(EINVAL): it is known that hardware decoding is not supported for
 *                       this configuration, or the device_ref is not supported
 *                       for the hwaccel referenced by hw_pix_fmt.
 */
int avcodec_get_hw_frames_parameters(AVCodecContext *avctx,
                                     AVBufferRef *device_ref,
                                     enum AVPixelFormat hw_pix_fmt,
                                     AVBufferRef **out_frames_ref);



/**
 * @defgroup lavc_parsing Frame parsing
 * @{
 */

enum AVPictureStructure {
    AV_PICTURE_STRUCTURE_UNKNOWN,      //< unknown
    AV_PICTURE_STRUCTURE_TOP_FIELD,    //< coded as top field
    AV_PICTURE_STRUCTURE_BOTTOM_FIELD, //< coded as bottom field
    AV_PICTURE_STRUCTURE_FRAME,        //< coded as frame
};

typedef struct AVCodecParserContext {
    void *priv_data;
    struct AVCodecParser *parser;
    int64_t frame_offset; /* offset of the current frame */
    int64_t cur_offset; /* current offset
                           (incremented by each av_parser_parse()) */
    int64_t next_frame_offset; /* offset of the next frame */
    /* video info */
    int pict_type; /* XXX: Put it back in AVCodecContext. */
    /**
     * This field is used for proper frame duration computation in lavf.
     * It signals, how much longer the frame duration of the current frame
     * is compared to normal frame duration.
     *
     * frame_duration = (1 + repeat_pict) * time_base
     *
     * It is used by codecs like H.264 to display telecined material.
     */
    int repeat_pict; /* XXX: Put it back in AVCodecContext. */
    int64_t pts;     /* pts of the current frame */
    int64_t dts;     /* dts of the current frame */

    /* private data */
    int64_t last_pts;
    int64_t last_dts;
    int fetch_timestamp;

#define AV_PARSER_PTS_NB 4
    int cur_frame_start_index;
    int64_t cur_frame_offset[AV_PARSER_PTS_NB];
    int64_t cur_frame_pts[AV_PARSER_PTS_NB];
    int64_t cur_frame_dts[AV_PARSER_PTS_NB];

    int flags;
#define PARSER_FLAG_COMPLETE_FRAMES           0x0001
#define PARSER_FLAG_ONCE                      0x0002
/// Set if the parser has a valid file offset
#define PARSER_FLAG_FETCHED_OFFSET            0x0004
#define PARSER_FLAG_USE_CODEC_TS              0x1000

    int64_t offset;      ///< byte offset from starting packet start
    int64_t cur_frame_end[AV_PARSER_PTS_NB];

    /**
     * Set by parser to 1 for key frames and 0 for non-key frames.
     * It is initialized to -1, so if the parser doesn't set this flag,
     * old-style fallback using AV_PICTURE_TYPE_I picture type as key frames
     * will be used.
     */
    int key_frame;

#if FF_API_CONVERGENCE_DURATION
    /**
     * @deprecated unused
     */
    attribute_deprecated
    int64_t convergence_duration;
#endif

    // Timestamp generation support:
    /**
     * Synchronization point for start of timestamp generation.
     *
     * Set to >0 for sync point, 0 for no sync point and <0 for undefined
     * (default).
     *
     * For example, this corresponds to presence of H.264 buffering period
     * SEI message.
     */
    int dts_sync_point;

    /**
     * Offset of the current timestamp against last timestamp sync point in
     * units of AVCodecContext.time_base.
     *
     * Set to INT_MIN when dts_sync_point unused. Otherwise, it must
     * contain a valid timestamp offset.
     *
     * Note that the timestamp of sync point has usually a nonzero
     * dts_ref_dts_delta, which refers to the previous sync point. Offset of
     * the next frame after timestamp sync point will be usually 1.
     *
     * For example, this corresponds to H.264 cpb_removal_delay.
     */
    int dts_ref_dts_delta;

    /**
     * Presentation delay of current frame in units of AVCodecContext.time_base.
     *
     * Set to INT_MIN when dts_sync_point unused. Otherwise, it must
     * contain valid non-negative timestamp delta (presentation time of a frame
     * must not lie in the past).
     *
     * This delay represents the difference between decoding and presentation
     * time of the frame.
     *
     * For example, this corresponds to H.264 dpb_output_delay.
     */
    int pts_dts_delta;

    /**
     * Position of the packet in file.
     *
     * Analogous to cur_frame_pts/dts
     */
    int64_t cur_frame_pos[AV_PARSER_PTS_NB];

    /**
     * Byte position of currently parsed frame in stream.
     */
    int64_t pos;

    /**
     * Previous frame byte position.
     */
    int64_t last_pos;

    /**
     * Duration of the current frame.
     * For audio, this is in units of 1 / AVCodecContext.sample_rate.
     * For all other types, this is in units of AVCodecContext.time_base.
     */
    int duration;

    enum AVFieldOrder field_order;

    /**
     * Indicate whether a picture is coded as a frame, top field or bottom field.
     *
     * For example, H.264 field_pic_flag equal to 0 corresponds to
     * AV_PICTURE_STRUCTURE_FRAME. An H.264 picture with field_pic_flag
     * equal to 1 and bottom_field_flag equal to 0 corresponds to
     * AV_PICTURE_STRUCTURE_TOP_FIELD.
     */
    enum AVPictureStructure picture_structure;

    /**
     * Picture number incremented in presentation or output order.
     * This field may be reinitialized at the first picture of a new sequence.
     *
     * For example, this corresponds to H.264 PicOrderCnt.
     */
    int output_picture_number;

    /**
     * Dimensions of the decoded video intended for presentation.
     */
    int width;
    int height;

    /**
     * Dimensions of the coded video.
     */
    int coded_width;
    int coded_height;

    /**
     * The format of the coded data, corresponds to enum AVPixelFormat for video
     * and for enum AVSampleFormat for audio.
     *
     * Note that a decoder can have considerable freedom in how exactly it
     * decodes the data, so the format reported here might be different from the
     * one returned by a decoder.
     */
    int format;
} AVCodecParserContext;

typedef struct AVCodecParser {
    int codec_ids[5]; /* several codec IDs are permitted */
    int priv_data_size;
    int (*parser_init)(AVCodecParserContext *s);
    /* This callback never returns an error, a negative value means that
     * the frame start was in a previous packet. */
    int (*parser_parse)(AVCodecParserContext *s,
                        AVCodecContext *avctx,
                        const uint8_t **poutbuf, int *poutbuf_size,
                        const uint8_t *buf, int buf_size);
    void (*parser_close)(AVCodecParserContext *s);
    int (*split)(AVCodecContext *avctx, const uint8_t *buf, int buf_size);
    struct AVCodecParser *next;
} AVCodecParser;

/**
 * Iterate over all registered codec parsers.
 *
 * @param opaque a pointer where libavcodec will store the iteration state. Must
 *               point to NULL to start the iteration.
 *
 * @return the next registered codec parser or NULL when the iteration is
 *         finished
 */
const AVCodecParser *av_parser_iterate(void **opaque);

attribute_deprecated
AVCodecParser *av_parser_next(const AVCodecParser *c);

attribute_deprecated
void av_register_codec_parser(AVCodecParser *parser);
AVCodecParserContext *av_parser_init(int codec_id);

/**
 * Parse a packet.
 *
 * @param s             parser context.
 * @param avctx         codec context.
 * @param poutbuf       set to pointer to parsed buffer or NULL if not yet finished.
 * @param poutbuf_size  set to size of parsed buffer or zero if not yet finished.
 * @param buf           input buffer.
 * @param buf_size      buffer size in bytes without the padding. I.e. the full buffer
                        size is assumed to be buf_size + AV_INPUT_BUFFER_PADDING_SIZE.
                        To signal EOF, this should be 0 (so that the last frame
                        can be output).
 * @param pts           input presentation timestamp.
 * @param dts           input decoding timestamp.
 * @param pos           input byte position in stream.
 * @return the number of bytes of the input bitstream used.
 *
 * Example:
 * @code
 *   while(in_len){
 *       len = av_parser_parse2(myparser, AVCodecContext, &data, &size,
 *                                        in_data, in_len,
 *                                        pts, dts, pos);
 *       in_data += len;
 *       in_len  -= len;
 *
 *       if(size)
 *          decode_frame(data, size);
 *   }
 * @endcode
 */
int av_parser_parse2(AVCodecParserContext *s,
                     AVCodecContext *avctx,
                     uint8_t **poutbuf, int *poutbuf_size,
                     const uint8_t *buf, int buf_size,
                     int64_t pts, int64_t dts,
                     int64_t pos);

/**
 * @return 0 if the output buffer is a subset of the input, 1 if it is allocated and must be freed
 * @deprecated use AVBitStreamFilter
 */
int av_parser_change(AVCodecParserContext *s,
                     AVCodecContext *avctx,
                     uint8_t **poutbuf, int *poutbuf_size,
                     const uint8_t *buf, int buf_size, int keyframe);
void av_parser_close(AVCodecParserContext *s);

/**
 * @}
 * @}
 */

/**
 * @addtogroup lavc_encoding
 * @{
 */

/**
 * Find a registered encoder with a matching codec ID.
 *
 * @param id AVCodecID of the requested encoder
 * @return An encoder if one was found, NULL otherwise.
 */
AVCodec *avcodec_find_encoder(enum AVCodecID id);

/**
 * Find a registered encoder with the specified name.
 *
 * @param name name of the requested encoder
 * @return An encoder if one was found, NULL otherwise.
 */
AVCodec *avcodec_find_encoder_by_name(const char *name);

/**
 * Encode a frame of audio.
 *
 * Takes input samples from frame and writes the next output packet, if
 * available, to avpkt. The output packet does not necessarily contain data for
 * the most recent frame, as encoders can delay, split, and combine input frames
 * internally as needed.
 *
 * @param avctx     codec context
 * @param avpkt     output AVPacket.
 *                  The user can supply an output buffer by setting
 *                  avpkt->data and avpkt->size prior to calling the
 *                  function, but if the size of the user-provided data is not
 *                  large enough, encoding will fail. If avpkt->data and
 *                  avpkt->size are set, avpkt->destruct must also be set. All
 *                  other AVPacket fields will be reset by the encoder using
 *                  av_init_packet(). If avpkt->data is NULL, the encoder will
 *                  allocate it. The encoder will set avpkt->size to the size
 *                  of the output packet.
 *
 *                  If this function fails or produces no output, avpkt will be
 *                  freed using av_packet_unref().
 * @param[in] frame AVFrame containing the raw audio data to be encoded.
 *                  May be NULL when flushing an encoder that has the
 *                  AV_CODEC_CAP_DELAY capability set.
 *                  If AV_CODEC_CAP_VARIABLE_FRAME_SIZE is set, then each frame
 *                  can have any number of samples.
 *                  If it is not set, frame->nb_samples must be equal to
 *                  avctx->frame_size for all frames except the last.
 *                  The final frame may be smaller than avctx->frame_size.
 * @param[out] got_packet_ptr This field is set to 1 by libavcodec if the
 *                            output packet is non-empty, and to 0 if it is
 *                            empty. If the function returns an error, the
 *                            packet can be assumed to be invalid, and the
 *                            value of got_packet_ptr is undefined and should
 *                            not be used.
 * @return          0 on success, negative error code on failure
 *
 * @deprecated use avcodec_send_frame()/avcodec_receive_packet() instead
 */
attribute_deprecated
int avcodec_encode_audio2(AVCodecContext *avctx, AVPacket *avpkt,
                          const AVFrame *frame, int *got_packet_ptr);

/**
 * Encode a frame of video.
 *
 * Takes input raw video data from frame and writes the next output packet, if
 * available, to avpkt. The output packet does not necessarily contain data for
 * the most recent frame, as encoders can delay and reorder input frames
 * internally as needed.
 *
 * @param avctx     codec context
 * @param avpkt     output AVPacket.
 *                  The user can supply an output buffer by setting
 *                  avpkt->data and avpkt->size prior to calling the
 *                  function, but if the size of the user-provided data is not
 *                  large enough, encoding will fail. All other AVPacket fields
 *                  will be reset by the encoder using av_init_packet(). If
 *                  avpkt->data is NULL, the encoder will allocate it.
 *                  The encoder will set avpkt->size to the size of the
 *                  output packet. The returned data (if any) belongs to the
 *                  caller, he is responsible for freeing it.
 *
 *                  If this function fails or produces no output, avpkt will be
 *                  freed using av_packet_unref().
 * @param[in] frame AVFrame containing the raw video data to be encoded.
 *                  May be NULL when flushing an encoder that has the
 *                  AV_CODEC_CAP_DELAY capability set.
 * @param[out] got_packet_ptr This field is set to 1 by libavcodec if the
 *                            output packet is non-empty, and to 0 if it is
 *                            empty. If the function returns an error, the
 *                            packet can be assumed to be invalid, and the
 *                            value of got_packet_ptr is undefined and should
 *                            not be used.
 * @return          0 on success, negative error code on failure
 *
 * @deprecated use avcodec_send_frame()/avcodec_receive_packet() instead
 */
attribute_deprecated
int avcodec_encode_video2(AVCodecContext *avctx, AVPacket *avpkt,
                          const AVFrame *frame, int *got_packet_ptr);

int avcodec_encode_subtitle(AVCodecContext *avctx, uint8_t *buf, int buf_size,
                            const AVSubtitle *sub);


/**
 * @}
 */

#if FF_API_AVPICTURE
/**
 * @addtogroup lavc_picture
 * @{
 */

/**
 * @deprecated unused
 */
attribute_deprecated
int avpicture_alloc(AVPicture *picture, enum AVPixelFormat pix_fmt, int width, int height);

/**
 * @deprecated unused
 */
attribute_deprecated
void avpicture_free(AVPicture *picture);

/**
 * @deprecated use av_image_fill_arrays() instead.
 */
attribute_deprecated
int avpicture_fill(AVPicture *picture, const uint8_t *ptr,
                   enum AVPixelFormat pix_fmt, int width, int height);

/**
 * @deprecated use av_image_copy_to_buffer() instead.
 */
attribute_deprecated
int avpicture_layout(const AVPicture *src, enum AVPixelFormat pix_fmt,
                     int width, int height,
                     unsigned char *dest, int dest_size);

/**
 * @deprecated use av_image_get_buffer_size() instead.
 */
attribute_deprecated
int avpicture_get_size(enum AVPixelFormat pix_fmt, int width, int height);

/**
 * @deprecated av_image_copy() instead.
 */
attribute_deprecated
void av_picture_copy(AVPicture *dst, const AVPicture *src,
                     enum AVPixelFormat pix_fmt, int width, int height);

/**
 * @deprecated unused
 */
attribute_deprecated
int av_picture_crop(AVPicture *dst, const AVPicture *src,
                    enum AVPixelFormat pix_fmt, int top_band, int left_band);

/**
 * @deprecated unused
 */
attribute_deprecated
int av_picture_pad(AVPicture *dst, const AVPicture *src, int height, int width, enum AVPixelFormat pix_fmt,
            int padtop, int padbottom, int padleft, int padright, int *color);

/**
 * @}
 */
#endif

/**
 * @defgroup lavc_misc Utility functions
 * @ingroup libavc
 *
 * Miscellaneous utility functions related to both encoding and decoding
 * (or neither).
 * @{
 */

/**
 * @defgroup lavc_misc_pixfmt Pixel formats
 *
 * Functions for working with pixel formats.
 * @{
 */

#if FF_API_GETCHROMA
/**
 * @deprecated Use av_pix_fmt_get_chroma_sub_sample
 */

attribute_deprecated
void avcodec_get_chroma_sub_sample(enum AVPixelFormat pix_fmt, int *h_shift, int *v_shift);
#endif

/**
 * Return a value representing the fourCC code associated to the
 * pixel format pix_fmt, or 0 if no associated fourCC code can be
 * found.
 */
unsigned int avcodec_pix_fmt_to_codec_tag(enum AVPixelFormat pix_fmt);

/**
 * @deprecated see av_get_pix_fmt_loss()
 */
int avcodec_get_pix_fmt_loss(enum AVPixelFormat dst_pix_fmt, enum AVPixelFormat src_pix_fmt,
                             int has_alpha);

/**
 * Find the best pixel format to convert to given a certain source pixel
 * format.  When converting from one pixel format to another, information loss
 * may occur.  For example, when converting from RGB24 to GRAY, the color
 * information will be lost. Similarly, other losses occur when converting from
 * some formats to other formats. avcodec_find_best_pix_fmt_of_2() searches which of
 * the given pixel formats should be used to suffer the least amount of loss.
 * The pixel formats from which it chooses one, are determined by the
 * pix_fmt_list parameter.
 *
 *
 * @param[in] pix_fmt_list AV_PIX_FMT_NONE terminated array of pixel formats to choose from
 * @param[in] src_pix_fmt source pixel format
 * @param[in] has_alpha Whether the source pixel format alpha channel is used.
 * @param[out] loss_ptr Combination of flags informing you what kind of losses will occur.
 * @return The best pixel format to convert to or -1 if none was found.
 */
enum AVPixelFormat avcodec_find_best_pix_fmt_of_list(const enum AVPixelFormat *pix_fmt_list,
                                            enum AVPixelFormat src_pix_fmt,
                                            int has_alpha, int *loss_ptr);

/**
 * @deprecated see av_find_best_pix_fmt_of_2()
 */
enum AVPixelFormat avcodec_find_best_pix_fmt_of_2(enum AVPixelFormat dst_pix_fmt1, enum AVPixelFormat dst_pix_fmt2,
                                            enum AVPixelFormat src_pix_fmt, int has_alpha, int *loss_ptr);

attribute_deprecated
enum AVPixelFormat avcodec_find_best_pix_fmt2(enum AVPixelFormat dst_pix_fmt1, enum AVPixelFormat dst_pix_fmt2,
                                            enum AVPixelFormat src_pix_fmt, int has_alpha, int *loss_ptr);

enum AVPixelFormat avcodec_default_get_format(struct AVCodecContext *s, const enum AVPixelFormat * fmt);

/**
 * @}
 */

#if FF_API_TAG_STRING
/**
 * Put a string representing the codec tag codec_tag in buf.
 *
 * @param buf       buffer to place codec tag in
 * @param buf_size size in bytes of buf
 * @param codec_tag codec tag to assign
 * @return the length of the string that would have been generated if
 * enough space had been available, excluding the trailing null
 *
 * @deprecated see av_fourcc_make_string() and av_fourcc2str().
 */
attribute_deprecated
size_t av_get_codec_tag_string(char *buf, size_t buf_size, unsigned int codec_tag);
#endif

void avcodec_string(char *buf, int buf_size, AVCodecContext *enc, int encode);

/**
 * Return a name for the specified profile, if available.
 *
 * @param codec the codec that is searched for the given profile
 * @param profile the profile value for which a name is requested
 * @return A name for the profile if found, NULL otherwise.
 */
const char *av_get_profile_name(const AVCodec *codec, int profile);

/**
 * Return a name for the specified profile, if available.
 *
 * @param codec_id the ID of the codec to which the requested profile belongs
 * @param profile the profile value for which a name is requested
 * @return A name for the profile if found, NULL otherwise.
 *
 * @note unlike av_get_profile_name(), which searches a list of profiles
 *       supported by a specific decoder or encoder implementation, this
 *       function searches the list of profiles from the AVCodecDescriptor
 */
const char *avcodec_profile_name(enum AVCodecID codec_id, int profile);

int avcodec_default_execute(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2),void *arg, int *ret, int count, int size);
int avcodec_default_execute2(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2, int, int),void *arg, int *ret, int count);
//FIXME func typedef

/**
 * Fill AVFrame audio data and linesize pointers.
 *
 * The buffer buf must be a preallocated buffer with a size big enough
 * to contain the specified samples amount. The filled AVFrame data
 * pointers will point to this buffer.
 *
 * AVFrame extended_data channel pointers are allocated if necessary for
 * planar audio.
 *
 * @param frame       the AVFrame
 *                    frame->nb_samples must be set prior to calling the
 *                    function. This function fills in frame->data,
 *                    frame->extended_data, frame->linesize[0].
 * @param nb_channels channel count
 * @param sample_fmt  sample format
 * @param buf         buffer to use for frame data
 * @param buf_size    size of buffer
 * @param align       plane size sample alignment (0 = default)
 * @return            >=0 on success, negative error code on failure
 * @todo return the size in bytes required to store the samples in
 * case of success, at the next libavutil bump
 */
int avcodec_fill_audio_frame(AVFrame *frame, int nb_channels,
                             enum AVSampleFormat sample_fmt, const uint8_t *buf,
                             int buf_size, int align);

/**
 * Reset the internal decoder state / flush internal buffers. Should be called
 * e.g. when seeking or when switching to a different stream.
 *
 * @note when refcounted frames are not used (i.e. avctx->refcounted_frames is 0),
 * this invalidates the frames previously returned from the decoder. When
 * refcounted frames are used, the decoder just releases any references it might
 * keep internally, but the caller's reference remains valid.
 */
void avcodec_flush_buffers(AVCodecContext *avctx);

/**
 * Return codec bits per sample.
 *
 * @param[in] codec_id the codec
 * @return Number of bits per sample or zero if unknown for the given codec.
 */
int av_get_bits_per_sample(enum AVCodecID codec_id);

/**
 * Return the PCM codec associated with a sample format.
 * @param be  endianness, 0 for little, 1 for big,
 *            -1 (or anything else) for native
 * @return  AV_CODEC_ID_PCM_* or AV_CODEC_ID_NONE
 */
enum AVCodecID av_get_pcm_codec(enum AVSampleFormat fmt, int be);

/**
 * Return codec bits per sample.
 * Only return non-zero if the bits per sample is exactly correct, not an
 * approximation.
 *
 * @param[in] codec_id the codec
 * @return Number of bits per sample or zero if unknown for the given codec.
 */
int av_get_exact_bits_per_sample(enum AVCodecID codec_id);

/**
 * Return audio frame duration.
 *
 * @param avctx        codec context
 * @param frame_bytes  size of the frame, or 0 if unknown
 * @return             frame duration, in samples, if known. 0 if not able to
 *                     determine.
 */
int av_get_audio_frame_duration(AVCodecContext *avctx, int frame_bytes);

/**
 * This function is the same as av_get_audio_frame_duration(), except it works
 * with AVCodecParameters instead of an AVCodecContext.
 */
int av_get_audio_frame_duration2(AVCodecParameters *par, int frame_bytes);

#if FF_API_OLD_BSF
typedef struct AVBitStreamFilterContext {
    void *priv_data;
    const struct AVBitStreamFilter *filter;
    AVCodecParserContext *parser;
    struct AVBitStreamFilterContext *next;
    /**
     * Internal default arguments, used if NULL is passed to av_bitstream_filter_filter().
     * Not for access by library users.
     */
    char *args;
} AVBitStreamFilterContext;
#endif

typedef struct AVBSFInternal AVBSFInternal;

/**
 * The bitstream filter state.
 *
 * This struct must be allocated with av_bsf_alloc() and freed with
 * av_bsf_free().
 *
 * The fields in the struct will only be changed (by the caller or by the
 * filter) as described in their documentation, and are to be considered
 * immutable otherwise.
 */
typedef struct AVBSFContext {
    /**
     * A class for logging and AVOptions
     */
    const AVClass *av_class;

    /**
     * The bitstream filter this context is an instance of.
     */
    const struct AVBitStreamFilter *filter;

    /**
     * Opaque libavcodec internal data. Must not be touched by the caller in any
     * way.
     */
    AVBSFInternal *internal;

    /**
     * Opaque filter-specific private data. If filter->priv_class is non-NULL,
     * this is an AVOptions-enabled struct.
     */
    void *priv_data;

    /**
     * Parameters of the input stream. This field is allocated in
     * av_bsf_alloc(), it needs to be filled by the caller before
     * av_bsf_init().
     */
    AVCodecParameters *par_in;

    /**
     * Parameters of the output stream. This field is allocated in
     * av_bsf_alloc(), it is set by the filter in av_bsf_init().
     */
    AVCodecParameters *par_out;

    /**
     * The timebase used for the timestamps of the input packets. Set by the
     * caller before av_bsf_init().
     */
    AVRational time_base_in;

    /**
     * The timebase used for the timestamps of the output packets. Set by the
     * filter in av_bsf_init().
     */
    AVRational time_base_out;
} AVBSFContext;

typedef struct AVBitStreamFilter {
    const char *name;

    /**
     * A list of codec ids supported by the filter, terminated by
     * AV_CODEC_ID_NONE.
     * May be NULL, in that case the bitstream filter works with any codec id.
     */
    const enum AVCodecID *codec_ids;

    /**
     * A class for the private data, used to declare bitstream filter private
     * AVOptions. This field is NULL for bitstream filters that do not declare
     * any options.
     *
     * If this field is non-NULL, the first member of the filter private data
     * must be a pointer to AVClass, which will be set by libavcodec generic
     * code to this class.
     */
    const AVClass *priv_class;

    /*****************************************************************
     * No fields below this line are part of the public API. They
     * may not be used outside of libavcodec and can be changed and
     * removed at will.
     * New public fields should be added right above.
     *****************************************************************
     */

    int priv_data_size;
    int (*init)(AVBSFContext *ctx);
    int (*filter)(AVBSFContext *ctx, AVPacket *pkt);
    void (*close)(AVBSFContext *ctx);
    void (*flush)(AVBSFContext *ctx);
} AVBitStreamFilter;

#if FF_API_OLD_BSF
/**
 * @deprecated the old bitstream filtering API (using AVBitStreamFilterContext)
 * is deprecated. Use the new bitstream filtering API (using AVBSFContext).
 */
attribute_deprecated
void av_register_bitstream_filter(AVBitStreamFilter *bsf);
/**
 * @deprecated the old bitstream filtering API (using AVBitStreamFilterContext)
 * is deprecated. Use av_bsf_get_by_name(), av_bsf_alloc(), and av_bsf_init()
 * from the new bitstream filtering API (using AVBSFContext).
 */
attribute_deprecated
AVBitStreamFilterContext *av_bitstream_filter_init(const char *name);
/**
 * @deprecated the old bitstream filtering API (using AVBitStreamFilterContext)
 * is deprecated. Use av_bsf_send_packet() and av_bsf_receive_packet() from the
 * new bitstream filtering API (using AVBSFContext).
 */
attribute_deprecated
int av_bitstream_filter_filter(AVBitStreamFilterContext *bsfc,
                               AVCodecContext *avctx, const char *args,
                               uint8_t **poutbuf, int *poutbuf_size,
                               const uint8_t *buf, int buf_size, int keyframe);
/**
 * @deprecated the old bitstream filtering API (using AVBitStreamFilterContext)
 * is deprecated. Use av_bsf_free() from the new bitstream filtering API (using
 * AVBSFContext).
 */
attribute_deprecated
void av_bitstream_filter_close(AVBitStreamFilterContext *bsf);
/**
 * @deprecated the old bitstream filtering API (using AVBitStreamFilterContext)
 * is deprecated. Use av_bsf_iterate() from the new bitstream filtering API (using
 * AVBSFContext).
 */
attribute_deprecated
const AVBitStreamFilter *av_bitstream_filter_next(const AVBitStreamFilter *f);
#endif

/**
 * @return a bitstream filter with the specified name or NULL if no such
 *         bitstream filter exists.
 */
const AVBitStreamFilter *av_bsf_get_by_name(const char *name);

/**
 * Iterate over all registered bitstream filters.
 *
 * @param opaque a pointer where libavcodec will store the iteration state. Must
 *               point to NULL to start the iteration.
 *
 * @return the next registered bitstream filter or NULL when the iteration is
 *         finished
 */
const AVBitStreamFilter *av_bsf_iterate(void **opaque);
#if FF_API_NEXT
attribute_deprecated
const AVBitStreamFilter *av_bsf_next(void **opaque);
#endif

/**
 * Allocate a context for a given bitstream filter. The caller must fill in the
 * context parameters as described in the documentation and then call
 * av_bsf_init() before sending any data to the filter.
 *
 * @param filter the filter for which to allocate an instance.
 * @param ctx a pointer into which the pointer to the newly-allocated context
 *            will be written. It must be freed with av_bsf_free() after the
 *            filtering is done.
 *
 * @return 0 on success, a negative AVERROR code on failure
 */
int av_bsf_alloc(const AVBitStreamFilter *filter, AVBSFContext **ctx);

/**
 * Prepare the filter for use, after all the parameters and options have been
 * set.
 */
int av_bsf_init(AVBSFContext *ctx);

/**
 * Submit a packet for filtering.
 *
 * After sending each packet, the filter must be completely drained by calling
 * av_bsf_receive_packet() repeatedly until it returns AVERROR(EAGAIN) or
 * AVERROR_EOF.
 *
 * @param pkt the packet to filter. The bitstream filter will take ownership of
 * the packet and reset the contents of pkt. pkt is not touched if an error occurs.
 * This parameter may be NULL, which signals the end of the stream (i.e. no more
 * packets will be sent). That will cause the filter to output any packets it
 * may have buffered internally.
 *
 * @return 0 on success, a negative AVERROR on error.
 */
int av_bsf_send_packet(AVBSFContext *ctx, AVPacket *pkt);

/**
 * Retrieve a filtered packet.
 *
 * @param[out] pkt this struct will be filled with the contents of the filtered
 *                 packet. It is owned by the caller and must be freed using
 *                 av_packet_unref() when it is no longer needed.
 *                 This parameter should be "clean" (i.e. freshly allocated
 *                 with av_packet_alloc() or unreffed with av_packet_unref())
 *                 when this function is called. If this function returns
 *                 successfully, the contents of pkt will be completely
 *                 overwritten by the returned data. On failure, pkt is not
 *                 touched.
 *
 * @return 0 on success. AVERROR(EAGAIN) if more packets need to be sent to the
 * filter (using av_bsf_send_packet()) to get more output. AVERROR_EOF if there
 * will be no further output from the filter. Another negative AVERROR value if
 * an error occurs.
 *
 * @note one input packet may result in several output packets, so after sending
 * a packet with av_bsf_send_packet(), this function needs to be called
 * repeatedly until it stops returning 0. It is also possible for a filter to
 * output fewer packets than were sent to it, so this function may return
 * AVERROR(EAGAIN) immediately after a successful av_bsf_send_packet() call.
 */
int av_bsf_receive_packet(AVBSFContext *ctx, AVPacket *pkt);

/**
 * Reset the internal bitstream filter state / flush internal buffers.
 */
void av_bsf_flush(AVBSFContext *ctx);

/**
 * Free a bitstream filter context and everything associated with it; write NULL
 * into the supplied pointer.
 */
void av_bsf_free(AVBSFContext **ctx);

/**
 * Get the AVClass for AVBSFContext. It can be used in combination with
 * AV_OPT_SEARCH_FAKE_OBJ for examining options.
 *
 * @see av_opt_find().
 */
const AVClass *av_bsf_get_class(void);

/**
 * Structure for chain/list of bitstream filters.
 * Empty list can be allocated by av_bsf_list_alloc().
 */
typedef struct AVBSFList AVBSFList;

/**
 * Allocate empty list of bitstream filters.
 * The list must be later freed by av_bsf_list_free()
 * or finalized by av_bsf_list_finalize().
 *
 * @return Pointer to @ref AVBSFList on success, NULL in case of failure
 */
AVBSFList *av_bsf_list_alloc(void);

/**
 * Free list of bitstream filters.
 *
 * @param lst Pointer to pointer returned by av_bsf_list_alloc()
 */
void av_bsf_list_free(AVBSFList **lst);

/**
 * Append bitstream filter to the list of bitstream filters.
 *
 * @param lst List to append to
 * @param bsf Filter context to be appended
 *
 * @return >=0 on success, negative AVERROR in case of failure
 */
int av_bsf_list_append(AVBSFList *lst, AVBSFContext *bsf);

/**
 * Construct new bitstream filter context given it's name and options
 * and append it to the list of bitstream filters.
 *
 * @param lst      List to append to
 * @param bsf_name Name of the bitstream filter
 * @param options  Options for the bitstream filter, can be set to NULL
 *
 * @return >=0 on success, negative AVERROR in case of failure
 */
int av_bsf_list_append2(AVBSFList *lst, const char * bsf_name, AVDictionary **options);
/**
 * Finalize list of bitstream filters.
 *
 * This function will transform @ref AVBSFList to single @ref AVBSFContext,
 * so the whole chain of bitstream filters can be treated as single filter
 * freshly allocated by av_bsf_alloc().
 * If the call is successful, @ref AVBSFList structure is freed and lst
 * will be set to NULL. In case of failure, caller is responsible for
 * freeing the structure by av_bsf_list_free()
 *
 * @param      lst Filter list structure to be transformed
 * @param[out] bsf Pointer to be set to newly created @ref AVBSFContext structure
 *                 representing the chain of bitstream filters
 *
 * @return >=0 on success, negative AVERROR in case of failure
 */
int av_bsf_list_finalize(AVBSFList **lst, AVBSFContext **bsf);

/**
 * Parse string describing list of bitstream filters and create single
 * @ref AVBSFContext describing the whole chain of bitstream filters.
 * Resulting @ref AVBSFContext can be treated as any other @ref AVBSFContext freshly
 * allocated by av_bsf_alloc().
 *
 * @param      str String describing chain of bitstream filters in format
 *                 `bsf1[=opt1=val1:opt2=val2][,bsf2]`
 * @param[out] bsf Pointer to be set to newly created @ref AVBSFContext structure
 *                 representing the chain of bitstream filters
 *
 * @return >=0 on success, negative AVERROR in case of failure
 */
int av_bsf_list_parse_str(const char *str, AVBSFContext **bsf);

/**
 * Get null/pass-through bitstream filter.
 *
 * @param[out] bsf Pointer to be set to new instance of pass-through bitstream filter
 *
 * @return
 */
int av_bsf_get_null_filter(AVBSFContext **bsf);

/* memory */

/**
 * Same behaviour av_fast_malloc but the buffer has additional
 * AV_INPUT_BUFFER_PADDING_SIZE at the end which will always be 0.
 *
 * In addition the whole buffer will initially and after resizes
 * be 0-initialized so that no uninitialized data will ever appear.
 */
void av_fast_padded_malloc(void *ptr, unsigned int *size, size_t min_size);

/**
 * Same behaviour av_fast_padded_malloc except that buffer will always
 * be 0-initialized after call.
 */
void av_fast_padded_mallocz(void *ptr, unsigned int *size, size_t min_size);

/**
 * Encode extradata length to a buffer. Used by xiph codecs.
 *
 * @param s buffer to write to; must be at least (v/255+1) bytes long
 * @param v size of extradata in bytes
 * @return number of bytes written to the buffer.
 */
unsigned int av_xiphlacing(unsigned char *s, unsigned int v);

#if FF_API_USER_VISIBLE_AVHWACCEL
/**
 * Register the hardware accelerator hwaccel.
 *
 * @deprecated  This function doesn't do anything.
 */
attribute_deprecated
void av_register_hwaccel(AVHWAccel *hwaccel);

/**
 * If hwaccel is NULL, returns the first registered hardware accelerator,
 * if hwaccel is non-NULL, returns the next registered hardware accelerator
 * after hwaccel, or NULL if hwaccel is the last one.
 *
 * @deprecated  AVHWaccel structures contain no user-serviceable parts, so
 *              this function should not be used.
 */
attribute_deprecated
AVHWAccel *av_hwaccel_next(const AVHWAccel *hwaccel);
#endif

#if FF_API_LOCKMGR
/**
 * Lock operation used by lockmgr
 *
 * @deprecated Deprecated together with av_lockmgr_register().
 */
enum AVLockOp {
  AV_LOCK_CREATE,  ///< Create a mutex
  AV_LOCK_OBTAIN,  ///< Lock the mutex
  AV_LOCK_RELEASE, ///< Unlock the mutex
  AV_LOCK_DESTROY, ///< Free mutex resources
};

/**
 * Register a user provided lock manager supporting the operations
 * specified by AVLockOp. The "mutex" argument to the function points
 * to a (void *) where the lockmgr should store/get a pointer to a user
 * allocated mutex. It is NULL upon AV_LOCK_CREATE and equal to the
 * value left by the last call for all other ops. If the lock manager is
 * unable to perform the op then it should leave the mutex in the same
 * state as when it was called and return a non-zero value. However,
 * when called with AV_LOCK_DESTROY the mutex will always be assumed to
 * have been successfully destroyed. If av_lockmgr_register succeeds
 * it will return a non-negative value, if it fails it will return a
 * negative value and destroy all mutex and unregister all callbacks.
 * av_lockmgr_register is not thread-safe, it must be called from a
 * single thread before any calls which make use of locking are used.
 *
 * @param cb User defined callback. av_lockmgr_register invokes calls
 *           to this callback and the previously registered callback.
 *           The callback will be used to create more than one mutex
 *           each of which must be backed by its own underlying locking
 *           mechanism (i.e. do not use a single static object to
 *           implement your lock manager). If cb is set to NULL the
 *           lockmgr will be unregistered.
 *
 * @deprecated This function does nothing, and always returns 0. Be sure to
 *             build with thread support to get basic thread safety.
 */
attribute_deprecated
int av_lockmgr_register(int (*cb)(void **mutex, enum AVLockOp op));
#endif

/**
 * Get the type of the given codec.
 */
enum AVMediaType avcodec_get_type(enum AVCodecID codec_id);

/**
 * Get the name of a codec.
 * @return  a static string identifying the codec; never NULL
 */
const char *avcodec_get_name(enum AVCodecID id);

/**
 * @return a positive value if s is open (i.e. avcodec_open2() was called on it
 * with no corresponding avcodec_close()), 0 otherwise.
 */
int avcodec_is_open(AVCodecContext *s);

/**
 * @return a non-zero number if codec is an encoder, zero otherwise
 */
int av_codec_is_encoder(const AVCodec *codec);

/**
 * @return a non-zero number if codec is a decoder, zero otherwise
 */
int av_codec_is_decoder(const AVCodec *codec);

/**
 * @return descriptor for given codec ID or NULL if no descriptor exists.
 */
const AVCodecDescriptor *avcodec_descriptor_get(enum AVCodecID id);

/**
 * Iterate over all codec descriptors known to libavcodec.
 *
 * @param prev previous descriptor. NULL to get the first descriptor.
 *
 * @return next descriptor or NULL after the last descriptor
 */
const AVCodecDescriptor *avcodec_descriptor_next(const AVCodecDescriptor *prev);

/**
 * @return codec descriptor with the given name or NULL if no such descriptor
 *         exists.
 */
const AVCodecDescriptor *avcodec_descriptor_get_by_name(const char *name);

/**
 * Allocate a CPB properties structure and initialize its fields to default
 * values.
 *
 * @param size if non-NULL, the size of the allocated struct will be written
 *             here. This is useful for embedding it in side data.
 *
 * @return the newly allocated struct or NULL on failure
 */
AVCPBProperties *av_cpb_properties_alloc(size_t *size);

/**
 * @}
 */

#endif /* AVCODEC_AVCODEC_H */