* set by user for input, always set by user for output (unless you are dealing
* with an AVFMT_NOFILE format).
*
+ * @section lavf_options Passing options to (de)muxers
+ * Lavf allows to configure muxers and demuxers using the @ref avoptions
+ * mechanism. Generic (format-independent) libavformat options are provided by
+ * AVFormatContext, they can be examined from a user program by calling
+ * av_opt_next() / av_opt_find() on an allocated AVFormatContext (or its AVClass
+ * from avformat_get_class()). Private (format-specific) options are provided by
+ * AVFormatContext.priv_data if and only if AVInputFormat.priv_class /
+ * AVOutputFormat.priv_class of the corresponding format struct is non-NULL.
+ * Further options may be provided by the @ref AVFormatContext.pb "I/O context",
+ * if its AVClass is non-NULL, and the protocols layer. See the discussion on
+ * nesting in @ref avoptions documentation to learn how to access those.
+ *
* @defgroup lavf_decoding Demuxing
* @{
* Demuxers read a media file and split it into chunks of data (@em packets). A
* your reading callbacks to it. Then set the @em pb field of your
* AVFormatContext to newly created AVIOContext.
*
+ * Since the format of the opened file is in general not known until after
+ * avformat_open_input() has returned, it is not possible to set demuxer private
+ * options on a preallocated context. Instead, the options should be passed to
+ * avformat_open_input() wrapped in an AVDictionary:
+ * @code
+ * AVDictionary *options = NULL;
+ * av_dict_set(&options, "video_size", "640x480", 0);
+ * av_dict_set(&options, "pixel_format", "rgb24", 0);
+ *
+ * if (avformat_open_input(&s, url, NULL, &options) < 0)
+ * abort();
+ * av_dict_free(&options);
+ * @endcode
+ * This code passes the private options 'video_size' and 'pixel_format' to the
+ * demuxer. They would be necessary for e.g. the rawvideo demuxer, since it
+ * cannot know how to interpret raw video data otherwise. If the format turns
+ * out to be something different than raw video, those options will not be
+ * recognized by the demuxer and therefore will not be applied. Such unrecognized
+ * options are then returned in the options dictionary (recognized options are
+ * consumed). The calling program can handle such unrecognized options as it
+ * wishes, e.g.
+ * @code
+ * AVDictionaryEntry *e;
+ * if (e = av_dict_get(options, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
+ * fprintf(stderr, "Option %s not recognized by the demuxer.\n", e->key);
+ * abort();
+ * }
+ * @endcode
+ *
* After you have finished reading the file, you must close it with
* avformat_close_input(). It will free everything associated with the file.
*
* @section lavf_decoding_read Reading from an opened file
+ * Reading data from an opened AVFormatContext is done by repeatedly calling
+ * av_read_frame() on it. Each call, if successful, will return an AVPacket
+ * containing encoded data for one AVStream, identified by
+ * AVPacket.stream_index. This packet may be passed straight into the libavcodec
+ * decoding functions avcodec_decode_video2(), avcodec_decode_audio4() or
+ * avcodec_decode_subtitle2() if the caller wishes to decode the data.
+ *
+ * AVPacket.pts, AVPacket.dts and AVPacket.duration timing information will be
+ * set if known. They may also be unset (i.e. AV_NOPTS_VALUE for
+ * pts/dts, 0 for duration) if the stream does not provide them. The timing
+ * information will be in AVStream.time_base units, i.e. it has to be
+ * multiplied by the timebase to convert them to seconds.
+ *
+ * The packet data belongs to the demuxer and is invalid after the next call to
+ * av_read_frame(). The user must free the packet with av_free_packet() before
+ * calling av_read_frame() again or closing the file.
*
* @section lavf_decoding_seek Seeking
* @}
#define AVFMT_NOGENSEARCH 0x4000 /**< Format does not allow to fallback to generic search */
#define AVFMT_NO_BYTE_SEEK 0x8000 /**< Format does not allow seeking by bytes */
#define AVFMT_ALLOW_FLUSH 0x10000 /**< Format allows flushing. If not set, the muxer will not receive a NULL packet in the write_packet function. */
+#define AVFMT_TS_NONSTRICT 0x20000 /**< Format does not require strictly
+ increasing timestamps, but they must
+ still be monotonic */
/**
* @addtogroup lavf_encoding
/**
* can use flags: AVFMT_NOFILE, AVFMT_NEEDNUMBER, AVFMT_RAWPICTURE,
* AVFMT_GLOBALHEADER, AVFMT_NOTIMESTAMPS, AVFMT_VARIABLE_FPS,
- * AVFMT_NODIMENSIONS, AVFMT_NOSTREAMS, AVFMT_ALLOW_FLUSH
+ * AVFMT_NODIMENSIONS, AVFMT_NOSTREAMS, AVFMT_ALLOW_FLUSH,
+ * AVFMT_TS_NONSTRICT
*/
int flags;
* encoding: set by the user
*/
int id;
- AVCodecContext *codec; /**< codec context */
+ /**
+ * Codec context associated with this stream. Allocated and freed by
+ * libavformat.
+ *
+ * - decoding: The demuxer exports codec information stored in the headers
+ * here.
+ * - encoding: The user sets codec information, the muxer writes it to the
+ * output. Mandatory fields as specified in AVCodecContext
+ * documentation must be set even if this AVCodecContext is
+ * not actually used for encoding.
+ */
+ AVCodecContext *codec;
/**
* Real base framerate of the stream.
* This is the lowest framerate with which all timestamps can be
/**
* This is the fundamental unit of time (in seconds) in terms
- * of which frame timestamps are represented. For fixed-fps content,
- * time base should be 1/framerate and timestamp increments should be 1.
+ * of which frame timestamps are represented.
+ *
* decoding: set by libavformat
- * encoding: set by libavformat in av_write_header
+ * encoding: set by libavformat in av_write_header. The muxer may use the
+ * user-provided value of @ref AVCodecContext.time_base "codec->time_base"
+ * as a hint.
*/
AVRational time_base;
*/
void *priv_data;
- /*
+ /**
* I/O context.
*
* decoding: either set by the user before avformat_open_input() (then
* @param s media file handle
* @param pkt The packet containing the data to be written. Libavformat takes
* ownership of the data and will free it when it sees fit using the packet's
+ * This can be NULL (at any time, not just at the end), to flush the
+ * interleaving queues.
* @ref AVPacket.destruct "destruct" field. The caller must not access the data
* after this function returns, as it may already be freed.
* Packet's @ref AVPacket.stream_index "stream_index" field must be set to the
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