2 * Copyright (c) 2012 Stefano Sabatini
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25 * Demuxing and decoding example.
27 * Show how to use the libavformat and libavcodec API to demux and
28 * decode audio and video data.
29 * @example demuxing_decoding.c
32 #include <libavutil/imgutils.h>
33 #include <libavutil/samplefmt.h>
34 #include <libavutil/timestamp.h>
35 #include <libavformat/avformat.h>
37 static AVFormatContext *fmt_ctx = NULL;
38 static AVCodecContext *video_dec_ctx = NULL, *audio_dec_ctx;
39 static int width, height;
40 static enum AVPixelFormat pix_fmt;
41 static AVStream *video_stream = NULL, *audio_stream = NULL;
42 static const char *src_filename = NULL;
43 static const char *video_dst_filename = NULL;
44 static const char *audio_dst_filename = NULL;
45 static FILE *video_dst_file = NULL;
46 static FILE *audio_dst_file = NULL;
48 static uint8_t *video_dst_data[4] = {NULL};
49 static int video_dst_linesize[4];
50 static int video_dst_bufsize;
52 static int video_stream_idx = -1, audio_stream_idx = -1;
53 static AVFrame *frame = NULL;
55 static int video_frame_count = 0;
56 static int audio_frame_count = 0;
58 static int decode_packet(int *got_frame, int cached)
61 int decoded = pkt.size;
65 if (pkt.stream_index == video_stream_idx) {
66 /* decode video frame */
67 ret = avcodec_decode_video2(video_dec_ctx, frame, got_frame, &pkt);
69 fprintf(stderr, "Error decoding video frame (%s)\n", av_err2str(ret));
75 if (frame->width != width || frame->height != height ||
76 frame->format != pix_fmt) {
77 /* To handle this change, one could call av_image_alloc again and
78 * decode the following frames into another rawvideo file. */
79 fprintf(stderr, "Error: Width, height and pixel format have to be "
80 "constant in a rawvideo file, but the width, height or "
81 "pixel format of the input video changed:\n"
82 "old: width = %d, height = %d, format = %s\n"
83 "new: width = %d, height = %d, format = %s\n",
84 width, height, av_get_pix_fmt_name(pix_fmt),
85 frame->width, frame->height,
86 av_get_pix_fmt_name(frame->format));
90 printf("video_frame%s n:%d coded_n:%d\n",
91 cached ? "(cached)" : "",
92 video_frame_count++, frame->coded_picture_number);
94 /* copy decoded frame to destination buffer:
95 * this is required since rawvideo expects non aligned data */
96 av_image_copy(video_dst_data, video_dst_linesize,
97 (const uint8_t **)(frame->data), frame->linesize,
98 pix_fmt, width, height);
100 /* write to rawvideo file */
101 fwrite(video_dst_data[0], 1, video_dst_bufsize, video_dst_file);
103 } else if (pkt.stream_index == audio_stream_idx) {
104 /* decode audio frame */
105 ret = avcodec_decode_audio4(audio_dec_ctx, frame, got_frame, &pkt);
107 fprintf(stderr, "Error decoding audio frame (%s)\n", av_err2str(ret));
110 /* Some audio decoders decode only part of the packet, and have to be
111 * called again with the remainder of the packet data.
112 * Sample: fate-suite/lossless-audio/luckynight-partial.shn
113 * Also, some decoders might over-read the packet. */
114 decoded = FFMIN(ret, pkt.size);
117 size_t unpadded_linesize = frame->nb_samples * av_get_bytes_per_sample(frame->format);
118 printf("audio_frame%s n:%d nb_samples:%d pts:%s\n",
119 cached ? "(cached)" : "",
120 audio_frame_count++, frame->nb_samples,
121 av_ts2timestr(frame->pts, &audio_dec_ctx->time_base));
123 /* Write the raw audio data samples of the first plane. This works
124 * fine for packed formats (e.g. AV_SAMPLE_FMT_S16). However,
125 * most audio decoders output planar audio, which uses a separate
126 * plane of audio samples for each channel (e.g. AV_SAMPLE_FMT_S16P).
127 * In other words, this code will write only the first audio channel
129 * You should use libswresample or libavfilter to convert the frame
131 fwrite(frame->extended_data[0], 1, unpadded_linesize, audio_dst_file);
136 av_frame_unref(frame);
141 static int open_codec_context(int *stream_idx,
142 AVCodecContext **dec_ctx, AVFormatContext *fmt_ctx, enum AVMediaType type)
144 int ret, stream_index;
147 AVDictionary *opts = NULL;
149 ret = av_find_best_stream(fmt_ctx, type, -1, -1, NULL, 0);
151 fprintf(stderr, "Could not find %s stream in input file '%s'\n",
152 av_get_media_type_string(type), src_filename);
156 st = fmt_ctx->streams[stream_index];
158 /* find decoder for the stream */
159 dec = avcodec_find_decoder(st->codecpar->codec_id);
161 fprintf(stderr, "Failed to find %s codec\n",
162 av_get_media_type_string(type));
163 return AVERROR(EINVAL);
166 /* Allocate a codec context for the decoder */
167 *dec_ctx = avcodec_alloc_context3(dec);
169 fprintf(stderr, "Failed to allocate the %s codec context\n",
170 av_get_media_type_string(type));
171 return AVERROR(ENOMEM);
174 /* Copy codec parameters from input stream to output codec context */
175 if ((ret = avcodec_parameters_to_context(*dec_ctx, st->codecpar)) < 0) {
176 fprintf(stderr, "Failed to copy %s codec parameters to decoder context\n",
177 av_get_media_type_string(type));
181 /* Init the decoders */
182 if ((ret = avcodec_open2(*dec_ctx, dec, &opts)) < 0) {
183 fprintf(stderr, "Failed to open %s codec\n",
184 av_get_media_type_string(type));
187 *stream_idx = stream_index;
193 static int get_format_from_sample_fmt(const char **fmt,
194 enum AVSampleFormat sample_fmt)
197 struct sample_fmt_entry {
198 enum AVSampleFormat sample_fmt; const char *fmt_be, *fmt_le;
199 } sample_fmt_entries[] = {
200 { AV_SAMPLE_FMT_U8, "u8", "u8" },
201 { AV_SAMPLE_FMT_S16, "s16be", "s16le" },
202 { AV_SAMPLE_FMT_S32, "s32be", "s32le" },
203 { AV_SAMPLE_FMT_FLT, "f32be", "f32le" },
204 { AV_SAMPLE_FMT_DBL, "f64be", "f64le" },
208 for (i = 0; i < FF_ARRAY_ELEMS(sample_fmt_entries); i++) {
209 struct sample_fmt_entry *entry = &sample_fmt_entries[i];
210 if (sample_fmt == entry->sample_fmt) {
211 *fmt = AV_NE(entry->fmt_be, entry->fmt_le);
217 "sample format %s is not supported as output format\n",
218 av_get_sample_fmt_name(sample_fmt));
222 int main (int argc, char **argv)
224 int ret = 0, got_frame;
227 fprintf(stderr, "usage: %s input_file video_output_file audio_output_file\n"
228 "API example program to show how to read frames from an input file.\n"
229 "This program reads frames from a file, decodes them, and writes decoded\n"
230 "video frames to a rawvideo file named video_output_file, and decoded\n"
231 "audio frames to a rawaudio file named audio_output_file.\n",
235 src_filename = argv[1];
236 video_dst_filename = argv[2];
237 audio_dst_filename = argv[3];
239 /* open input file, and allocate format context */
240 if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0) {
241 fprintf(stderr, "Could not open source file %s\n", src_filename);
245 /* retrieve stream information */
246 if (avformat_find_stream_info(fmt_ctx, NULL) < 0) {
247 fprintf(stderr, "Could not find stream information\n");
251 if (open_codec_context(&video_stream_idx, &video_dec_ctx, fmt_ctx, AVMEDIA_TYPE_VIDEO) >= 0) {
252 video_stream = fmt_ctx->streams[video_stream_idx];
254 video_dst_file = fopen(video_dst_filename, "wb");
255 if (!video_dst_file) {
256 fprintf(stderr, "Could not open destination file %s\n", video_dst_filename);
261 /* allocate image where the decoded image will be put */
262 width = video_dec_ctx->width;
263 height = video_dec_ctx->height;
264 pix_fmt = video_dec_ctx->pix_fmt;
265 ret = av_image_alloc(video_dst_data, video_dst_linesize,
266 width, height, pix_fmt, 1);
268 fprintf(stderr, "Could not allocate raw video buffer\n");
271 video_dst_bufsize = ret;
274 if (open_codec_context(&audio_stream_idx, &audio_dec_ctx, fmt_ctx, AVMEDIA_TYPE_AUDIO) >= 0) {
275 audio_stream = fmt_ctx->streams[audio_stream_idx];
276 audio_dst_file = fopen(audio_dst_filename, "wb");
277 if (!audio_dst_file) {
278 fprintf(stderr, "Could not open destination file %s\n", audio_dst_filename);
284 /* dump input information to stderr */
285 av_dump_format(fmt_ctx, 0, src_filename, 0);
287 if (!audio_stream && !video_stream) {
288 fprintf(stderr, "Could not find audio or video stream in the input, aborting\n");
293 frame = av_frame_alloc();
295 fprintf(stderr, "Could not allocate frame\n");
296 ret = AVERROR(ENOMEM);
300 /* initialize packet, set data to NULL, let the demuxer fill it */
301 av_init_packet(&pkt);
306 printf("Demuxing video from file '%s' into '%s'\n", src_filename, video_dst_filename);
308 printf("Demuxing audio from file '%s' into '%s'\n", src_filename, audio_dst_filename);
310 /* read frames from the file */
311 while (av_read_frame(fmt_ctx, &pkt) >= 0) {
312 AVPacket orig_pkt = pkt;
314 ret = decode_packet(&got_frame, 0);
319 } while (pkt.size > 0);
320 av_packet_unref(&orig_pkt);
323 /* flush cached frames */
327 decode_packet(&got_frame, 1);
330 printf("Demuxing succeeded.\n");
333 printf("Play the output video file with the command:\n"
334 "ffplay -f rawvideo -pix_fmt %s -video_size %dx%d %s\n",
335 av_get_pix_fmt_name(pix_fmt), width, height,
340 enum AVSampleFormat sfmt = audio_dec_ctx->sample_fmt;
341 int n_channels = audio_dec_ctx->channels;
344 if (av_sample_fmt_is_planar(sfmt)) {
345 const char *packed = av_get_sample_fmt_name(sfmt);
346 printf("Warning: the sample format the decoder produced is planar "
347 "(%s). This example will output the first channel only.\n",
348 packed ? packed : "?");
349 sfmt = av_get_packed_sample_fmt(sfmt);
353 if ((ret = get_format_from_sample_fmt(&fmt, sfmt)) < 0)
356 printf("Play the output audio file with the command:\n"
357 "ffplay -f %s -ac %d -ar %d %s\n",
358 fmt, n_channels, audio_dec_ctx->sample_rate,
363 avcodec_free_context(&video_dec_ctx);
364 avcodec_free_context(&audio_dec_ctx);
365 avformat_close_input(&fmt_ctx);
367 fclose(video_dst_file);
369 fclose(audio_dst_file);
370 av_frame_free(&frame);
371 av_free(video_dst_data[0]);