FFmpeg 4.2.2
demuxing_decoding.c
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1/*
2 * Copyright (c) 2012 Stefano Sabatini
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a copy
5 * of this software and associated documentation files (the "Software"), to deal
6 * in the Software without restriction, including without limitation the rights
7 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8 * copies of the Software, and to permit persons to whom the Software is
9 * furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice shall be included in
12 * all copies or substantial portions of the Software.
13 *
14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
17 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
20 * THE SOFTWARE.
21 */
22
23/**
24 * @file
25 * Demuxing and decoding example.
26 *
27 * Show how to use the libavformat and libavcodec API to demux and
28 * decode audio and video data.
29 * @example demuxing_decoding.c
30 */
31
32#include <libavutil/imgutils.h>
33#include <libavutil/samplefmt.h>
34#include <libavutil/timestamp.h>
36
37static AVFormatContext *fmt_ctx = NULL;
39static int width, height;
41static AVStream *video_stream = NULL, *audio_stream = NULL;
42static const char *src_filename = NULL;
43static const char *video_dst_filename = NULL;
44static const char *audio_dst_filename = NULL;
45static FILE *video_dst_file = NULL;
46static FILE *audio_dst_file = NULL;
47
48static uint8_t *video_dst_data[4] = {NULL};
49static int video_dst_linesize[4];
51
52static int video_stream_idx = -1, audio_stream_idx = -1;
53static AVFrame *frame = NULL;
55static int video_frame_count = 0;
56static int audio_frame_count = 0;
57
58/* Enable or disable frame reference counting. You are not supposed to support
59 * both paths in your application but pick the one most appropriate to your
60 * needs. Look for the use of refcount in this example to see what are the
61 * differences of API usage between them. */
62static int refcount = 0;
63
64static int decode_packet(int *got_frame, int cached)
65{
66 int ret = 0;
67 int decoded = pkt.size;
68
69 *got_frame = 0;
70
72 /* decode video frame */
73 ret = avcodec_decode_video2(video_dec_ctx, frame, got_frame, &pkt);
74 if (ret < 0) {
75 fprintf(stderr, "Error decoding video frame (%s)\n", av_err2str(ret));
76 return ret;
77 }
78
79 if (*got_frame) {
80
81 if (frame->width != width || frame->height != height ||
82 frame->format != pix_fmt) {
83 /* To handle this change, one could call av_image_alloc again and
84 * decode the following frames into another rawvideo file. */
85 fprintf(stderr, "Error: Width, height and pixel format have to be "
86 "constant in a rawvideo file, but the width, height or "
87 "pixel format of the input video changed:\n"
88 "old: width = %d, height = %d, format = %s\n"
89 "new: width = %d, height = %d, format = %s\n",
93 return -1;
94 }
95
96 printf("video_frame%s n:%d coded_n:%d\n",
97 cached ? "(cached)" : "",
99
100 /* copy decoded frame to destination buffer:
101 * this is required since rawvideo expects non aligned data */
103 (const uint8_t **)(frame->data), frame->linesize,
105
106 /* write to rawvideo file */
108 }
109 } else if (pkt.stream_index == audio_stream_idx) {
110 /* decode audio frame */
111 ret = avcodec_decode_audio4(audio_dec_ctx, frame, got_frame, &pkt);
112 if (ret < 0) {
113 fprintf(stderr, "Error decoding audio frame (%s)\n", av_err2str(ret));
114 return ret;
115 }
116 /* Some audio decoders decode only part of the packet, and have to be
117 * called again with the remainder of the packet data.
118 * Sample: fate-suite/lossless-audio/luckynight-partial.shn
119 * Also, some decoders might over-read the packet. */
120 decoded = FFMIN(ret, pkt.size);
121
122 if (*got_frame) {
123 size_t unpadded_linesize = frame->nb_samples * av_get_bytes_per_sample(frame->format);
124 printf("audio_frame%s n:%d nb_samples:%d pts:%s\n",
125 cached ? "(cached)" : "",
128
129 /* Write the raw audio data samples of the first plane. This works
130 * fine for packed formats (e.g. AV_SAMPLE_FMT_S16). However,
131 * most audio decoders output planar audio, which uses a separate
132 * plane of audio samples for each channel (e.g. AV_SAMPLE_FMT_S16P).
133 * In other words, this code will write only the first audio channel
134 * in these cases.
135 * You should use libswresample or libavfilter to convert the frame
136 * to packed data. */
137 fwrite(frame->extended_data[0], 1, unpadded_linesize, audio_dst_file);
138 }
139 }
140
141 /* If we use frame reference counting, we own the data and need
142 * to de-reference it when we don't use it anymore */
143 if (*got_frame && refcount)
145
146 return decoded;
147}
148
149static int open_codec_context(int *stream_idx,
151{
152 int ret, stream_index;
153 AVStream *st;
154 AVCodec *dec = NULL;
155 AVDictionary *opts = NULL;
156
157 ret = av_find_best_stream(fmt_ctx, type, -1, -1, NULL, 0);
158 if (ret < 0) {
159 fprintf(stderr, "Could not find %s stream in input file '%s'\n",
161 return ret;
162 } else {
163 stream_index = ret;
164 st = fmt_ctx->streams[stream_index];
165
166 /* find decoder for the stream */
168 if (!dec) {
169 fprintf(stderr, "Failed to find %s codec\n",
171 return AVERROR(EINVAL);
172 }
173
174 /* Allocate a codec context for the decoder */
176 if (!*dec_ctx) {
177 fprintf(stderr, "Failed to allocate the %s codec context\n",
179 return AVERROR(ENOMEM);
180 }
181
182 /* Copy codec parameters from input stream to output codec context */
183 if ((ret = avcodec_parameters_to_context(*dec_ctx, st->codecpar)) < 0) {
184 fprintf(stderr, "Failed to copy %s codec parameters to decoder context\n",
186 return ret;
187 }
188
189 /* Init the decoders, with or without reference counting */
190 av_dict_set(&opts, "refcounted_frames", refcount ? "1" : "0", 0);
191 if ((ret = avcodec_open2(*dec_ctx, dec, &opts)) < 0) {
192 fprintf(stderr, "Failed to open %s codec\n",
194 return ret;
195 }
196 *stream_idx = stream_index;
197 }
198
199 return 0;
200}
201
202static int get_format_from_sample_fmt(const char **fmt,
203 enum AVSampleFormat sample_fmt)
204{
205 int i;
206 struct sample_fmt_entry {
207 enum AVSampleFormat sample_fmt; const char *fmt_be, *fmt_le;
208 } sample_fmt_entries[] = {
209 { AV_SAMPLE_FMT_U8, "u8", "u8" },
210 { AV_SAMPLE_FMT_S16, "s16be", "s16le" },
211 { AV_SAMPLE_FMT_S32, "s32be", "s32le" },
212 { AV_SAMPLE_FMT_FLT, "f32be", "f32le" },
213 { AV_SAMPLE_FMT_DBL, "f64be", "f64le" },
214 };
215 *fmt = NULL;
216
217 for (i = 0; i < FF_ARRAY_ELEMS(sample_fmt_entries); i++) {
218 struct sample_fmt_entry *entry = &sample_fmt_entries[i];
219 if (sample_fmt == entry->sample_fmt) {
220 *fmt = AV_NE(entry->fmt_be, entry->fmt_le);
221 return 0;
222 }
223 }
224
225 fprintf(stderr,
226 "sample format %s is not supported as output format\n",
227 av_get_sample_fmt_name(sample_fmt));
228 return -1;
229}
230
231int main (int argc, char **argv)
232{
233 int ret = 0, got_frame;
234
235 if (argc != 4 && argc != 5) {
236 fprintf(stderr, "usage: %s [-refcount] input_file video_output_file audio_output_file\n"
237 "API example program to show how to read frames from an input file.\n"
238 "This program reads frames from a file, decodes them, and writes decoded\n"
239 "video frames to a rawvideo file named video_output_file, and decoded\n"
240 "audio frames to a rawaudio file named audio_output_file.\n\n"
241 "If the -refcount option is specified, the program use the\n"
242 "reference counting frame system which allows keeping a copy of\n"
243 "the data for longer than one decode call.\n"
244 "\n", argv[0]);
245 exit(1);
246 }
247 if (argc == 5 && !strcmp(argv[1], "-refcount")) {
248 refcount = 1;
249 argv++;
250 }
251 src_filename = argv[1];
252 video_dst_filename = argv[2];
253 audio_dst_filename = argv[3];
254
255 /* open input file, and allocate format context */
256 if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0) {
257 fprintf(stderr, "Could not open source file %s\n", src_filename);
258 exit(1);
259 }
260
261 /* retrieve stream information */
262 if (avformat_find_stream_info(fmt_ctx, NULL) < 0) {
263 fprintf(stderr, "Could not find stream information\n");
264 exit(1);
265 }
266
269
270 video_dst_file = fopen(video_dst_filename, "wb");
271 if (!video_dst_file) {
272 fprintf(stderr, "Could not open destination file %s\n", video_dst_filename);
273 ret = 1;
274 goto end;
275 }
276
277 /* allocate image where the decoded image will be put */
282 width, height, pix_fmt, 1);
283 if (ret < 0) {
284 fprintf(stderr, "Could not allocate raw video buffer\n");
285 goto end;
286 }
287 video_dst_bufsize = ret;
288 }
289
292 audio_dst_file = fopen(audio_dst_filename, "wb");
293 if (!audio_dst_file) {
294 fprintf(stderr, "Could not open destination file %s\n", audio_dst_filename);
295 ret = 1;
296 goto end;
297 }
298 }
299
300 /* dump input information to stderr */
302
303 if (!audio_stream && !video_stream) {
304 fprintf(stderr, "Could not find audio or video stream in the input, aborting\n");
305 ret = 1;
306 goto end;
307 }
308
310 if (!frame) {
311 fprintf(stderr, "Could not allocate frame\n");
312 ret = AVERROR(ENOMEM);
313 goto end;
314 }
315
316 /* initialize packet, set data to NULL, let the demuxer fill it */
318 pkt.data = NULL;
319 pkt.size = 0;
320
321 if (video_stream)
322 printf("Demuxing video from file '%s' into '%s'\n", src_filename, video_dst_filename);
323 if (audio_stream)
324 printf("Demuxing audio from file '%s' into '%s'\n", src_filename, audio_dst_filename);
325
326 /* read frames from the file */
327 while (av_read_frame(fmt_ctx, &pkt) >= 0) {
328 AVPacket orig_pkt = pkt;
329 do {
330 ret = decode_packet(&got_frame, 0);
331 if (ret < 0)
332 break;
333 pkt.data += ret;
334 pkt.size -= ret;
335 } while (pkt.size > 0);
336 av_packet_unref(&orig_pkt);
337 }
338
339 /* flush cached frames */
340 pkt.data = NULL;
341 pkt.size = 0;
342 do {
343 decode_packet(&got_frame, 1);
344 } while (got_frame);
345
346 printf("Demuxing succeeded.\n");
347
348 if (video_stream) {
349 printf("Play the output video file with the command:\n"
350 "ffplay -f rawvideo -pix_fmt %s -video_size %dx%d %s\n",
353 }
354
355 if (audio_stream) {
357 int n_channels = audio_dec_ctx->channels;
358 const char *fmt;
359
360 if (av_sample_fmt_is_planar(sfmt)) {
361 const char *packed = av_get_sample_fmt_name(sfmt);
362 printf("Warning: the sample format the decoder produced is planar "
363 "(%s). This example will output the first channel only.\n",
364 packed ? packed : "?");
365 sfmt = av_get_packed_sample_fmt(sfmt);
366 n_channels = 1;
367 }
368
369 if ((ret = get_format_from_sample_fmt(&fmt, sfmt)) < 0)
370 goto end;
371
372 printf("Play the output audio file with the command:\n"
373 "ffplay -f %s -ac %d -ar %d %s\n",
374 fmt, n_channels, audio_dec_ctx->sample_rate,
376 }
377
378end:
382 if (video_dst_file)
383 fclose(video_dst_file);
384 if (audio_dst_file)
385 fclose(audio_dst_file);
388
389 return ret < 0;
390}
Main libavformat public API header.
#define FFMIN(a, b)
Definition: common.h:96
#define AV_NE(be, le)
Definition: common.h:50
#define FF_ARRAY_ELEMS(a)
Definition: common.h:100
static uint8_t * video_dst_data[4]
static int audio_stream_idx
static int width
static AVCodecContext * video_dec_ctx
int main(int argc, char **argv)
static AVPacket pkt
static AVFormatContext * fmt_ctx
static int audio_frame_count
static int get_format_from_sample_fmt(const char **fmt, enum AVSampleFormat sample_fmt)
static int refcount
static enum AVPixelFormat pix_fmt
static const char * video_dst_filename
static int video_dst_bufsize
static int video_dst_linesize[4]
static AVStream * video_stream
static const char * audio_dst_filename
static AVStream * audio_stream
static int open_codec_context(int *stream_idx, AVCodecContext **dec_ctx, AVFormatContext *fmt_ctx, enum AVMediaType type)
static FILE * video_dst_file
static int video_frame_count
static int height
static const char * src_filename
static AVFrame * frame
static AVCodecContext * audio_dec_ctx
static FILE * audio_dst_file
static int video_stream_idx
static int decode_packet(int *got_frame, int cached)
static AVCodecContext * dec_ctx
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
int avcodec_parameters_to_context(AVCodecContext *codec, const AVCodecParameters *par)
Fill the codec context based on the values from the supplied codec parameters.
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer.
AVCodec * avcodec_find_decoder(enum AVCodecID id)
Find a registered decoder with a matching codec ID.
attribute_deprecated int avcodec_decode_video2(AVCodecContext *avctx, AVFrame *picture, int *got_picture_ptr, const AVPacket *avpkt)
Decode the video frame of size avpkt->size from avpkt->data into picture.
attribute_deprecated int avcodec_decode_audio4(AVCodecContext *avctx, AVFrame *frame, int *got_frame_ptr, const AVPacket *avpkt)
Decode the audio frame of size avpkt->size from avpkt->data into frame.
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
void av_init_packet(AVPacket *pkt)
Initialize optional fields of a packet with default values.
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
Return the next frame of a stream.
int av_find_best_stream(AVFormatContext *ic, enum AVMediaType type, int wanted_stream_nb, int related_stream, AVCodec **decoder_ret, int flags)
Find the "best" stream in the file.
int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
Read packets of a media file to get stream information.
void avformat_close_input(AVFormatContext **s)
Close an opened input AVFormatContext.
int avformat_open_input(AVFormatContext **ps, const char *url, ff_const59 AVInputFormat *fmt, AVDictionary **options)
Open an input stream and read the header.
void av_dump_format(AVFormatContext *ic, int index, const char *url, int is_output)
Print detailed information about the input or output format, such as duration, bitrate,...
struct AVDictionary AVDictionary
Definition: dict.h:86
int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags)
Set the given entry in *pm, overwriting an existing entry.
#define av_err2str(errnum)
Convenience macro, the return value should be used only directly in function arguments but never stan...
Definition: error.h:119
#define AVERROR(e)
Definition: error.h:43
void av_frame_unref(AVFrame *frame)
Unreference all the buffers referenced by frame and reset the frame fields.
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
void av_free(void *ptr)
Free a memory block which has been allocated with a function of av_malloc() or av_realloc() family.
const char * av_get_media_type_string(enum AVMediaType media_type)
Return a string describing the media_type enum, NULL if media_type is unknown.
AVMediaType
Definition: avutil.h:199
@ AVMEDIA_TYPE_AUDIO
Definition: avutil.h:202
@ AVMEDIA_TYPE_VIDEO
Definition: avutil.h:201
void av_image_copy(uint8_t *dst_data[4], int dst_linesizes[4], const uint8_t *src_data[4], const int src_linesizes[4], enum AVPixelFormat pix_fmt, int width, int height)
Copy image in src_data to dst_data.
int av_image_alloc(uint8_t *pointers[4], int linesizes[4], int w, int h, enum AVPixelFormat pix_fmt, int align)
Allocate an image with size w and h and pixel format pix_fmt, and fill pointers and linesizes accordi...
int av_sample_fmt_is_planar(enum AVSampleFormat sample_fmt)
Check if the sample format is planar.
int av_get_bytes_per_sample(enum AVSampleFormat sample_fmt)
Return number of bytes per sample.
enum AVSampleFormat av_get_packed_sample_fmt(enum AVSampleFormat sample_fmt)
Get the packed alternative form of the given sample format.
const char * av_get_sample_fmt_name(enum AVSampleFormat sample_fmt)
Return the name of sample_fmt, or NULL if sample_fmt is not recognized.
AVSampleFormat
Audio sample formats.
Definition: samplefmt.h:58
@ AV_SAMPLE_FMT_FLT
float
Definition: samplefmt.h:63
@ AV_SAMPLE_FMT_S32
signed 32 bits
Definition: samplefmt.h:62
@ AV_SAMPLE_FMT_U8
unsigned 8 bits
Definition: samplefmt.h:60
@ AV_SAMPLE_FMT_DBL
double
Definition: samplefmt.h:64
@ AV_SAMPLE_FMT_S16
signed 16 bits
Definition: samplefmt.h:61
misc image utilities
const char * av_get_pix_fmt_name(enum AVPixelFormat pix_fmt)
Return the short name for a pixel format, NULL in case pix_fmt is unknown.
AVPixelFormat
Pixel format.
Definition: pixfmt.h:64
main external API structure.
Definition: avcodec.h:1565
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:1775
int width
picture width / height.
Definition: avcodec.h:1738
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:2233
int sample_rate
samples per second
Definition: avcodec.h:2225
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented.
Definition: avcodec.h:1688
int channels
number of audio channels
Definition: avcodec.h:2226
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: avcodec.h:3957
AVCodec.
Definition: avcodec.h:3481
Format I/O context.
Definition: avformat.h:1342
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1410
This structure describes decoded (raw) audio or video data.
Definition: frame.h:295
int coded_picture_number
picture number in bitstream order
Definition: frame.h:409
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:361
int64_t pts
Presentation timestamp in time_base units (time when frame should be shown to user).
Definition: frame.h:388
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:309
int width
Definition: frame.h:353
int height
Definition: frame.h:353
int linesize[AV_NUM_DATA_POINTERS]
For video, size in bytes of each picture line.
Definition: frame.h:326
int format
format of the frame, -1 if unknown or unset Values correspond to enum AVPixelFormat for video frames,...
Definition: frame.h:368
uint8_t ** extended_data
pointers to the data planes/channels.
Definition: frame.h:342
This structure stores compressed data.
Definition: avcodec.h:1454
int stream_index
Definition: avcodec.h:1479
int size
Definition: avcodec.h:1478
uint8_t * data
Definition: avcodec.h:1477
Stream structure.
Definition: avformat.h:870
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1017
timestamp utils, mostly useful for debugging/logging purposes
#define av_ts2timestr(ts, tb)
Convenience macro, the return value should be used only directly in function arguments but never stan...
Definition: timestamp.h:76