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MediaSPIP v0.2
21 juin 2013, parMediaSPIP 0.2 est la première version de MediaSPIP stable.
Sa date de sortie officielle est le 21 juin 2013 et est annoncée ici.
Le fichier zip ici présent contient uniquement les sources de MediaSPIP en version standalone.
Comme pour la version précédente, il est nécessaire d’installer manuellement l’ensemble des dépendances logicielles sur le serveur.
Si vous souhaitez utiliser cette archive pour une installation en mode ferme, il vous faudra également procéder à d’autres modifications (...) -
Librairies et logiciels spécifiques aux médias
10 décembre 2010, parPour un fonctionnement correct et optimal, plusieurs choses sont à prendre en considération.
Il est important, après avoir installé apache2, mysql et php5, d’installer d’autres logiciels nécessaires dont les installations sont décrites dans les liens afférants. Un ensemble de librairies multimedias (x264, libtheora, libvpx) utilisées pour l’encodage et le décodage des vidéos et sons afin de supporter le plus grand nombre de fichiers possibles. Cf. : ce tutoriel ; FFMpeg avec le maximum de décodeurs et (...) -
Organiser par catégorie
17 mai 2013, parDans MédiaSPIP, une rubrique a 2 noms : catégorie et rubrique.
Les différents documents stockés dans MédiaSPIP peuvent être rangés dans différentes catégories. On peut créer une catégorie en cliquant sur "publier une catégorie" dans le menu publier en haut à droite ( après authentification ). Une catégorie peut être rangée dans une autre catégorie aussi ce qui fait qu’on peut construire une arborescence de catégories.
Lors de la publication prochaine d’un document, la nouvelle catégorie créée sera proposée (...)
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OCPA, FDBR and TDPSA – What you need to know about the US’s new privacy laws
22 juillet 2024, par Daniel Crough -
ffmpeg : Trying to access Ebur128Context->integrated_loudness but unsuccessful
12 avril 2019, par Sourabh Jain[FFMPEG] Trying to access Ebur128Context->integrated_loudness but unsuccessful
I am trying to run ebur128Filter on audio file . similar to be doing
[http://ffmpeg.org/doxygen/2.6/f__ebur128_8c_source.html#l00135]ffmpeg -i sample.wav -filter_complex ebur128=peak=true -f null -
result of which is :
[Parsed_ebur128_0 @ 0x7f9d38403ec0] Summary:
Integrated loudness:
I: -15.5 LUFS
Threshold: -25.6 LUFS
Loudness range:
LRA: 1.5 LU
Threshold: -35.5 LUFS
LRA low: -16.3 LUFS
LRA high: -14.8 LUFS
True peak:
Peak: -0.4 dBFS/*
* Copyright (c) 2010 Nicolas George
* Copyright (c) 2011 Stefano Sabatini
* Copyright (c) 2012 Clément Bœsch
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/**
* @file
* API example for audio decoding and filtering
* @example filtering_audio.c
*/
#include
#include <libavcodec></libavcodec>avcodec.h>
#include <libavformat></libavformat>avformat.h>
#include <libavfilter></libavfilter>buffersink.h>
#include <libavfilter></libavfilter>buffersrc.h>
#include <libavutil></libavutil>opt.h>
#define MAX_CHANNELS 63
static const char *filter_descr = "ebur128=peak=true";
static AVFormatContext *fmt_ctx;
static AVCodecContext *dec_ctx;
AVFilterContext *buffersink_ctx;
AVFilterContext *buffersrc_ctx;
AVFilterGraph *filter_graph;
static int audio_stream_index = -1;
struct rect { int x, y, w, h; };
struct hist_entry {
int count; ///< how many times the corresponding value occurred
double energy; ///< E = 10^((L + 0.691) / 10)
double loudness; ///< L = -0.691 + 10 * log10(E)
};
struct integrator {
double *cache[MAX_CHANNELS]; ///< window of filtered samples (N ms)
int cache_pos; ///< focus on the last added bin in the cache array
double sum[MAX_CHANNELS]; ///< sum of the last N ms filtered samples (cache content)
int filled; ///< 1 if the cache is completely filled, 0 otherwise
double rel_threshold; ///< relative threshold
double sum_kept_powers; ///< sum of the powers (weighted sums) above absolute threshold
int nb_kept_powers; ///< number of sum above absolute threshold
struct hist_entry *histogram; ///< histogram of the powers, used to compute LRA and I
};
typedef struct EBUR128Context {
const AVClass *class; ///< AVClass context for log and options purpose
/* peak metering */
int peak_mode; ///< enabled peak modes
double *true_peaks; ///< true peaks per channel
double *sample_peaks; ///< sample peaks per channel
double *true_peaks_per_frame; ///< true peaks in a frame per channel
#if CONFIG_SWRESAMPLE
SwrContext *swr_ctx; ///< over-sampling context for true peak metering
double *swr_buf; ///< resampled audio data for true peak metering
int swr_linesize;
#endif
/* video */
int do_video; ///< 1 if video output enabled, 0 otherwise
int w, h; ///< size of the video output
struct rect text; ///< rectangle for the LU legend on the left
struct rect graph; ///< rectangle for the main graph in the center
struct rect gauge; ///< rectangle for the gauge on the right
AVFrame *outpicref; ///< output picture reference, updated regularly
int meter; ///< select a EBU mode between +9 and +18
int scale_range; ///< the range of LU values according to the meter
int y_zero_lu; ///< the y value (pixel position) for 0 LU
int y_opt_max; ///< the y value (pixel position) for 1 LU
int y_opt_min; ///< the y value (pixel position) for -1 LU
int *y_line_ref; ///< y reference values for drawing the LU lines in the graph and the gauge
/* audio */
int nb_channels; ///< number of channels in the input
double *ch_weighting; ///< channel weighting mapping
int sample_count; ///< sample count used for refresh frequency, reset at refresh
/* Filter caches.
* The mult by 3 in the following is for X[i], X[i-1] and X[i-2] */
double x[MAX_CHANNELS * 3]; ///< 3 input samples cache for each channel
double y[MAX_CHANNELS * 3]; ///< 3 pre-filter samples cache for each channel
double z[MAX_CHANNELS * 3]; ///< 3 RLB-filter samples cache for each channel
#define I400_BINS (48000 * 4 / 10)
#define I3000_BINS (48000 * 3)
struct integrator i400; ///< 400ms integrator, used for Momentary loudness (M), and Integrated loudness (I)
struct integrator i3000; ///< 3s integrator, used for Short term loudness (S), and Loudness Range (LRA)
/* I and LRA specific */
double integrated_loudness; ///< integrated loudness in LUFS (I)
double loudness_range; ///< loudness range in LU (LRA)
double lra_low, lra_high; ///< low and high LRA values
/* misc */
int loglevel; ///< log level for frame logging
int metadata; ///< whether or not to inject loudness results in frames
int dual_mono; ///< whether or not to treat single channel input files as dual-mono
double pan_law; ///< pan law value used to calculate dual-mono measurements
int target; ///< target level in LUFS used to set relative zero LU in visualization
int gauge_type; ///< whether gauge shows momentary or short
int scale; ///< display scale type of statistics
} EBUR128Context;
void dump_ebur128_context(void *priv);
static int open_input_file(const char *filename)
{
int ret;
AVCodec *dec;
if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
return ret;
}
if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
return ret;
}
/* select the audio stream */
ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &dec, 0);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot find an audio stream in the input file\n");
return ret;
}
audio_stream_index = ret;
/* create decoding context */
dec_ctx = avcodec_alloc_context3(dec);
if (!dec_ctx)
return AVERROR(ENOMEM);
avcodec_parameters_to_context(dec_ctx, fmt_ctx->streams[audio_stream_index]->codecpar);
/* init the audio decoder */
if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot open audio decoder\n");
return ret;
}
return 0;
}
static int init_filters(const char *filters_descr)
{
char args[512];
int ret = 0;
const AVFilter *abuffersrc = avfilter_get_by_name("abuffer");
const AVFilter *abuffersink = avfilter_get_by_name("abuffersink");
AVFilterInOut *outputs = avfilter_inout_alloc();
AVFilterInOut *inputs = avfilter_inout_alloc();
static const enum AVSampleFormat out_sample_fmts[] = { AV_SAMPLE_FMT_S16, -1 };
static const int64_t out_channel_layouts[] = { AV_CH_LAYOUT_MONO, -1 };
static const int out_sample_rates[] = { 8000, -1 };
const AVFilterLink *outlink;
AVRational time_base = fmt_ctx->streams[audio_stream_index]->time_base;
filter_graph = avfilter_graph_alloc();
if (!outputs || !inputs || !filter_graph) {
ret = AVERROR(ENOMEM);
goto end;
}
/* buffer audio source: the decoded frames from the decoder will be inserted here. */
if (!dec_ctx->channel_layout)
dec_ctx->channel_layout = av_get_default_channel_layout(dec_ctx->channels);
snprintf(args, sizeof(args),
"time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
time_base.num, time_base.den, dec_ctx->sample_rate,
av_get_sample_fmt_name(dec_ctx->sample_fmt), dec_ctx->channel_layout);
ret = avfilter_graph_create_filter(&buffersrc_ctx, abuffersrc, "in",
args, NULL, filter_graph);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
goto end;
}
/* buffer audio sink: to terminate the filter chain. */
ret = avfilter_graph_create_filter(&buffersink_ctx, abuffersink, "out",
NULL, NULL, filter_graph);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
goto end;
}
ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
AV_OPT_SEARCH_CHILDREN);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
goto end;
}
ret = av_opt_set_int_list(buffersink_ctx, "channel_layouts", out_channel_layouts, -1,
AV_OPT_SEARCH_CHILDREN);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
goto end;
}
ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
AV_OPT_SEARCH_CHILDREN);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
goto end;
}
/*
* Set the endpoints for the filter graph. The filter_graph will
* be linked to the graph described by filters_descr.
*/
/*
* The buffer source output must be connected to the input pad of
* the first filter described by filters_descr; since the first
* filter input label is not specified, it is set to "in" by
* default.
*/
outputs->name = av_strdup("in");
outputs->filter_ctx = buffersrc_ctx;
outputs->pad_idx = 0;
outputs->next = NULL;
/*
* The buffer sink input must be connected to the output pad of
* the last filter described by filters_descr; since the last
* filter output label is not specified, it is set to "out" by
* default.
*/
inputs->name = av_strdup("out");
inputs->filter_ctx = buffersink_ctx;
inputs->pad_idx = 0;
inputs->next = NULL;
if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
&inputs, &outputs, NULL)) < 0)
goto end;
if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
goto end;
/* Print summary of the sink buffer
* Note: args buffer is reused to store channel layout string */
outlink = buffersink_ctx->inputs[0];
av_get_channel_layout_string(args, sizeof(args), -1, outlink->channel_layout);
av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
(int)outlink->sample_rate,
(char *)av_x_if_null(av_get_sample_fmt_name(outlink->format), "?"),
args);
end:
avfilter_inout_free(&inputs);
avfilter_inout_free(&outputs);
return ret;
}
static void print_frame(const AVFrame *frame)
{
// const int n = frame->nb_samples * av_get_channel_layout_nb_channels(frame->channel_layout);
// const uint16_t *p = (uint16_t*)frame->data[0];
// const uint16_t *p_end = p + n;
//
// while (p < p_end) {
// fputc(*p & 0xff, stdout);
// fputc(*p>>8 & 0xff, stdout);
// p++;
// }
// fflush(stdout);
}
int main(int argc, char **argv)
{
av_log_set_level(AV_LOG_DEBUG);
int ret;
AVPacket packet;
AVFrame *frame = av_frame_alloc();
AVFrame *filt_frame = av_frame_alloc();
if (!frame || !filt_frame) {
perror("Could not allocate frame");
exit(1);
}
if ((ret = open_input_file(argv[1])) < 0)
goto end;
if ((ret = init_filters(filter_descr)) < 0)
goto end;
/* read all packets */
while (1) {
if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
break;
if (packet.stream_index == audio_stream_index) {
ret = avcodec_send_packet(dec_ctx, &packet);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error while sending a packet to the decoder\n");
break;
}
while (ret >= 0) {
ret = avcodec_receive_frame(dec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
break;
} else if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error while receiving a frame from the decoder\n");
goto end;
}
if (ret >= 0) {
/* push the audio data from decoded frame into the filtergraph */
if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0) {
av_log(NULL, AV_LOG_ERROR, "Error while feeding the audio filtergraph\n");
break;
}
/* pull filtered audio from the filtergraph */
while (1) {
ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
break;
if (ret < 0)
goto end;
print_frame(filt_frame);
av_frame_unref(filt_frame);
}
av_frame_unref(frame);
}
}
}
av_packet_unref(&packet);
}
if(filter_graph->nb_filters){
av_log(filter_graph, AV_LOG_INFO, "hello : %d \n",
filter_graph->nb_filters);
int i;
for (int i = 0; i < filter_graph->nb_filters; i++){
av_log(filter_graph, AV_LOG_INFO, "name : %s \n",
filter_graph->filters[i]->name);
}
}
av_log(filter_graph, AV_LOG_INFO, "name : %s \n",
filter_graph->filters[2]->name);
void* priv = filter_graph->filters[2]->priv;
dump_ebur128_context(&priv);
end:
avfilter_graph_free(&filter_graph);
avcodec_free_context(&dec_ctx);
avformat_close_input(&fmt_ctx);
av_frame_free(&frame);
av_frame_free(&filt_frame);
if (ret < 0 && ret != AVERROR_EOF) {
fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
exit(1);
}
exit(0);
}
void dump_ebur128_context(void *priv){
EBUR128Context *ebur128 = priv;
av_log(ebur128, AV_LOG_INFO, "integrated_loudness : %5.1f \n",
ebur128->integrated_loudness);
av_log(ebur128, AV_LOG_INFO, "lra_low : %5.1f \n",
ebur128->lra_low);
av_log(ebur128, AV_LOG_INFO, "lra_high : %5.1f \n",
ebur128->lra_high);
}program fails while accessing integrated loudness in dump_ebur128_context.
can someone guide me about , how I should proceed in here.
-
Getting shifted timestamps when encoding a fragmented h264 mp4 with ffmpeg
14 septembre 2022, par Martin CastinI am trying to encode a fragmented h264 mp4 with ffmpeg. I tried the following command :


ffmpeg -i input.mp4 -movflags +frag_keyframe+separate_moof+omit_tfhd_offset+empty_moov output.mp4



It does give me a fragmented mp4 but the timestamps of the frames seem to be shifted by 0.04s when I read the video with mpv. The first frame has a timestamp of 0.04s instead of 0s, as in the input video (1920x1080, 50 fps). I encountered the problem both with ffmpeg 5.1 and ffmpeg 3.4.11.


I tried to add several flags, as
-avoid_negative_ts make_zero
or-copyts -output_ts_offset -0.04
, but it did not help.

I am also trying to achieve this using the ffmpeg libav libraries in C++ but did not get to better result. Here are the code fragments I used.


avformat_alloc_output_context2(&oc, NULL, NULL, filename);

 if (oc_->oformat->flags & AVFMT_GLOBALHEADER) {
 codecCtx_->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
 }
...
 AVDictionary* opts = NULL;

 av_dict_set(&opts, "movflags", "frag_keyframe+separate_moof+omit_tfhd_offset+empty_moov", 0);

 ret = avformat_write_header(oc_, &opts);



Do you know how to avoid this behaviour of shifted timestamps for fragmented mp4, either with ffmpeg or libav ?


Edit : example videos and complete code example


I also tried with the following ffmpeg build


ffmpeg version 5.0.1-static https://johnvansickle.com/ffmpeg/ Copyright (c) 2000-2022 the FFmpeg developers
built with gcc 8 (Debian 8.3.0-6)
configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libdav1d --enable-libxvid --enable-libzvbi --enable-libzimg
libavutil 57. 17.100 / 57. 17.100
libavcodec 59. 18.100 / 59. 18.100
libavformat 59. 16.100 / 59. 16.100
libavdevice 59. 4.100 / 59. 4.100
libavfilter 8. 24.100 / 8. 24.100
libswscale 6. 4.100 / 6. 4.100
libswresample 4. 3.100 / 4. 3.100
libpostproc 56. 3.100 / 56. 3.100



and with the sintel trailer as input video, which is 24fps, and I thus get a timeshift of 83ms. Here is the output I get.


Here is a complete code example, slightly adapted from the
muxing.c
ffmpeg example (audio removed and adapted for c++). This code shows exactly the same problem.

You can just comment the line 383 (that is calling
av_dict_set
) to switch back to a not fragmented mp4 that will not have the timestamp shift.

/*
 * Copyright (c) 2003 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/**
 * @file
 * libavformat API example.
 *
 * Output a media file in any supported libavformat format. The default
 * codecs are used.
 * @example muxing.c
 */

#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <cmath>

extern "C"
{
#define __STDC_CONSTANT_MACROS
#include <libavutil></libavutil>avassert.h>
#include <libavutil></libavutil>channel_layout.h>
#include <libavutil></libavutil>opt.h>
#include <libavutil></libavutil>mathematics.h>
#include <libavutil></libavutil>timestamp.h>
#include <libavcodec></libavcodec>avcodec.h>
#include <libavformat></libavformat>avformat.h>
#include <libswscale></libswscale>swscale.h>
#include <libswresample></libswresample>swresample.h>
}

#define STREAM_DURATION 10.0
#define STREAM_FRAME_RATE 25 /* 25 images/s */
#define STREAM_PIX_FMT AV_PIX_FMT_YUV420P /* default pix_fmt */

#define SCALE_FLAGS SWS_BICUBIC

// a wrapper around a single output AVStream
typedef struct OutputStream {
 AVStream *st;
 AVCodecContext *enc;

 /* pts of the next frame that will be generated */
 int64_t next_pts;
 int samples_count;

 AVFrame *frame;
 AVFrame *tmp_frame;

 AVPacket *tmp_pkt;

 float t, tincr, tincr2;

 struct SwsContext *sws_ctx;
 struct SwrContext *swr_ctx;
} OutputStream;

static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt)
{
 AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;

// printf("pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
// av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base),
// av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base),
// av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base),
// pkt->stream_index);
}

static int write_frame(AVFormatContext *fmt_ctx, AVCodecContext *c,
 AVStream *st, AVFrame *frame, AVPacket *pkt)
{
 int ret;

 // send the frame to the encoder
 ret = avcodec_send_frame(c, frame);
 if (ret < 0) {
 fprintf(stderr, "Error sending a frame to the encoder");
 exit(1);
 }

 while (ret >= 0) {
 ret = avcodec_receive_packet(c, pkt);
 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
 break;
 else if (ret < 0) {
 fprintf(stderr, "Error encoding a frame\n");
 exit(1);
 }

 /* rescale output packet timestamp values from codec to stream timebase */
 av_packet_rescale_ts(pkt, c->time_base, st->time_base);
 pkt->stream_index = st->index;

 /* Write the compressed frame to the media file. */
 log_packet(fmt_ctx, pkt);
 ret = av_interleaved_write_frame(fmt_ctx, pkt);
 /* pkt is now blank (av_interleaved_write_frame() takes ownership of
 * its contents and resets pkt), so that no unreferencing is necessary.
 * This would be different if one used av_write_frame(). */
 if (ret < 0) {
 fprintf(stderr, "Error while writing output packet\n");
 exit(1);
 }
 }

 return ret == AVERROR_EOF ? 1 : 0;
}

/* Add an output stream. */
static void add_stream(OutputStream *ost, AVFormatContext *oc,
 const AVCodec **codec,
 enum AVCodecID codec_id)
{
 AVCodecContext *c;
 int i;

 /* find the encoder */
 *codec = avcodec_find_encoder(codec_id);
 if (!(*codec)) {
 fprintf(stderr, "Could not find encoder for '%s'\n",
 avcodec_get_name(codec_id));
 exit(1);
 }

 ost->tmp_pkt = av_packet_alloc();
 if (!ost->tmp_pkt) {
 fprintf(stderr, "Could not allocate AVPacket\n");
 exit(1);
 }

 ost->st = avformat_new_stream(oc, NULL);
 if (!ost->st) {
 fprintf(stderr, "Could not allocate stream\n");
 exit(1);
 }
 ost->st->id = oc->nb_streams-1;
 c = avcodec_alloc_context3(*codec);
 if (!c) {
 fprintf(stderr, "Could not alloc an encoding context\n");
 exit(1);
 }
 ost->enc = c;

 switch ((*codec)->type) {
 case AVMEDIA_TYPE_VIDEO:
 c->codec_id = codec_id;

 c->bit_rate = 400000;
 /* Resolution must be a multiple of two. */
 c->width = 352;
 c->height = 288;
 /* timebase: 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
 * identical to 1. */
 ost->st->time_base = (AVRational){ 1, STREAM_FRAME_RATE };
 c->time_base = ost->st->time_base;

 c->gop_size = 12; /* emit one intra frame every twelve frames at most */
 c->pix_fmt = STREAM_PIX_FMT;
 if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
 /* just for testing, we also add B-frames */
 c->max_b_frames = 2;
 }
 if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
 /* Needed to avoid using macroblocks in which some coeffs overflow.
 * This does not happen with normal video, it just happens here as
 * the motion of the chroma plane does not match the luma plane. */
 c->mb_decision = 2;
 }
 break;

 default:
 break;
 }

 /* Some formats want stream headers to be separate. */
 if (oc->oformat->flags & AVFMT_GLOBALHEADER)
 c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
}

/**************************************************************/
/* video output */

static AVFrame *alloc_picture(enum AVPixelFormat pix_fmt, int width, int height)
{
 AVFrame *picture;
 int ret;

 picture = av_frame_alloc();
 if (!picture)
 return NULL;

 picture->format = pix_fmt;
 picture->width = width;
 picture->height = height;

 /* allocate the buffers for the frame data */
 ret = av_frame_get_buffer(picture, 0);
 if (ret < 0) {
 fprintf(stderr, "Could not allocate frame data.\n");
 exit(1);
 }

 return picture;
}

static void open_video(AVFormatContext *oc, const AVCodec *codec,
 OutputStream *ost, AVDictionary *opt_arg)
{
 int ret;
 AVCodecContext *c = ost->enc;
 AVDictionary *opt = NULL;

 av_dict_copy(&opt, opt_arg, 0);

 /* open the codec */
 ret = avcodec_open2(c, codec, &opt);
 av_dict_free(&opt);
 if (ret < 0) {
 fprintf(stderr, "Could not open video codec\n");
 exit(1);
 }

 /* allocate and init a re-usable frame */
 ost->frame = alloc_picture(c->pix_fmt, c->width, c->height);
 if (!ost->frame) {
 fprintf(stderr, "Could not allocate video frame\n");
 exit(1);
 }

 /* If the output format is not YUV420P, then a temporary YUV420P
 * picture is needed too. It is then converted to the required
 * output format. */
 ost->tmp_frame = NULL;
 if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
 ost->tmp_frame = alloc_picture(AV_PIX_FMT_YUV420P, c->width, c->height);
 if (!ost->tmp_frame) {
 fprintf(stderr, "Could not allocate temporary picture\n");
 exit(1);
 }
 }

 /* copy the stream parameters to the muxer */
 ret = avcodec_parameters_from_context(ost->st->codecpar, c);
 if (ret < 0) {
 fprintf(stderr, "Could not copy the stream parameters\n");
 exit(1);
 }
}

/* Prepare a dummy image. */
static void fill_yuv_image(AVFrame *pict, int frame_index,
 int width, int height)
{
 int x, y, i;

 i = frame_index;

 /* Y */
 for (y = 0; y < height; y++)
 for (x = 0; x < width; x++)
 pict->data[0][y * pict->linesize[0] + x] = x + y + i * 3;

 /* Cb and Cr */
 for (y = 0; y < height / 2; y++) {
 for (x = 0; x < width / 2; x++) {
 pict->data[1][y * pict->linesize[1] + x] = 128 + y + i * 2;
 pict->data[2][y * pict->linesize[2] + x] = 64 + x + i * 5;
 }
 }
}

static AVFrame *get_video_frame(OutputStream *ost)
{
 AVCodecContext *c = ost->enc;

 /* check if we want to generate more frames */
 if (av_compare_ts(ost->next_pts, c->time_base,
 STREAM_DURATION, (AVRational){ 1, 1 }) > 0)
 return NULL;

 /* when we pass a frame to the encoder, it may keep a reference to it
 * internally; make sure we do not overwrite it here */
 if (av_frame_make_writable(ost->frame) < 0)
 exit(1);

 if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
 /* as we only generate a YUV420P picture, we must convert it
 * to the codec pixel format if needed */
 if (!ost->sws_ctx) {
 ost->sws_ctx = sws_getContext(c->width, c->height,
 AV_PIX_FMT_YUV420P,
 c->width, c->height,
 c->pix_fmt,
 SCALE_FLAGS, NULL, NULL, NULL);
 if (!ost->sws_ctx) {
 fprintf(stderr,
 "Could not initialize the conversion context\n");
 exit(1);
 }
 }
 fill_yuv_image(ost->tmp_frame, ost->next_pts, c->width, c->height);
 sws_scale(ost->sws_ctx, (const uint8_t * const *) ost->tmp_frame->data,
 ost->tmp_frame->linesize, 0, c->height, ost->frame->data,
 ost->frame->linesize);
 } else {
 fill_yuv_image(ost->frame, ost->next_pts, c->width, c->height);
 }

 ost->frame->pts = ost->next_pts++;

 return ost->frame;
}

/*
 * encode one video frame and send it to the muxer
 * return 1 when encoding is finished, 0 otherwise
 */
static int write_video_frame(AVFormatContext *oc, OutputStream *ost)
{
 return write_frame(oc, ost->enc, ost->st, get_video_frame(ost), ost->tmp_pkt);
}

static void close_stream(AVFormatContext *oc, OutputStream *ost)
{
 avcodec_free_context(&ost->enc);
 av_frame_free(&ost->frame);
 av_frame_free(&ost->tmp_frame);
 av_packet_free(&ost->tmp_pkt);
 sws_freeContext(ost->sws_ctx);
 swr_free(&ost->swr_ctx);
}

/**************************************************************/
/* media file output */

int main(int argc, char **argv)
{
 OutputStream video_st = { 0 }, audio_st = { 0 };
 const AVOutputFormat *fmt;
 const char *filename;
 AVFormatContext *oc;
 const AVCodec *audio_codec, *video_codec;
 int ret;
 int have_video = 0, have_audio = 0;
 int encode_video = 0, encode_audio = 0;
 AVDictionary *opt = NULL;
 int i;

 if (argc < 2) {
 printf("usage: %s output_file\n"
 "API example program to output a media file with libavformat.\n"
 "This program generates a synthetic audio and video stream, encodes and\n"
 "muxes them into a file named output_file.\n"
 "The output format is automatically guessed according to the file extension.\n"
 "Raw images can also be output by using '%%d' in the filename.\n"
 "\n", argv[0]);
 return 1;
 }

 filename = argv[1];

 av_dict_set(&opt, "movflags", "frag_keyframe+separate_moof+omit_tfhd_offset+empty_moov", 0);

 /* allocate the output media context */
 avformat_alloc_output_context2(&oc, NULL, NULL, filename);
 if (!oc) {
 printf("Could not deduce output format from file extension: using MPEG.\n");
 avformat_alloc_output_context2(&oc, NULL, "mpeg", filename);
 }
 if (!oc)
 return 1;

 fmt = oc->oformat;

 /* Add the audio and video streams using the default format codecs
 * and initialize the codecs. */
 if (fmt->video_codec != AV_CODEC_ID_NONE) {
 add_stream(&video_st, oc, &video_codec, fmt->video_codec);
 have_video = 1;
 encode_video = 1;
 }

 /* Now that all the parameters are set, we can open the audio and
 * video codecs and allocate the necessary encode buffers. */
 if (have_video)
 open_video(oc, video_codec, &video_st, opt);


 av_dump_format(oc, 0, filename, 1);

 /* open the output file, if needed */
 if (!(fmt->flags & AVFMT_NOFILE)) {
 ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);
 if (ret < 0) {
 fprintf(stderr, "Could not open '%s'\n", filename);
 return 1;
 }
 }

 /* Write the stream header, if any. */
 ret = avformat_write_header(oc, &opt);
 if (ret < 0) {
 fprintf(stderr, "Error occurred when opening output file\n");
 return 1;
 }

 while (encode_video || encode_audio) {
 /* select the stream to encode */
 if (encode_video &&
 (!encode_audio || av_compare_ts(video_st.next_pts, video_st.enc->time_base,
 audio_st.next_pts, audio_st.enc->time_base) <= 0)) {
 encode_video = !write_video_frame(oc, &video_st);
 }
 }

 av_write_trailer(oc);

 /* Close each codec. */
 if (have_video)
 close_stream(oc, &video_st);
 if (have_audio)
 close_stream(oc, &audio_st);

 if (!(fmt->flags & AVFMT_NOFILE))
 /* Close the output file. */
 avio_closep(&oc->pb);

 /* free the stream */
 avformat_free_context(oc);

 return 0;
}
</cmath></cstring></cstdio></cstdlib>