[Libav-user] RTSP Audio/Video Synchronization
NITIN GOYAL
nitinkumgoyal at gmail.com
Sat Mar 28 10:58:53 CET 2015
In this case only PTS matters if the simple raw data is in RTP packets.
If there is MPEG then you have to use PTS and PCR values as well.
Generally, data sync happens during the playback and the simple stream are
stored in the file.
On Wed, Mar 25, 2015 at 4:15 AM, Alessio Volpe <alessio.volpe.av at gmail.com>
wrote:
> Thanks for the reply.
>
> I whant to save the audio and video streams synchronized into a file avi.
> Il 24/Mar/2015 21:12 "wm4" <nfxjfg at googlemail.com> ha scritto:
>
>> On Tue, 24 Mar 2015 17:31:16 +0100
>> Alessio Volpe <alessio.volpe.av at gmail.com> wrote:
>>
>> > Hi, this is my program:
>> >
>> > -------------------------------------------------------------
>> >
>> > #include <stdio.h>
>> > #include <stdlib.h>
>> > #include <libavcodec/avcodec.h>
>> > #include <libavformat/avformat.h>
>> > #include <libavformat/avio.h>
>> > #include <sys/time.h>
>> >
>> > time_t get_time()
>> > {
>> > struct timeval tv;
>> >
>> > gettimeofday( &tv, NULL );
>> >
>> > return tv.tv_sec;
>> > }
>> >
>> > int main( int argc, char* argv[] )
>> > {
>> > AVFormatContext *ifcx = NULL;
>> > AVInputFormat *ifmt;
>> > AVCodecContext *iccx_video, *iccx_audio;
>> > AVCodec *icodec;
>> > AVStream *ist_video, *ist_audio;
>> > int i_index_video, i_index_audio;
>> > time_t timenow, timestart;
>> > int got_key_frame = 0;
>> >
>> > AVFormatContext *ofcx;
>> > AVOutputFormat *ofmt;
>> > AVCodecContext *occx;
>> > AVCodec *ocodec;
>> > AVStream *ost_video, *ost_audio;
>> > int o_index_video, o_index_audio;
>> >
>> > AVPacket pkt;
>> >
>> > int ix, ix_video, ix_audio;
>> >
>> > const char *sFileInput;
>> > const char *sFileOutput;
>> > int bRunTime;
>> >
>> > //Indirizzo RTSP
>> > sFileInput = "rtsp://10.4.1.175/media/video1";
>> >
>> > //File di output
>> > sFileOutput = "camera.avi";
>> >
>> > //Tempo di run dell'acquisizione
>> > bRunTime = 15; //Registra 15 secondi
>> >
>> > // Initialize library
>> > av_log_set_level( AV_LOG_DEBUG );
>> > av_register_all();
>> > avcodec_register_all();
>> > avformat_network_init();
>> >
>> > //
>> > // Input
>> > //
>> >
>> > //open rtsp
>> > if ( avformat_open_input( &ifcx, sFileInput, NULL, NULL) != 0 ) {
>> > printf( "ERROR: Cannot open input file\n" );
>> > return EXIT_FAILURE;
>> > }
>> >
>> > if ( avformat_find_stream_info( ifcx, NULL ) < 0 ) {
>> > printf( "ERROR: Cannot find stream info\n" );
>> > avformat_close_input( &ifcx );
>> > return EXIT_FAILURE;
>> > }
>> >
>> > snprintf( ifcx->filename, sizeof( ifcx->filename ), "%s", sFileInput
>> );
>> >
>> > //search video stream
>> > i_index_video = -1;
>> > for ( ix = 0; ix < ifcx->nb_streams; ix++ ) {
>> > iccx_video = ifcx->streams[ ix ]->codec;
>> > if ( iccx_video->codec_type == AVMEDIA_TYPE_VIDEO ) {
>> > ist_video = ifcx->streams[ ix ];
>> > i_index_video = ix;
>> > break;
>> > }
>> > }
>> > if ( i_index_video < 0 ) {
>> > printf( "ERROR: Cannot find input video stream\n" );
>> > avformat_close_input( &ifcx );
>> > return EXIT_FAILURE;
>> > }
>> >
>> >
>> > //search audio stream
>> > i_index_audio = -1;
>> > for ( ix = 0; ix < ifcx->nb_streams; ix++ ) {
>> > iccx_audio = ifcx->streams[ ix ]->codec;
>> > if ( iccx_audio->codec_type == AVMEDIA_TYPE_AUDIO ) {
>> > ist_audio = ifcx->streams[ ix ];
>> > i_index_audio = ix;
>> > break;
>> > }
>> > }
>> > if ( i_index_audio < 0 ) {
>> > printf( "ERROR: Cannot find input video stream\n" );
>> > avformat_close_input( &ifcx );
>> > return EXIT_FAILURE;
>> > }
>> >
>> > //
>> > // Output
>> > //
>> >
>> > //open output file
>> > ofmt = av_guess_format( NULL, sFileOutput, NULL ); //Return the output
>> > format
>> > ofcx = avformat_alloc_context();
>> > ofcx->oformat = ofmt;
>> > avio_open2( &ofcx->pb, sFileOutput, AVIO_FLAG_WRITE, NULL, NULL );
>> >
>> > // Create Video output stream
>> > ost_video = avformat_new_stream( ofcx, NULL );
>> > ost_audio = avformat_new_stream( ofcx, NULL );
>> >
>> > avcodec_copy_context( ost_video->codec, iccx_video ); //Copia il codec
>> > dello stream di input
>> > avcodec_copy_context( ost_audio->codec, iccx_audio );
>> >
>> >
>> > ost_video->sample_aspect_ratio.num =
>> iccx_video->sample_aspect_ratio.num;
>> > ost_video->sample_aspect_ratio.den =
>> iccx_video->sample_aspect_ratio.den;
>> >
>> > // Assume r_frame_rate is accurate
>> > ost_video->r_frame_rate = ist_video->r_frame_rate;
>> > ost_video->avg_frame_rate = ost_video->r_frame_rate;
>> > ost_video->time_base = (AVRational){ost_video->r_frame_rate.den,
>> > ost_video->r_frame_rate.num}; //ost->time_base = av_inv_q(
>> > ost->r_frame_rate ); //error
>> > ost_video->codec->time_base = ost_video->time_base;
>> >
>> > // Create Audio output stream
>> > ost_audio->sample_aspect_ratio.num =
>> iccx_audio->sample_aspect_ratio.num;
>> > ost_audio->sample_aspect_ratio.den =
>> iccx_audio->sample_aspect_ratio.den;
>> >
>> >
>> > ost_audio->r_frame_rate = ist_audio->r_frame_rate;
>> > ost_audio->avg_frame_rate = ost_audio->r_frame_rate;
>> > ost_audio->time_base = (AVRational){ost_audio->r_frame_rate.den,
>> > ost_audio->r_frame_rate.num}; //ost->time_base = av_inv_q(
>> > ost->r_frame_rate ); //error
>> > ost_audio->codec->time_base = ost_audio->time_base;
>> >
>> > avformat_write_header( ofcx, NULL );
>> >
>> > snprintf( ofcx->filename, sizeof( ofcx->filename ), "%s", sFileOutput
>> );
>> >
>> > //start reading packets from stream and write them to file
>> >
>> > av_dump_format( ifcx, 0, ifcx->filename, 0 ); //INFO INPUT
>> > av_dump_format( ofcx, 0, ofcx->filename, 1 ); //INFO OUTPUT
>> >
>> > timestart = timenow = get_time();
>> >
>> > ix_video = 0;
>> > ix_audio = 0;
>> >
>> > double video_pts, audio_pts;
>> >
>> > av_init_packet( &pkt );
>> >
>> > double audio_time, video_time;
>> >
>> > while ( av_read_frame( ifcx, &pkt ) >= 0 && timenow - timestart <=
>> > bRunTime ) { //&& (getchar() != 'q')){
>> > av_packet_rescale_ts(&pkt,
>> > ofcx->streams[i_index_video]->codec->time_base,
>> > ifcx->streams[i_index_video]->time_base);
>> > if ( pkt.stream_index == i_index_video ) { //packet is video
>> > //Make sure we start on a key frame - UN I-FRAME
>> > if ( timestart == timenow && ! ( pkt.flags & AV_PKT_FLAG_KEY ) ) {
>> > timestart = timenow = get_time();
>> > continue;
>> > }
>> > got_key_frame = 1;
>> >
>> > // video_pts = (double)ost_video->pts.val *
>> ost_video->time_base.num /
>> > ost_video->time_base.den;
>> > // audio_pts = (double)ost_audio->pts.val *
>> ost_audio->time_base.num /
>> > ost_audio->time_base.den;
>> >
>> > pkt.stream_index = ost_video->id;
>> > // /* prepare packet for muxing */
>> > // pkt.dts = av_rescale_q_rnd(pkt.dts,
>> > ofcx->streams[i_index_video]->codec->time_base,
>> > ofcx->streams[i_index_video]->time_base,
>> > AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
>> > // pkt.pts = av_rescale_q_rnd(pkt.pts,
>> > ofcx->streams[i_index_video]->codec->time_base,
>> > ofcx->streams[i_index_video]->time_base,
>> > AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
>> > // pkt.duration = av_rescale_q(pkt.duration,
>> > ofcx->streams[i_index_video]->codec->time_base,
>> > ofcx->streams[i_index_video]->time_base);
>> >
>> >
>> > pkt.pts = ix_video++;
>> > pkt.dts = pkt.pts;
>> >
>> > // /*Also, some streams have multiple ticks-per-frame, so if the
>> video
>> > runs at double speed you might need to this right below the above line:
>> >
>> > // pkt.pts *= ifcx->streams[0]->codec->ticks_per_frame;
>> > // pkt.dts *= ifcx->streams[0]->codec->ticks_per_frame;
>> >
>> > //av_write_frame( ofcx, &pkt );
>> > av_interleaved_write_frame( ofcx, &pkt );
>> > }
>> > else{ //packet is audio
>> >
>> > pkt.pts = ix_video++;
>> > pkt.dts = pkt.pts;
>> >
>> > //av_write_frame( ofcx, &pkt );
>> > av_interleaved_write_frame( ofcx, &pkt );
>> >
>> > }
>> >
>> > //CICLO PER SINCRONIZZARE E SCRIVERE SU DISCO
>> >
>> > // printf("vpcopy[%d].pts = %d", i, vpcopy[i].pts);
>> > // printf("\n");
>> >
>> > // if(i == 30) {
>> > // for(j=0; j<30-1; j++)
>> > // {
>> > // min = j;
>> >
>> > // for(k=j+1; k<30; k++)
>> > // if(vpcopy[j].pts < vpcopy[min].pts) //cambiare questa
>> > condizione per invertire l'ordine
>> > // min = k;
>> >
>> > // temp=vpcopy[min];
>> > // vpcopy[min]=vpcopy[j];
>> > // vpcopy[j]=temp;
>> >
>> > // printf("vpcopy[%d].pts = %d", i, vpcopy[i].pts);
>> > // printf("\n");
>> >
>> > // av_interleaved_write_frame( ofcx, &vpcopy[j] );
>> > // }
>> > // i = 0;
>> > // }
>> >
>> >
>> > av_free_packet( &pkt );
>> > av_init_packet( &pkt );
>> >
>> > timenow = get_time();
>> > }
>> > av_read_pause( ifcx );
>> > av_write_trailer( ofcx );
>> > avio_close( ofcx->pb );
>> > avformat_free_context( ofcx );
>> >
>> > avformat_network_deinit();
>> >
>> > return EXIT_SUCCESS;
>> > }
>> >
>> > -------------------------------------------------------------
>> >
>> > I would like to synchronize the video and audio.
>> >
>> > How should I use the pts and dts?
>>
>> It looks like you just want to receive the data and display it. This
>> should be helpful: http://dranger.com/ffmpeg/ (it starts with the
>> basics, but also touches A/V sync).
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>> Libav-user mailing list
>> Libav-user at ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/libav-user
>>
>
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