[Libav-user] RTSP Audio/Video Synchronization

[Alessio Volpe]

Hi, this is my program:

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#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;
}

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I would like to synchronize the video and audio.

How should I use the pts and dts?
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