Record RTSP stream with FFmpeg libavformat

Question

I'm trying to record RTSP stream from Axis camera with FFmpeg libavformat. I can grab video from files and then save it to another file, this is OK. But camera sends strange data, FPS is 100 and camera sends every 4th frame so result FPS is about 25. But libavformat set packets dts/pts for 90000 fps (default?) and new file stream has 100fps. Result is one hour video with only 100 frames.

Here is my code

#include <stdio.h>
#include <stdlib.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavformat/avio.h>


int main(int argc, char** argv) {

    AVFormatContext* context = avformat_alloc_context();
    int video_stream_index;

    av_register_all();
    avcodec_register_all();
    avformat_network_init();

    //open rtsp
    if(avformat_open_input(&context, "rtsp://195.200.199.8/mpeg4/media.amp",NULL,NULL) != 0){
        return EXIT_FAILURE;
    }

    if(avformat_find_stream_info(context,NULL) < 0){
        return EXIT_FAILURE;
    }

    //search video stream
    for(int i =0;i<context->nb_streams;i++){
        if(context->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
            video_stream_index = i;
    }

    AVPacket packet;
    av_init_packet(&packet);

    //open output file
    AVOutputFormat* fmt = av_guess_format(NULL,"test2.avi",NULL);
    AVFormatContext* oc = avformat_alloc_context();
    oc->oformat = fmt;
    avio_open2(&oc->pb, "test.avi", AVIO_FLAG_WRITE,NULL,NULL);

    AVStream* stream=NULL;
    int cnt = 0;
    //start reading packets from stream and write them to file

    av_read_play(context);//play RTSP
    while(av_read_frame(context,&packet)>=0 && cnt <100){//read 100 frames
        if(packet.stream_index == video_stream_index){//packet is video               
            if(stream == NULL){//create stream in file
                stream = avformat_new_stream(oc,context->streams[video_stream_index]->codec->codec);
                avcodec_copy_context(stream->codec,context->streams[video_stream_index]->codec);
                stream->sample_aspect_ratio = context->streams[video_stream_index]->codec->sample_aspect_ratio;
                avformat_write_header(oc,NULL);
            }
            packet.stream_index = stream->id;

            av_write_frame(oc,&packet);
            cnt++;
        }
        av_free_packet(&packet);
        av_init_packet(&packet);
    }
    av_read_pause(context);
    av_write_trailer(oc);
    avio_close(oc->pb);
    avformat_free_context(oc);

    return (EXIT_SUCCESS);
}

Result file is here: http://dl.dropbox.com/u/1243577/test.avi

Thanks for any advice

Answer 1

Here's how I do it. What I found was when receiving H264 the framerate in the stream is not correct. It sends 1/90000 Timebase. I skip initializing the new stream from the incoming stream and just copy certain parameters. The incoming r_frame_rate should be accurate if max_analyze_frames works correctly.

#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;
  AVCodec *icodec;
  AVStream *ist;
  int i_index;
  time_t timenow, timestart;
  int got_key_frame = 0;

  AVFormatContext *ofcx;
  AVOutputFormat *ofmt;
  AVCodecContext *occx;
  AVCodec *ocodec;
  AVStream *ost;
  int o_index;

  AVPacket pkt;

  int ix;

  const char *sProg = argv[ 0 ];
  const char *sFileInput;
  const char *sFileOutput;
  int bRunTime;

  if ( argc != 4 ) {
    printf( "Usage: %s url outfile runtime\n", sProg );
    return EXIT_FAILURE;
  } 
  sFileInput = argv[ 1 ];
  sFileOutput = argv[ 2 ];
  bRunTime = atoi( argv[ 3 ] );

  // 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 = -1;
  for ( ix = 0; ix < ifcx->nb_streams; ix++ ) {
    iccx = ifcx->streams[ ix ]->codec;
    if ( iccx->codec_type == AVMEDIA_TYPE_VIDEO ) {
      ist = ifcx->streams[ ix ];
      i_index = ix;
      break;
    }
  }
  if ( i_index < 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 );
  ofcx = avformat_alloc_context();
  ofcx->oformat = ofmt;
  avio_open2( &ofcx->pb, sFileOutput, AVIO_FLAG_WRITE, NULL, NULL );

  // Create output stream
  //ost = avformat_new_stream( ofcx, (AVCodec *) iccx->codec );
  ost = avformat_new_stream( ofcx, NULL );
  avcodec_copy_context( ost->codec, iccx );

  ost->sample_aspect_ratio.num = iccx->sample_aspect_ratio.num;
  ost->sample_aspect_ratio.den = iccx->sample_aspect_ratio.den;

  // Assume r_frame_rate is accurate
  ost->r_frame_rate = ist->r_frame_rate;
  ost->avg_frame_rate = ost->r_frame_rate;
  ost->time_base = av_inv_q( ost->r_frame_rate );
  ost->codec->time_base = ost->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 );
  av_dump_format( ofcx, 0, ofcx->filename, 1 );

  timestart = timenow = get_time();

  ix = 0;
  //av_read_play(context);//play RTSP (Shouldn't need this since it defaults to playing on connect)
  av_init_packet( &pkt );
  while ( av_read_frame( ifcx, &pkt ) >= 0 && timenow - timestart <= bRunTime ) {
    if ( pkt.stream_index == i_index ) { //packet is video               
      // Make sure we start on a key frame
      if ( timestart == timenow && ! ( pkt.flags & AV_PKT_FLAG_KEY ) ) {
        timestart = timenow = get_time();
        continue;
      }
      got_key_frame = 1;

      pkt.stream_index = ost->id;

      pkt.pts = ix++;
      pkt.dts = pkt.pts;

      av_interleaved_write_frame( ofcx, &pkt );
    }
    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;
}