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• av_read_frame and time stamps C++

  19 avril 2014, par halfwaythru

  I am recording an RTSP H264 stream from an Axis IP camera using libavformat. This camera is supposed to stamp every frame with the time that the frame was acquired, and this information is supposed to be in the RTP packet header.

  This is the code that I am using to read in the frames.

  AVFormatContext *inputFormatCtxt = NULL;
  
  avformat_open_input(&inputFormatCtxt, inputURL, NULL, NULL) 
  
  avformat_find_stream_info(inputFormatCtxt, NULL )
  
  
  
  while(av_read_frame(inputFormatCtxt, &packet) >=0)
  
  {
  
      if(packet.stream_index == videoStreamIndex)
  
      {
  
         // Do something to video packet.
  
      }
  
      else
  
      {
  
         // Do something to audio packet. 
  
      }
  
  
  
      if (packet.pts != AV_NOPTS_VALUE)
  
          packet.dts = packet.pts    = av_rescale_q(packet.pts, stream->time_base, oStream->time_base);
  
      else
  
          NSLog(@"packet.pts == AV_NOPTS_VALUE");
  
  
  
      if(av_interleaved_write_frame(outputFormatCtxt, &packet) < 0)
  
          NSLog(@"Could not write out frame.");
  
  
  
      av_free_packet(&packet);
  
  }

  Now in AVPacket, the only time-related information is the pts and the dts. After converting them into seconds, these are supposed to be the offset of the packet (in seconds) from the start of the stream.

  My question is : How do I get the start time of the stream ?

  These are the many things that I have tried :

  1.) In AVFormatContext there is a variable start_time_realtime that is "supposed" to be the start time of the stream in real world time, in microseconds. This is exactly what I need. But no matter what I do, this value is always 0, and never changes. Am I missing a step in initialization that this never get set ?

  2.) Looking at this link, I added an RTPDemuxContext object to my code :

  RTSPState* rtsp_state = (RTSPState*) inputFormatCtxt->priv_data;
  
  RTSPStream* rtsp_stream = rtsp_state->rtsp_streams[0];
  
  RTPDemuxContext* rtp_demux_context = (RTPDemuxContext*) rtsp_stream->transport_priv;

  When I tried to look at the last_rtcp_reception_time, last_rtcp_ntp_time, last_rtcp_timestamp timestamps within the RTPDemuxContext object, these values are also 0 always, and dont change.

  3.) With the last point, I tried to force fetch a packet using ff_rtsp_fetch_packet(inputFormatCtxt, &packet). This did update the RTPDemuxContext timestamps, but only while stepping through code. If I just ran the code in a loop, it always remained the same as whatever was in the RTDemuxContext object before the loop.

  int64_t x = 0;
  
  x = rtp_demux_context->last_rtcp_reception_time;   // x is 0.
  
  while(ff_rtsp_fetch_packet(inputFormatCtxt, &packet))
  
  {
  
      x = rtp_demux_context->last_rtcp_reception_time;   // x changes only when stepping through code. else remains 0 
  
  }

  At this point I have no idea what I am doing wrong. I cant seem to get this timestamp information, no matter what I try. Any help is much appreciated. Thanks !

• Revision d24f4e49c1 : Removing CONFIG_MD5. We don't need compile time md5 configuration because —md5

  28 décembre 2013, par Dmitry Kovalev

  Changed Paths :
   Modify /configure

  
   Modify /vpxdec.c

  
  
  Removing CONFIG_MD5.

  We don't need compile time md5 configuration because —md5 is a runtime
  option.

  Change-Id : Ic0a2427ae5de5a18f31e5ee60c3732481b377ca1

• How to detect black screen at play time in ijkplayer ?

  31 août 2019, par seaguest

  I am using ijkplayer,I am wondering if it is possible to know if current player is black screen at play time ?

  because some old model mobiles do not support hard-decode and get black screen, I need to know this case then switch to soft-decode.