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• What FFMPEG return when camera is disabled (unplug)

  21 août 2017, par hung

  I use FFMPEG to connect to a IP camera via RTSP stream. I try to detect if connection is lost. I create timeout with interrupt_callback, and check the output of av_read_frame(), sometime it work and can reconnect to camera. But if I disable the camera (unplug the network cable), it’s blocked and pause forever.
  Hope someone has similar issue and can help me.
  Here what I try :

  Setting for interrupt_callback :

  ifmt_ctx = avformat_alloc_context();
  
  ifmt_ctx->interrupt_callback.callback = interruptCallback;
  
  ifmt_ctx->interrupt_callback.opaque = this;
  
  
  
  if ((ret = avformat_open_input(&ifmt_ctx, in_file, 0, &options)) != 0) {
  
      log.error("Could not open input stream {}", in_file);
  
      return 1;
  
  }

  interrupt_callback function :

  int CtFfmpeg::interruptCallback(void *ctx)
  
  {
  
      CtFfmpeg* camera = reinterpret_cast(ctx);
  
      struct tm *tm;
  
      time_t now;
  
      now = time(0);
  
      tm = localtime (&now);
  
      int nowTime_callback = tm->tm_sec;
  
      if ((nowTime_callback - camera->initTime_callback) > 15) { //Timeout after 20 seconds
  
          Logger log{__func__};
  
          log.error("Time out");
  
          return 1;
  
      }
  
  
  
      return 0;
  
  }

  Try to restart connection :

  ff->ret = av_read_frame(ff->ifmt_ctx, &(ff->tmp_pkt));
  
  
  
      if (ff->ret < 0){
  
      // do restart here
  
  }

• How to capture UDP packets from ffmpeg with Wireshark ?

  15 septembre 2017, par Davis8988

  I have 2 laptops connected via LAN cable and static ip’s (v4).
  I use ffmpeg to capture desktop from laptop1 and stream it to laptop2 :

  ffmpeg -y -rtbufsize 100M -f gdigrab -framerate 30 -probesize 10M -draw_mouse 1  
  
  -i desktop -c:v libx264 -r 30 -preset Medium -tune zerolatency -crf 25 -f mpegts   
  
  udp://150.50.1.2:1080  

  And I use ffplay to recieve the stream on laptop2 and play it and it works - I can see laptop1’s desktop :

  ffplay -fflags nobuffer -sync ext udp://127.0.0.1:1080  

  Now I want also to capture the udp packets sent by ffmpeg to laptop2 via Wireshark(I start Wireshark on laptop2).
  But when I start Wireshark and press "capture" - I don’t see any packets beeing sent from the ip (as source) of laptop1. I see some few lines in Wireshark beeing added every 1 minute or so but from different ip’s.

  Why I can’t see the stream sent by ffmpeg in laptop1 to laptop2 ?

• Record UDP stream with ffmpeg video+klv-data

  26 septembre 2017, par mfreiholz

  I’d like to record an MPEGTS UDP stream with ffmpeg binary to disk.

  This works in a stable network :

  ffmpeg.exe -i "udp://224.10.10.10:15006?multicast=1&timeout=360000000&reuse=1" -f mpegts -map 0:0? -map 0:1? -map 0:2? -c copy "C:/test.ts"

  The entire stream is saved to test.ts.

  Live Environment

  In my live environment it is possible that the connection is very bad or is not available at all (cable disconnect, device reboot, ...) for a few minutes. I want ffmpeg to simply continue writing upcoming frames to *.ts file. I don’t need the lost frames.

  Currently the following errors appears, if there was a too long brake between UDP frames :

  [mpegts @ 00000000003cf920] Application provided invalid, non monotonically increasing dts to muxer in stream 1: 11606399 >= 2084534
  
  av_interleaved_write_frame(): Invalid argument

  It looks like to be a problem with the timestamp. My idea would be to tell FFMPEG to ignore those errors and simply continue.

  Is it even possible with the ffmpeg binary or do I have to solve the problem with a custom C/C++ implementation using the library ?

  Thank you

  Update 1

  If I only record the video stream -map 0:0? and not the others it seems to work. Looks like the problem is associated with the second stream (No.1) which is KLV encoded data.