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• How to get accurate time information from ffmpeg audio outputs ?

  11 février 2016, par user2192778

  I want to figure out the best way to have accurate (down to millisecond) time information encoded into a web stream audio recording. So, if I wanted to know what was streaming at exactly 07:57:25 yesterday, I could retrieve that information using my program code. How can I do this in my ffmpeg function ?

  So far I have a python script that calls the following ffmpeg function every hour :

  ffmpeg -i http://webstreamurl.mp3 -t 01:30:00 outputname.mp3

  It will record 1.5 hours of my stream every hour. This leaves me with many 1.5 hour-long clips which together (due to some overlap) will give me audio at every moment.

  I don’t know how I will sync these clips with their stream times, however. Is there a way to put timestamps in the audio and have python read it ? Or is there a way to name these output files such that python could calculate the times itself ? Any other way ?

• How to restart RTMP dump bash script if it closes / dies ?

  9 février 2016, par Shashwat Singh

  I’m using this script to dump a live stream, say "stream1.sh" etc

  #! /bin/bash
  
  function INT_cleanup()
  
  {
  
      kill `jobs -p`
  
      exit
  
  }
  
  
  
  trap INT_cleanup INT
  
  
  
  count=0
  
  while [[ $count < 10 ]] # Try 10 times
  
  do
  
      rtmpdump -r "rtmp://<ipaddress>" -a "live" -f "WIN 11,9,900,117" -W "http://xyz.swf" -p "" -y "xyz" --live | ffmpeg -re -i  - -sn  -vcodec copy -acodec copy -f flv "<ipaddress>" 
  
      count=$((count + 1))
  
  done }
  
  </ipaddress></ipaddress>

  It runs perfectly fine for 3-4 hours then it quits automatically due to packet loss or something, however if I restart it, it again starts working.
  So, What should I do to restart this particular script IF it dies ? Will it require cronjob ? If yes, then please explain how ?

• Correct Use Of avcodec_encode_video2() Flush

  5 février 2016, par mFeinstein

  I have a camera sending pictures to a callback function and I want to make a movie with this pictures using FFmpeg. I have followed the decoding_encoding example here but am not sure how to use the got_output for flushing the encoder and getting the delayed frames.

  1. Shoud I encode all my camera’s pictures when they arrive, and later when I want to stop capturing and close the video, I do the flush loop ?

  Or

  2. Should I do the flush periodically, let’s say, every 100 pictures received ?

  My video capture program could be running for hours, so I am worried about how this delayed frames work in memory consumption, if they stack up there until the flush, this could take all my memory.

  ---

  This is the encoding performed by the example, it makes 25 dummy Frames for 1 second of video, and later, in the end, it loop through avcodec_encode_video2() looking for got_output for delayed frames :

  /////  Prepare the Frame, CodecContext and some aditional logic.....
  
  
  
  /* encode 1 second of video */
  
  for (i = 0; i < 25; i++) {
  
      av_init_packet(&pkt);
  
      pkt.data = NULL;    // packet data will be allocated by the encoder
  
      pkt.size = 0;
  
      fflush(stdout);
  
      /* prepare a dummy image */
  
      /* Y */
  
      for (y = 0; y < c->height; y++) {
  
          for (x = 0; x < c->width; x++) {
  
              frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
  
          }
  
      }
  
      /* Cb and Cr */
  
      for (y = 0; y < c->height/2; y++) {
  
          for (x = 0; x < c->width/2; x++) {
  
              frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
  
              frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
  
          }
  
      }
  
      frame->pts = i;
  
      /* encode the image */
  
      ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
  
      if (ret < 0) {
  
          fprintf(stderr, "Error encoding frame\n");
  
          exit(1);
  
      }
  
      if (got_output) {
  
          printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
          fwrite(pkt.data, 1, pkt.size, f);
  
          av_free_packet(&pkt);
  
      }
  
  }
  
  /* get the delayed frames */
  
  for (got_output = 1; got_output; i++) {
  
      fflush(stdout);
  
      ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
  
      if (ret < 0) {
  
          fprintf(stderr, "Error encoding frame\n");
  
          exit(1);
  
      }
  
      if (got_output) {
  
          printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
          fwrite(pkt.data, 1, pkt.size, f);
  
          av_free_packet(&pkt);
  
      }
  
  }
  
  
  
  /////  Closes the file and finishes.....