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• Pause/resume ffmpeg transcoding process

  27 janvier 2014, par XXX

  In my Android application I use Ffmpeg library written in C++. I use ffmpeg command ffmpeg -y -i in.mp4 -s 320x240 -c:a copy out.mp4 to reduce the size of media files on Android. Everything works well. But if the file is too large, then the smartphone's battery heats up. And I have a question : is it possible to stop a ffmpeg process, and then continue it later on ? When I am converting a large file, I would like to be able to start from where I left off. Or is there any way to avoid heating the battery. May be this way : cut the file into pieces, reduce each separately and paste together ?

  UPDATE

  I found this Pause any process you want in Linux. So I decided to try to apply it on Android.

  public static void pause()
  
  {
  
      try
  
      {
  
          Process      sh = Runtime.getRuntime().exec("su", null,null);
  
          OutputStream os = sh.getOutputStream();
  
          os.write(("sudo -kill -STOP (pidof Thread-10)").getBytes("ASCII"));
  
          Log.e("!!", "process stopped!");
  
          os.flush();
  
          os.close();
  
          sh.waitFor();
  
      }
  
      catch(Throwable t){t.printStackTrace();}
  
  }

  But the process doesn't stop. Thread-10 it's the name of ffmpeg transcoding process. Whats wrong ?

• What's wrong with my use of timestamps/timebases for frame seeking/reading using libav (ffmpeg) ?

  17 septembre 2013, par mtree

  So I want to grab a frame from a video at a specific time using libav for the use as a thumbnail.

  What I'm using is the following code. It compiles and works fine (in regards to retrieving a picture at all), yet I'm having a hard time getting it to retrieve the right picture.

  I simply can't get my head around the all but clear logic behind libav's apparent use of multiple time-bases per video. Specifically figuring out which functions expect/return which type of time-base.

  The docs were of basically no help whatsoever, unfortunately. SO to the rescue ?

  #define ABORT(x) do {fprintf(stderr, x); exit(1);} while(0)
  
  
  
  av_register_all();
  
  
  
  AVFormatContext *format_context = ...;
  
  AVCodec *codec = ...;
  
  AVStream *stream = ...;
  
  AVCodecContext *codec_context = ...;
  
  int stream_index = ...;
  
  
  
  // open codec_context, etc.
  
  
  
  AVRational stream_time_base = stream->time_base;
  
  AVRational codec_time_base = codec_context->time_base;
  
  
  
  printf("stream_time_base: %d / %d = %.5f\n", stream_time_base.num, stream_time_base.den, av_q2d(stream_time_base));
  
  printf("codec_time_base: %d / %d = %.5f\n\n", codec_time_base.num, codec_time_base.den, av_q2d(codec_time_base));
  
  
  
  AVFrame *frame = avcodec_alloc_frame();
  
  
  
  printf("duration: %lld @ %d/sec (%.2f sec)\n", format_context->duration, AV_TIME_BASE, (double)format_context->duration / AV_TIME_BASE);
  
  printf("duration: %lld @ %d/sec (stream time base)\n\n", format_context->duration / AV_TIME_BASE * stream_time_base.den, stream_time_base.den);
  
  printf("duration: %lld @ %d/sec (codec time base)\n", format_context->duration / AV_TIME_BASE * codec_time_base.den, codec_time_base.den);
  
  
  
  double request_time = 10.0; // 10 seconds. Video's total duration is ~20sec
  
  int64_t request_timestamp = request_time / av_q2d(stream_time_base);
  
  printf("requested: %.2f (sec)\t-> %2lld (pts)\n", request_time, request_timestamp);
  
  
  
  av_seek_frame(format_context, stream_index, request_timestamp, 0);
  
  
  
  AVPacket packet;
  
  int frame_finished;
  
  do {
  
      if (av_read_frame(format_context, &packet) < 0) {
  
          break;
  
      } else if (packet.stream_index != stream_index) {
  
          av_free_packet(&packet);
  
          continue;
  
      }
  
      avcodec_decode_video2(codec_context, frame, &frame_finished, &packet);
  
  } while (!frame_finished);
  
  
  
  // do something with frame
  
  
  
  int64_t received_timestamp = frame->pkt_pts;
  
  double received_time = received_timestamp * av_q2d(stream_time_base);
  
  printf("received:  %.2f (sec)\t-> %2lld (pts)\n\n", received_time, received_timestamp);

  Running this with a test movie file I get this output :

      stream_time_base: 1 / 30000 = 0.00003
  
      codec_time_base: 50 / 2997 = 0.01668
  
  
  
      duration: 20062041 @ 1000000/sec (20.06 sec)
  
      duration: 600000 @ 30000/sec (stream time base)
  
      duration: 59940 @ 2997/sec (codec time base)
  
  
  
      requested: 10.00 (sec)  -> 300000 (pts)
  
      received:  0.07 (sec)   -> 2002 (pts)

  The times don't match. What's going on here ? What am I doing wrong ?

  ---

  While searching for clues I stumbled upon this this statement from the libav-users mailing list…

  [...] packet PTS/DTS are in units of the format context's time_base,
  where the AVFrame->pts value is in units of the codec context's time_base.

  In other words, the container can have (and usually does) a different
  time_base than the codec. Most libav players don't bother using the
  codec's time_base or pts since not all codecs have one, but most
  containers do. (This is why the dranger tutorial says to ignore AVFrame->pts)

  …which confused me even more, given that I couldn't find any such mention in the official docs.

  Anyway, I replaced…

  double received_time = received_timestamp * av_q2d(stream_time_base);

  …with…

  double received_time = received_timestamp * av_q2d(codec_time_base);

  …and the output changed to this…

  ...
  
  
  
  requested: 10.00 (sec)  -> 300000 (pts)
  
  received:  33.40 (sec)  -> 2002 (pts)

  Still no match. What's wrong ?

• Révision 22344 : Report de r22343 : Fix #3494 : quand la date de redaction anterieure est utilisee...

  26 juillet 2015, par cedric -

  On robustifie traiter() en verifiant le droit a edition qui a ete calcule dans charger() avant de prendre en compte les request, ce qui evite tout risque de manipulation du form et d’injection d’input en html
  + Report de r22338 au passage