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• Find better VP8 parameters for robustness in UDP streaming with libav/ffmpeg

  24 octobre 2014, par lmNt

  I’m facing some problems in my video chat application, which is using libav libraries. I am sending 1080p videos encoded in VP8 as WebM container via UDP and it works quite well. Most of the time, the decoder on either side recovers from packet losses due to the transmission.

  However at some point in time it just freezes and never recovers again. This happens on both sides eventually. I was searching for VP8 codec parameters to set for increased robustness, when sending over lossy transmission channels. And I combined some of which I found, in order to increase robustness. However, it still freezes after some time of video chat.

  Here are the parameters I am currently using.

    pVidCodecCtx->codec_id     = AV_CODEC_ID_VP8;
  
    pVidCodecCtx->codec_type   = AVMEDIA_TYPE_VIDEO;
  
    pVidCodecCtx->width        = frmQ->pCodecCtx->width; //1920
  
    pVidCodecCtx->height       = frmQ->pCodecCtx->height; //1080
  
    pVidCodecCtx->time_base    = frmQ->pCodecCtx->time_base;
  
    pVidCodecCtx->pix_fmt      = PIX_FMT_YUV420P;
  
    pVidCodecCtx->qmin         = 4;
  
    pVidCodecCtx->qmax         = 56;
  
    pVidCodecCtx->bit_rate     = pVidCodecCtx->width * pVidCodecCtx->height * 6;
  
    pVidCodecCtx->slices       = 8;
  
    pVidCodecCtx->profile      = 3;
  
    pVidCodecCtx->thread_count = 3;
  
    pVidCodecCtx->keyint_min   = 5;
  
    av_dict_set(&pDictCodecOpts, "rc_lookahead", "0", 0);
  
    av_dict_set(&pDictCodecOpts, "quality", "realtime", 0);
  
    av_dict_set(&pDictCodecOpts, "deadline", "realtime", 0);
  
    av_dict_set(&pDictCodecOpts, "max-intra-rate", "0", 0);
  
    av_dict_set(&pDictCodecOpts, "qcomp", "0", 0);
  
    av_dict_set(&pDictCodecOpts, "default", "er", 0);
  
    av_dict_set(&pDictCodecOpts, "error_resilient", "er", 0);
  
    av_dict_set(&pDictCodecOpts, "partitions", "er", 0);

  Most of the parameters I extracted from the ffmpeg code for the vpx encoder.

  Do I also have to set parameters for the decoder in order to increase error resilience ?
  Or am I missing some parameters in the encoder or setting them incorrectly. Any help or hints are greatly appreciated.

• flac : Fix encoder and decode progress messages with —ogg.

  28 juin 2014, par Erik de Castro Lopo

  flac : Fix encoder and decode progress messages with —ogg.
  Problem discussed here :
     http://lists.xiph.org/pipermail/flac-dev/2014-June/004808.html
  The values for the interval between two updates (e->stats_mask,
  
  e->stats_frames_interval) were set 10 years ago, and it is small
  
  for current CPUs. It was now been increased too (0x3f -> 0xff, etc).
  
  The update interval is still less than 1 second.
  Patch-from : lvqcl <lvqcl.mail@gmail.com>
  

  • [DH] src/flac/decode.c
  • [DH] src/flac/encode.c

• Encode photos into (some) video format in Android

  17 juillet 2014, par user2011769

  In my app I need to convert photos (taken by the user) into some playable (on both Android device and pc web browser) vide format.

  My first and obvious choice was GIF, I’ve managed to get it working using this https://github.com/nbadal/android-gif-encoder but the result was of very poor quality. What I didn’t now was gif is a terrible standard - only 256 colors per frame, virtually no compression, so for my purposes it’s useless.

  I know it is possible to use ffmpeg for this, but I have no experience with NDK (and I’ve used C only at the university).

  Are there any other options worth exploring ?

  EDIT : it needs to work on ICS (minSdkVersion=15)