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• How to choose the playlist of highest quality in FFMpeg

  20 février 2015, par Isilmë O.

  I’m trying to convert stream media in .m3u8 files to MP4. In my case, there are several choices of video quality in each of them. For instance, 960x540, 720p and 1080p. The problem is that I can tell FFMpeg to choose 1080p, however, there are multiple links, which are all 1080p but are different in quality. In fact, my client app choose from them dynamically based on the bandwidth.

  My question is : Is there any option that gives me control to choose the last link in .m3u8 files ? (The last link always links to the best quality.)

• 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.

• Revision 46ea9ec719 : Enable real-time version reference motion vector search This commit enables a f

  24 juin 2014, par Jingning Han

  Changed Paths :
   Modify /vp9/common/vp9_mvref_common.c

  
   Modify /vp9/common/vp9_mvref_common.h

  
   Modify /vp9/encoder/vp9_pickmode.c

  
  
  Enable real-time version reference motion vector search

  This commit enables a fast reference motion vector search scheme.
  It checks the nearest top and left neighboring blocks to decide the
  most probable predicted motion vector. If it finds the two have
  the same motion vectors, it then skip finding exterior range for
  the second most probable motion vector, and correspondingly skips
  the check for NEARMV.

  The runtime of speed -5 goes down
  pedestrian at 1080p 29377 ms -> 27783 ms
  vidyo at 720p 11830 ms -> 10990 ms
  i.e., 6%-8% speed-up.

  For rtc set, the compression performance
  goes down by about -1.3% for both speed -5 and -6.

  Change-Id : I2a7794fa99734f739f8b30519ad4dfd511ab91a5