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• Revision 0d2517ce1b : vpxdec : support scaling output Adds an option, —scale, that will rescale any f

  26 février 2013, par John Koleszar

  Changed Paths : Modify /examples.mk Modify /vpxdec.c vpxdec : support scaling output Adds an option, —scale, that will rescale any frames produced by the decoder that don't match the resolution of the first frame to that resolution. This is useful for playback of files that use spatial (...)

• Too small ffmpeg rtsp decoding buffer

  30 janvier 2013, par gregoiregentil

  I'm decoding rtsp on Android with ffmpeg, and I quickly see pixelization when the image updates quickly or with a high resolution :

  

  

  After googling, I found that it might be correlated to the UDP buffer size. I have then recompiled the ffmpeg library with the following parameters inside ffmpeg/libavformat/udp.c

  #define UDP_TX_BUF_SIZE 327680
  
  #define UDP_MAX_PKT_SIZE 655360

  It seems to improve but it still starts to fail at some point. Any idea which buffer I should increase and how ?

• H264 encoder settings

  30 novembre 2011, par Chris Robinson

  I'm using xuggler to encode a series of images to an MP4 file. I use the following code to setup the IStreamCoder and specify the H264 codec :

  // only set if codec is H264
  
  Configuration.configure("/usr/local/xuggler/share/ffmpeg/libx264-hq.ffpreset",
  
              outStreamCoder);
  
  
  
  outStreamCoder.setNumPicturesInGroupOfPictures(12);
  
  outStreamCoder.setCodec(codec);
  
  outStreamCoder.setBitRate(videoSettings.getBitrate());
  
  outStreamCoder.setBitRateTolerance(videoSettings.getBitrateTolerance());
  
  outStreamCoder.setPixelType(IPixelFormat.Type.YUV420P);
  
  outStreamCoder.setHeight(videoSettings.getResolution().height);
  
  outStreamCoder.setWidth(videoSettings.getResolution().width);
  
  outStreamCoder.setFlag(IStreamCoder.Flags.FLAG_QSCALE, true);
  
  outStreamCoder.setGlobalQuality(0);
  
  fps = IRational.make((int) videoSettings.getFramerate(), 1);
  
  outStreamCoder.setFrameRate(fps);
  
  outStreamCoder.setTimeBase(IRational.make(fps.getDenominator(), fps.getNumerator()));

  which yields the following output :

  Codec: CODEC_ID_H264
  
  Resolution: 1280x720
  
  Bitrate: 25000
  
  Bitrate Tolerance: 1000
  
  Framerate: 25.0

  

  Now when I specify the MPEG4 codec, I get the following output :

  Codec: CODEC_ID_MPEG4
  
  Resolution: 1280x720
  
  Bitrate: 25000
  
  Bitrate Tolerance: 1000
  
  Framerate: 25.0

  

  As you can see, the only difference is the ICodec type (MPEG4 instead of H264) and the use of the preset (which is required by xuggler when using an H264 codec). Can anyone explain to me the huge difference in quality and tell me how to resolve the issue ?