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• avcodec/mediacodecdec : warn when input buffers are not configured with proper size

  5 septembre 2019, par Aman Gupta

  avcodec/mediacodecdec : warn when input buffers are not configured with proper size
  In rare circumstances, if the codec is not configured with the
  
  proper parameters the input buffers can be allocated with a size
  
  that's too small to hold an individual packet. Since MediaCodec
  
  expects exactly one incoming buffer with a given PTS, it is not
  
  valid to split data for a given PTS across two input buffers.
  See https://developer.android.com/reference/android/media/MediaCodec#data-processing:
    > Do not submit multiple input buffers with the same timestamp
  Signed-off-by : Aman Gupta <aman@tmm1.net>
  

  • [DH] libavcodec/mediacodecdec.c

• huffyuvdec : implement trick

  3 juin 2014, par Christophe Gisquet

  huffyuvdec : implement trick
  When the joint table does not contain a valid entry, the decoding restarts
  
  from scratch. By implementing the trick of jumping to the 2nd level of the
  
  individual table (and inlining the whole), a speed improvement of 5-10%
  
  is possible.
  On a 1000-frames YUV4:2:0 video, before :
  
  362851 decicycles in 422, 262094 runs, 50 skips
  
  182488 decicycles in gray, 262087 runs, 57 skips
  
  Object size : 23584
  
  Overall time : 8.377
  After :
  
  346800 decicycles in 422, 262079 runs, 65 skips
  
  168197 decicycles in gray, 262077 runs, 67 skips
  
  Object size : 23188
  
  Overall time : 7.878
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/huffyuvdec.c

• Efficiently write a movie directly from np.array using pipes

  16 juin 2017, par Matt Billman

  I have a 4D numpy array of movie frames. I’m looking for a function to write them to a movie, at a given framerate. I have FFMPEG installed on my OS, and as I can see from these answers, the most efficient way to do so is via pipes.

  However, I have very little experience using pipes, and the explanations in the link above make little sense to me. Furthermore, very few of the answers seem actually implement pipes, and the one that does uses mencoder, not FFMPEG. I am relatively inexperienced with FFMPEG, so am not sure how to modify the command string from the mencoder answer to make it work in FFMPEG.

  WHAT I WOULD LIKE :

  A function of the following form :

  animate_np_array(4d_array, framerate) -> output.mp4 (or other video codec)

  Which implements pipes to send frames one after the other to FFMPEG, and which I can copy-paste into my existing code.

  Furthermore, it is absolutely necessary that this function never actually plots any of the frames, as calls to the matplotlib.imshow() function (as I have most typically seen used) slow things down considerably.