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• Revision af660715c0 : Make coefficient skip condition an explicit RD choice. This commit replaces zru

  28 juin 2013, par Ronald S. Bultje

  Changed Paths :
   Modify /vp9/common/vp9_rtcd_defs.sh

  
   Modify /vp9/encoder/vp9_block.h

  
   Modify /vp9/encoder/vp9_onyx_int.h

  
   Modify /vp9/encoder/vp9_quantize.c

  
   Modify /vp9/encoder/vp9_rdopt.c

  
   Modify /vp9/encoder/x86/vp9_error_sse2.asm

  
  
  Make coefficient skip condition an explicit RD choice.

  This commit replaces zrun_zbin_boost, a method of biasing non-zero
  coefficients following runs of zero-coefficients to be rounded towards
  zero, with an explicit skip-block choice in the RD loop.

  The logic is basically that if individual coefficients should be rounded
  towards zero (from a RD point of view), the trellis/optimize loop should
  take care of it. If whole blocks should be zero (from a RD point of
  view), a single RD check is much more efficient than a complete
  serialization of the quantization loop.

  Quality change : derf +0.5% psnr, +1.6% ssim ; yt +0.6% psnr, +1.1% ssim.
  SIMD for quantize will follow in a separate patch. Results for other
  test sets pending.

  Change-Id : Ife5fa641163ac5150ac428011e87188f1937c1f4

• 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.

• 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