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• avcodec/h264_slice : Fix decoding undamaged input with slices

  24 mars 2022, par Andreas Rheinhardt

  avcodec/h264_slice : Fix decoding undamaged input with slices
  ff_er_frame_start() initializes ERContext.error_count
  
  to three times the number of macroblocks to decode.
  
  Later ff_er_add_slice() reduces this number by the amount
  
  of macroblocks whose AC resp. DC resp. MV have been finished
  
  (so every correctly decoded MB counts three times).
  
  So the frame has been decoded correctly if error_count is zero
  
  at the end.
  The H.264 decoder uses multiple ERContexts when using
  
  slice threading and therefore combines these error counts :
  
  The first slice's ERContext is intended to be initialized
  
  by ff_er_frame_start(), error_count of all the other
  
  slice contexts is intended to be zeroed initially and
  
  all afterwards all the error_counts are summed.
  Yet commit 43b434210e597d484aef57c4139c3126d22b7e2b
  
  (probably unintentionally) changed the code to set
  
  the first slice's error_count to zero as well.
  
  This leads to bogus error messages in case one decodes
  
  an input video using multiple slices with slice threading
  
  with error concealment enabled (which is not the default)
  
  ("concealing 0 DC, 0 AC, 0 MV errors in [IPB] frame") ;
  
  furthermore the returned frame is marked as corrupt as well
  
  (ffmpeg reports "corrupt decoded frame in stream %d" for this).
  This can be fixed easily given that only the first ERContext
  
  is really used since 7be2d2a70cd20d88fd826a83f87037d14681a579 :
  
  Don't reset the error_count ; and don't sum the error counts as well.
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/h264_slice.c

• Revision 16738 : Patch by Chris Pearce to tweak indexing in ffmpeg2theora to make it more ...

  27 novembre 2009, par j — Log

  Patch by Chris Pearce to tweak indexing in ffmpeg2theora to make it more accurate. Fixes : 1. Use ogg_int64_t to calculate and store presentation times of frames, rather than transitioning through double just to cast back to ogg_int64_t. Prevents floating point rounding errors from making frames (...)

• How to speed-up ffmpeg encoding for the 'qtrle' codec

  20 mai 2024, par userxxxxxxxxx

  Need you guys help for
that I'm facing kinda limit of performance to encode clips with the codec 'qtrle'.

  


  In short,

  


  

  1. Is there GPU option or technic for the qtrle encoding by GPU ?
Can I get ANY of technic for qtrle ?

  


  2. Does NVMe m.2 upgrade helps performance for ffmpeg concat and encoding ? (Currently SKHynix P41 M.2 1TB on PCIe 4 board)

  


  


  (Several multiple times of re-encoding betewwen clips again again again in one loop, so that I cannot use h254 stuff.)