[Ffmpeg-devel] [PATCH] Chinese AVS video decoder

Stefan Gehrer stefan.gehrer
Sat Jul 1 13:05:44 CEST 2006

second try of a patch, following points addressed:

- reuse frame_rate_tab from mpeg12.c

- use ff_zigzag_direct as scan table

- simplified intra deblocking as Michael suggested

- create new file cavsdsp.c for DSP functions. In consequence, there is
  also a header file for the prototypes and some put/avg_pixels8/16
  functions in dsputil.c are made non-static. Is this acceptable?

- reduced size of constant tables

- output delayed frame when called with buffer size zero

- branchless mv_pred_direct, although it looks a bit obfuscated now

- moved all divisions in MV prediction to frame level

- fixed ffmpeg transcoding: disabled check_for_slice for now. It
  is not needed in the sample clips available. Strangely, the
  show_bits_long call in it returned wrong and different results
  when running in ffmpeg rather than ffplay.

- Better handling of open GOPs by using ff_cavs_flush, this avoids 
  the artefacts after seek

- use get/release_buffer() from AVCodecContext

Points which are still open:

- AMD64 bug reported by Benjamin. All my 64bit knowledge comes
  from Wikipedia :)
  Is it correct to assume that I have to deal with LP64 data model?
  So I only need to check for wrong assumptions about pointer size?
  (I have not used any 'long')

- Doxygen comments.
  Well, the code is written in C, ergo self-explaining.
  But seriously, what are the requirements?

- ABSCMP macros suggested by Michael. I have not done any benchmarks
  yet whatsoever.

- Artefacts reported by Roberto and Matthieu
  Roberto helped me a bit more off-list to circle in on it, but I am
  still unable to reproduce. Maybe I fixed it by accident.

Stefan Gehrer


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