[Ffmpeg-devel] Re: idct_mmi.c license in FFmpeg

leon l.vanstuivenberg
Tue Sep 5 14:49:52 CEST 2006


Michel Lespinasse wrote:

> Since you've been able to recalculate the values after adjusting the code,
> you must have figured out what the trick is.
> 
> Before that people used to fudge the 16-bit values in the column IDCT to
> avoid IDCT bias. The rounder trick replaces that.
> 
Right, sorry about that, yes the trick is still in the mmi version. The 
outputs of one row have an extra offset to take care of the 2nd rounding 
  in the column transform as well. Well, this certainly triggered a few 
parity errors in my wetware :-)

<leon/>




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