[FFmpeg-devel] new open source h.264 source
Rich Felker
dalias
Thu Feb 21 06:41:34 CET 2008
On Thu, Feb 21, 2008 at 04:28:14AM +0100, Michael Niedermayer wrote:
> > I don't think AAN is the best IDCT algorithm, though - maybe it would
> > be better to port ppc/idct_altivec.c?
>
> btw, speaking about dcts ...
> there is something strange
> trunk/Framewave/domain/fwJPEG/src/JPEGDCT.cpp:
> #define W1 F 0.70710678118654752438 // cos(pi*4/16)
> #define W2 F 0.54119610014619698435 // cos(pi*6/16)sqrt(2)
> #define W5 F 0.38268343236508977170 // cos(pi*6/16)
> #define W4 F 1.30656296487637652774 // cos(pi*2/16)sqrt(2)
>
> libavcodec/faandct.c
> #define A1 0.70710678118654752438 // cos(pi*4/16)
> #define A2 0.54119610014619698435 // cos(pi*6/16)sqrt(2)
> #define A5 0.38268343236508977170 // cos(pi*6/16)
> #define A4 1.30656296487637652774 // cos(pi*2/16)sqrt(2)
>
> Also googling for these constants shows only libavcodec as hit.
> And the code upon which my faandct was based IIRC (jfdctfst.c)
> contains only less accurate constants.
>
> Also the actual code looks strangely similar to libavcodec/faandct.c
Hmm sounds like time to ask AMD to fix the license. :-)
Rich
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