[FFmpeg-devel] [PATCH] SPARC VIS simple_idct

[Michael Niedermayer]

Hi

On Fri, Aug 24, 2007 at 11:02:29PM -0700, Michel Lespinasse wrote:
> On Sat, Aug 25, 2007 at 01:20:45AM +0200, Balatoni Denes wrote:
> 
> > ps: there is a half as fast version of this idct, but that's
> > accurate (32 bit multiplies) - I am wondering if maybe that would
> > make more sense in ffmpeg.  Or there could be three sparc idcts: one
> > slow (but faster than the C version) and accurate, one faster but
> > less accurate, and then the mlib (fastest, very inaccurate, mpeg4
> > routinely turns pink while viewing). Maybe it's not a good idea.
> 
> One can make an accurate enough IDCT using VIS, the 8x16 bit multiplies
> make that very hard but not quite entirely impossible.
> 
> I finally dug out the old test code I had written in september 2003,
> at the time david miller was interested to convert that to asm and then
> he got busy with other things. It works on columns, then transposes
> the table and does another pass. David thought he could make it faster
> than the VIS one, but hey, talk is cheap :) The test code is in C but
> I believe the muls/mulu functions match what VIS implements. idct() is
> what you'd want to be fast, idct_vis() is the C function I used to hook
> this into my IEEE1180 test framework, it reorders input coefficients
> and preshifts them by 4 (libmpeg2 prescales IDCT during stream parsing).
> 
> Don't know if there is any interest or how it compares with the simple-idct
> derived code - but, it is (barely) IEEE1180 compliant and does not use
> 32-bit multiplies.
> 
> Hope this helps,

of course it does

btw you dont maybe also have that in asm() form?

btw2, if you ever want a ffmpeg svn write account ... just ask

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In a rich man's house there is no place to spit but his face.
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