[XviD-devel] [CVS commit] devapi4 -- Dmitry iDCT SSE2 code back

Michael Militzer michael at xvid.org
Mon Nov 3 02:33:44 CET 2003


Hi,

just two remarks:

1) Skal's fdct is much more accurate than Dmitry's implementation. Don't
know how speed is in comparison, but I'd go with Skal's code.

2) Do _NOT_ make any idct different from Walken the default idct for any
platform (especially not for a popular platform): this would give idct
mismatch then. It doesn't matter whether the idct implemetations are
IEEE1180 compliant or not: there is still a mismatch (which can be very
visible). The only way we can be sure that all XviD content can at least
be played back correctly with XviD itself is by only using Walken idct
in XviD and nothing else. If we want to make use of SSE2 for the idct
and gain some minor speed improvement, we should rather try to create
an SSE2 version of the Walken idct. Refer to my mail to the team list
for further details about the idct mismatch problem...

bye,
Michael

Quoting Edouard Gomez <ed.gomez at free.fr>:

> As promised, the SSE2 iDCT from dmitry is back, so we have IEEE1180
> compliant code.
> 
> Though i know the fdct has not to be compliant with anything because its
> errors are compensated...  skal, how's your code performing  ? If dmitry
> code was more accurate, it would be good to add it back and just fix the
> buffer usage. Waiting for your opinion.
> 
> Complete Changelog:
> 
> 2003-11-02 23:01:43 GMT patch-87
>                                                                              
>   
>     Summary:
>       SSE2 update
>     Revision:
>       xvidcore--devapi4--1.0--patch-87
>                                                                              
>   
>     * Added Dmitry SSE2 iDCT code back.
>     * Plugged Dmitry iDCT as default for SSE2
>     * Fixed a bug in xvid_bench that was making it would test some CPU
>       instruction set w/o host CPU support. xvidcore init was simply
>       discarding irrelevant cpu flags.
>  
>     new files:
>      src/dct/x86_asm/idct_sse2_dmitry.asm
>  
>     modified files:
>      build/generic/sources.inc build/win32/libxvidcore.dsp
>      examples/xvid_bench.c src/dct/fdct.h src/dct/idct.h src/xvid.c
> 
> -- 
> Edouard Gomez
> _______________________________________________
> XviD-devel mailing list
> XviD-devel at xvid.org
> http://list.xvid.org/mailman/listinfo/xvid-devel
> 





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