[FFmpeg-devel] [PATCH] Fix VP3 dequantization matrices when an IDCT permutation is used

David Conrad lessen42
Wed Sep 17 21:36:37 CEST 2008

On Sep 17, 2008, at 6:53 AM, Michael Niedermayer wrote:

> On Wed, Sep 17, 2008 at 01:07:47AM -0400, David Conrad wrote:
>> Hi,
>> It appears that the reason why the VP3 SSE/MMX IDCTs weren't  
>> bitexact to
>> the C version was because the dct coefficients weren't being  
>> dequantized
>> correctly when a permutation was needed. The coefficients are  
>> permutated
>> correctly in unpack_vlcs() but the dequantization matrices are built
>> assuming no permutation. This fix allows both the SSE2 and MMX IDCTs
>> produce bitexact output for the VP3 and Theora samples I have.
> patches look ok

I also forgot to mention that it doesn't change VP5 or VP6  
bitexactness either.

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