[XviD-devel] quant functions b0rked

Radek Czyz syskin at ihug.com.au
Mon Jul 14 20:17:56 CEST 2003


Hi everyone,

I have some bad news.

Two asm functions - quant4_intra_xmm and quant_intra_3dne are broken.
When quantizing DC coefficient and this coefficient is negative, their
result is decreased by one.
It's not a huge problem usually (intra blocks are a bit darker), but
breaks BITS intra decision - after dequantization, total distortion is
much bigger (usually doubled, more or less).

I couldn't check sse2, but it might cause trouble as well. I'll try to
find a person with P4 for a test.

I'm disbaling the two functions. I don't think thay are speed critical
(mmx versions work well). If someone fixes them, please enable again.

Regards,
Radek

PS if anyone is interested - if we used "real" quarterpel filter for
halfpel/qpel refinement, instead of this 6-tap approximation, we
would gain about 0.07 dB. I can't judge the speed because I still
don't have mmx-ed interpolate functions (where are they ???)



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