[XviD-devel] zero-biased dequant/idct

daniel smith xvid-devel@xvid.org
Mon, 29 Jul 2002 01:31:15 +0800


i just remembered a paper i skimmed over that i 
wanted to try out to speed decoding (i will 
benchmark this afternoon unless someone's 
already tried it):

- trap the number of bits required to store coeffs 
during mb decoding
- if coeff bitcount for block is below a threshold, 
call versions of dequant_inter / idct which include 
a zero-byte skip check for every 8 bytes of 
block[64]

yes we lose time with branch mispredictions, but 
is the zeroed content of inter blocks high enough 
to justify?  has anyone already tried this out with 
our mmx code?

this could perhaps aid encoding speed as well, 
using the sum of quantized coeffs as a trigger 
during dequant/idct stage.

dan

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