[XviD-devel] [RFC] Decoder speedup
Michael Militzer
michael at xvid.org
Mon Jun 14 18:01:27 CEST 2004
Hi,
Quoting skal <skal at planet-d.net>:
> On Sun, 2004-06-13 at 22:32, Edouard Gomez wrote:
>
> > BENCHMARKs: VC: 255,768s VO: 0,189s A: 0,000s Sys: 12,763s = 268,720s
> <-- 1.0.1
> > BENCHMARKs: VC: 249,709s VO: 0,193s A: 0,000s Sys: 13,287s = 263,189s
> <-- 1.0.1 + get_coeff optimization
> > BENCHMARKs: VC: 222,033s VO: 0,196s A: 0,000s Sys: 12,269s = 234,498s
> <-- head
> > BENCHMARKs: VC: 217,613s VO: 0,187s A: 0,000s Sys: 12,141s = 229,940s
> <-- head + get_coeff optimization
> >
> > So now the reason why i call for comments...
> >
>
> What is the average quant of your bitstream??
>
> Because there's a big difference between ffmpeg and xvid:
> ffmpeg is dequantizing the coeffs on-the-fly, so that
> this operation scales as the number of non-zero coeffs.
> XviD, contrary, dequantizes every 64 coeffs with SIMD.
> It's faster, but inefficient if only few coeffs are
> non-zero.
Skal is right - this may be espcially useful for clips with b-frames as
these usually have a bit larger quants. Speaking of that: what features did
your test clip had? B-frames? Qpel? GMC? Which Quant? What resolution?
Michael
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