[XviD-devel] Profilign XVID, Part II

Michael Militzer michael at xvid.org
Sat Mar 1 18:11:31 CET 2003


Hi,

Quoting Christoph Lampert <chl at math.uni-bonn.de>:

> Hi, now the decoding part: 
> 
> Without Qpel, MMX and XMM are rather similar: 
> yv12_to_yv12 and transfer8x8_copy dominate 
> 
> GOAL 4)  _again_ try to sqeeze the last out of  yv12_to_yv12 
>          and transfer-functions. 

again: forget it. Memory transfers are unfortunately even more dominant for 
decoding than for encoding. And you have just profiled decoding with yv12 
output. Just try the same for rgb output: rgb conversion needs more time than 
the whole decoding process...

ok, you can now conclude that our colorspace transformations are slow. However 
I'd rather say that our decoder is just damn fast ;-)
 
> With QPel, it's the interpolation again. 
> 
> GOAL 5) _again_ try to create (partial?) SIMD version of  
>         interpolate16x16_lowpass_v_c
>         interpolate16x16_lowpass_h_c
>         interpolate8x8_lowpass_v_c
>         interpolate8x8_lowpass_h_c
> 
> 
> It seems that with those we would optimize encoder and decoder at the same
> time, a rare opportunity. 

Same thing: there should be asmed code for all of these. Don't know what's 
wrong here, but I'll have a look...

bye,
Michael


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