[XviD-devel] Global Motion Compensation

[Michael Niedermayer]

Hi

On Thursday 24 October 2002 13:27, Christoph Lampert wrote:
[...]
> > > Maybe more tweaks are possible for fast decoding, too.
> > > (pre calculated tables or something...)
> >
> > hmm, i doubt it a bit
>
> Me, too... but who knows ;-) Is GMC decoding MMX/XMMed? Maybe it's
> 3dnow/SSE/SSE2able?
no its not, and i doubt it could be done in MMX/SSE(2) but who knows ... :)

>
> > > The only argument would be that you don't gain anything from GMC, which
> > > may be true for most videos, but sometimes it seems to help during
> > > zoom/pan, so I'll at least have a look.
> >
> > hmm, its allways a question of complexity vs. compression gain, never
> > just compression alone, or why dont we all do full ME search?
>
> Okay, partly agreed. A slow feature should only be enabled if there is
> a sufficient gain, but what "sufficient" means depends on the application.
>
> Full search ME is an extreme example of slowdown at hardly any
> better ME results (than PMVfast/EPZS) in all sequences I know.
> If GMC gives 1dB gain in 5% of sequences and nothing in 95%, it's somehow
> a different story... those things can be tested and the feature only
> actived when needed.
agree, if there is significant gain then GMC is a good idea, i just disslike 
the idea that a significant number of people would have to spend lots of 
money to buy new CPUs ...

btw the question isnt if GMC has a significant gain over non gmc, but the 
question is if GMC with more then 1 warp point (zoom, rotate, ...) has a 
significant advantage over translational only GMC 

[...]

Michael