[XviD-devel] Coefficient thresholding

Christoph Lampert xvid-devel@xvid.org
Sun, 18 Aug 2002 15:54:13 +0200 (CEST)


On Sun, 18 Aug 2002, Michael Militzer wrote:

> > We make coefficient threshholding a flag. If it's switched off,
> > a value of 1 (no threshholding) is used for quant>=2 and a value of 2
> > is used for quant=1. I doubt that for quant=1 the effect will be
> > very visisble...
> 
> yes, that's good. I agree that a TOO_SMALL_LIMIT of 2 will not noticeably
> decrease quant=1 quality. However I would prefer an integer value for coeff
> thresholding instead of a flag: API 3.0 will be introduced in the nearer
> future and an addtional integer option would be no problem then...

Except for that people will be able to change it.  ;-)

Thing is, I don't like a new integer when there are only
2 or 3 "sensible" values. 
Take e.g. framedrop, there it's it's okay. 0-100 is a sensible range.
But having the choice between 2, 3 and maybe 4? As you heard, a hardcoded
value of 3 is too much already in some cases... 
Maybe also we shouldn't take the sum, but the sum-of-squares, because 
four times 1 might give completely different results from one times four.

I rather think we should implement some more clever "automatic" for
this (like in H26.L), instead of giving people the chance to "optimize"
their setting for one movie, then encode another one with the same
setting, which give horrible artefacts and they don't remember what the
did...

Christoph 

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