[XviD-devel] Global Motion Compensation

[Christoph Lampert]

On Fri, 25 Oct 2002, Marco Al wrote:

> Christoph Lampert wrote:
> 
> >> Least median of squares seems to be the most popular method.
> >
> > Smolic starts with "structured" blocks only and uses a Maximum-Likelihood
> > approach after that. He claims results are very good (and fast).
> 
> That might be nicely combined with a MB classifier for adaptive quantization. He
> uses a faster (but slightly less-) robust estimator than LMedS.
> 
> Since you talked with him ... why does he in the "Real Time ..." paper only use
> the robust estimator for finding an estimate for the translation and not the
> other parameters of the affine transform? He does do so in his thesis for
> finding global motion from the MPEG-2 motion vectors, but he does not refine
> them afterwards for some reason ... he must have considered it, estimating all
> parameters before gradient descent search, but Id still like to know the reasons
> why it was not a good idea :)

He uses the coefficients from previous frame as start values. Maybe
those were simply superior to the poor estimates from block motion
vectors... 

gruel