[Theora-dev] Re: [Fwd: Re: Theora mcomp tuning...]
Timothy B. Terriberry
tterribe at vt.edu
Fri Sep 17 14:05:21 PDT 2004
Adam D. Moss wrote:
>> Although SSD may seem to be a nicer theoretical quantity to work with,
>> this is only true when errors come from a Gaussian source.
> Okay -- I guess that's true of most of my experiments on estimation
> of perceptible quantization error.
Motion compensation does not deal with quantization error, but
prediction error, which has altogether different statistics. The errors
are better approximated by an exponential distribution, for which SAD is
the optimal metric. It's still only an approximation. A Cauchy
distribution can do an even better job, but the optimal error
metric---log(1+d^2/a^2) for some constant a---imposes too heavy a
computational burden to be practical, and the gains are minor.
More information about the Theora-dev