Re[6]: [XviD-devel] Quality optimization

[Christoph Lampert]

On Sat, 25 Jan 2003, Radek Czyz wrote:
> >> if (x) { // 50% incorrect prediction
> >>   x = ABS(x) // ~40% incorrect prediction
> >> ...
> >> ... and the same for y.
> 
> > Where the heck in the code is this line???
> 
> Well, it looks like this:
> 
>         if (x) {
>                 x = ABS(x);
>                 x += (1 << (iFcode - 1)) - 1;
>                 x >>= (iFcode - 1);
>                 if (x > 32) x = 32;
>                 xb = mvtab[x] + iFcode;
>         } else xb = 1;

Oh, okay, so it's more than just the "x=ABS(x)" within the if-block. 
Then of course, it can't simply be dropped (although one still might find
a more clever solution).

e.g. result would still be the same if mvtab[0]=1. 
Can you check how often (x) really _is_ zero? If this is small, below 10%
or so, it might be better to do all the stuff regardless what x is.

gruel