[XviD-devel] SAD cache

Radek Czyz radoslaw at airnet.com.au
Tue Mar 11 23:17:18 CET 2003


Hi,

> If it's 10-20% of _all_ checks, that's okay, because we check up to 8
> predictors or so, many of them will coincide. We could only call SAD-cache
> for predictor check and don't use a hash during diamond phase.

I just checked it myself. My procedure remembers the pointer of
reference picture which is being sad-ed, so it even intercepts a
double-check made between two macroblocks. The cache is reset only at
new picture.

It's not so bad after all.
For advdiamond/diamond and no extsearch, where make_mask() prevents a
double check even if a predictor is in range of initial diamond,
there is little multiple checks - average 2.7% of all (with standard
deviation +/-3.1 so it's not always so nice. There is 22% in one
picture...)

For motion precision 6, with square and extsearch, it becomes a bit
worse: (11.0 +/- 3.7)% .
Not very bad still, especially when we remember that it's almost
impossible to prevent them without extra cache.

Any comments?

Radek



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