[FFmpeg-devel] [PATCH 1/4] zmbvenc: don't sum the entropy when blocks are equal

Tomas Härdin tjoppen at acc.umu.se
Sat Dec 22 14:11:09 EET 2018

tor 2018-12-20 klockan 17:46 +0000 skrev Matthew Fearnley:
> > On Thu, 20 Dec 2018 at 16:30, Tomas Härdin <tjoppen at acc.umu.se> wrote:
> > I have a feeling this could be sped up further by just doing *xored =
> > histogram[0] == ZMBV_BLOCK*ZMBV_BLOCK after the loops, if [PATCH 3/4]
> > is applied before this. Computing both histogram and xored in the loop
> > seems pointless.
> > 
> You're right, that speedup didn't occur to me.  It makes the logic a bit
> more tenuous, but it would be more efficient.

Eh, I wouldn't really call "we have xored data to output if and only if
number of zeroes < number of pixel" fairly easy to grasp. A comment
might be good tho

> Note that bw,bh aren't guaranteed to equal ZMBV_BLOCK, so `histogram[0] ==
> bw*bh` would have to be used to guard against those (literal) edge cases.

Right, yes. But if we have block sizes other than ZMBV_BLOCK^2 then we
need score tables for those sizes too.


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