[FFmpeg-devel] [PATCH] RV40 Loop Filter
Michael Niedermayer
michaelni
Mon Oct 27 13:38:35 CET 2008
On Mon, Oct 27, 2008 at 02:26:45PM +0200, Kostya wrote:
[...]
> I just treated this as a sum of four consequent coeffs multiplied
> by 26 with some additional changes - the first one (or the last one)
> should be (26-1)*coefficient, so I subtract one (here's the "sub" name)
> and depending on the last coefficient position we have either 25 or
> 26+25 multiplier.
[...]
> 0 - horizontal, 1 - vertical
this should be in the doxy ...
>
> [filter horror]
>
> > i will not accept this mess, sorry.
> > If you dont (or cant) clean this up i will try eventually but that might not
> > be soon.
> > as is, this is too much of a mess and iam unwilling to belive that h264
> > drafts required such mess.
>
> Me neither. Another example is that they use 1/4th pel interpolation filter
> (1*X[-2] - 5*X[-1] + 52*X[0] + 20*X[1] - 5*X[2] + 1*X[3] + 32) >> 6
> instead of calculating halfpel value first and then averaging it,
> which leads to some rounding errors.
(1*X[-2] - 5*X[-1] + 52*X[0] + 20*X[1] - 5*X[2] + 1*X[3] + 32) >> 6
=
((1*X[-2] - 5*X[-1] + 20*X[0] + 20*X[1] - 5*X[2] + 1*X[3]) >> 5 + X[0] + 1) >> 1
though intermediates can be outside 0..255
>
> Since I've fixed some quantization-related bugs, it looks more decent
> even without loop filter, so I'm tempted to try less sophisticated
> loop filter (for low-power CPUs) from the same codecs, it looks simple
> and sane.
ill try to find some unused vomit proof bags and see if i can simplify
this darn rv loop filter.
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Awnsering whenever a program halts or runs forever is
On a turing machine, in general impossible (turings halting problem).
On any real computer, always possible as a real computer has a finite number
of states N, and will either halt in less than N cycles or never halt.
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