[FFmpeg-devel] [PATCH] ALAC Encoder

[Michael Niedermayer]

On Mon, Aug 18, 2008 at 07:54:58PM +0200, matthieu castet wrote:
> Michael Niedermayer wrote:
> > On Mon, Aug 18, 2008 at 07:24:23PM +0200, Michael Niedermayer wrote:
> >> On Mon, Aug 18, 2008 at 09:55:10PM +0530, Jai Menon wrote:
> >> The decoder does:
> >>             cl -= (cr * W) >> S;
> >>             cr += cl;
> >>
> >>             l = cr;
> >>             r = cl;
> >> the encoder does:
> >>             l -= r;
> >>             r += (l * W) >> S;
> >>
> >>             cr = l;
> >>             cl = r;
> >>
> >> These hold true for all values of W and S
> >>
> >> with W=0,S=1  you get l-r, r
> >> with W=1,S=1  you get l-r, (r+l)>>1
> >> with W=2,S=1  you get l-r, l
> > 
> > i just realized my suggestion has a little bug, the silly thing only
> > applies decorrelation when W!=0 ...
> 
> Note that could be a bug in our decoder.

then there has to be another way the decorrelation is signaled which means
either R,L or all of the R-L based ones would likely fail to decode correctly
with the binary decoder. Has anyone tested that?


> 
> BTW, may be W can be signed.

If so that wouldnt be too usefull ...
unless you think somethingg like l-r, 2*r-l would compress well


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato 
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