[FFmpeg-devel] [PATCH] ALAC Encoder

Michael Niedermayer michaelni
Sun Aug 17 15:15:17 CEST 2008


On Sun, Aug 17, 2008 at 09:09:00AM +0530, Jai Menon wrote:
> Hi,
> 
> On Sunday 17 Aug 2008 8:05:14 am Michael Niedermayer wrote:
> > On Sun, Aug 17, 2008 at 04:14:43AM +0530, Jai Menon wrote:
[...]
> > > +static void alac_stereo_decorrelation(AlacEncodeContext *s)
> > > +{
> > > +    int32_t *left = s->sample_buf[0], *right = s->sample_buf[1];
> > > +    int32_t tmp;
> > > +    int i;
> > > +
> > > +    for(i=0; i<s->avctx->frame_size; i++) {
> > > +        tmp = left[i];
> > > +        left[i] = (tmp + right[i]) >> 1;
> > > +        right[i] = tmp - right[i];
> > > +    }
> > >
> > > +    s->interlacing_leftweight = 1;
> > > +    s->interlacing_shift = 1;
> >
> > i do not belive this is optimal
> >
> 
> It may not be optimal in the sense that I do not adaptively select the 
> decorrelation scheme, but this is just the first iteration which aims at 
> getting a basic encoder into svn. And it is better than doing no 
> deorrelation. I did initially try out an adaptive approach but the difference 
> in compression wasn't that great. I'm looking into how this can be done in a 
> better manner. Till then, I was hoping if we could go with this.

see the pca.c/h i posted in a reply to ramiro a few days ago
it might be worth a try ... (and dont hesitate to ask if you have no clue
on how to use it ...)


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

Many things microsoft did are stupid, but not doing something just because
microsoft did it is even more stupid. If everything ms did were stupid they
would be bankrupt already.
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