[FFmpeg-devel] [PATCH] ALAC Encoder

[Ramiro Polla]

On Sun, Aug 17, 2008 at 12:55 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Sun, Aug 17, 2008 at 11:17:27AM -0300, Ramiro Polla wrote:
>> On Sun, Aug 17, 2008 at 10:15 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> > 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 ...
>>
>> Speaking of that... I haven't finished integrating it in MLP (I'm
>> working on some other stuff atm), but it seems to be what I need.
>
>> Could you get it cleaned up and committed like you suggested?
>
> done

Thanks. I think the TEST could also be added to lavu/Makefile.

Ramiro Polla