[FFmpeg-devel] [RFC v5] libavcodec: add a native Daala decoder

[Ronald S. Bultje]

Hi,

On Wed, Jan 6, 2016 at 11:16 PM, Ganesh Ajjanagadde <gajjanag at mit.edu>
wrote:

> On Wed, Jan 6, 2016 at 5:22 PM, Ronald S. Bultje <rsbultje at gmail.com>
> wrote:
> > Hello,
> >
> [...]
> >
> >> +#define DAALA_QM_SCALE (1 << 15)
> >> +#define DAALA_QM_SCALE_MAX (DAALA_QM_SCALE - 1)
> >> +#define DAALA_QM_SCALE_UNIT (1.0f/DAALA_QM_SCALE_MAX)
> >> +#define DAALA_QM_INV_SCALE (1 << 12)
> >> +#define DAALA_QM_INV_SCALE_UNIT (1.0f/DAALA_QM_INV_SCALE)
> >> +#define DAALA_QM_BSIZE (DAALA_BSIZE_MAX*DAALA_BSIZE_MAX)
> >> +#define DAALA_QM_BUFFER_SIZE (DAALA_NBSIZES*2*DAALA_QM_BSIZE)
> >
> > Floats in a video decoder? That looks strange. I’m pretty sure these are
> > placeholders for integer arithmetic?
>
> Just my curiosity, but isn't it easier while developing video codecs
> to work with floats, and then convert to fixed point arithmetic? It
> can be hard while designing algorithms from the start to agonize over
> fixed point at the very beginning, echoing your remark about
> placeholders.


Certainly, in the academic phase of a project. At the point where you get
>1 decoder, it's probably time to do away with the floats.

Or conversely, if you're still designing algorithms, you probably don't
want to have to deal with >1 decoder.

Ronald