[FFmpeg-devel] [PATCH] ALS decoder

[Reimar Döffinger]

On Tue, Aug 25, 2009 at 03:37:11PM +0200, Thilo Borgmann wrote:
> >> +        ctx->last_frame_length = samples % ctx->sconf.frame_length;
> >> +        if (!ctx->last_frame_length) {
> >> +            ctx->last_frame_length = sconf->frame_length;
> >> +        }
> > 
> > thats the same as
> > (L-1) % F + 1
> > i think (unchecked though)
> Missing lvalue and independent of samples?

l == samples and F == ctx->sconf.frame_length
Though I have to wonder what the difference between
ctx->sconf.frame_length and sconf->frame_length is...

> >> +            // damaged block, write zero for the rest of the frame
> >> +            while (b < ctx->num_blocks) {
> >> +                memset(raw_sample, 0, div_blocks[b]);
> >> +                raw_sample += div_blocks[b];
> >> +                b++;
> >> +            }
> >> +            return -1;
> > [...]
> >> +            // damaged block, write zero for the rest of the frame
> >> +            while (b < ctx->num_blocks) {
> >> +                memset(raw_samples_L, 0, div_blocks[b]);
> >> +                memset(raw_samples_R, 0, div_blocks[b]);
> >> +                raw_samples_L += div_blocks[b];
> >> +                raw_samples_R += div_blocks[b];
> >> +                b++;
> >> +            }
> > [...]
> >> +                // damaged block, write zero for the rest of the frame
> >> +                while (b < ctx->num_blocks) {
> >> +                    memset(raw_samples_L, 0, div_blocks[b]);
> >> +                    raw_samples_L += div_blocks[b];
> >> +                    b++;
> >> +                }
> > 
> > cant these be factored/combined?
> They could be factored into decode_frame() but several parameters would
> have to be passed somehow to know wich samples of which channel could be
> decoded correctly already.
> Alternative 1) loose all samples of the current RA unit.
> Alternative 2) infunction {while() memset;} but this would add a second
> loop for the code block in the middle.
> Which way to go?

Hm, neither?
get_remain_count():
  while (b < ctx->num_blocks) sum += div_blocks[b];
  return sum;

count = get_remain_count();
memset(raw_samples_L, 0, count);
raw_samples_L += count;
memset(raw_samples_R, 0, count);
raw_samples_R += count;

Though personally I'd suggest expanding the memset+increment
into a bytestream_fill_byte() that does both.