[FFmpeg-devel] AAC encoder questions

[Kostya]

On Fri, Apr 24, 2009 at 01:04:56PM -0400, Alex Converse wrote:
> On Fri, Apr 24, 2009 at 9:34 AM, Kostya <kostya.shishkov at gmail.com> wrote:
> > On Fri, Apr 24, 2009 at 03:51:13AM -0400, Alex Converse wrote:
> >> On Fri, Apr 24, 2009 at 3:16 AM, Kostya <kostya.shishkov at gmail.com> wrote:
> >> > On Fri, Apr 24, 2009 at 03:07:18AM -0400, Alex Converse wrote:
[...]
> 
> Trying to work through the logic of it:
> 
> Normally we do t - pow(clip(floor(pow(t * Q, .75)+0.4504), 8191), 1.333)*IQ
> the top case is a shortcut where we know that the clip will resolve to
> 8191. (I'm also not sure why we are using 8192 up there, but that is a
> separate issue. "The maximum allowed absolute amplitude for x_quant is
> 8191.")

That value is still < pow(8192, 4.0/3), so it resolves to 8191 after all.
 
> Assuming we use this shortcut then out expression is pow(8191, 1.333)
> * IQ which resolves to 165140*IQ (or 165113*IQ for 8191...).