[FFmpeg-devel] [Issue 664] [PATCH] Fix AAC PNS Scaling

Robert Swain robert.swain
Tue Oct 14 18:31:06 CEST 2008

2008/10/10 Michael Niedermayer <michaelni at gmx.at>:
> On Fri, Oct 10, 2008 at 12:15:30PM +0100, Robert Swain wrote:
>> 2008/10/8 Michael Niedermayer <michaelni at gmx.at>:
>> [...]
>> > so it seems the gcc version makes a very significant difference as well
>> It seems there isn't really a good all-round solution here. What shall
>> we do? I would be inclined to look toward the future and use doubles
>> for the sums and sqrtf() as this performs best on a modern CPU with
>> GCC 4.3, but what do you think? I suppose less powerful older cpus
>> would need better performance more, but obviously ideally we would
>> want to use whatever is best on the machine in question. Maybe a macro
>> and configure time testing/identification and mapping based on CPU?
> Iam still thinking that 1 second of normalized random vectors might be
> worth considering. That would avoid the sqrt() completely unless iam
> missing something.

Previously you said:

"precalculate a second of noise normalized to the band sizes and
randomly pick from these"

Could you elaborate on what you have in mind please?

At the moment I'm thinking that all band sizes would have to be found
from the swb_offset[] tables. Then I don't really understand what
you're suggesting we have for each band size.


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