[FFmpeg-devel] [PATCH] AAC decoder

Robert Swain robert.swain
Fri May 23 11:08:47 CEST 2008

2008/4/2 Michael Niedermayer <michaelni at gmx.at>:
> On Tue, Apr 01, 2008 at 04:56:48PM +0200, Andreas ?man wrote:
>> Andreas ?man wrote:


>> +static inline float ivquant(AACContext * ac, int a) {
>> +    static const float sign[2] = { -1., 1. };
>> +    int tmp = (a>>31);
>> +    int abs_a = (a^tmp)-tmp;
>> +    if (abs_a < sizeof(ac->ivquant_tab)/sizeof(ac->ivquant_tab[0]))
>> +        return sign[tmp+1] * ac->ivquant_tab[abs_a];
> What is the point of the sign splitout? it seems that it would be simpler
> to have that in teh table as well

Kostya is in favour of removing the ivquant_tab table because it
caches only a small number of possible values and its general impact
on decoding speedup is not obvious.

Attached is a patch that removes the ivquant_tab table and simplifies
and moves the ivquant() functionality into the calling loop and
removes the ivquant() function altogether as it isn't really needed to
wrap pow().

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