[Ffmpeg-devel] AAC decoder

[Mike Melanson]

Mike Melanson wrote:
>     One question: Is it really necessary to include tables for sine and 
> KBD values? I know the sine table can easily be generated at runtime. 
> The same probably applies for the KBD values.

	I decided to put my code where my mouth is. What follows is a program 
to generate the sine tables, and also validates them against the tables 
in your aac.h file. This will eliminate the hard-coding of 
sine_long_1024[] and sine_short_128[]. I will see if I can figure out an 
algorithm for the KBD stuff as well.

-- 
	-Mike Melanson


#include <stdio.h>
#include <math.h>

#include "aac.h"

int main(int argc, char *argv[])
{
     int i;
     float sine_long[1024];
     float sine_short[128];

     for (i = 0; i < 1024; i++) {
         sine_long[i] = sin((i * 2 + 1) * M_PI / 4096);
         if (sine_long[i] - sine_long_1024[i] > 0.0000001)
             printf ("%d: calculated = %f, original = %f\n", i,
             sine_long[i], sine_long_1024[i]);
     }

     for (i = 0; i < 128; i++) {
         sine_short[i] = sin((i * 2 + 1) * M_PI / 512);
         if (sine_short[i] - sine_short_128[i] > 0.0000001)
             printf ("%d: calculated = %f, original = %f\n", i,
             sine_short[i], sine_short_128[i]);
     }

     return 0;
}