[Ffmpeg-devel] AAC decoder

Mike Melanson mike
Tue Mar 21 22:13:28 CET 2006

Benjamin Larsson wrote:
> And the sine_short table should be a subset of sine_long.

	That seems intuitive, but I don't think it's true in this case. The 
short values are derived as:

   for odd values i in 1..127
     sine_value = sin(i * PI / 512)

For long values:

   for odd values in 1..1023
     sine_value = sin(i * PI / 4096)

In the short formula, you could multiply (i * PI / 512) by (8/8) to get 
the same denominator as in the long formula. But multiplying by 8 would 
make the numerator even and thus the sine value would not occur in the 
long table.

	(I think.)
	-Mike Melanson

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