hi,

i am working on a project trying to make aac decoder, i use fixed point 32 bit numbers.

my problem is with the SBR part, there according to the specs you have to divide energy envalopes
(ISO 14496-3:2005(E) pg 234)
the numbers are going real high - i could manage to get there to 64 bit but what does anybodey know what is the real region of numbers could work with?

There is a fixed point HE AAC encoder and decoder with source code from the 3gpp consortium. Maybe it helps to have a look at the source?

http://www.3gpp.org/ftp/Specs/html-info/26411.htm

thanks, i am going over it

but what is that version? is it free could anyone use it?

You'll have to pay license fees

http://www.vialicensing.com/licensing/MPEG...oduct=MPEG-4AAC

thanks,

looking at his source i see that i did almost the same - moving to mantisas and exp,
the thing is, as i see in the limiting and the spec, that all the final results can fit to 32 bits.

if i knew what could be the values of the inward calculation and knew that they are going to be 64 or maybe if they are higher i could cut them i would not turn to mantisas and exponents and do it in less complexity.