opus - Feb 2011 - Modifications of kiss_fft/compatibility with original kiss_fft code?

Hi,

some time ago I compiled celt (version 0.7.0) on a NiosII processor (for
those who don't know the NiosII, this is a soft core processor for FPGAs
from Altera) which worked pretty well. In order to take away some of the
processing load from the processor, I have now developed a FFT
co-processor which is basically compatible to the original kiss_fft
algorithm. Before I start now to integrate my co-processor into the celt
code, I would like to check whether the changes, that were made to the
original kiss_fft code, change the actual behaviour of the kiss_fft
function or whether they were only made for speed improvement or
cosmetic reasons. In other words, could I still replace the functions
"kiss_fft_alloc" and "kiss_fft" with the original code
(apart from the
fact that there are now functions for the inverse transformation in celt)?

Many thanks and best regards,
Frank

> code, I would like to check whether the changes, that were made to the
> original kiss_fft code, change the actual behaviour of the kiss_fft
> function or whether they were only made for speed improvement or
> cosmetic reasons. In other words, could I still replace the functions
> "kiss_fft_alloc" and "kiss_fft" with the original code
(apart from the
> fact that there are now functions for the inverse transformation in celt)?
They were made mostly for data organization reasons (i.e., to allow 
static data and sharing of twiddles between FFTs of different sizes). 
The actual transforms should be the same. I'd need to double-check for 
fixed-point, but in my decoder re-implementation, I was able to start 
from the current kisfft release and achieve compatibility with the float 
code without changing the actual calculations involved.