[CELT-dev] Modifications of kiss_fft/compatibility with original kiss_fft code?

Frank Storm Frank.Storm at gmx.net
Mon Feb 21 09:42:20 PST 2011

Ok, many thanks for the info!

Best regards,

Am 21.02.2011 01:14, schrieb Jean-Marc Valin:
> It's more than just a reorganization of the code/data. The original 
> fixed-point kiss-fft supported either 16-bit precision or 32-bit 
> precision. Instead, the modified version we use in CELT uses 32-bit data 
> with 16-bit twiddles.
> 	Jean-Marc
> On 11-02-20 06:30 PM, Timothy B. Terriberry wrote:
>>> 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.
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