[opus] [Opus][RFC][FFT][Fixed-Point][NEON] NEON-Optimize Fixed-Point FFT?

[Jean-Marc Valin]

There is definitely some use for a Neon fixed-point FFT. How much
exactly I'm not sure. Fixed-point is a bit more than just a fall-back
for CPUs with no FPU. There are CPUs for which fixed-point is still
faster. It depends on the exact model but also on what you run. For
example, even on x86 I believe that SILK encoding is slightly faster in
fixed-point, even though CELT is faster in float.

Cheers,

	Jean-Marc

On 24/12/14 01:29 AM, Phil Wang wrote:
> Hi,
> 
>  
> 
> I am working on DSP module of Ne10. I see there are fixed-point and
> floating-point FFT inside Opus. Is fixed-point FFT only a fall back for
> CPU without VFP? On ARMv7-A and ARMv8-A, benchmark result shows that
> fixed-point (int32) and floating-point (float32) FFT have similar
> performance. I guess fixed-point version is not often used on these
> platforms. Is it worth the effort to NEON-optimize fixed-point FFT?
> 
>  
> 
> Best Regards,
> 
> Phil Wang
> 
> 
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