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HiFi5 NatureDSP RFFT output scaling issue for different FFT sizes

BR202501213237 — Thu, 01 Oct 2026 14:37:13 GMT

Hi,

I am working on standalone RFFT testing on Xtensa HiFi5 using the NatureDSP library.

I am testing different FFT sizes and comparing the fft_real32x32() output against my reference FFT data.

I am seeing the FFT output matches for 128, 512 and 2048 points, but does not match for 64, 256 and 1024 points.

My question is:

How should I correctly interpret/compensate the RFFT output for different FFT sizes and the returned fft_shifts value?

Is there any additional normalization or scaling required when comparing the HiFi5 fft_real32x32() output with a floating-point/reference FFT?

Also, has anyone observed this kind of behavior where:The FFT output matches for 128, 512 and 2048 points

with fft_real32x32() / ifft_real32x32() on HiFi5?

Any guidance on the correct FFT/IFFT scaling interpretation would be appreciated.

Platform: Xtensa HiFi5
Library: NatureDSP HiFi5
Functions: fft_real32x32() / ifft_real32x32()
Scaling option: 3

Thanks.

Grid Settings

JE202605133419 — Tue, 07 Jul 2026 07:17:24 GMT

Currently, in my Allegro X, even after changing and applying grid settings for different layers and checking again, the intended settings are not reflected. Only the "All Etch" setting applies to all layers. However, this is changeable other versions such as 17.4.

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