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Sparse Fast Fourier Transform, The faster-than-fast Fourier transform
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post Feb 10 2012, 19:55
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I don't know if this topic was already mentioned here (I wasn't able to find it).

Somebody here could find it interesting:

MIT news article: The faster-than-fast Fourier transform

sFFT web page: sFFT: Sparse Fast Fourier Transform

Best regards.

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post Sep 23 2012, 00:48
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QUOTE (saratoga @ Sep 22 2012, 20:30) *
QUOTE (m45t3r @ Sep 22 2012, 19:25) *
Well, on Rockbox at least the FFT part of decoding can take up to 50% of CPU time (http://www.rockbox.org/wiki/FasterMDCT).

Well it did until stripwax, mt and I rewrote it using a modern, efficient split radix FFT. Now its quite a bit faster.

QUOTE (m45t3r @ Sep 22 2012, 19:25) *
It's true that audio decoding is not really that much CPU intensive, but video encoding/decoding probably is another mater.

Sure, but the DCT is usually only a pretty small portion of that. And of course you can already use approximations if you want (though usually people don't since its not very slow to begin with).

Interesting, so how much CPU time does FFT uses on Rockbox nowadays?
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post Sep 23 2012, 01:01
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QUOTE (m45t3r @ Sep 22 2012, 19:48) *
Interesting, so how much CPU time does FFT uses on Rockbox nowadays?

To be honest its been so long I don't remember. Probably 10MHz or so though on arm7tdmi, less on a more modern ARM chip.
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