Linus Torvalds 43bb0b86e0 Add skeleton of a host side fft test ...

.. and a horrible tuning WAV of me plucking strings like some kind of
deranged monkey.  That guitar is roughly tuned in DADGAD just to make it
be that worst-case thing.

[ Ok, the worst-case thing is my playing, but you get the idea.

  The WAV is just a mono export from Audacity, recorded by using the
  guitar pedal as a USB audio interface, and the guitar was tuned to
  DADGAD with the pedal.

  But don't blame the pedal for my bad playing or any bad tuning. That's
  all entirely on me ]

The idea is that this C part exactly emulates the pedal and uses
fastsincos() etc.  I had to teach reverse_n_bits() to have a generic
version that didn't rely on ARM inline assembly, but otherwise it's the
exact existing same code for the math.

Then in the next step we can do a python visualizer with SciPy and
friends that not only show the data the pedal uses, but compares it to
alternate ways of doing it (and in the process also verifies that
fastsincos() and our special quarter_sin[] hanning function etc are
correct - they are).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2026-06-12 13:40:39 -07:00

6.7 MiB

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