Hector Martin (@marcan@treehouse.systems)
s3.eu-central-2.wasabisys.com
Attached: 1 video Tested 12.4 and 13.5 on M2 MBA, sounds just as bad, so this has been going on for a *long* time now. M1 MBA does not have this problem, nor does M1 MBP 16". This might be an M2 MBA specific problem. It is very, *very* obvious if you just play a 300Hz sine with any random frequency generator website and crank the volume up. Upgrading to Sonoma now, but I doubt they fixed it... it seems this has *always* been broken on at least the M2 13" MBA. Edit: Still there in Sonoma.
  • towerful@programming.dev
    11·
    9 months ago

    They go on to deduce it’s an off-by-one error in the time domain.
    So instead of 0-127 it’s processing 0-126 samples (a classing i < 127 instead of i <= 127 in a for loop)

    https://social.treehouse.systems/@marcan/111160552044972689

    The train of thought was:

    • The aliasing is every 375 Hz.
    • 48000 / 375 = 128 so this is some fourier thing with a block size 128???
    • Wait no, this could be time domain, aliasing like that is what you get when you upsample without lowpassing.
    • Specifically, when you upsample with zero-sample padding (standard), that is, when one sample out of 128 has the low frequency content.
    • So this is like taking the average of a 128-sample block and adding it to just one sample?
    • Wait, isn’t that almost equivalent to zeroing out one sample?

    numpy time

    fs, signal = wavfile.read("sweep.wav")
signal[::128] = 0
wavfile.write("lol.wav", fs, signal)

    And the rest is history.

    Edit:
    Stupid less-than symbol getting html-coded