· by positron26.bsky.social ·1d ago · view on bsky.app ↗

SOUND WARNING 🔊👂 To test the downsampling lowpass (which is on-GPU) I rigged the DFT to draw the 8x downsample up to the Nyquist limit (3kHz). Exactly as planned, the folded signal starts reflecting into the transition band and gets obliterated before making it halfway back down.

1 comments — live from bluesky

Positron · 0 · 1d ago

Only the black halves of the screen are "safe" for use, so the folded part is never consumed. Gain is 100x for the test, so these pure tones would light up like a freak show if the attenuation wasn't crushing everything in the stop band. Thanks, Parks McClellen and Remez!

Positron · 0 · 1d ago

It was almost unexpected that the output would be correct on the first pass. All of the problems were in the plumbing, not the compute kernel or any of its control data. I'm moving way more haphazardly than if building airplanes, so there's definitely some luck at work.