Aliasing and quantization distotion

[unfa]

I've noticed two problems with the sound quality, even when using the "HQ" option.

• Aliasing distortion for high pitched notes (best heard with Saw waveforms)

• Quantization distortion for quiet notes (best heard with quiet Sine wavesforms with long decay)

Here's a video demonstrating this (you'll need to listen loudly to be able to hear that, but the spectrogram shows the problems very cleanly):

https://youtu.be/8kb7at02WgM

[mkruselj]

Quantization distortion is to be expected since bit-depth of waveforms is 11-bit...

oxefmsynth/src/synth/constants.h

Line 31 in fe078ea

#define WAVEFORM_BIT_DEPTH 11

FM usually works with mathematically precise waveforms (not band-limited oscillators), so yeah aliasing is inherent in it, especially with non-sine waveforms.