Aliasing and quantization distotion

oxesoft / oxefmsynth

Oxe FM Synth official repository

https://oxesoft.wordpress.com/

GNU General Public License v3.0

178 stars 27 forks source link

Aliasing and quantization distotion #19

Open unfa opened 7 years ago

unfa commented 7 years ago

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 commented 3 years ago

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

https://github.com/oxesoft/oxefmsynth/blob/fe078ea036991081c3a28bb388a3fecd0e8e3a5d/src/synth/constants.h#L31

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