Implementing oversampling in plug-ins.

[husamalhomsi]

• Synthesizers:
When playing high notes on a synthesizer using a harmonically rich wave like a saw wave, there are probably some frequencies that will go above the nyquist frequency, so aliasing occurs.

Just play the note C8 on TripleOscillator using a saw wave to hear the aliasing noise.

My idea of the UI implementation is radio buttons in the plugin tab of each synthesizer offering oversampling factors in powers of 2.

• Effect plug-ins:
There are 2 types of plug-ins that would benefit from using oversampling (as far as I know).

(1) Waveshapers, distorters, overdrivers, bitcrushers and Lo-fi effects (or anything that generates a lot of overtones).
When using any of the effects above on a sound, extra overtones are being added to it, and if these overtones go above the nyquist frequency, aliasing occurs.

Spectrum of a heavily waveshaped sine wave.

Spectrum of the same sound but with 16x oversampling.

My idea of the UI implementation is a slider in each of these plug-ins mentioned earlier offering oversampling factors in powers of 2.

(2) Equalizers.
When a band (of any type) in the equalizer gets close to the nyquist frequency, its shape distorts.

A normal low-pass filter at 1000 Hz looks like this:

The same filter but at 16000 Hz looks like this:

Using oversampling will prevent this distortion and improve audio quality, particularly at high frequencies.
My idea of the UI implementation is an off/on "Oversampling" button on each equalizer plug-in effect that uses a specific oversampling factor that is just enough to prevent the distortion without introducing excess CPU load.

[PaulBatchelor]

Have you looked at the oversampling options in the export menu?

[husamalhomsi]

Have you looked at the oversampling options in the export menu?

Yes, but they don't even work at the moment, and even if they do work, they're on export only.

[grejppi]

IIRC the Oscillator class has band-limited waveforms available, which are available in LB302 and Monstro, but they are not enabled for TripleOscillator.

[husamalhomsi]

IIRC the Oscillator class has band-limited waveforms available, which are available in LB302 and Monstro, but they are not enabled for TripleOscillator.

Band-limited waveforms are a good idea, but modulation of said waveforms could still cause aliasing.

[PaulBatchelor]

This feature would require a lot of internal refactoring of the plugin and classes, as well as introduce new UI. It's a very tall order, but the code is there if you'd like to take a stab at it and make a PR. I'm not also entirely convinced that this would be an effective new feature. Oversampling is very much a brute-force approach to alias reduction. I'd be more keen on approaching more specific solutions to alias reduction for particular plugins and effects, rather than try cram a "one shoe fits all" feature. Or better yet, just build new instruments and effects that sound better.

[Rossmaxx]

Oversampling is gone entirely since #7228

[Rossmaxx]

@sakertooth close?

[zonkmachine]

Oversampling is gone entirely since #7228

The description of that PR says should really be an option on a per-plugin basis, which this issue is all about. If someone want's to implement oversampling in a plugin or two, why not?

[Rossmaxx]

Oops, another misread.