Arbitrary wave table for a custom oscillator

Question

I need to create a specific custom waveform for an oscillator for use with Web Audio API.

I have a Javascript function to output the desired waveform (calculating a y between -1 and 1 for any given x), and the plotted result looks like this:

However the Web Audio API documentation only lets you create custom wavetables based on harmonic tables via the createPeriodicWave function, which can then be used to configure a custom oscillator via setPeriodicWave. Is there a generic technique that can be used to compute the harmonic tables based on my waveform function?

Answer 1

A DFT (or FFT) with a length of exactly one period of your custom waveform will produce a harmonic table. Just low-pass filter and sample your waveform 2^N times, and feed that to a generic library FFT. (Choose a large enough 2^N to be at least more than 2X the low-pass filter's or your waveform's intrinsic highest frequency content). The magnitudes of the FFT's resulting complex bins will be your harmonic power levels.