Phase distortion: a cosine read at a warped phase. More...

#include <phase_distortion.hpp>

Public Member Functions
void	set_sample_rate (double sr)
void	set_frequency (double hz)
void	set_shape (PhaseDistortionShape shape)
void	set_amount (double amount)
	How far the phase is warped, 0 (an undistorted cosine) to 1.
void	set_resonant_depth (double multiples)
	Highest carrier multiple the resonant shapes reach at full amount.
void	reset ()
double	phase () const
SampleType	process ()

Detailed Description

template<typename SampleType = float>
class pulp::signal::PhaseDistortionOscT< SampleType >

Phase distortion: a cosine read at a warped phase.

The oscillator is always a cosine. What changes is how fast the phase moves through it — slowly through one part of the cycle and quickly through another — and that alone turns a sine into a saw, a pulse, or a resonant sweep. Nothing is filtered and nothing is added, so the output is exactly as band-limited as a cosine is, which is why the technique produced clean bright tones on hardware that could not afford a filter.

The resonant shapes are the distinctive ones and they work differently: the cosine is read at a multiple of the phase, and the result is multiplied by a window that falls once per cycle. The multiple is what sets the apparent resonant peak and the window is what makes it a formant rather than a tone, so sweeping the amount sounds like opening a resonant filter even though no filter exists. That illusion is the reason the technique is worth having alongside a real filter rather than instead of one.

Lineage: Casio's phase-distortion patent, US 4,658,691 (1987, expired). Implemented from the published description of the technique.

RT contract: every member allocates nothing and takes no locks.