BogaudioModules

commit 405193687ea68bc76ab6d8d32aa93ec713dc6e75
parent 5e0d39c205a97068fb668330091d2a71f7be547a
Author: Matt Demanett <matt@demanett.net>
Date:   Mon, 10 Jan 2022 22:59:30 -0500

Fix pops/glitches in oscillator pulse outputs when using audio rate PWM. #193

Diffstat:
M
src/dsp/oscillator.cpp
 | 
23
++++++++++++++++++-----
M
src/dsp/oscillator.hpp
 | 
10
++++++----

2 files changed, 24 insertions(+), 9 deletions(-)
diff --git a/src/dsp/oscillator.cpp b/src/dsp/oscillator.cpp
@@ -171,10 +171,15 @@ void SquareOscillator::setPulseWidth(float pw) {
 	else if (pw <= minPulseWidth) {
 		pw = minPulseWidth;
 	}
-	_pulseWidth = cyclePhase * pw;
+	_nextPulseWidth = cyclePhase * pw;
 }
 
 float SquareOscillator::nextForPhase(phase_t phase) {
+	phase_t cycle = phase / cyclePhase;
+	if (_lastCycle != cycle) {
+		_lastCycle = cycle;
+		_pulseWidth = _nextPulseWidth;
+	}
 	phase %= cyclePhase;
 
 	if (positive) {
@@ -205,19 +210,27 @@ void BandLimitedSquareOscillator::setPulseWidth(float pw, bool dcCorrection) {
 	else if (pw <= minPulseWidth) {
 		pw = minPulseWidth;
 	}
-	_pulseWidth = cyclePhase * pw;
+	_nextPulseWidth = cyclePhase * pw;
 
 	if (pw > 0.5) {
-		_offset = 2.0f * pw - 1.0f;
+		_nextOffset = 2.0f * pw - 1.0f;
 	}
 	else {
-		_offset = -(1.0f - 2.0f * pw);
+		_nextOffset = -(1.0f - 2.0f * pw);
 	}
 
-	_dcOffset = _dcCorrection ? 1.0f - 2.0f * pw : 0.0f;
+	_nextDcOffset = _dcCorrection ? 1.0f - 2.0f * pw : 0.0f;
 }
 
 float BandLimitedSquareOscillator::nextForPhase(phase_t phase) {
+	phase_t cycle = phase / cyclePhase;
+	if (_lastCycle != cycle) {
+		_lastCycle = cycle;
+		_pulseWidth = _nextPulseWidth;
+		_offset = _nextOffset;
+		_dcOffset = _nextDcOffset;
+	}
+
 	float sample = -BandLimitedSawOscillator::nextForPhase(phase);
 	sample += BandLimitedSawOscillator::nextForPhase(phase - _pulseWidth);
 	return sample + _offset + _dcOffset;
diff --git a/src/dsp/oscillator.hpp b/src/dsp/oscillator.hpp
@@ -219,7 +219,8 @@ struct SquareOscillator : Phasor {
 	static constexpr float maxPulseWidth = 1.0f - minPulseWidth;
 	static constexpr float defaultPulseWidth = 0.5f;
 	float _pulseWidthInput;
-	phase_t _pulseWidth = cyclePhase * defaultPulseWidth;
+	phase_t _lastCycle = -1;
+	phase_t _pulseWidth = cyclePhase * defaultPulseWidth, _nextPulseWidth = cyclePhase * defaultPulseWidth;
 	bool positive = true;
 
 	SquareOscillator(
@@ -239,9 +240,10 @@ struct BandLimitedSquareOscillator : BandLimitedSawOscillator {
 	const float maxPulseWidth = 1.0f - minPulseWidth;
 	float _pulseWidthInput= -1.0f;
 	bool _dcCorrection = false;
-	phase_delta_t _pulseWidth;
-	float _offset;
-	float _dcOffset;
+	phase_t _lastCycle = -1;
+	phase_delta_t _pulseWidth = 0, _nextPulseWidth = 0;
+	float _offset = 0.0f, _nextOffset = 0.0f;
+	float _dcOffset = 0.0f, _nextDcOffset = 0.0f;
 
 	BandLimitedSquareOscillator(
 		float sampleRate = 1000.0f,