BogaudioModules

commit 0869c830ff65f5243e0f7a9ef7f9a427d54083c9
parent c5ba1c6b7cc7d386cbe6d820496528513a7848c9
Author: Matt Demanett <matt@demanett.net>
Date:   Tue,  5 Jun 2018 22:04:46 -0400

Use table to speed up tanh; use that for saw saturation.

Diffstat:
A
src/dsp/math.cpp
 | 
25
+++++++++++++++++++++++++
A
src/dsp/math.hpp
 | 
24
++++++++++++++++++++++++
M
src/dsp/oscillator.cpp
 | 
3
+--
M
src/dsp/oscillator.hpp
 | 
2
++

4 files changed, 52 insertions(+), 2 deletions(-)
diff --git a/src/dsp/math.cpp b/src/dsp/math.cpp
@@ -0,0 +1,25 @@
+
+#include <stdlib.h>
+#include <math.h>
+
+#include "math.hpp"
+
+using namespace bogaudio::dsp;
+
+void FastTanhf::TanhfTable::_generate() {
+	_table[0] = -1.0f;
+	_table[_length - 1] = 1.0f;
+	for (int i = 1, n = _length - 1; i < n; ++i) {
+		_table[i] = tanhf((((i / (float)_length) * 2.0f) - 1.0f) * M_PI);
+	}
+}
+
+float FastTanhf::value(float radians) {
+	if (radians <= -M_PI) {
+		return -1.0f;
+	}
+	if (radians >= M_PI) {
+		return 1.0f;
+	}
+	return _table.value(((radians + M_PI) / (2.0f * M_PI)) * _table.length());
+}
diff --git a/src/dsp/math.hpp b/src/dsp/math.hpp
@@ -0,0 +1,24 @@
+#pragma once
+
+#include "base.hpp"
+#include "table.hpp"
+
+namespace bogaudio {
+namespace dsp {
+
+struct FastTanhf {
+	struct TanhfTable : Table {
+		TanhfTable(int n) : Table(n) {}
+		void _generate() override;
+	};
+	struct StaticTanhfTable : StaticTable<TanhfTable, 11> {};
+	const Table& _table;
+
+	FastTanhf() : _table(StaticTanhfTable::table())	{
+	}
+
+	float value(float radians);
+};
+
+} // namespace dsp
+} // namespace bogaudio
diff --git a/src/dsp/oscillator.cpp b/src/dsp/oscillator.cpp
@@ -1,4 +1,3 @@
-#include <math.h>
 
 #include "oscillator.hpp"
 
@@ -116,7 +115,7 @@ void SaturatingSawOscillator::setSaturation(float saturation) {
 float SaturatingSawOscillator::_nextForPhase(phase_t phase) {
 	float sample = SawOscillator::_nextForPhase(phase);
 	if (_saturation >= 0.1f) {
-		sample = tanhf(sample * _saturation * M_PI) * _saturationNormalization;
+		sample = _tanhf.value(sample * _saturation * M_PI) * _saturationNormalization;
 	}
 	return sample;
 }
diff --git a/src/dsp/oscillator.hpp b/src/dsp/oscillator.hpp
@@ -6,6 +6,7 @@
 #include <vector>
 
 #include "base.hpp"
+#include "math.hpp"
 #include "table.hpp"
 
 namespace bogaudio {
@@ -172,6 +173,7 @@ struct SawOscillator : Phasor {
 struct SaturatingSawOscillator : SawOscillator {
 	float _saturation;
 	float _saturationNormalization;
+	FastTanhf _tanhf;
 
 	SaturatingSawOscillator(
 		float sampleRate = 1000.0f,