* Add local state data to Oscillator

- Need to find a better way to do that...
* Noise oscillator generates colored noise
- Inspired by Dave Smith Instruments Prophet-12
- Controlled by Width parameter
- 0%: red noise (-6dB/octave)
- 25%: pink noise (-3dB/octave)
- 50%: white noise (0dB/octave)
- 75%: blue noise (+3dB/octave)
- 100%: violet noise (+6dB/octave)

Author: [email protected]

Oscillator.cpp

@@ -15,6 +15,7 @@ void OscillatorState::Reset()
 {
 	phase = 0.0f;
 	index = 0;
+	memset(f, 0, sizeof(f));
 }
 
 // start oscillator
@@ -26,9 +27,6 @@ void OscillatorState::Start()
 // update oscillator
 float OscillatorState::Update(OscillatorConfig const &config, float const step)
 {
-	if (!config.enable)
-		return 0.0f;
-
 	float const delta = config.frequency * config.adjust * step;
 
 	// compute oscillator value
@@ -50,6 +48,25 @@ float OscillatorState::Compute(OscillatorConfig const &config, float delta)
 void OscillatorState::Advance(OscillatorConfig const &config, float delta)
 {
 	phase += delta;
+#if 1
+	if (config.sync_enable)
+	{
+		if (phase >= config.sync_phase - index)
+		{
+			phase -= config.sync_phase - index;
+			index = 0;
+		}
+	}
+	else
+	{
+		int const advance = FloorInt(phase);
+		if (advance)
+		{
+			phase -= advance;
+			index += advance;
+		}
+	}
+#else
 	if (phase >= config.sync_phase)
 	{
 		// wrap phase around
@@ -74,4 +91,5 @@ void OscillatorState::Advance(OscillatorConfig const &config, float delta)
 		if (index < 0)
 			index += cycle;
 	}
+#endif
 }

Oscillator.h

@@ -56,6 +56,13 @@ class OscillatorState
 	float phase;
 	int index;
 
+	// state values usable by wave functions
+	union
+	{
+		float f[8];
+		int i[8];
+	};
+
 	OscillatorState()
 	{
 		Reset();

WaveNoise.cpp

@@ -8,9 +8,148 @@ White Noise
 
 #include "Random.h"
 #include "WaveNoise.h"
+#include "Oscillator.h"
+#include "Math.h"
 
-// white noise wave
+// http://www.firstpr.com.au/dsp/pink-noise/
+//b0 = 0.99765f * b0 + white * 0.0990460f;	// x42.147234f
+//b1 = 0.96300f * b1 + white * 0.2965164f;	// x8.013957f
+//b2 = 0.57000f * b2 + white * 1.0526913f;	// x2.448119f
+//float const pink = 0.25f * (b0 + b1 + b2 + white * 0.1848f);
+
+#define FILTERS 3
+
+// low-pass filter bank for colored noise
+#if FILTERS == 3
+static const float a[3] =
+{
+	1 - 0.997907817f,	// 1 - expf(-2 * M_PI * 16 / 48000);
+	1 - 0.967044930f,	// 1 - expf(-2 * M_PI * 256 / 48000);
+	1 - 0.584987297f,	// 1 - expf(-2 * M_PI * 4096 / 48000);
+};
+static const float falloff = 0.25;	// sqrtf(1.f / 16.0f)
+static float const w0 = 1 - falloff;
+static float const w1 = w0 * falloff;
+static float const w2 = w1 * falloff;
+static const float w3 = falloff - w1 - w2;
+#elif FILTERS == 4
+static const float a[4] =
+{
+	1 - 0.997907817f,	// 1 - expf(-2 * M_PI * 16 / 48000);
+	1 - 0.983384430f,	// 1 - expf(-2 * M_PI * 128 / 48000);
+	1 - 0.874553978f,	// 1 - expf(-2 * M_PI * 1024 / 48000);
+	1 - 0.342210114f,	// 1 - expf(-2 * M_PI * 8192 / 48000);
+};
+static const float falloff = 0.353553385f;	// sqrtf(1.f / 8.f);
+static float const w0 = 1 - falloff;
+static float const w1 = w0 * falloff;
+static float const w2 = w1 * falloff;
+static float const w3 = w2 * falloff;
+static float const w4 = falloff - w1 - w2 - w3;
+#elif FILTERS == 5
+static const float a[5] =
+{
+	1 - 0.997907817f,	// 1 - expf(-2 * M_PI * 16 / 48000);
+	1 - 0.991657414f,	// 1 - expf(-2 * M_PI * 64 / 48000);
+	1 - 0.967044930f,	// 1 - expf(-2 * M_PI * 256 / 48000);
+	1 - 0.874553978f,	// 1 - expf(-2 * M_PI * 1024 / 48000);
+	1 - 0.584987297f,	// 1 - expf(-2 * M_PI * 4096 / 48000);
+};
+static const float falloff = 0.25f;	//sqrtf(1.f / 4.f);
+static float const w0 = 1 - falloff;
+static float const w1 = w0 * falloff;
+static float const w2 = w1 * falloff;
+static float const w3 = w2 * falloff;
+static float const w4 = w3 * falloff;
+static float const w5 = falloff - w1 - w2 - w3 - w4;
+#endif
+
+// noise wave
 float OscillatorNoise(OscillatorConfig const &config, OscillatorState &state, float step)
 {
+#if 1
+	// whte noise
+	float white = Random::Float() * 2.0f - 1.0f;
+
+	// if generating pure white noise, return that
+	if (config.waveparam == 0.5f)
+		return white;
+
+	float param = config.waveparam;
+
+	// low-pass filter bank
+	for (int i = 0; i < FILTERS; ++i)
+		state.f[i] += (white - state.f[i]) * a[i];
+
+
+	// desired spectral tilt:
+	// param=0.00 red -6dB/oct
+	// param=0.25 pink -3dB/oct, 
+	// param=0.50 white 0dB/oct
+	// param=0.75 blue +3dB/oct
+	// param=1.00 violet +6dB/oct
+
+	// if generating red/pink...
+	if (config.waveparam < 0.5f)
+	{
+		// -3dB/oct pink noise
+#if FILTERS == 3
+		float const pink = 8 * (w0 * state.f[0] + w1 * state.f[1] + w2 * state.f[2] + w3 * white);
+#elif FILTERS == 4
+		float const pink = 8 * (w0 * state.f[0] + w1 * state.f[1] + w2 * state.f[2] + w3 * state.f[3] + w4 * white);
+#elif FILTERS == 5
+		float const pink = 8 * (w0 * state.f[0] + w1 * state.f[1] + w2 * state.f[2] + w3 * state.f[3] + w2 * state.f[4] + w5 * white);
+#endif
+
+		// if generating pure pink noise, return that
+		if (param == 0.25f)
+			return pink;
+
+		if (param < 0.25)
+		{
+			// -6dB/oct red noise
+			float const red = 16 * state.f[0];
+
+			// blend between red and pink
+			float const s = param * 4;
+			return red + (pink - red) * s;
+		}
+		else
+		{
+			// bend between white and pink
+			float const s = param * 4 - 1;
+			return pink + (white - pink) * s;
+		}
+	}
+	else
+	{
+		// +3dB/oct blue noise
+#if FILTERS == 3
+		float const blue = 2 * (white - w2 * state.f[0] - w1 * state.f[1] - w0 * state.f[2]);
+#elif FILTERS == 4
+		float const blue = 2 * (white - w3 * state.f[0] - w2 * state.f[1] - w1 * state.f[2] - w0 * state.f[3]);
+#elif FILTERS == 5
+		float const blue = 2 * (white - w4 * state.f[0] - w3 * state.f[1] - w2 * state.f[2] - w1 * state.f[3] - w0 * state.f[4]);
+#endif
+
+		if (param < 0.75f)
+		{
+			// blend between white and blue
+			float const s = param * 4 - 2;
+			return white + (blue - white) * s;
+		}
+		else
+		{
+			// +6dB/oct violet noise
+			float const violet = 1.41421356f *(white - state.f[FILTERS]);
+			state.f[FILTERS] = white;
+
+			// blend between blue and violet
+			float const s = param * 4 - 3;
+			return blue + (violet - blue) * s;
+		}
+	}
+#else
 	return Random::Float() * 2.0f - 1.0f;
+#endif
 }