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implement Gordon-Smith 2-pole quadrature oscillator

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Craig Hansen-Sturm 2014-09-14 12:22:29 -07:00
parent 2f4ab716f9
commit 85f68662b0
1 changed files with 24 additions and 8 deletions
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32
libraries/audio/src/AudioSourceTone.h
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@ -12,6 +12,7 @@
#ifndef hifi_AudioSourceTone_h #ifndef hifi_AudioSourceTone_h
#define hifi_AudioSourceTone_h #define hifi_AudioSourceTone_h
// Implemenbts a Gordon-Smith oscillator
class AudioSourceTone class AudioSourceTone
{ {
static uint32_t _frameOffset; static uint32_t _frameOffset;
@ -19,6 +20,16 @@ class AudioSourceTone
float32_t _amplitude; float32_t _amplitude;
float32_t _sampleRate; float32_t _sampleRate;
float32_t _omega; float32_t _omega;
float32_t _epsilon;
float32_t _yq1;
float32_t _y1;
void updateCoefficients() {
_omega = _frequency / _sampleRate * TWO_PI;
_epsilon = 2.0f * sinf(_omega / 2.0f);
_yq1 = cosf(-1.0f * _omega);
_y1 = sinf(+1.04 * _omega);
}
public: public:
AudioSourceTone() { AudioSourceTone() {
@ -30,22 +41,20 @@ public:
} }
void initialize() { void initialize() {
_frameOffset = 0; setParameters(SAMPLE_RATE, 220.0f, 0.708f);
setParameters(SAMPLE_RATE, 220.0f, 0.9f);
} }
void finalize() { void finalize() {
} }
void reset() { void reset() {
_frameOffset = 0;
} }
void setParameters(const float32_t sampleRate, const float32_t frequency, const float32_t amplitude) { void setParameters(const float32_t sampleRate, const float32_t frequency, const float32_t amplitude) {
_sampleRate = std::max(sampleRate, 1.0f); _sampleRate = std::max(sampleRate, 1.0f);
_frequency = std::max(frequency, 1.0f); _frequency = std::max(frequency, 1.0f);
_amplitude = std::max(amplitude, 1.0f); _amplitude = std::max(amplitude, 1.0f);
_omega = _frequency / _sampleRate * TWO_PI; updateCoefficients();
} }
void getParameters(float32_t& sampleRate, float32_t& frequency, float32_t& amplitude) { void getParameters(float32_t& sampleRate, float32_t& frequency, float32_t& amplitude) {
@ -56,15 +65,22 @@ public:
void render(AudioBufferFloat32& frameBuffer) { void render(AudioBufferFloat32& frameBuffer) {
// note: this is a placeholder implementation. final version will not include any transcendental ops in our render loop
float32_t** samples = frameBuffer.getFrameData(); float32_t** samples = frameBuffer.getFrameData();
float32_t yq;
float32_t y;
for (uint16_t i = 0; i < frameBuffer.getFrameCount(); ++i) { for (uint16_t i = 0; i < frameBuffer.getFrameCount(); ++i) {
yq = _yq1 - (_epsilon * _y1);
y = _y1 + (_epsilon * yq);
// update delays
_yq1 = yq;
_y1 = y;
for (uint16_t j = 0; j < frameBuffer.getChannelCount(); ++j) { for (uint16_t j = 0; j < frameBuffer.getChannelCount(); ++j) {
samples[j][i] = sinf((i + _frameOffset) * _omega); samples[j][i] = _amplitude * y;
} }
} }
_frameOffset += frameBuffer.getFrameCount();
} }
}; };