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103 lines
3.1 KiB
C++
103 lines
3.1 KiB
C++
//
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// AudioSourceNoise.h
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// hifi
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//
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// Created by Craig Hansen-Sturm on 9/1/14.
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// Copyright 2014 High Fidelity, Inc.
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//
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// Distributed under the Apache License, Version 2.0.
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// See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
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//
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// Adapted from code by Phil Burk http://www.firstpr.com.au/dsp/pink-noise/
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//
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#ifndef hifi_AudioSourceNoise_h
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#define hifi_AudioSourceNoise_h
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template< const uint16_t N = 30>
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class AudioSourceNoise
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{
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static const uint16_t _randomRows = N;
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static const uint16_t _randomBits = 24;
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static const uint16_t _randomShift = (sizeof(int32_t) * 8) - _randomBits;
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static uint32_t _randomSeed;
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int32_t _rows[_randomRows];
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int32_t _runningSum; // used to optimize summing of generators.
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uint16_t _index; // incremented each sample.
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uint16_t _indexMask; // index wrapped by ANDing with this mask.
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float32_t _scale; // used to scale within range of -1.0 to +1.0
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static uint32_t generateRandomNumber() {
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_randomSeed = (_randomSeed * 196314165) + 907633515;
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return _randomSeed >> _randomShift;
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}
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public:
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AudioSourceNoise() {
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initialize();
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}
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~AudioSourceNoise() {
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finalize();
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}
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void initialize() {
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memset(_rows, 0, _randomRows * sizeof(int32_t));
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_runningSum = 0;
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_index = 0;
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_indexMask = (uint16_t)((1 << _randomRows) - 1);
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_scale = 1.0f / ((_randomRows + 1) * (1 << (_randomBits - 1)));
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}
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void finalize() {
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}
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void reset() {
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initialize();
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}
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void setParameters(void) {
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}
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void getParameters(void) {
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}
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void render(AudioBufferFloat32& frameBuffer) {
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uint32_t randomNumber;
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float32_t** samples = frameBuffer.getFrameData();
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for (uint32_t i = 0; i < frameBuffer.getFrameCount(); ++i) {
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for (uint32_t j = 0; j < frameBuffer.getChannelCount(); ++j) {
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_index = (_index + 1) & _indexMask; // increment and mask index.
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if (_index != 0) { // if index is zero, don't update any random values.
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uint32_t numZeros = 0; // determine how many trailing zeros in _index
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uint32_t tmp = _index;
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while ((tmp & 1) == 0) {
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tmp >>= 1;
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numZeros++;
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}
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// replace the indexed _rows random value. subtract and add back to _runningSum instead
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// of adding all the random values together. only one value changes each time.
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_runningSum -= _rows[numZeros];
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randomNumber = generateRandomNumber();
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_runningSum += randomNumber;
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_rows[numZeros] = randomNumber;
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}
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// add extra white noise value and scale between -1.0 and +1.0
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samples[j][i] = (_runningSum + generateRandomNumber()) * _scale;
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}
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}
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}
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};
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typedef AudioSourceNoise<> AudioSourcePinkNoise;
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#endif // AudioSourceNoise_h
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