new pink noise generator audio source object

libraries/audio/src/AudioSourceNoise.cpp

@@ -0,0 +1,21 @@
+//
+//  AudioSourceNoise.cpp
+//  hifi
+//
+//  Created by Craig Hansen-Sturm on 8/10/14.
+//  Copyright 2014 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#include <assert.h>
+#include <math.h>
+#include <SharedUtil.h>
+#include "AudioRingBuffer.h"
+#include "AudioFormat.h"
+#include "AudioBuffer.h"
+#include "AudioSourceNoise.h"
+
+template<> 
+uint32_t AudioSourcePinkNoise::_randomSeed = 1974; // a truly random number

libraries/audio/src/AudioSourceNoise.h

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