implemented new audio panning object which implements constant power sin^2+cos^2=1 law

interface/src/Audio.h

@@ -26,6 +26,7 @@
 #include "AudioSourceTone.h"
 #include "AudioSourceNoise.h"
 #include "AudioGain.h"
+#include "AudioPan.h"
 #include "AudioFilter.h"
 #include "AudioFilterBank.h"
 

libraries/audio/src/AudioPan.cpp

@@ -0,0 +1,23 @@
+//
+//  AudioSourceTone.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 "AudioPan.h"
+
+float32_t AudioPan::ONE_MINUS_EPSILON = 1.0f - EPSILON;
+float32_t AudioPan::ZERO_PLUS_EPSILON = 0.0f + EPSILON;
+float32_t AudioPan::ONE_HALF_MINUS_EPSILON = 0.5f - EPSILON;
+float32_t AudioPan::ONE_HALF_PLUS_EPSILON = 0.5f + EPSILON;

libraries/audio/src/AudioPan.h

@@ -0,0 +1,141 @@
+//
+//  AudioPan.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
+//
+
+#ifndef hifi_AudioPan_h
+#define hifi_AudioPan_h
+
+class AudioPan
+{
+    float32_t _pan;
+    float32_t _gainLeft;
+    float32_t _gainRight;
+  
+    static float32_t ONE_MINUS_EPSILON;
+    static float32_t ZERO_PLUS_EPSILON;
+    static float32_t ONE_HALF_MINUS_EPSILON;
+    static float32_t ONE_HALF_PLUS_EPSILON;
+    
+    void updateCoefficients() {
+        
+        // implement constant power sin^2 + cos^2 = 1 panning law
+        
+        if (_pan >= ONE_MINUS_EPSILON) { // full right
+            _gainLeft = 0.0f;
+            _gainRight = 1.0f;
+        }
+        else if (_pan <= ZERO_PLUS_EPSILON) { // full left
+            _gainLeft = 1.0f;
+            _gainRight = 0.0f;
+        }
+        else if ((_pan >= ONE_HALF_MINUS_EPSILON) && (_pan <= ONE_HALF_PLUS_EPSILON)) {  // center
+            _gainLeft = 1.0f / SQUARE_ROOT_OF_2;
+            _gainRight = 1.0f / SQUARE_ROOT_OF_2;
+        }
+        else { // intermediate cases
+            _gainLeft = cosf( TWO_PI * _pan );
+            _gainRight = sinf( TWO_PI * _pan );
+        }
+    }
+    
+public:
+    AudioPan() {
+        initialize();
+    }
+    
+    ~AudioPan() {
+        finalize();
+    }
+    
+    void initialize() {
+        setParameters(0.5f);
+    }
+    
+    void finalize() {
+    }
+    
+    void reset() {
+        initialize();
+    }
+    
+    void setParameters(const float32_t pan) {
+        // pan ranges between 0.0 and 1.0f inclusive.  0.5f is midpoint between full left and full right
+        _pan = std::min(std::max(pan, 0.0f), 1.0f);
+        updateCoefficients();
+    }
+    
+    void getParameters(float32_t& pan) {
+        pan = _pan;
+    }
+    
+    void render(AudioBufferFloat32& frameBuffer) {
+        
+        if (frameBuffer.getChannelCount() != 2) {
+            return;
+        }
+        
+        float32_t** samples = frameBuffer.getFrameData();
+        
+        bool frameAlignment16 = (frameBuffer.getFrameCount() & 0x0F) == 0;
+        if (frameAlignment16) {
+            
+            if (frameBuffer.getChannelCount() == 2) {
+                
+                for (uint16_t i = 0; i < frameBuffer.getFrameCount(); i += 16) {
+                    samples[0][i + 0] *= _gainLeft;
+                    samples[0][i + 1] *= _gainLeft;
+                    samples[0][i + 2] *= _gainLeft;
+                    samples[0][i + 3] *= _gainLeft;
+                    samples[0][i + 4] *= _gainLeft;
+                    samples[0][i + 5] *= _gainLeft;
+                    samples[0][i + 6] *= _gainLeft;
+                    samples[0][i + 7] *= _gainLeft;
+                    samples[0][i + 8] *= _gainLeft;
+                    samples[0][i + 9] *= _gainLeft;
+                    samples[0][i + 10] *= _gainLeft;
+                    samples[0][i + 11] *= _gainLeft;
+                    samples[0][i + 12] *= _gainLeft;
+                    samples[0][i + 13] *= _gainLeft;
+                    samples[0][i + 14] *= _gainLeft;
+                    samples[0][i + 15] *= _gainLeft;
+                    samples[1][i + 0] *= _gainRight;
+                    samples[1][i + 1] *= _gainRight;
+                    samples[1][i + 2] *= _gainRight;
+                    samples[1][i + 3] *= _gainRight;
+                    samples[1][i + 4] *= _gainRight;
+                    samples[1][i + 5] *= _gainRight;
+                    samples[1][i + 6] *= _gainRight;
+                    samples[1][i + 7] *= _gainRight;
+                    samples[1][i + 8] *= _gainRight;
+                    samples[1][i + 9] *= _gainRight;
+                    samples[1][i + 10] *= _gainRight;
+                    samples[1][i + 11] *= _gainRight;
+                    samples[1][i + 12] *= _gainRight;
+                    samples[1][i + 13] *= _gainRight;
+                    samples[1][i + 14] *= _gainRight;
+                    samples[1][i + 15] *= _gainRight;
+                }
+            }
+            else {
+                assert("unsupported channel format");
+            }
+        }
+        else {
+            for (uint16_t i = 0; i < frameBuffer.getFrameCount(); i += 1) {
+                samples[0][i] *= _gainLeft;
+                samples[1][i] *= _gainRight;
+            }
+        }
+    }
+};
+
+#endif // AudioPan_h
+
+