1 /*
2  * Copyright (C) 2011 Google Inc. All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
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8  * 1.  Redistributions of source code must retain the above copyright
9  *     notice, this list of conditions and the following disclaimer.
10  * 2.  Redistributions in binary form must reproduce the above copyright
11  *     notice, this list of conditions and the following disclaimer in the
12  *     documentation and/or other materials provided with the distribution.
13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
14  *     its contributors may be used to endorse or promote products derived
15  *     from this software without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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27  */
28 
29 #ifndef DynamicsCompressorKernel_h
30 #define DynamicsCompressorKernel_h
31 
32 #include "nsTArray.h"
33 #include "mozilla/MemoryReporting.h"
34 #include "mozilla/UniquePtr.h"
35 
36 namespace WebCore {
37 
38 class DynamicsCompressorKernel {
39  public:
40   DynamicsCompressorKernel(float sampleRate, unsigned numberOfChannels);
41 
42   void setNumberOfChannels(unsigned);
43 
44   // Performs stereo-linked compression.
45   void process(float* sourceChannels[], float* destinationChannels[],
46                unsigned numberOfChannels, unsigned framesToProcess,
47 
48                float dbThreshold, float dbKnee, float ratio, float attackTime,
49                float releaseTime, float preDelayTime, float dbPostGain,
50                float effectBlend,
51 
52                float releaseZone1, float releaseZone2, float releaseZone3,
53                float releaseZone4);
54 
55   void reset();
56 
latencyFrames()57   unsigned latencyFrames() const { return m_lastPreDelayFrames; }
58 
sampleRate()59   float sampleRate() const { return m_sampleRate; }
60 
meteringGain()61   float meteringGain() const { return m_meteringGain; }
62 
63   size_t sizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
64 
65  protected:
66   float m_sampleRate;
67 
68   float m_detectorAverage;
69   float m_compressorGain;
70 
71   // Metering
72   float m_meteringReleaseK;
73   float m_meteringGain;
74 
75   // Lookahead section.
76   enum { MaxPreDelayFrames = 1024 };
77   enum { MaxPreDelayFramesMask = MaxPreDelayFrames - 1 };
78   enum {
79     DefaultPreDelayFrames = 256
80   };  // setPreDelayTime() will override this initial value
81   unsigned m_lastPreDelayFrames;
82   void setPreDelayTime(float);
83 
84   nsTArray<mozilla::UniquePtr<float[]>> m_preDelayBuffers;
85   int m_preDelayReadIndex;
86   int m_preDelayWriteIndex;
87 
88   float m_maxAttackCompressionDiffDb;
89 
90   // Static compression curve.
91   float kneeCurve(float x, float k);
92   float saturate(float x, float k);
93   float slopeAt(float x, float k);
94   float kAtSlope(float desiredSlope);
95 
96   float updateStaticCurveParameters(float dbThreshold, float dbKnee,
97                                     float ratio);
98 
99   // Amount of input change in dB required for 1 dB of output change.
100   // This applies to the portion of the curve above m_kneeThresholdDb (see
101   // below).
102   float m_ratio;
103   float m_slope;  // Inverse ratio.
104 
105   // The input to output change below the threshold is linear 1:1.
106   float m_linearThreshold;
107   float m_dbThreshold;
108 
109   // m_dbKnee is the number of dB above the threshold before we enter the
110   // "ratio" portion of the curve. m_kneeThresholdDb = m_dbThreshold + m_dbKnee
111   // The portion between m_dbThreshold and m_kneeThresholdDb is the "soft knee"
112   // portion of the curve which transitions smoothly from the linear portion to
113   // the ratio portion.
114   float m_dbKnee;
115   float m_kneeThreshold;
116   float m_kneeThresholdDb;
117   float m_ykneeThresholdDb;
118 
119   // Internal parameter for the knee portion of the curve.
120   float m_K;
121 };
122 
123 }  // namespace WebCore
124 
125 #endif  // DynamicsCompressorKernel_h
126