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:
7 *
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 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
18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#ifndef DynamicsCompressorKernel_h
30#define DynamicsCompressorKernel_h
31
32#include "AudioArray.h"
33#include <memory>
34
35namespace WebCore {
36
37class DynamicsCompressorKernel {
38public:
39    DynamicsCompressorKernel(float sampleRate, unsigned numberOfChannels);
40
41    void setNumberOfChannels(unsigned);
42
43    // Performs stereo-linked compression.
44    void process(float* sourceChannels[],
45                 float* destinationChannels[],
46                 unsigned numberOfChannels,
47                 unsigned framesToProcess,
48
49                 float dbThreshold,
50                 float dbKnee,
51                 float ratio,
52                 float attackTime,
53                 float releaseTime,
54                 float preDelayTime,
55                 float dbPostGain,
56                 float effectBlend,
57
58                 float releaseZone1,
59                 float releaseZone2,
60                 float releaseZone3,
61                 float releaseZone4
62                 );
63
64    void reset();
65
66    unsigned latencyFrames() const { return m_lastPreDelayFrames; }
67
68    float sampleRate() const { return m_sampleRate; }
69
70    float meteringGain() const { return m_meteringGain; }
71
72protected:
73    float m_sampleRate;
74
75    float m_detectorAverage;
76    float m_compressorGain;
77
78    // Metering
79    float m_meteringReleaseK;
80    float m_meteringGain;
81
82    // Lookahead section.
83    enum { MaxPreDelayFrames = 1024 };
84    enum { MaxPreDelayFramesMask = MaxPreDelayFrames - 1 };
85    enum { DefaultPreDelayFrames = 256 }; // setPreDelayTime() will override this initial value
86    unsigned m_lastPreDelayFrames;
87    void setPreDelayTime(float);
88
89    Vector<std::unique_ptr<AudioFloatArray>> m_preDelayBuffers;
90    int m_preDelayReadIndex;
91    int m_preDelayWriteIndex;
92
93    float m_maxAttackCompressionDiffDb;
94
95    // Static compression curve.
96    float kneeCurve(float x, float k);
97    float saturate(float x, float k);
98    float slopeAt(float x, float k);
99    float kAtSlope(float desiredSlope);
100
101    float updateStaticCurveParameters(float dbThreshold, float dbKnee, float ratio);
102
103    // Amount of input change in dB required for 1 dB of output change.
104    // This applies to the portion of the curve above m_kneeThresholdDb (see below).
105    float m_ratio;
106    float m_slope; // Inverse ratio.
107
108    // The input to output change below the threshold is linear 1:1.
109    float m_linearThreshold;
110    float m_dbThreshold;
111
112    // m_dbKnee is the number of dB above the threshold before we enter the "ratio" portion of the curve.
113    // m_kneeThresholdDb = m_dbThreshold + m_dbKnee
114    // The portion between m_dbThreshold and m_kneeThresholdDb is the "soft knee" portion of the curve
115    // which transitions smoothly from the linear portion to the ratio portion.
116    float m_dbKnee;
117    float m_kneeThreshold;
118    float m_kneeThresholdDb;
119    float m_ykneeThresholdDb;
120
121    // Internal parameter for the knee portion of the curve.
122    float m_K;
123};
124
125} // namespace WebCore
126
127#endif // DynamicsCompressorKernel_h
128