DynamicsCompressor.h   [plain text]

/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
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 *     notice, this list of conditions and the following disclaimer.
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 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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#ifndef DynamicsCompressor_h
#define DynamicsCompressor_h

#include "AudioArray.h"
#include "DynamicsCompressorKernel.h"
#include "ZeroPole.h"
#include <memory>

namespace WebCore {

class AudioBus;

// DynamicsCompressor implements a flexible audio dynamics compression effect such as
// is commonly used in musical production and game audio. It lowers the volume
// of the loudest parts of the signal and raises the volume of the softest parts,
// making the sound richer, fuller, and more controlled.

class DynamicsCompressor {
public:
    enum {
        ParamThreshold,
        ParamKnee,
        ParamRatio,
        ParamAttack,
        ParamRelease,
        ParamPreDelay,
        ParamReleaseZone1,
        ParamReleaseZone2,
        ParamReleaseZone3,
        ParamReleaseZone4,
        ParamPostGain,
        ParamFilterStageGain,
        ParamFilterStageRatio,
        ParamFilterAnchor,
        ParamEffectBlend,
        ParamReduction,
        ParamLast
    };

    DynamicsCompressor(float sampleRate, unsigned numberOfChannels);

    void process(const AudioBus* sourceBus, AudioBus* destinationBus, unsigned framesToProcess);
    void reset();
    void setNumberOfChannels(unsigned);

    void setParameterValue(unsigned parameterID, float value);
    float parameterValue(unsigned parameterID);

    float sampleRate() const { return m_sampleRate; }
    float nyquist() const { return m_sampleRate / 2; }

    double tailTime() const { return 0; }
    double latencyTime() const { return m_compressor.latencyFrames() / static_cast<double>(sampleRate()); }

protected:
    unsigned m_numberOfChannels;

    // m_parameters holds the tweakable compressor parameters.
    float m_parameters[ParamLast];
    void initializeParameters();

    float m_sampleRate;

    // Emphasis filter controls.
    float m_lastFilterStageRatio;
    float m_lastAnchor;
    float m_lastFilterStageGain;

    typedef struct {
        ZeroPole filters[4];
    } ZeroPoleFilterPack4;

    // Per-channel emphasis filters.
    Vector<std::unique_ptr<ZeroPoleFilterPack4>> m_preFilterPacks;
    Vector<std::unique_ptr<ZeroPoleFilterPack4>> m_postFilterPacks;

    std::unique_ptr<const float*[]> m_sourceChannels;
    std::unique_ptr<float*[]> m_destinationChannels;

    void setEmphasisStageParameters(unsigned stageIndex, float gain, float normalizedFrequency /* 0 -> 1 */);
    void setEmphasisParameters(float gain, float anchorFreq, float filterStageRatio);

    // The core compressor.
    DynamicsCompressorKernel m_compressor;
};

} // namespace WebCore

#endif // DynamicsCompressor_h