DynamicsCompressor.h   [plain text]

/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions
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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 "DynamicsCompressorKernel.h"
#include "ZeroPole.h"
#include <memory>
#include <wtf/UniqueArray.h>

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 final {
    WTF_MAKE_FAST_ALLOCATED;
    WTF_MAKE_NONCOPYABLE(DynamicsCompressor);
public:
    enum {
        ParamThreshold,
        ParamKnee,
        ParamRatio,
        ParamAttack,
        ParamRelease,
        ParamPreDelay,
        ParamReleaseZone1,
        ParamReleaseZone2,
        ParamReleaseZone3,
        ParamReleaseZone4,
        ParamPostGain,
        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 m_compressor.tailTime(); }
    double latencyTime() const { return m_compressor.latencyFrames() / static_cast<double>(sampleRate()); }
    bool requiresTailProcessing() const
    {
        // Always return true even if the tail time and latency might both be zero.
        return true;
    }

protected:
    unsigned m_numberOfChannels;

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

    float m_sampleRate;

    UniqueArray<const float*> m_sourceChannels;
    UniqueArray<float*> m_destinationChannels;

    // The core compressor.
    DynamicsCompressorKernel m_compressor;
};

} // namespace WebCore

#endif // DynamicsCompressor_h