DynamicsCompressor.h   [plain text]

/*
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#ifndef DynamicsCompressor_h
#define DynamicsCompressor_h

#include "AudioArray.h"
#include "DynamicsCompressorKernel.h"
#include "ZeroPole.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 {
public:
    enum {
        ParamThreshold,
        ParamHeadroom,
        ParamAttack,
        ParamRelease,
        ParamPreDelay,
        ParamReleaseZone1,
        ParamReleaseZone2,
        ParamReleaseZone3,
        ParamReleaseZone4,
        ParamPostGain,
        ParamFilterStageGain,
        ParamFilterStageRatio,
        ParamFilterAnchor,
        ParamEffectBlend,
        ParamLast
    };

    DynamicsCompressor(bool isStereo, double sampleRate);

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

    double parameterValue(unsigned parameterID);

    bool isStereo() const { return m_isStereo; }
    double sampleRate() const { return m_sampleRate; }
    double nyquist() const { return 0.5 * m_sampleRate; }

protected:
    // m_parameters holds the tweakable compressor parameters.
    // FIXME: expose some of the most important ones (such as threshold, attack, release)
    // as DynamicsCompressorNode attributes.
    double m_parameters[ParamLast];
    void initializeParameters();

    bool m_isStereo;
    double m_sampleRate;

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

    // Emphasis filters.
    ZeroPole m_preFilter[4];
    ZeroPole m_preFilterR[4];
    ZeroPole m_postFilter[4];
    ZeroPole m_postFilterR[4];

    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