DynamicsCompressorKernel.h

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/*

 * Copyright (C) 2011 Google Inc. All rights reserved.

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 *     notice, this list of conditions and the following disclaimer in the

 *     documentation and/or other materials provided with the distribution.

 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of

 *     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

 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

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*/

#ifndef DynamicsCompressorKernel_h

#define DynamicsCompressorKernel_h

#include "nsTArray.h"

#include "mozilla/MemoryReporting.h"

#include "mozilla/UniquePtr.h"

namespace WebCore {

class DynamicsCompressorKernel {

 public:

  DynamicsCompressorKernel(float sampleRate, unsigned numberOfChannels);

  void setNumberOfChannels(unsigned);

  // Performs stereo-linked compression.

  void process(float* sourceChannels[], float* destinationChannels[],

               unsigned numberOfChannels, unsigned framesToProcess,

               float dbThreshold, float dbKnee, float ratio, float attackTime,

               float releaseTime, float preDelayTime, float dbPostGain,

               float effectBlend,

               float releaseZone1, float releaseZone2, float releaseZone3,

               float releaseZone4);

  void reset();

  unsigned latencyFrames() const { return m_lastPreDelayFrames; }

  float sampleRate() const { return m_sampleRate; }

  float meteringGain() const { return m_meteringGain; }

  size_t sizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;

 protected:

  float m_sampleRate;

  float m_detectorAverage;

  float m_compressorGain;

  // Metering

  float m_meteringReleaseK;

  float m_meteringGain;

  // Lookahead section.

  enum { MaxPreDelayFrames = 1024 };

  enum { MaxPreDelayFramesMask = MaxPreDelayFrames - 1 };

  enum {

    DefaultPreDelayFrames = 256

  };  // setPreDelayTime() will override this initial value

  unsigned m_lastPreDelayFrames;

  void setPreDelayTime(float);

  nsTArray<mozilla::UniquePtr<float[]>> m_preDelayBuffers;

  int m_preDelayReadIndex;

  int m_preDelayWriteIndex;

  float m_maxAttackCompressionDiffDb;

  // Static compression curve.

  float kneeCurve(float x, float k);

  float saturate(float x, float k);

  float slopeAt(float x, float k);

  float kAtSlope(float desiredSlope);

  float updateStaticCurveParameters(float dbThreshold, float dbKnee,

                                    float ratio);

  // Amount of input change in dB required for 1 dB of output change.

  // This applies to the portion of the curve above m_kneeThresholdDb (see

  // below).

  float m_ratio;

  float m_slope;  // Inverse ratio.

  // The input to output change below the threshold is linear 1:1.

  float m_linearThreshold;

  float m_dbThreshold;

  // m_dbKnee is the number of dB above the threshold before we enter the

  // "ratio" portion of the curve. m_kneeThresholdDb = m_dbThreshold + m_dbKnee

  // The portion between m_dbThreshold and m_kneeThresholdDb is the "soft knee"

  // portion of the curve which transitions smoothly from the linear portion to

  // the ratio portion.

  float m_dbKnee;

  float m_kneeThreshold;

  float m_kneeThresholdDb;

  float m_ykneeThresholdDb;

  // Internal parameter for the knee portion of the curve.

  float m_K;

};

}  // namespace WebCore

#endif  // DynamicsCompressorKernel_h