Quelle DynamicsCompressorKernel.h

Sprache: C

/*
* Copyright (C) 2011 Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1.  Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
* 2.  Redistributions in binary form must reproduce the above copyright
*     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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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#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

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