text: /*
   * 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
   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
   * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #ifndef DynamicsCompressor_h
  #define DynamicsCompressor_h
  
  #include "platform/audio/AudioArray.h"
  #include "platform/audio/DynamicsCompressorKernel.h"
  #include "platform/audio/ZeroPole.h"
  #include "wtf/Allocator.h"
  #include "wtf/Noncopyable.h"
  #include <memory>
  
  namespace blink {
  
  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 PLATFORM_EXPORT DynamicsCompressor {
      USING_FAST_MALLOC(DynamicsCompressor);
      WTF_MAKE_NONCOPYABLE(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;
  
      std::unique_ptr<const float*[]> m_sourceChannels;
      std::unique_ptr<float*[]> m_destinationChannels;
  
      // The core compressor.
      DynamicsCompressorKernel m_compressor;
  };
  
  } // namespace blink
  
  #endif // DynamicsCompressor_h
  