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      1 /*
      2  * Copyright (C) 2011 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  *
      8  * 1.  Redistributions of source code must retain the above copyright
      9  *     notice, this list of conditions and the following disclaimer.
     10  * 2.  Redistributions in binary form must reproduce the above copyright
     11  *     notice, this list of conditions and the following disclaimer in the
     12  *     documentation and/or other materials provided with the distribution.
     13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
     14  *     its contributors may be used to endorse or promote products derived
     15  *     from this software without specific prior written permission.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
     18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
     24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #ifndef DynamicsCompressor_h
     30 #define DynamicsCompressor_h
     31 
     32 #include "platform/audio/AudioArray.h"
     33 #include "platform/audio/DynamicsCompressorKernel.h"
     34 #include "platform/audio/ZeroPole.h"
     35 #include "wtf/Noncopyable.h"
     36 #include "wtf/OwnPtr.h"
     37 
     38 namespace blink {
     39 
     40 class AudioBus;
     41 
     42 // DynamicsCompressor implements a flexible audio dynamics compression effect such as
     43 // is commonly used in musical production and game audio. It lowers the volume
     44 // of the loudest parts of the signal and raises the volume of the softest parts,
     45 // making the sound richer, fuller, and more controlled.
     46 
     47 class PLATFORM_EXPORT DynamicsCompressor {
     48     WTF_MAKE_NONCOPYABLE(DynamicsCompressor);
     49 public:
     50     enum {
     51         ParamThreshold,
     52         ParamKnee,
     53         ParamRatio,
     54         ParamAttack,
     55         ParamRelease,
     56         ParamPreDelay,
     57         ParamReleaseZone1,
     58         ParamReleaseZone2,
     59         ParamReleaseZone3,
     60         ParamReleaseZone4,
     61         ParamPostGain,
     62         ParamFilterStageGain,
     63         ParamFilterStageRatio,
     64         ParamFilterAnchor,
     65         ParamEffectBlend,
     66         ParamReduction,
     67         ParamLast
     68     };
     69 
     70     DynamicsCompressor(float sampleRate, unsigned numberOfChannels);
     71 
     72     void process(const AudioBus* sourceBus, AudioBus* destinationBus, unsigned framesToProcess);
     73     void reset();
     74     void setNumberOfChannels(unsigned);
     75 
     76     void setParameterValue(unsigned parameterID, float value);
     77     float parameterValue(unsigned parameterID);
     78 
     79     float sampleRate() const { return m_sampleRate; }
     80     float nyquist() const { return m_sampleRate / 2; }
     81 
     82     double tailTime() const { return 0; }
     83     double latencyTime() const { return m_compressor.latencyFrames() / static_cast<double>(sampleRate()); }
     84 
     85 protected:
     86     unsigned m_numberOfChannels;
     87 
     88     // m_parameters holds the tweakable compressor parameters.
     89     float m_parameters[ParamLast];
     90     void initializeParameters();
     91 
     92     float m_sampleRate;
     93 
     94     // Emphasis filter controls.
     95     float m_lastFilterStageRatio;
     96     float m_lastAnchor;
     97     float m_lastFilterStageGain;
     98 
     99     OwnPtr<const float*[]> m_sourceChannels;
    100     OwnPtr<float*[]> m_destinationChannels;
    101 
    102     // The core compressor.
    103     DynamicsCompressorKernel m_compressor;
    104 };
    105 
    106 } // namespace blink
    107 
    108 #endif // DynamicsCompressor_h
    109