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      1 /*
      2  * Copyright (C) 2010, 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  * 1.  Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2.  Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     15  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     16  * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     17  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     18  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     19  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
     20  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     22  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     23  */
     24 
     25 #ifndef GainNode_h
     26 #define GainNode_h
     27 
     28 #include "modules/webaudio/AudioNode.h"
     29 #include "modules/webaudio/AudioParam.h"
     30 #include "wtf/PassRefPtr.h"
     31 #include "wtf/Threading.h"
     32 
     33 namespace blink {
     34 
     35 class AudioContext;
     36 
     37 // GainNode is an AudioNode with one input and one output which applies a gain (volume) change to the audio signal.
     38 // De-zippering (smoothing) is applied when the gain value is changed dynamically.
     39 
     40 class GainNode FINAL : public AudioNode {
     41     DEFINE_WRAPPERTYPEINFO();
     42 public:
     43     static GainNode* create(AudioContext* context, float sampleRate)
     44     {
     45         return adoptRefCountedGarbageCollectedWillBeNoop(new GainNode(context, sampleRate));
     46     }
     47 
     48     // AudioNode
     49     virtual void process(size_t framesToProcess) OVERRIDE;
     50 
     51     // Called in the main thread when the number of channels for the input may have changed.
     52     virtual void checkNumberOfChannelsForInput(AudioNodeInput*) OVERRIDE;
     53 
     54     // JavaScript interface
     55     AudioParam* gain() { return m_gain.get(); }
     56 
     57     virtual void trace(Visitor*) OVERRIDE;
     58 
     59 private:
     60     virtual double tailTime() const OVERRIDE { return 0; }
     61     virtual double latencyTime() const OVERRIDE { return 0; }
     62 
     63     GainNode(AudioContext*, float sampleRate);
     64 
     65     float m_lastGain; // for de-zippering
     66     Member<AudioParam> m_gain;
     67 
     68     AudioFloatArray m_sampleAccurateGainValues;
     69 };
     70 
     71 } // namespace blink
     72 
     73 #endif // GainNode_h
     74