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 AudioGainNode_h 26 #define AudioGainNode_h 27 28 #include "AudioGain.h" 29 #include "AudioNode.h" 30 #include <wtf/PassRefPtr.h> 31 #include <wtf/Threading.h> 32 33 namespace WebCore { 34 35 class AudioContext; 36 37 // AudioGainNode 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 AudioGainNode : public AudioNode { 41 public: create(AudioContext * context,double sampleRate)42 static PassRefPtr<AudioGainNode> create(AudioContext* context, double sampleRate) 43 { 44 return adoptRef(new AudioGainNode(context, sampleRate)); 45 } 46 47 // AudioNode 48 virtual void process(size_t framesToProcess); 49 virtual void reset(); 50 51 // Called in the main thread when the number of channels for the input may have changed. 52 virtual void checkNumberOfChannelsForInput(AudioNodeInput*); 53 54 // JavaScript interface gain()55 AudioGain* gain() { return m_gain.get(); } 56 57 private: 58 AudioGainNode(AudioContext*, double sampleRate); 59 60 double m_lastGain; // for de-zippering 61 RefPtr<AudioGain> m_gain; 62 63 // This synchronizes live channel count changes which require an uninitialization / re-initialization. 64 // FIXME: this can go away when we implement optimization for mixing with gain directly in summing junction of AudioNodeInput. 65 mutable Mutex m_processLock; 66 }; 67 68 } // namespace WebCore 69 70 #endif // AudioGainNode_h 71