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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 #include "config.h"
     26 
     27 #if ENABLE(WEB_AUDIO)
     28 
     29 #include "AudioGainNode.h"
     30 
     31 #include "AudioBus.h"
     32 #include "AudioNodeInput.h"
     33 #include "AudioNodeOutput.h"
     34 
     35 namespace WebCore {
     36 
     37 AudioGainNode::AudioGainNode(AudioContext* context, double sampleRate)
     38     : AudioNode(context, sampleRate)
     39     , m_lastGain(1.0)
     40 {
     41     m_gain = AudioGain::create("gain", 1.0, 0.0, 1.0);
     42 
     43     addInput(adoptPtr(new AudioNodeInput(this)));
     44     addOutput(adoptPtr(new AudioNodeOutput(this, 1)));
     45 
     46     setType(NodeTypeGain);
     47 
     48     initialize();
     49 }
     50 
     51 void AudioGainNode::process(size_t /*framesToProcess*/)
     52 {
     53     // FIXME: there is a nice optimization to avoid processing here, and let the gain change
     54     // happen in the summing junction input of the AudioNode we're connected to.
     55     // Then we can avoid all of the following:
     56 
     57     AudioBus* outputBus = output(0)->bus();
     58     ASSERT(outputBus);
     59 
     60     // The realtime thread can't block on this lock, so we call tryLock() instead.
     61     if (m_processLock.tryLock()) {
     62         if (!isInitialized() || !input(0)->isConnected())
     63             outputBus->zero();
     64         else {
     65             AudioBus* inputBus = input(0)->bus();
     66 
     67             // Apply the gain with de-zippering into the output bus.
     68             outputBus->copyWithGainFrom(*inputBus, &m_lastGain, gain()->value());
     69         }
     70 
     71         m_processLock.unlock();
     72     } else {
     73         // Too bad - the tryLock() failed.  We must be in the middle of re-connecting and were already outputting silence anyway...
     74         outputBus->zero();
     75     }
     76 }
     77 
     78 void AudioGainNode::reset()
     79 {
     80     // Snap directly to desired gain.
     81     m_lastGain = gain()->value();
     82 }
     83 
     84 // FIXME: this can go away when we do mixing with gain directly in summing junction of AudioNodeInput
     85 //
     86 // As soon as we know the channel count of our input, we can lazily initialize.
     87 // Sometimes this may be called more than once with different channel counts, in which case we must safely
     88 // uninitialize and then re-initialize with the new channel count.
     89 void AudioGainNode::checkNumberOfChannelsForInput(AudioNodeInput* input)
     90 {
     91     ASSERT(input && input == this->input(0));
     92     if (input != this->input(0))
     93         return;
     94 
     95     unsigned numberOfChannels = input->numberOfChannels();
     96 
     97     if (isInitialized() && numberOfChannels != output(0)->numberOfChannels()) {
     98         // We're already initialized but the channel count has changed.
     99         // We need to be careful since we may be actively processing right now, so synchronize with process().
    100         MutexLocker locker(m_processLock);
    101         uninitialize();
    102     }
    103 
    104     if (!isInitialized()) {
    105         // This will propagate the channel count to any nodes connected further downstream in the graph.
    106         output(0)->setNumberOfChannels(numberOfChannels);
    107         initialize();
    108     }
    109 }
    110 
    111 } // namespace WebCore
    112 
    113 #endif // ENABLE(WEB_AUDIO)
    114