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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 "modules/webaudio/GainNode.h"
     30 
     31 #include "platform/audio/AudioBus.h"
     32 #include "modules/webaudio/AudioNodeInput.h"
     33 #include "modules/webaudio/AudioNodeOutput.h"
     34 
     35 namespace blink {
     36 
     37 GainNode::GainNode(AudioContext* context, float sampleRate)
     38     : AudioNode(context, sampleRate)
     39     , m_lastGain(1.0)
     40     , m_sampleAccurateGainValues(AudioNode::ProcessingSizeInFrames) // FIXME: can probably share temp buffer in context
     41 {
     42     m_gain = AudioParam::create(context, 1.0);
     43 
     44     addInput();
     45     addOutput(AudioNodeOutput::create(this, 1));
     46 
     47     setNodeType(NodeTypeGain);
     48 
     49     initialize();
     50 }
     51 
     52 void GainNode::process(size_t framesToProcess)
     53 {
     54     // FIXME: for some cases there is a nice optimization to avoid processing here, and let the gain change
     55     // happen in the summing junction input of the AudioNode we're connected to.
     56     // Then we can avoid all of the following:
     57 
     58     AudioBus* outputBus = output(0)->bus();
     59     ASSERT(outputBus);
     60 
     61     if (!isInitialized() || !input(0)->isConnected())
     62         outputBus->zero();
     63     else {
     64         AudioBus* inputBus = input(0)->bus();
     65 
     66         if (gain()->hasSampleAccurateValues()) {
     67             // Apply sample-accurate gain scaling for precise envelopes, grain windows, etc.
     68             ASSERT(framesToProcess <= m_sampleAccurateGainValues.size());
     69             if (framesToProcess <= m_sampleAccurateGainValues.size()) {
     70                 float* gainValues = m_sampleAccurateGainValues.data();
     71                 gain()->calculateSampleAccurateValues(gainValues, framesToProcess);
     72                 outputBus->copyWithSampleAccurateGainValuesFrom(*inputBus, gainValues, framesToProcess);
     73             }
     74         } else {
     75             // Apply the gain with de-zippering into the output bus.
     76             outputBus->copyWithGainFrom(*inputBus, &m_lastGain, gain()->value());
     77         }
     78     }
     79 }
     80 
     81 // FIXME: this can go away when we do mixing with gain directly in summing junction of AudioNodeInput
     82 //
     83 // As soon as we know the channel count of our input, we can lazily initialize.
     84 // Sometimes this may be called more than once with different channel counts, in which case we must safely
     85 // uninitialize and then re-initialize with the new channel count.
     86 void GainNode::checkNumberOfChannelsForInput(AudioNodeInput* input)
     87 {
     88     ASSERT(context()->isAudioThread() && context()->isGraphOwner());
     89 
     90     ASSERT(input && input == this->input(0));
     91     if (input != this->input(0))
     92         return;
     93 
     94     unsigned numberOfChannels = input->numberOfChannels();
     95 
     96     if (isInitialized() && numberOfChannels != output(0)->numberOfChannels()) {
     97         // We're already initialized but the channel count has changed.
     98         uninitialize();
     99     }
    100 
    101     if (!isInitialized()) {
    102         // This will propagate the channel count to any nodes connected further downstream in the graph.
    103         output(0)->setNumberOfChannels(numberOfChannels);
    104         initialize();
    105     }
    106 
    107     AudioNode::checkNumberOfChannelsForInput(input);
    108 }
    109 
    110 void GainNode::trace(Visitor* visitor)
    111 {
    112     visitor->trace(m_gain);
    113     AudioNode::trace(visitor);
    114 }
    115 
    116 } // namespace blink
    117 
    118 #endif // ENABLE(WEB_AUDIO)
    119