Source/WebCore/Modules/webaudio/ChannelMergerNode.cpp

/*
 * Copyright (C) 2010 Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions
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 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "ChannelMergerNode.h"

#include "AudioContext.h"
#include "AudioNodeInput.h"
#include "AudioNodeOutput.h"

const unsigned DefaultNumberOfOutputChannels = 1;

namespace WebCore {

RefPtr<ChannelMergerNode> ChannelMergerNode::create(AudioContext& context, float sampleRate, unsigned numberOfInputs)
{
    if (!numberOfInputs || numberOfInputs > AudioContext::maxNumberOfChannels())
        return nullptr;
    
    return adoptRef(*new ChannelMergerNode(context, sampleRate, numberOfInputs));      
}

ChannelMergerNode::ChannelMergerNode(AudioContext& context, float sampleRate, unsigned numberOfInputs)
    : AudioNode(context, sampleRate)
    , m_desiredNumberOfOutputChannels(DefaultNumberOfOutputChannels)
{
    // Create the requested number of inputs.
    for (unsigned i = 0; i < numberOfInputs; ++i)
        addInput(std::make_unique<AudioNodeInput>(this));

    addOutput(std::make_unique<AudioNodeOutput>(this, 1));
    
    setNodeType(NodeTypeChannelMerger);
    
    initialize();
}

void ChannelMergerNode::process(size_t framesToProcess)
{
    AudioNodeOutput* output = this->output(0);
    ASSERT(output);
    ASSERT_UNUSED(framesToProcess, framesToProcess == output->bus()->length());

    // Output bus not updated yet, so just output silence.
    if (m_desiredNumberOfOutputChannels != output->numberOfChannels()) {
        output->bus()->zero();
        return;
    }
    
    // Merge all the channels from all the inputs into one output.
    unsigned outputChannelIndex = 0;
    for (unsigned i = 0; i < numberOfInputs(); ++i) {
        AudioNodeInput* input = this->input(i);
        if (input->isConnected()) {
            unsigned numberOfInputChannels = input->bus()->numberOfChannels();
            
            // Merge channels from this particular input.
            for (unsigned j = 0; j < numberOfInputChannels; ++j) {
                AudioChannel* inputChannel = input->bus()->channel(j);
                AudioChannel* outputChannel = output->bus()->channel(outputChannelIndex);
                outputChannel->copyFrom(inputChannel);
                
                ++outputChannelIndex;
            }
        }
    }
    
    ASSERT(outputChannelIndex == output->numberOfChannels());
}

void ChannelMergerNode::reset()
{
}

// Any time a connection or disconnection happens on any of our inputs, we potentially need to change the
// number of channels of our output.
void ChannelMergerNode::checkNumberOfChannelsForInput(AudioNodeInput* input)
{
    ASSERT(context().isAudioThread() && context().isGraphOwner());

    // Count how many channels we have all together from all of the inputs.
    unsigned numberOfOutputChannels = 0;
    for (unsigned i = 0; i < numberOfInputs(); ++i) {
        AudioNodeInput* input = this->input(i);
        if (input->isConnected())
            numberOfOutputChannels += input->numberOfChannels();
    }

    // Set the correct number of channels on the output
    AudioNodeOutput* output = this->output(0);
    ASSERT(output);
    output->setNumberOfChannels(numberOfOutputChannels);
    // There can in rare cases be a slight delay before the output bus is updated to the new number of
    // channels because of tryLocks() in the context's updating system. So record the new number of
    // output channels here.
    m_desiredNumberOfOutputChannels = numberOfOutputChannels;

    AudioNode::checkNumberOfChannelsForInput(input);
}

} // namespace WebCore

#endif // ENABLE(WEB_AUDIO)