Source/modules/webaudio/MediaStreamAudioSourceNode.cpp

/*
 * Copyright (C) 2012, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *    documentation and/or other materials provided with the distribution.
 *
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "modules/webaudio/MediaStreamAudioSourceNode.h"

#include "platform/Logging.h"
#include "modules/webaudio/AudioContext.h"
#include "modules/webaudio/AudioNodeOutput.h"
#include "wtf/Locker.h"

namespace WebCore {

PassRefPtr<MediaStreamAudioSourceNode> MediaStreamAudioSourceNode::create(AudioContext* context, MediaStream* mediaStream, AudioSourceProvider* audioSourceProvider)
{
    return adoptRef(new MediaStreamAudioSourceNode(context, mediaStream, audioSourceProvider));
}

MediaStreamAudioSourceNode::MediaStreamAudioSourceNode(AudioContext* context, MediaStream* mediaStream, AudioSourceProvider* audioSourceProvider)
    : AudioSourceNode(context, context->sampleRate())
    , m_mediaStream(mediaStream)
    , m_audioSourceProvider(audioSourceProvider)
    , m_sourceNumberOfChannels(0)
{
    ScriptWrappable::init(this);
    // Default to stereo. This could change depending on the format of the MediaStream's audio track.
    addOutput(adoptPtr(new AudioNodeOutput(this, 2)));

    setNodeType(NodeTypeMediaStreamAudioSource);

    initialize();
}

MediaStreamAudioSourceNode::~MediaStreamAudioSourceNode()
{
    uninitialize();
}

void MediaStreamAudioSourceNode::setFormat(size_t numberOfChannels, float sourceSampleRate)
{
    if (numberOfChannels != m_sourceNumberOfChannels || sourceSampleRate != sampleRate()) {
        // The sample-rate must be equal to the context's sample-rate.
        if (!numberOfChannels || numberOfChannels > AudioContext::maxNumberOfChannels() || sourceSampleRate != sampleRate()) {
            // process() will generate silence for these uninitialized values.
            LOG(Media, "MediaStreamAudioSourceNode::setFormat(%u, %f) - unhandled format change", static_cast<unsigned>(numberOfChannels), sourceSampleRate);
            m_sourceNumberOfChannels = 0;
            return;
        }

        // Synchronize with process().
        MutexLocker locker(m_processLock);

        m_sourceNumberOfChannels = numberOfChannels;

        {
            // The context must be locked when changing the number of output channels.
            AudioContext::AutoLocker contextLocker(context());

            // Do any necesssary re-configuration to the output's number of channels.
            output(0)->setNumberOfChannels(numberOfChannels);
        }
    }
}

void MediaStreamAudioSourceNode::process(size_t numberOfFrames)
{
    AudioBus* outputBus = output(0)->bus();

    if (!audioSourceProvider()) {
        outputBus->zero();
        return;
    }

    if (!mediaStream() || m_sourceNumberOfChannels != outputBus->numberOfChannels()) {
        outputBus->zero();
        return;
    }

    // Use a tryLock() to avoid contention in the real-time audio thread.
    // If we fail to acquire the lock then the MediaStream must be in the middle of
    // a format change, so we output silence in this case.
    MutexTryLocker tryLocker(m_processLock);
    if (tryLocker.locked())
        audioSourceProvider()->provideInput(outputBus, numberOfFrames);
    else {
        // We failed to acquire the lock.
        outputBus->zero();
    }
}

void MediaStreamAudioSourceNode::reset()
{
}

} // namespace WebCore

#endif // ENABLE(WEB_AUDIO)