Source/WebCore/Modules/webaudio/MediaElementAudioSourceNode.cpp

/*
 * Copyright (C) 2011, Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
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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) && ENABLE(VIDEO)

#include "MediaElementAudioSourceNode.h"

#include "AudioContext.h"
#include "AudioNodeOutput.h"
#include "Logging.h"
#include "MediaPlayer.h"
#include <wtf/IsoMallocInlines.h>
#include <wtf/Locker.h>

// These are somewhat arbitrary limits, but we need to do some kind of sanity-checking.
const unsigned minSampleRate = 8000;
const unsigned maxSampleRate = 192000;

namespace WebCore {

WTF_MAKE_ISO_ALLOCATED_IMPL(MediaElementAudioSourceNode);

Ref<MediaElementAudioSourceNode> MediaElementAudioSourceNode::create(AudioContext& context, HTMLMediaElement& mediaElement)
{
    return adoptRef(*new MediaElementAudioSourceNode(context, mediaElement));
}

MediaElementAudioSourceNode::MediaElementAudioSourceNode(AudioContext& context, HTMLMediaElement& mediaElement)
    : AudioNode(context, context.sampleRate())
    , m_mediaElement(mediaElement)
    , m_sourceNumberOfChannels(0)
    , m_sourceSampleRate(0)
{
    setNodeType(NodeTypeMediaElementAudioSource);

    // Default to stereo. This could change depending on what the media element .src is set to.
    addOutput(std::make_unique<AudioNodeOutput>(this, 2));

    initialize();
}

MediaElementAudioSourceNode::~MediaElementAudioSourceNode()
{
    m_mediaElement->setAudioSourceNode(nullptr);
    uninitialize();
}

void MediaElementAudioSourceNode::setFormat(size_t numberOfChannels, float sourceSampleRate)
{
    m_muted = wouldTaintOrigin();

    if (numberOfChannels != m_sourceNumberOfChannels || sourceSampleRate != m_sourceSampleRate) {
        if (!numberOfChannels || numberOfChannels > AudioContext::maxNumberOfChannels() || sourceSampleRate < minSampleRate || sourceSampleRate > maxSampleRate) {
            // process() will generate silence for these uninitialized values.
            LOG(Media, "MediaElementAudioSourceNode::setFormat(%u, %f) - unhandled format change", static_cast<unsigned>(numberOfChannels), sourceSampleRate);
            m_sourceNumberOfChannels = 0;
            m_sourceSampleRate = 0;
            return;
        }

        m_sourceNumberOfChannels = numberOfChannels;
        m_sourceSampleRate = sourceSampleRate;

        // Synchronize with process().
        std::lock_guard<MediaElementAudioSourceNode> lock(*this);

        if (sourceSampleRate != sampleRate()) {
            double scaleFactor = sourceSampleRate / sampleRate();
            m_multiChannelResampler = std::make_unique<MultiChannelResampler>(scaleFactor, numberOfChannels);
        } else {
            // Bypass resampling.
            m_multiChannelResampler = nullptr;
        }

        {
            // 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);
        }
    }
}

bool MediaElementAudioSourceNode::wouldTaintOrigin()
{
    if (!m_mediaElement->hasSingleSecurityOrigin())
        return true;

    if (m_mediaElement->didPassCORSAccessCheck())
        return false;

    if (auto* origin = context().origin())
        return m_mediaElement->wouldTaintOrigin(*origin);

    return true;
}

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

    if (m_muted || !m_sourceNumberOfChannels || !m_sourceSampleRate) {
        outputBus->zero();
        return;
    }

    // Use a std::try_to_lock to avoid contention in the real-time audio thread.
    // If we fail to acquire the lock then the HTMLMediaElement must be in the middle of
    // reconfiguring its playback engine, so we output silence in this case.
    std::unique_lock<Lock> lock(m_processMutex, std::try_to_lock);
    if (!lock.owns_lock()) {
        // We failed to acquire the lock.
        outputBus->zero();
        return;
    }

    if (AudioSourceProvider* provider = mediaElement().audioSourceProvider()) {
        if (m_multiChannelResampler.get()) {
            ASSERT(m_sourceSampleRate != sampleRate());
            m_multiChannelResampler->process(provider, outputBus, numberOfFrames);
        } else {
            // Bypass the resampler completely if the source is at the context's sample-rate.
            ASSERT(m_sourceSampleRate == sampleRate());
            provider->provideInput(outputBus, numberOfFrames);
        }
    } else {
        // Either this port doesn't yet support HTMLMediaElement audio stream access,
        // or the stream is not yet available.
        outputBus->zero();
    }
}

void MediaElementAudioSourceNode::reset()
{
}

void MediaElementAudioSourceNode::lock()
{
    ref();
    m_processMutex.lock();
}

void MediaElementAudioSourceNode::unlock()
{
    m_processMutex.unlock();
    deref();
}

} // namespace WebCore

#endif // ENABLE(WEB_AUDIO)