root/AudioScheduledSourceNode.cpp

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 * Copyright (C) 2012, Google Inc. All rights reserved.
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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "modules/webaudio/AudioScheduledSourceNode.h"

#include "core/dom/Event.h"
#include "core/platform/audio/AudioUtilities.h"
#include "modules/webaudio/AudioContext.h"
#include <algorithm>
#include "wtf/MathExtras.h"

using namespace std;

namespace WebCore {

const double AudioScheduledSourceNode::UnknownTime = -1;

AudioScheduledSourceNode::AudioScheduledSourceNode(AudioContext* context, float sampleRate)
    : AudioSourceNode(context, sampleRate)
    , m_playbackState(UNSCHEDULED_STATE)
    , m_startTime(0)
    , m_endTime(UnknownTime)
    , m_hasEndedListener(false)
{
}

void AudioScheduledSourceNode::updateSchedulingInfo(size_t quantumFrameSize,
                                                    AudioBus* outputBus,
                                                    size_t& quantumFrameOffset,
                                                    size_t& nonSilentFramesToProcess)
{
    ASSERT(outputBus);
    if (!outputBus)
        return;

    ASSERT(quantumFrameSize == AudioNode::ProcessingSizeInFrames);
    if (quantumFrameSize != AudioNode::ProcessingSizeInFrames)
        return;

    double sampleRate = this->sampleRate();

    // quantumStartFrame     : Start frame of the current time quantum.
    // quantumEndFrame       : End frame of the current time quantum.
    // startFrame            : Start frame for this source.
    // endFrame              : End frame for this source.
    size_t quantumStartFrame = context()->currentSampleFrame();
    size_t quantumEndFrame = quantumStartFrame + quantumFrameSize;
    size_t startFrame = AudioUtilities::timeToSampleFrame(m_startTime, sampleRate);
    size_t endFrame = m_endTime == UnknownTime ? 0 : AudioUtilities::timeToSampleFrame(m_endTime, sampleRate);

    // If we know the end time and it's already passed, then don't bother doing any more rendering this cycle.
    if (m_endTime != UnknownTime && endFrame <= quantumStartFrame)
        finish();

    if (m_playbackState == UNSCHEDULED_STATE || m_playbackState == FINISHED_STATE || startFrame >= quantumEndFrame) {
        // Output silence.
        outputBus->zero();
        nonSilentFramesToProcess = 0;
        return;
    }

    // Check if it's time to start playing.
    if (m_playbackState == SCHEDULED_STATE) {
        // Increment the active source count only if we're transitioning from SCHEDULED_STATE to PLAYING_STATE.
        m_playbackState = PLAYING_STATE;
        context()->incrementActiveSourceCount();
    }

    quantumFrameOffset = startFrame > quantumStartFrame ? startFrame - quantumStartFrame : 0;
    quantumFrameOffset = min(quantumFrameOffset, quantumFrameSize); // clamp to valid range
    nonSilentFramesToProcess = quantumFrameSize - quantumFrameOffset;

    if (!nonSilentFramesToProcess) {
        // Output silence.
        outputBus->zero();
        return;
    }

    // Handle silence before we start playing.
    // Zero any initial frames representing silence leading up to a rendering start time in the middle of the quantum.
    if (quantumFrameOffset) {
        for (unsigned i = 0; i < outputBus->numberOfChannels(); ++i)
            memset(outputBus->channel(i)->mutableData(), 0, sizeof(float) * quantumFrameOffset);
    }

    // Handle silence after we're done playing.
    // If the end time is somewhere in the middle of this time quantum, then zero out the
    // frames from the end time to the very end of the quantum.
    if (m_endTime != UnknownTime && endFrame >= quantumStartFrame && endFrame < quantumEndFrame) {
        size_t zeroStartFrame = endFrame - quantumStartFrame;
        size_t framesToZero = quantumFrameSize - zeroStartFrame;

        bool isSafe = zeroStartFrame < quantumFrameSize && framesToZero <= quantumFrameSize && zeroStartFrame + framesToZero <= quantumFrameSize;
        ASSERT(isSafe);

        if (isSafe) {
            if (framesToZero > nonSilentFramesToProcess)
                nonSilentFramesToProcess = 0;
            else
                nonSilentFramesToProcess -= framesToZero;

            for (unsigned i = 0; i < outputBus->numberOfChannels(); ++i)
                memset(outputBus->channel(i)->mutableData() + zeroStartFrame, 0, sizeof(float) * framesToZero);
        }

        finish();
    }

    return;
}

void AudioScheduledSourceNode::start(double when)
{
    ASSERT(isMainThread());
    if (m_playbackState != UNSCHEDULED_STATE)
        return;

    m_startTime = when;
    m_playbackState = SCHEDULED_STATE;
}

void AudioScheduledSourceNode::stop(double when)
{
    ASSERT(isMainThread());
    if (!(m_playbackState == SCHEDULED_STATE || m_playbackState == PLAYING_STATE))
        return;

    when = max(0.0, when);
    m_endTime = when;
}

void AudioScheduledSourceNode::noteOn(double when)
{
    start(when);
}

void AudioScheduledSourceNode::noteOff(double when)
{
    stop(when);
}

void AudioScheduledSourceNode::setOnended(PassRefPtr<EventListener> listener, DOMWrapperWorld* isolatedWorld)
{
    m_hasEndedListener = listener;
    setAttributeEventListener(eventNames().endedEvent, listener, isolatedWorld);
}

void AudioScheduledSourceNode::finish()
{
    if (m_playbackState != FINISHED_STATE) {
        // Let the context dereference this AudioNode.
        context()->notifyNodeFinishedProcessing(this);
        m_playbackState = FINISHED_STATE;
        context()->decrementActiveSourceCount();
    }

    if (m_hasEndedListener)
        callOnMainThread(&AudioScheduledSourceNode::notifyEndedDispatch, this);
}

void AudioScheduledSourceNode::notifyEndedDispatch(void* userData)
{
    static_cast<AudioScheduledSourceNode*>(userData)->notifyEnded();
}

void AudioScheduledSourceNode::notifyEnded()
{
    RefPtr<Event> event = Event::create(eventNames().endedEvent, FALSE, FALSE);
    event->setTarget(this);
    dispatchEvent(event.get());
}

} // namespace WebCore

#endif // ENABLE(WEB_AUDIO)