ScriptProcessorNode.cpp   [plain text]

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "ScriptProcessorNode.h"

#include "AudioBuffer.h"
#include "AudioBus.h"
#include "AudioContext.h"
#include "AudioNodeInput.h"
#include "AudioNodeOutput.h"
#include "AudioProcessingEvent.h"
#include "Document.h"
#include "EventNames.h"
#include <runtime/Float32Array.h>
#include <wtf/MainThread.h>

namespace WebCore {

Ref<ScriptProcessorNode> ScriptProcessorNode::create(AudioContext& context, float sampleRate, size_t bufferSize, unsigned numberOfInputChannels, unsigned numberOfOutputChannels)
{
    return adoptRef(*new ScriptProcessorNode(context, sampleRate, bufferSize, numberOfInputChannels, numberOfOutputChannels));
}

ScriptProcessorNode::ScriptProcessorNode(AudioContext& context, float sampleRate, size_t bufferSize, unsigned numberOfInputChannels, unsigned numberOfOutputChannels)
    : AudioNode(context, sampleRate)
    , m_doubleBufferIndex(0)
    , m_doubleBufferIndexForEvent(0)
    , m_bufferSize(bufferSize)
    , m_bufferReadWriteIndex(0)
    , m_isRequestOutstanding(false)
    , m_numberOfInputChannels(numberOfInputChannels)
    , m_numberOfOutputChannels(numberOfOutputChannels)
    , m_internalInputBus(AudioBus::create(numberOfInputChannels, AudioNode::ProcessingSizeInFrames, false))
    , m_hasAudioProcessListener(false)
{
    // Regardless of the allowed buffer sizes, we still need to process at the granularity of the AudioNode.
    if (m_bufferSize < AudioNode::ProcessingSizeInFrames)
        m_bufferSize = AudioNode::ProcessingSizeInFrames;

    ASSERT(numberOfInputChannels <= AudioContext::maxNumberOfChannels());

    addInput(std::make_unique<AudioNodeInput>(this));
    addOutput(std::make_unique<AudioNodeOutput>(this, numberOfOutputChannels));

    setNodeType(NodeTypeJavaScript);

    initialize();
}

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

void ScriptProcessorNode::initialize()
{
    if (isInitialized())
        return;

    float sampleRate = context().sampleRate();

    // Create double buffers on both the input and output sides.
    // These AudioBuffers will be directly accessed in the main thread by JavaScript.
    for (unsigned i = 0; i < 2; ++i) {
        RefPtr<AudioBuffer> inputBuffer = m_numberOfInputChannels ? AudioBuffer::create(m_numberOfInputChannels, bufferSize(), sampleRate) : 0;
        RefPtr<AudioBuffer> outputBuffer = m_numberOfOutputChannels ? AudioBuffer::create(m_numberOfOutputChannels, bufferSize(), sampleRate) : 0;

        m_inputBuffers.append(inputBuffer);
        m_outputBuffers.append(outputBuffer);
    }

    AudioNode::initialize();
}

void ScriptProcessorNode::uninitialize()
{
    if (!isInitialized())
        return;

    m_inputBuffers.clear();
    m_outputBuffers.clear();

    AudioNode::uninitialize();
}

void ScriptProcessorNode::process(size_t framesToProcess)
{
    // Discussion about inputs and outputs:
    // As in other AudioNodes, ScriptProcessorNode uses an AudioBus for its input and output (see inputBus and outputBus below).
    // Additionally, there is a double-buffering for input and output which is exposed directly to JavaScript (see inputBuffer and outputBuffer below).
    // This node is the producer for inputBuffer and the consumer for outputBuffer.
    // The JavaScript code is the consumer of inputBuffer and the producer for outputBuffer.

    // Check if audioprocess listener is set.
    if (!m_hasAudioProcessListener)
        return;

    // Get input and output busses.
    AudioBus* inputBus = this->input(0)->bus();
    AudioBus* outputBus = this->output(0)->bus();

    // Get input and output buffers. We double-buffer both the input and output sides.
    unsigned doubleBufferIndex = this->doubleBufferIndex();
    bool isDoubleBufferIndexGood = doubleBufferIndex < 2 && doubleBufferIndex < m_inputBuffers.size() && doubleBufferIndex < m_outputBuffers.size();
    ASSERT(isDoubleBufferIndexGood);
    if (!isDoubleBufferIndexGood)
        return;
    
    AudioBuffer* inputBuffer = m_inputBuffers[doubleBufferIndex].get();
    AudioBuffer* outputBuffer = m_outputBuffers[doubleBufferIndex].get();

    // Check the consistency of input and output buffers.
    unsigned numberOfInputChannels = m_internalInputBus->numberOfChannels();
    bool buffersAreGood = outputBuffer && bufferSize() == outputBuffer->length() && m_bufferReadWriteIndex + framesToProcess <= bufferSize();

    // If the number of input channels is zero, it's ok to have inputBuffer = 0.
    if (m_internalInputBus->numberOfChannels())
        buffersAreGood = buffersAreGood && inputBuffer && bufferSize() == inputBuffer->length();

    ASSERT(buffersAreGood);
    if (!buffersAreGood)
        return;

    // We assume that bufferSize() is evenly divisible by framesToProcess - should always be true, but we should still check.
    bool isFramesToProcessGood = framesToProcess && bufferSize() >= framesToProcess && !(bufferSize() % framesToProcess);
    ASSERT(isFramesToProcessGood);
    if (!isFramesToProcessGood)
        return;

    unsigned numberOfOutputChannels = outputBus->numberOfChannels();

    bool channelsAreGood = (numberOfInputChannels == m_numberOfInputChannels) && (numberOfOutputChannels == m_numberOfOutputChannels);
    ASSERT(channelsAreGood);
    if (!channelsAreGood)
        return;

    for (unsigned i = 0; i < numberOfInputChannels; i++)
        m_internalInputBus->setChannelMemory(i, inputBuffer->channelData(i)->data() + m_bufferReadWriteIndex, framesToProcess);

    if (numberOfInputChannels)
        m_internalInputBus->copyFrom(*inputBus);

    // Copy from the output buffer to the output. 
    for (unsigned i = 0; i < numberOfOutputChannels; ++i)
        memcpy(outputBus->channel(i)->mutableData(), outputBuffer->channelData(i)->data() + m_bufferReadWriteIndex, sizeof(float) * framesToProcess);

    // Update the buffering index.
    m_bufferReadWriteIndex = (m_bufferReadWriteIndex + framesToProcess) % bufferSize();

    // m_bufferReadWriteIndex will wrap back around to 0 when the current input and output buffers are full.
    // When this happens, fire an event and swap buffers.
    if (!m_bufferReadWriteIndex) {
        // Avoid building up requests on the main thread to fire process events when they're not being handled.
        // This could be a problem if the main thread is very busy doing other things and is being held up handling previous requests.
        if (m_isRequestOutstanding) {
            // We're late in handling the previous request. The main thread must be very busy.
            // The best we can do is clear out the buffer ourself here.
            outputBuffer->zero();            
        } else {
            // Reference ourself so we don't accidentally get deleted before fireProcessEvent() gets called.
            ref();
            
            // Fire the event on the main thread, not this one (which is the realtime audio thread).
            m_doubleBufferIndexForEvent = m_doubleBufferIndex;
            m_isRequestOutstanding = true;

            callOnMainThread([this] {
                if (!m_hasAudioProcessListener)
                    return;

                fireProcessEvent();

                // De-reference to match the ref() call in process().
                deref();
            });
        }

        swapBuffers();
    }
}

void ScriptProcessorNode::fireProcessEvent()
{
    ASSERT(isMainThread() && m_isRequestOutstanding);
    
    bool isIndexGood = m_doubleBufferIndexForEvent < 2;
    ASSERT(isIndexGood);
    if (!isIndexGood)
        return;
        
    AudioBuffer* inputBuffer = m_inputBuffers[m_doubleBufferIndexForEvent].get();
    AudioBuffer* outputBuffer = m_outputBuffers[m_doubleBufferIndexForEvent].get();
    ASSERT(outputBuffer);
    if (!outputBuffer)
        return;

    // Avoid firing the event if the document has already gone away.
    if (context().scriptExecutionContext()) {
        // Let the audio thread know we've gotten to the point where it's OK for it to make another request.
        m_isRequestOutstanding = false;

        // Calculate playbackTime with the buffersize which needs to be processed each time when onaudioprocess is called.
        // The outputBuffer being passed to JS will be played after exhausting previous outputBuffer by double-buffering.
        double playbackTime = (context().currentSampleFrame() + m_bufferSize) / static_cast<double>(context().sampleRate());

        // Call the JavaScript event handler which will do the audio processing.
        dispatchEvent(AudioProcessingEvent::create(inputBuffer, outputBuffer, playbackTime));
    }
}

void ScriptProcessorNode::reset()
{
    m_bufferReadWriteIndex = 0;
    m_doubleBufferIndex = 0;

    for (unsigned i = 0; i < 2; ++i) {
        m_inputBuffers[i]->zero();
        m_outputBuffers[i]->zero();
    }
}

double ScriptProcessorNode::tailTime() const
{
    return std::numeric_limits<double>::infinity();
}

double ScriptProcessorNode::latencyTime() const
{
    return std::numeric_limits<double>::infinity();
}

bool ScriptProcessorNode::addEventListener(const AtomicString& eventType, Ref<EventListener>&& listener, const AddEventListenerOptions& options)
{
    bool success = AudioNode::addEventListener(eventType, WTFMove(listener), options);
    if (success && eventType == eventNames().audioprocessEvent)
        m_hasAudioProcessListener = hasEventListeners(eventNames().audioprocessEvent);
    return success;
}

bool ScriptProcessorNode::removeEventListener(const AtomicString& eventType, EventListener& listener, const ListenerOptions& options)
{
    bool success = AudioNode::removeEventListener(eventType, listener, options);
    if (success && eventType == eventNames().audioprocessEvent)
        m_hasAudioProcessListener = hasEventListeners(eventNames().audioprocessEvent);
    return success;
}

void ScriptProcessorNode::removeAllEventListeners()
{
    m_hasAudioProcessListener = false;
    AudioNode::removeAllEventListeners();
}

} // namespace WebCore

#endif // ENABLE(WEB_AUDIO)