AudioDestinationChromium.cpp   [plain text]

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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "AudioDestinationChromium.h"

#include "AudioPullFIFO.h"
#include "WebKit.h"
#include "platform/WebKitPlatformSupport.h"

#include <public/Platform.h>

using namespace WebKit;

namespace WebCore {

// Buffer size at which the web audio engine will render.
const unsigned renderBufferSize = 128;

// Size of the FIFO
const size_t fifoSize = 8192;

// FIXME: add support for multi-channel.
const unsigned numberOfChannels = 2;

// Factory method: Chromium-implementation
PassOwnPtr<AudioDestination> AudioDestination::create(AudioSourceProvider& provider, float sampleRate)
{
    return adoptPtr(new AudioDestinationChromium(provider, sampleRate));
}

AudioDestinationChromium::AudioDestinationChromium(AudioSourceProvider& provider, float sampleRate)
    : m_provider(provider)
    , m_renderBus(numberOfChannels, renderBufferSize, false)
    , m_sampleRate(sampleRate)
    , m_isPlaying(false)
{
    // Use the optimal buffer size recommended by the audio backend.
    m_callbackBufferSize = WebKit::Platform::current()->audioHardwareBufferSize();

    // Quick exit if the requested size is too large.
    ASSERT(m_callbackBufferSize + renderBufferSize <= fifoSize);
    if (m_callbackBufferSize + renderBufferSize > fifoSize)
        return;
    
    m_audioDevice = adoptPtr(WebKit::Platform::current()->createAudioDevice(m_callbackBufferSize, numberOfChannels, sampleRate, this));
    ASSERT(m_audioDevice);

    // Create a FIFO to handle the possibility of the callback size
    // not being a multiple of the render size. If the FIFO already
    // contains enough data, the data will be provided directly.
    // Otherwise, the FIFO will call the provider enough times to
    // satisfy the request for data.
    m_fifo = adoptPtr(new AudioPullFIFO(provider, numberOfChannels, fifoSize, renderBufferSize));
}

AudioDestinationChromium::~AudioDestinationChromium()
{
    stop();
}

void AudioDestinationChromium::start()
{
    if (!m_isPlaying && m_audioDevice) {
        m_audioDevice->start();
        m_isPlaying = true;
    }
}

void AudioDestinationChromium::stop()
{
    if (m_isPlaying && m_audioDevice) {
        m_audioDevice->stop();
        m_isPlaying = false;
    }
}

float AudioDestination::hardwareSampleRate()
{
    return static_cast<float>(WebKit::Platform::current()->audioHardwareSampleRate());
}

// Pulls on our provider to get the rendered audio stream.
void AudioDestinationChromium::render(const WebVector<float*>& audioData, size_t numberOfFrames)
{
    bool isNumberOfChannelsGood = audioData.size() == numberOfChannels;
    if (!isNumberOfChannelsGood) {
        ASSERT_NOT_REACHED();
        return;
    }
        
    bool isBufferSizeGood = numberOfFrames == m_callbackBufferSize;
    if (!isBufferSizeGood) {
        ASSERT_NOT_REACHED();
        return;
    }

    m_renderBus.setChannelMemory(0, audioData[0], numberOfFrames);
    m_renderBus.setChannelMemory(1, audioData[1], numberOfFrames);
    m_fifo->consume(&m_renderBus, numberOfFrames);
}

} // namespace WebCore

#endif // ENABLE(WEB_AUDIO)