Source/WebCore/Modules/webaudio/WaveShaperDSPKernel.cpp

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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "WaveShaperDSPKernel.h"

#include "WaveShaperProcessor.h"
#include <algorithm>
#include <wtf/MainThread.h>
#include <wtf/Threading.h>

const unsigned RenderingQuantum = 128;

namespace WebCore {

WaveShaperDSPKernel::WaveShaperDSPKernel(WaveShaperProcessor* processor)
    : AudioDSPKernel(processor)
{
    if (processor->oversample() != WaveShaperProcessor::OverSampleNone)
        lazyInitializeOversampling();
}

void WaveShaperDSPKernel::lazyInitializeOversampling()
{
    ASSERT(isMainThread());

    if (!m_tempBuffer) {
        m_tempBuffer = makeUnique<AudioFloatArray>(RenderingQuantum * 2);
        m_tempBuffer2 = makeUnique<AudioFloatArray>(RenderingQuantum * 4);
        m_upSampler = makeUnique<UpSampler>(RenderingQuantum);
        m_downSampler = makeUnique<DownSampler>(RenderingQuantum * 2);
        m_upSampler2 = makeUnique<UpSampler>(RenderingQuantum * 2);
        m_downSampler2 = makeUnique<DownSampler>(RenderingQuantum * 4);
    }
}

void WaveShaperDSPKernel::process(const float* source, float* destination, size_t framesToProcess)
{
    switch (waveShaperProcessor()->oversample()) {
    case WaveShaperProcessor::OverSampleNone:
        processCurve(source, destination, framesToProcess);
        break;
    case WaveShaperProcessor::OverSample2x:
        processCurve2x(source, destination, framesToProcess);
        break;
    case WaveShaperProcessor::OverSample4x:
        processCurve4x(source, destination, framesToProcess);
        break;

    default:
        ASSERT_NOT_REACHED();
    }
}

void WaveShaperDSPKernel::processCurve(const float* source, float* destination, size_t framesToProcess)
{
    ASSERT(source && destination && waveShaperProcessor());

    Float32Array* curve = waveShaperProcessor()->curve();
    if (!curve) {
        // Act as "straight wire" pass-through if no curve is set.
        memcpy(destination, source, sizeof(float) * framesToProcess);
        return;
    }

    float* curveData = curve->data();
    int curveLength = curve->length();

    ASSERT(curveData);

    if (!curveData || !curveLength) {
        memcpy(destination, source, sizeof(float) * framesToProcess);
        return;
    }

    // Apply waveshaping curve.
    for (unsigned i = 0; i < framesToProcess; ++i) {
        const float input = source[i];

        // Calculate a virtual index based on input -1 -> +1 with 0 being at the center of the curve data.
        // Then linearly interpolate between the two points in the curve.
        double virtualIndex = 0.5 * (input + 1) * curveLength;
        int index1 = static_cast<int>(virtualIndex);
        int index2 = index1 + 1;
        double interpolationFactor = virtualIndex - index1;

        // Clip index to the input range of the curve.
        // This takes care of input outside of nominal range -1 -> +1
        index1 = std::max(index1, 0);
        index1 = std::min(index1, curveLength - 1);
        index2 = std::max(index2, 0);
        index2 = std::min(index2, curveLength - 1);

        double value1 = curveData[index1];
        double value2 = curveData[index2];

        double output = (1.0 - interpolationFactor) * value1 + interpolationFactor * value2;
        destination[i] = output;
    }
}

void WaveShaperDSPKernel::processCurve2x(const float* source, float* destination, size_t framesToProcess)
{
    bool isSafe = framesToProcess == RenderingQuantum;
    ASSERT(isSafe);
    if (!isSafe)
        return;

    float* tempP = m_tempBuffer->data();

    m_upSampler->process(source, tempP, framesToProcess);

    // Process at 2x up-sampled rate.
    processCurve(tempP, tempP, framesToProcess * 2);

    m_downSampler->process(tempP, destination, framesToProcess * 2);
}

void WaveShaperDSPKernel::processCurve4x(const float* source, float* destination, size_t framesToProcess)
{
    bool isSafe = framesToProcess == RenderingQuantum;
    ASSERT(isSafe);
    if (!isSafe)
        return;

    float* tempP = m_tempBuffer->data();
    float* tempP2 = m_tempBuffer2->data();

    m_upSampler->process(source, tempP, framesToProcess);
    m_upSampler2->process(tempP, tempP2, framesToProcess * 2);

    // Process at 4x up-sampled rate.
    processCurve(tempP2, tempP2, framesToProcess * 4);

    m_downSampler2->process(tempP2, tempP, framesToProcess * 4);
    m_downSampler->process(tempP, destination, framesToProcess * 2);
}

void WaveShaperDSPKernel::reset()
{
    if (m_upSampler) {
        m_upSampler->reset();
        m_downSampler->reset();
        m_upSampler2->reset();
        m_downSampler2->reset();
    }
}

double WaveShaperDSPKernel::latencyTime() const
{
    size_t latencyFrames = 0;
    WaveShaperDSPKernel* kernel = const_cast<WaveShaperDSPKernel*>(this);

    switch (kernel->waveShaperProcessor()->oversample()) {
    case WaveShaperProcessor::OverSampleNone:
        break;
    case WaveShaperProcessor::OverSample2x:
        latencyFrames += m_upSampler->latencyFrames();
        latencyFrames += m_downSampler->latencyFrames();
        break;
    case WaveShaperProcessor::OverSample4x:
        {
            // Account for first stage upsampling.
            latencyFrames += m_upSampler->latencyFrames();
            latencyFrames += m_downSampler->latencyFrames();

            // Account for second stage upsampling.
            // and divide by 2 to get back down to the regular sample-rate.
            size_t latencyFrames2 = (m_upSampler2->latencyFrames() + m_downSampler2->latencyFrames()) / 2;
            latencyFrames += latencyFrames2;
            break;
        }
    default:
        ASSERT_NOT_REACHED();
    }

    return static_cast<double>(latencyFrames) / sampleRate();
}

} // namespace WebCore

#endif // ENABLE(WEB_AUDIO)