gelyk/Source/EqualizerDSP.cpp

#include "EqualizerDSP.h"

namespace gelyk
{

// ---------------------------------------------------------------------------
// FilterBand
// ---------------------------------------------------------------------------

void FilterBand::prepare(double sampleRate, int blockSize)
{
    juce::dsp::ProcessSpec spec;
    spec.sampleRate = sampleRate;
    spec.maximumBlockSize = (juce::uint32) blockSize;
    spec.numChannels = 2;

    left.prepare(spec);
    right.prepare(spec);

    Coeffs::Ptr c;
    const float db = juce::jlimit(-24.0f, 24.0f, gainDb);
    switch (type)
    {
        case Type::lowShelf:
            c = new Coeffs(Coeffs::makeLowShelf(sampleRate, freq, q, juce::Decibels::decibelsToGain(db)));
            break;
        case Type::highShelf:
            c = new Coeffs(Coeffs::makeHighShelf(sampleRate, freq, q, juce::Decibels::decibelsToGain(db)));
            break;
        case Type::peak:
        default:
            c = new Coeffs(Coeffs::makePeakFilter(sampleRate, freq, q, juce::Decibels::decibelsToGain(db)));
            break;
    }

    left.coefficients = c;
    right.coefficients = c;
}

void FilterBand::reset()
{
    left.reset();
    right.reset();
}

void FilterBand::process(juce::dsp::AudioBlock<float>& block)
{
    if (block.getNumChannels() < 2)
        return;

    // Smooth the coefficients to avoid zipper noise, then process.
    left.snapToZero();
    right.snapToZero();
    left.process(juce::dsp::ProcessContextReplacing<float>(block));
    right.process(juce::dsp::ProcessContextReplacing<float>(block));
}

// ---------------------------------------------------------------------------
// SpectrumAnalyser
// ---------------------------------------------------------------------------

SpectrumAnalyser::SpectrumAnalyser()
{
    // The timer drives periodic background analysis.
    startTimerHz(30);
}

void SpectrumAnalyser::prepare(double sr, int maxBlockSize)
{
    const int size = 4096;
    sampleRate = sr;
    ring.setSize(2, size);
    ring.clear();
    ringFill = 0;
    ringChannels = 2;
}

void SpectrumAnalyser::push(const float* const* channels, int numChannels, int numSamples)
{
    if (!enabled.load() || ring.getNumSamples() == 0)
        return;

    const int n = (int) ring.getNumSamples();
    const int c = juce::jmin(ringChannels, numChannels);

    for (int i = 0; i < numSamples; ++i)
    {
        const int dst = (ringFill + i) % n;
        for (int ch = 0; ch < c; ++ch)
            ring.setSample(ch, dst, channels[ch][i]);
    }
    ringFill = (ringFill + numSamples) % n;
}

void SpectrumAnalyser::startBackground()
{
    startTimerHz(30);
}

void SpectrumAnalyser::stopBackground()
{
    stopTimer();
}

void SpectrumAnalyser::timerCallback()
{
    if (!enabled.load())
        return;
    runAnalysis();
}

void SpectrumAnalyser::runAnalysis()
{
    const int n = (int) ring.getNumSamples();
    if (n == 0)
        return;

    juce::AudioBuffer<float> block(1, n);
    // Mesa of the two channels and window with a Hann.
    block.copyFrom(0, 0, ring, 0, 0, n);
    if (ringChannels > 1)
        block.addFrom(0, 0, ring, 1, 0, n);

    juce::dsp::FFT fft(12); // 4096 point
    juce::HeapBlock<std::complex<float>> fftData;
    fftData.calloc((size_t) n);
    for (int i = 0; i < n; ++i)
    {
        float v = block.getSample(0, i) * 0.5f;
        const float win = 0.5f * (1.0f - std::cos(2.0f * juce::MathConstants<float>::pi * i / (n - 1)));
        fftData[i] = std::complex<float>(v * win, 0.0f);
    }
    fft.perform((juce::dsp::Complex<float>*) fftData.getData(), false);

    const int numBins = n / 2;
    juce::Array<float> mags;
    mags.ensureStorageAllocated(numBins);
    for (int i = 1; i < numBins; ++i)
    {
        float re = fftData[i].real();
        float im = fftData[i].imag();
        float mag = std::sqrt(re * re + im * im);
        float db = 20.0f * std::log10(mag + 1.0e-9f);
        mags.add(db);
    }

    {
        juce::ScopedLock sl(spectrumLock);
        readySpectrum = mags;
    }
}

int SpectrumAnalyser::copySpectrum(juce::Array<float>& dest, juce::Array<float>& freqBins,
                                   int maxBins) const
{
    juce::Array<float> snapshot;
    {
        juce::ScopedLock sl(spectrumLock);
        snapshot = readySpectrum;
    }

    if (snapshot.size() == 0)
    {
        dest.clear();
        freqBins.clear();
        return 0;
    }

    // Log-spaced aggregation from ~20 Hz to 20 kHz.
    const float fMin = 20.0f;
    const float fMax = 20000.0f;
    const double nfft = (double)(snapshot.size() * 2);
    const float binFreq = (float)(sampleRate / nfft);

    dest.clear();
    freqBins.clear();

    const int bands = juce::jmin(maxBins, snapshot.size());
    for (int b = 0; b < bands; ++b)
    {
        const float f = fMin * std::pow(fMax / fMin, (float) b / (float) (bands - 1));
        freqBins.add(f);
        const int startBin = juce::jmax(1, (int) std::floor(f / binFreq));
        const int endBin = juce::jmin(snapshot.size() - 1, (int) std::ceil((f * 1.5f) / binFreq));
        float total = 0.0f;
        int count = 0;
        for (int i = startBin; i <= endBin; ++i)
        {
            total += snapshot[i];
            ++count;
        }
        dest.add(count > 0 ? total / count : -96.0f);
    }

    return dest.size();
}

void SpectrumAnalyser::setEnabled(bool e)
{
    enabled.store(e);
}

} // namespace gelyk