gelyk/Source/EqualizerDSP.cpp

#include "EqualizerDSP.h"

namespace gelyk
{

void computeEQResponse(const FilterBand::Type* types,
                       const float* gains, const float* freqs, const float* qs,
                       int numBands, double sampleRate, float* outDb, int numBins)
{
    if (numBins <= 0)
        return;

    for (int b = 0; b < numBins; ++b)
        outDb[b] = 0.0f;

    const float fMin = 20.0f;
    const float fMax = 20000.0f;
    const float logMin = std::log10(fMin);
    const float logMax = std::log10(fMax);

    for (int i = 0; i < numBands; ++i)
    {
        const float g = juce::jlimit(-24.0f, 24.0f, gains[i]);
        const float gainFactor = juce::Decibels::decibelsToGain(g);
        const float f = juce::jlimit(20.0f, 20000.0f, freqs[i]);
        const float q = juce::jlimit(0.1f, 6.0f, qs[i]);

        FilterBand::Coeffs::Ptr c;
        switch (types[i])
        {
            case FilterBand::Type::lowShelf:
                c = FilterBand::Coeffs::makeLowShelf(sampleRate, f, q, gainFactor);
                break;
            case FilterBand::Type::highShelf:
                c = FilterBand::Coeffs::makeHighShelf(sampleRate, f, q, gainFactor);
                break;
            case FilterBand::Type::peak:
            default:
                c = FilterBand::Coeffs::makePeakFilter(sampleRate, f, q, gainFactor);
                break;
        }

        for (int b = 0; b < numBins; ++b)
        {
            const float ratio = (float) b / (float) (numBins - 1);
            const double freq = std::pow(10.0, logMin + ratio * (logMax - logMin));
            outDb[b] += 20.0f * std::log10((float) c->getMagnitudeForFrequency(freq, sampleRate));
        }
    }
}

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

void FilterBand::prepare(double sampleRate, int blockSize)
{
    this->sampleRate = sampleRate;

    juce::dsp::ProcessSpec spec;
    spec.sampleRate = sampleRate;
    spec.maximumBlockSize = (juce::uint32) blockSize;
    spec.numChannels = 2;

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

    // Start from the current (target) parameters with no ramp.
    targetGain = gainDb;
    targetFreq = freq;
    targetQ = q;
    curGain = gainDb;
    curFreq = freq;
    curQ = q;

    updateCoeffs();
}

void FilterBand::setTargets(float gain, float freq, float q)
{
    gainDb = gain;
    this->freq = freq;
    this->q = q;
    targetGain = gain;
    targetFreq = freq;
    targetQ = q;
}

void FilterBand::updateCoeffs()
{
    const float db = juce::jlimit(-24.0f, 24.0f, curGain);
    Coeffs::Ptr c;
    switch (type)
    {
        case Type::lowShelf:
            c = Coeffs::makeLowShelf(sampleRate, curFreq, curQ, juce::Decibels::decibelsToGain(db));
            break;
        case Type::highShelf:
            c = Coeffs::makeHighShelf(sampleRate, curFreq, curQ, juce::Decibels::decibelsToGain(db));
            break;
        case Type::peak:
        default:
            c = Coeffs::makePeakFilter(sampleRate, curFreq, curQ, 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)
{
    const int numSamples = (int) block.getNumSamples();
    const auto numChannels = block.getNumChannels();

    // One-pole (exponential) smoothing evaluated at block rate, using the real
    // number of samples in this block so the ramp is independent of host buffer
    // size. ~50 ms time constant: starts responding immediately and settles
    // within ~200 ms, giving a gentle glide without the multi-second lag the old
    // per-sample SmoothedValue ramp produced when only advanced once per block.
    if (numSamples > 0 && numChannels > 0)
    {
        const float alpha = 1.0f - std::exp(-(float) numSamples / (sampleRate * 0.05f));

        const float g = curGain + (targetGain - curGain) * alpha;
        const float f = curFreq + (targetFreq - curFreq) * alpha;
        const float qv = curQ + (targetQ - curQ) * alpha;

        if (std::abs(g - curGain) > 0.001f ||
            std::abs(f - curFreq) > 0.01f ||
            std::abs(qv - curQ) > 0.001f)
        {
            curGain = g;
            curFreq = f;
            curQ = qv;
            updateCoeffs();
        }
    }

    if (numChannels < 1)
        return;

    // JUCE's IIR::Filter only processes mono (one channel pointer), so each
    // instance must be run on a single channel's own block. Previously the whole
    // (stereo) block was passed in, which made both filters operate on channel 0
    // only: the left went through twice and the right not at all. Splitting the
    // channels fixes the dead right channel and the doubled (rumble) low end.
    left.snapToZero();
    right.snapToZero();

    auto leftBlock  = block.getSingleChannelBlock(0);
    left.process(juce::dsp::ProcessContextReplacing<float>(leftBlock));

    if (numChannels > 1)
    {
        auto rightBlock = block.getSingleChannelBlock(1);
        right.process(juce::dsp::ProcessContextReplacing<float>(rightBlock));
    }
}

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

SpectrumAnalyser::SpectrumAnalyser()
    : fft(12) // 4096 point FFT
{
    const int size = fft.getSize();
    fftBuffer.resize((size_t) (size * 2), 0.0f);
    // The timer drives periodic background analysis.
    startTimerHz(30);
}

void SpectrumAnalyser::prepare(double sr, int maxBlockSize)
{
    const int size = 4096;
    (void) maxBlockSize;
    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;

    // Mesa of the two channels, Hann-windowed into the FFT buffer.
    const auto fftSize = fft.getSize();
    for (int i = 0; i < fftSize; ++i)
    {
        const int src = (ringFill - fftSize + i + n) % n; // contiguously oldest of last fftSize
        float v = ring.getSample(0, src);
        if (ringChannels > 1)
            v = 0.5f * (v + ring.getSample(1, src));
        const float win = 0.5f * (1.0f - std::cos(2.0f * juce::MathConstants<float>::pi * i / (fftSize - 1)));
        fftBuffer[(size_t) i] = v * win;
    }
    for (size_t i = (size_t) fftSize; i < fftBuffer.size(); ++i)
        fftBuffer[i] = 0.0f;

    fft.performFrequencyOnlyForwardTransform(fftBuffer.data());

    // Magnitude values (non-negative frequencies) are in the first size/2+1 entries.
    // Normalise so a full-scale sine reads as ~0 dB: JUCE's frequency-only FFT gives
    // a magnitude of ~N/2 for a unit sine at its bin, and the Hann window halves that
    // to N/4. Dividing by that reference keeps the -72..+12 dB display range meaningful.
    const float norm = 0.25f * (float) fftSize;
    const int numBins = juce::jmin((int) fftBuffer.size(), fftSize / 2 + 1);
    juce::Array<float> mags;
    mags.ensureStorageAllocated(numBins);
    for (int i = 0; i < numBins; ++i)
    {
        float mag = fftBuffer[(size_t) i];
        float db = 20.0f * std::log10(mag / norm + 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