MultiChannelSpectralNode.cpp

MultiChannelSpectralNode.cpp

#include "MultiChannelSpectralNode.h"

using namespace ci;
using namespace ci::audio;
using namespace std;

MultiChannelSpectralNode::MultiChannelSpectralNode( const Format &format )
    : MonitorNode( format ), mFftSize( format.getFftSize() ), mWindowType( format.getWindowType() ),
    mSmoothingFactor( 0.5f ), mLastFrameMagSpectrumComputed( 0 ) { }

MultiChannelSpectralNode::~MultiChannelSpectralNode(){}

void MultiChannelSpectralNode::initialize(){
    MonitorNode::initialize();
    
    if( mFftSize < mWindowSize )
        mFftSize = mWindowSize;
    if( ! isPowerOf2( mFftSize ) )
        mFftSize = nextPowerOf2( static_cast<uint32_t>( mFftSize ) );
    
    mFft = unique_ptr<dsp::Fft>( new dsp::Fft( mFftSize ) );
    mFftBuffer = audio::Buffer( mFftSize );
    mBufferSpectral = audio::BufferSpectral( mFftSize );
    
    mMagSpectrum.resize(getNumChannels());
    for(int i = 0; i < getNumChannels(); i++){
        mMagSpectrum[i].resize( mFftSize / 2 );
    }
    
    mWindowingTable = makeAlignedArray<float>( mWindowSize );
    generateWindow( mWindowType, mWindowingTable.get(), mWindowSize );
}


void MultiChannelSpectralNode::prepareProcessing(){
    uint64_t numFramesProcessed = getContext()->getNumProcessedFrames();
    if( mLastFrameMagSpectrumComputed == numFramesProcessed )
        return;
    mLastFrameMagSpectrumComputed = numFramesProcessed;
    fillCopiedBuffer();
}

const std::vector<float>& MultiChannelSpectralNode::getMagSpectrum(size_t channel){
    if(channel >= getNumChannels()) return mMagSpectrum[0];
    
    // window the copied buffer and compute forward FFT transform
    dsp::mul( mCopiedBuffer.getChannel(channel), mWindowingTable.get(), mFftBuffer.getData(), mWindowSize );
    mFft->forward( &mFftBuffer, &mBufferSpectral );
    
    float *real = mBufferSpectral.getReal();
    float *imag = mBufferSpectral.getImag();
    
    // remove Nyquist component
    imag[0] = 0.0f;
    
    // compute normalized magnitude spectrum
    const float  magScale = 10.f / mFft->getSize();
    const size_t specSize = mMagSpectrum[channel].size();
    
    for( size_t i = 0; i < specSize; i++ ) {
        float re = real[i];
        float im = imag[i];
        mMagSpectrum[channel][i] = mMagSpectrum[channel][i] * mSmoothingFactor + std::sqrt( re * re + im * im ) * magScale * ( 1 - mSmoothingFactor );
    }
    
    return mMagSpectrum[channel];
}

float MultiChannelSpectralNode::getSpectralCentroid(size_t channel){
    const auto &magSpectrum = getMagSpectrum(channel);
    return dsp::spectralCentroid( magSpectrum.data(), magSpectrum.size(), getSampleRate() );
}

void MultiChannelSpectralNode::setSmoothingFactor( float factor ){
    mSmoothingFactor = math<float>::clamp( factor );
}

float MultiChannelSpectralNode::getFreqForBin( size_t bin ){
    return bin * getSampleRate() / (float)getFftSize();
}