Method HRTFKernel

src/internal/src/HRTFPanner.cpp:474–504

}

HRTFKernel::HRTFKernel(AudioChannel * channel, int fftSize, float sampleRate)
    : m_frameDelay(0)
    , m_sampleRate(sampleRate)
{
    ASSERT(channel);

    // Determine the leading delay (average group delay) for the response.
    m_frameDelay = ExtractAverageGroupDelay(channel, fftSize / 2);

    float * impulseResponse = channel->mutableData();
    int responseLength = channel->length();

    // We need to truncate to fit into 1/2 the FFT size (with zero padding) in order to do proper convolution.
    int truncatedResponseLength = std::min(responseLength, fftSize / 2);  // truncate if necessary to max impulse response length allowed by FFT

    // Quick fade-out (apply window) at truncation point
    int numberOfFadeOutFrames = static_cast<unsigned>(sampleRate / 4410);  // 10 sample-frames @44.1KHz sample-rate
    ASSERT(numberOfFadeOutFrames < truncatedResponseLength);

    if (numberOfFadeOutFrames < truncatedResponseLength)
    {
        for (int i = truncatedResponseLength - numberOfFadeOutFrames; i < truncatedResponseLength; ++i)
        {
            float x = 1.0f - static_cast<float>(i - (truncatedResponseLength - numberOfFadeOutFrames)) / numberOfFadeOutFrames;
            impulseResponse[i] *= x;
        }
    }

    m_fftFrame = std::unique_ptr<FFTFrame>(new FFTFrame(fftSize));
    m_fftFrame->doPaddedFFT(impulseResponse, truncatedResponseLength);
}

std::unique_ptr<AudioChannel> HRTFKernel::createImpulseResponse()
{