Method LowPassFilter

examples/sound_effects/SoundEffects.cpp:835–851

struct LowPassFilter : BiquadFilter
{
    LowPassFilter() : BiquadFilter("Low-pass Filter")
    {
        static constexpr auto cutoffFrequency = 500.f;

        const auto c = 1.f / std::tan(pi * cutoffFrequency /
                                      static_cast<float>(sf::PlaybackDevice::getDeviceSampleRate().value_or(44100)));

        Coefficients coefficients;

        coefficients.a0 = 1.f / (1.f + sqrt2 * c + std::pow(c, 2.f));
        coefficients.a1 = 2.f * coefficients.a0;
        coefficients.a2 = coefficients.a0;
        coefficients.b1 = 2.f * coefficients.a0 * (1.f - std::pow(c, 2.f));
        coefficients.b2 = coefficients.a0 * (1.f - sqrt2 * c + std::pow(c, 2.f));

        setCoefficients(coefficients);
    }
};