marvin::dsp::filters::SmoothedBiquadCoefficients< SampleType, InterpolationType, NumStages > Class Template Reference

Helper class to simplify smoothly changing BiquadCoefficients with no zippering. More...

#include <marvin_SmoothedBiquadCoefficients.h>

Public Member Functions
void	reset (int periodSamples) noexcept
void	reset (double sampleRate, double timeMs) noexcept
void	setCurrentAndTargetCoeffs (size_t stage, BiquadCoefficients< SampleType > target) noexcept
void	setTargetCoeffs (size_t stage, BiquadCoefficients< SampleType > target) noexcept
BiquadCoefficients< SampleType >	current (size_t stage) const noexcept
BiquadCoefficients< SampleType >	target (size_t stage) const noexcept
void	interpolate () noexcept

Detailed Description

template<FloatType SampleType, utils::SmoothingType InterpolationType, size_t NumStages>
requires (NumStages > 0)
class marvin::dsp::filters::SmoothedBiquadCoefficients< SampleType, InterpolationType, NumStages >

Helper class to simplify smoothly changing BiquadCoefficients with no zippering.

See marvin::utils::SmoothingType for options for smoothing. Internally just runs a marvin::utils::SmoothedValue per biquad coefficient.
Usage example:

using namespace marvin::dsp::filters;
using namespace marvin::utils;
class FilterSmoothingDemo final {
public:
    void initialise(double sampleRate) {
        constexpr static auto periodMs{ 5.0f }; // 5ms duration
        m_sampleRate = sampleRate;
        m_updateRate = static_cast<int>((periodMs / 1000.0f) * static_cast<float>(sampleRate));
        const auto lpfCoeffs = rbj::lowpass<float>(sampleRate, 2000.0f, 0.5f);
        const auto hpfCoeffs = rbj::highpass<float>(sampleRate, 200.0f, 0.5f);
        m_smoothedCoeffs.reset(sampleRate, periodMs);
        m_smoothedCoeffs.setCurrentAndTargetCoeffs(lpfCoeffs, 0); // stage 0
        m_smoothedCoeffs.setCurrentAndTargetCoeffs(hpfCoeffs, 1); // stage 1
        m_filter.setCoeffs(0, m_smoothedCoeffs.current(0));
        m_filter.setCoeffs(1, m_smoothedCoeffs.current(1));
    }
 
    [[nodiscard]] float operator()(float x, float newLpfCutoff, float newHpfCutoff) noexcept {
        if(m_samplesUntilUpdate == 0) {
            const auto newLpfCoeffs = rbj::lowpass<float>(m_sampleRate, newLpfCutoff, 0.5f);
            const auto newHpfCoeffs = rbj::highpass<float>(m_sampleRate, newHpfCutoff, 0.5f);
            m_smoothedCoeffs.setTargetCoeffs(newLpfCoeffs, 0);
            m_smoothedCoeffs.setTargetCoeffs(newHpfCoeffs, 1);
            m_samplesUntilUpdate = m_updateRate;
        }
        m_smoothedCoeffs(); // Interpolate the coeffs
        m_filter.setCoeffs(0, m_smoothedCoeffs.current(0));
        m_filter.setCoeffs(1, m_smoothedCoeffs.current(1));
        const auto filtered = m_filter(x);
        --m_samplesUntilUpdate;
        return filtered;
    }
 
    void reset() noexcept {
        m_filter.reset();
    }
 
private:
    double m_sampleRate;
    int m_updateRate;
    int m_samplesUntilUpdate{ 0 };
    Biquad<float, 2> m_filter;
    SmoothedBiquadCoefficients<float, SmoothingType::Exponential, 2> m_smoothedCoeffs{};
};

Member Function Documentation

current()

template<FloatType SampleType, utils::SmoothingType InterpolationType, size_t NumStages>

BiquadCoefficients< SampleType > marvin::dsp::filters::SmoothedBiquadCoefficients< SampleType, InterpolationType, NumStages >::current ( size_t stage ) const

inlinenodiscardnoexcept

Retrieves the smoothed coeffs for a given stage.

Parameters

stage

The index of the stage to retrieve.

Returns

The smoothed coefficients for the target stage.

interpolate()

template<FloatType SampleType, utils::SmoothingType InterpolationType, size_t NumStages>

void marvin::dsp::filters::SmoothedBiquadCoefficients< SampleType, InterpolationType, NumStages >::interpolate ( )

inlinenoexcept

Performs a single tick of smoothing towards the target in all stages.

reset() [1/2]

template<FloatType SampleType, utils::SmoothingType InterpolationType, size_t NumStages>

void marvin::dsp::filters::SmoothedBiquadCoefficients< SampleType, InterpolationType, NumStages >::reset ( double sampleRate, double timeMs )

inlinenoexcept

Sets the duration of the smoothing, and sets the target value to the current value.

Parameters

sampleRate	The currently used sample rate.
timeMs	The duration of the smoothing, in milliseconds.

reset() [2/2]

template<FloatType SampleType, utils::SmoothingType InterpolationType, size_t NumStages>

void marvin::dsp::filters::SmoothedBiquadCoefficients< SampleType, InterpolationType, NumStages >::reset ( int periodSamples )

inlinenoexcept

Sets the duration of the smoothing, and sets the target value to the current value.

Parameters

periodSamples

The duration of the smoothing, in samples.

setCurrentAndTargetCoeffs()

template<FloatType SampleType, utils::SmoothingType InterpolationType, size_t NumStages>

void marvin::dsp::filters::SmoothedBiquadCoefficients< SampleType, InterpolationType, NumStages >::setCurrentAndTargetCoeffs ( size_t stage, BiquadCoefficients< SampleType > target )

inlinenoexcept

Sets both the current value of the coeffs, and the target value of the coeffs for a given stage.

Parameters

stage	The stage index to target.
target	The coeffs to set.

setTargetCoeffs()

template<FloatType SampleType, utils::SmoothingType InterpolationType, size_t NumStages>

void marvin::dsp::filters::SmoothedBiquadCoefficients< SampleType, InterpolationType, NumStages >::setTargetCoeffs ( size_t stage, BiquadCoefficients< SampleType > target )

inlinenoexcept

Sets the target value for the coeffs to smooth to for a give stage.

Parameters

stage	The stage index to target.
target	The coeffs to set.

target()

template<FloatType SampleType, utils::SmoothingType InterpolationType, size_t NumStages>

BiquadCoefficients< SampleType > marvin::dsp::filters::SmoothedBiquadCoefficients< SampleType, InterpolationType, NumStages >::target ( size_t stage ) const

inlinenodiscardnoexcept

Retrieves the target coeffs for a given stage.

Parameters

stage

The index of the stage to retrieve.

Returns

The target coefficients for the given stage.

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The documentation for this class was generated from the following file:

• /home/runner/work/mostly-harmless/mostly-harmless/modules/marvin/include/marvin/dsp/filters/biquad/marvin_SmoothedBiquadCoefficients.h