#include <GainReductionComputer.h>

Collaboration diagram for DanielRudrich::GainReductionComputer:

Public Member Functions
	GainReductionComputer ()

	~GainReductionComputer ()

void	setAttackTime (const float attackTimeInSeconds)

void	setReleaseTime (const float releaseTimeInSeconds)

void	setKnee (const float kneeInDecibels)

const float	getKnee ()

void	setThreshold (const float thresholdInDecibels)

const float	getThreshold ()

void	setMakeUpGain (const float makeUpGainInDecibels)

const float	getMakeUpGain ()

void	setRatio (const float ratio)

void	getCharacteristic (float inputLevelsInDecibels, float destination, const int numSamples)

float	getCharacteristicSample (const float inputLevelInDecibels)

void	prepare (const double sampleRate)

void	reset ()

void	computeGainInDecibelsFromSidechainSignal (const float sideChainSignal, float destination, const int numSamples)

void	computeLinearGainFromSidechainSignal (const float sideChainSignal, float destination, const int numSamples)

const float	getMaxInputLevelInDecibels ()

const float	getMaxGainReductionInDecibels ()

Static Public Member Functions
static float	getCharacteristicSample (float inputLevelInDecibels, float kneeInDecibels, float thresholdInDecibels, float ratio, float makeUpGainInDecibels)

Private Member Functions
const float	timeToGain (const float timeInSeconds)

const float	applyCharacteristicToOverShoot (const float overShootInDecibels)

Static Private Member Functions
static float	applyCharacteristicToOverShoot (float overShootInDecibels, float knee, float slope)

Private Attributes
double	sampleRate

float	knee

float	kneeHalf

float	threshold

float	attackTime

float	releaseTime

float	slope

float	makeUpGain

std::atomic< float >	maxInputLevel {-std::numeric_limits<float>::infinity()}

std::atomic< float >	maxGainReduction {0}

float	state

float	alphaAttack

float	alphaRelease

Detailed Description

This class acts as the side-chain path of a dynamic range compressor. It processes a given side-chain signal and computes the gain reduction samples depending on the parameters threshold, knee, attack-time, release-time, ratio, and make-up gain.

Definition at line 30 of file GainReductionComputer.h.

Constructor & Destructor Documentation

◆ GainReductionComputer()

DanielRudrich::GainReductionComputer::GainReductionComputer ( )

Definition at line 41 of file GainReductionComputer.cpp.

{
    sampleRate = 0.0f;
 
    threshold = -10.0f;
    knee = 0.0f;
    kneeHalf = 0.0f;
    attackTime = 0.01f;
    releaseTime = 0.15f;
    setRatio (2); // 2 : 1
    makeUpGain = 0.0f;
    reset();
}

References attackTime, knee, kneeHalf, makeUpGain, releaseTime, reset(), sampleRate, setRatio(), and threshold.

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◆ ~GainReductionComputer()

DanielRudrich::GainReductionComputer::~GainReductionComputer ( )

inline

Definition at line 34 of file GainReductionComputer.h.

34{}

Member Function Documentation

◆ applyCharacteristicToOverShoot() [1/2]

const float DanielRudrich::GainReductionComputer::applyCharacteristicToOverShoot ( const float overShootInDecibels )

inlineprivate

Definition at line 102 of file GainReductionComputer.cpp.

{
    return applyCharacteristicToOverShoot(overShootInDecibels, knee, slope);
}

References applyCharacteristicToOverShoot(), knee, and slope.

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◆ applyCharacteristicToOverShoot() [2/2]

float DanielRudrich::GainReductionComputer::applyCharacteristicToOverShoot	(	float	overShootInDecibels,
		float	knee,
		float	slope
	)

staticprivate

Definition at line 107 of file GainReductionComputer.cpp.

{
    const auto kneeHalf = knee / 2;
    if (overShootInDecibels <= -kneeHalf)
        return 0.0f;
    else if (overShootInDecibels > -kneeHalf && overShootInDecibels <= kneeHalf)
        return 0.5f * slope * (overShootInDecibels + kneeHalf) * (overShootInDecibels + kneeHalf) / knee;
    else
        return slope * overShootInDecibels;
}

References knee, kneeHalf, and slope.

Referenced by applyCharacteristicToOverShoot(), computeGainInDecibelsFromSidechainSignal(), and getCharacteristicSample().

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◆ computeGainInDecibelsFromSidechainSignal()

void DanielRudrich::GainReductionComputer::computeGainInDecibelsFromSidechainSignal	(	const float *	sideChainSignal,
		float *	destination,
		const int	numSamples
	)

Computes the gain reduction for a given side-chain signal. The values will be in decibels and will NOT contain the make-up gain.

Definition at line 119 of file GainReductionComputer.cpp.

{
    maxInputLevel = -std::numeric_limits<float>::infinity();
    maxGainReduction = 0.0f;
 
    for (int i = 0; i < numSamples; ++i)
    {
        // convert sample to decibels
        const float levelInDecibels =
           log2ToDb * FastLog2(std::abs(sideChainSignal[i]));
 
        if (levelInDecibels > maxInputLevel)
            maxInputLevel = levelInDecibels;
 
        // calculate overshoot and apply knee and ratio
        const float overShoot = levelInDecibels - threshold;
        const float gainReduction = applyCharacteristicToOverShoot (overShoot);
 
        // apply ballistics
        const float diff = gainReduction - state;
        if (diff < 0.0f) // wanted gain reduction is below state -> attack phase
            state += alphaAttack * diff;
        else // release phase
            state += alphaRelease * diff;
 
        // write back gain reduction
        destination[i] = state;
 
        if (state < maxGainReduction)
            maxGainReduction = state;
    }
}

References alphaAttack, alphaRelease, applyCharacteristicToOverShoot(), FastLog2(), log2ToDb, maxGainReduction, maxInputLevel, state, and threshold.

Referenced by computeLinearGainFromSidechainSignal().

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◆ computeLinearGainFromSidechainSignal()

void DanielRudrich::GainReductionComputer::computeLinearGainFromSidechainSignal	(	const float *	sideChainSignal,
		float *	destination,
		const int	numSamples
	)

Computes the linear gain including make-up gain for a given side-chain signal. The gain written to the destination can be directly applied to the signals which should be compressed.

Definition at line 152 of file GainReductionComputer.cpp.

{
    computeGainInDecibelsFromSidechainSignal (sideChainSignal, destination, numSamples);
    for (int i = 0; i < numSamples; ++i)
        destination[i] = std::pow (10.0f, 0.05f * (destination[i] + makeUpGain));
}

References computeGainInDecibelsFromSidechainSignal(), and makeUpGain.

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◆ getCharacteristic()

void DanielRudrich::GainReductionComputer::getCharacteristic	(	float *	inputLevelsInDecibels,
		float *	destination,
		const int	numSamples
	)

Computes the static output levels for an array of input levels in decibels. Useful for visualization of the compressor's characteristic. Will contain make-up gain.

Definition at line 160 of file GainReductionComputer.cpp.

{
    for (int i = 0; i < numSamples; ++i)
        dest[i] = getCharacteristicSample (inputLevelsInDecibels[i]);
}

References getCharacteristicSample().

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◆ getCharacteristicSample() [1/2]

float DanielRudrich::GainReductionComputer::getCharacteristicSample ( const float inputLevelInDecibels )

Computes the static output levels for a given input level in decibels. Useful for visualization of the compressor's characteristic. Will contain make-up gain.

Definition at line 166 of file GainReductionComputer.cpp.

{
    return getCharacteristicSample(inputLevelInDecibels, knee, threshold,
                                   getRatio(slope), makeUpGain);
}

References getCharacteristicSample(), DanielRudrich::anonymous_namespace{GainReductionComputer.cpp}::getRatio(), knee, makeUpGain, slope, and threshold.

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◆ getCharacteristicSample() [2/2]

float DanielRudrich::GainReductionComputer::getCharacteristicSample	(	float	inputLevelInDecibels,
		float	kneeInDecibels,
		float	thresholdInDecibels,
		float	ratio,
		float	makeUpGainInDecibels
	)

static

Definition at line 29 of file GainReductionComputer.cpp.

{
   const auto slope = getSlope(ratio);
   float overShoot = inputLevelInDecibels - thresholdInDecibels;
   overShoot = applyCharacteristicToOverShoot(overShoot, kneeInDecibels, slope);
   return overShoot + inputLevelInDecibels + makeUpGainInDecibels;
}

References applyCharacteristicToOverShoot(), DanielRudrich::anonymous_namespace{GainReductionComputer.cpp}::getSlope(), and slope.

Referenced by CompressorProcessor::EvaluateTransferFunction(), getCharacteristic(), and getCharacteristicSample().

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◆ getKnee()

const float DanielRudrich::GainReductionComputer::getKnee ( )

inline

Definition at line 56 of file GainReductionComputer.h.

56{ return knee; }

References knee.

◆ getMakeUpGain()

const float DanielRudrich::GainReductionComputer::getMakeUpGain ( )

inline

Definition at line 68 of file GainReductionComputer.h.

68{ return makeUpGain; }

References makeUpGain.

◆ getMaxGainReductionInDecibels()

const float DanielRudrich::GainReductionComputer::getMaxGainReductionInDecibels ( )

inline

Definition at line 108 of file GainReductionComputer.h.

108{ return maxGainReduction; }

References maxGainReduction.

◆ getMaxInputLevelInDecibels()

const float DanielRudrich::GainReductionComputer::getMaxInputLevelInDecibels ( )

inline

Definition at line 107 of file GainReductionComputer.h.

107{ return maxInputLevel; }

References maxInputLevel.

◆ getThreshold()

const float DanielRudrich::GainReductionComputer::getThreshold ( )

inline

Definition at line 62 of file GainReductionComputer.h.

62{ return threshold; }

References threshold.

◆ prepare()

void DanielRudrich::GainReductionComputer::prepare ( const double sampleRate )

Prepares the compressor with sampleRate and expected blockSize. Make sure you call this before you do any processing!

Definition at line 55 of file GainReductionComputer.cpp.

{
    sampleRate = newSampleRate;
 
    alphaAttack = 1.0f - timeToGain (attackTime);
    alphaRelease = 1.0f - timeToGain (releaseTime);
}

References alphaAttack, alphaRelease, attackTime, releaseTime, sampleRate, and timeToGain().

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◆ reset()

void DanielRudrich::GainReductionComputer::reset ( )

inline

Resets the internal state of the compressor.

Definition at line 95 of file GainReductionComputer.h.

95{ state = 0.0f; }

References state.

Referenced by GainReductionComputer().

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◆ setAttackTime()

void DanielRudrich::GainReductionComputer::setAttackTime ( const float attackTimeInSeconds )

Sets the attack time of the compressor in seconds.

Definition at line 63 of file GainReductionComputer.cpp.

{
    attackTime = attackTimeInSeconds;
    alphaAttack = 1.0f - timeToGain (attackTime);
}

References alphaAttack, attackTime, and timeToGain().

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◆ setKnee()

void DanielRudrich::GainReductionComputer::setKnee ( const float kneeInDecibels )

Sets the knee-width in decibels.

Definition at line 80 of file GainReductionComputer.cpp.

{
    knee = kneeInDecibels;
    kneeHalf = knee / 2.0f;
}

References knee, and kneeHalf.

◆ setMakeUpGain()

void DanielRudrich::GainReductionComputer::setMakeUpGain ( const float makeUpGainInDecibels )

Sets the make-up-gain of the compressor in decibels.

Definition at line 91 of file GainReductionComputer.cpp.

{
    makeUpGain = makeUpGainInDecibels;
}

References makeUpGain.

◆ setRatio()

void DanielRudrich::GainReductionComputer::setRatio ( const float ratio )

Sets the ratio of input-output signal above threshold. Set to 1 for no compression, up to infinity for a brickwall limiter.

Definition at line 96 of file GainReductionComputer.cpp.

{
    slope = getSlope(ratio);
}

References DanielRudrich::anonymous_namespace{GainReductionComputer.cpp}::getSlope(), and slope.

Referenced by GainReductionComputer().

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◆ setReleaseTime()

void DanielRudrich::GainReductionComputer::setReleaseTime ( const float releaseTimeInSeconds )

Sets the release time of the compressorin seconds

Definition at line 69 of file GainReductionComputer.cpp.

{
    releaseTime = releaseTimeInSeconds;
    alphaRelease = 1.0f - timeToGain (releaseTime);
}

References alphaRelease, releaseTime, and timeToGain().

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◆ setThreshold()

void DanielRudrich::GainReductionComputer::setThreshold ( const float thresholdInDecibels )

Sets the threshold above which the compressor will start to compress the signal.

Definition at line 86 of file GainReductionComputer.cpp.

{
    threshold = thresholdInDecibels;
}

References threshold.

◆ timeToGain()

const float DanielRudrich::GainReductionComputer::timeToGain ( const float timeInSeconds )

inlineprivate

Definition at line 75 of file GainReductionComputer.cpp.

{
    return std::exp (-1.0f / (static_cast<float> (sampleRate) * timeInSeconds));
}

References sampleRate.

Referenced by prepare(), setAttackTime(), and setReleaseTime().

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Member Data Documentation

◆ alphaAttack

float DanielRudrich::GainReductionComputer::alphaAttack

private

Definition at line 133 of file GainReductionComputer.h.

Referenced by computeGainInDecibelsFromSidechainSignal(), prepare(), and setAttackTime().

◆ alphaRelease

float DanielRudrich::GainReductionComputer::alphaRelease

private

Definition at line 134 of file GainReductionComputer.h.

Referenced by computeGainInDecibelsFromSidechainSignal(), prepare(), and setReleaseTime().

◆ attackTime

float DanielRudrich::GainReductionComputer::attackTime

private

Definition at line 122 of file GainReductionComputer.h.

Referenced by GainReductionComputer(), prepare(), and setAttackTime().

◆ knee

float DanielRudrich::GainReductionComputer::knee

private

Definition at line 120 of file GainReductionComputer.h.

Referenced by applyCharacteristicToOverShoot(), GainReductionComputer(), getCharacteristicSample(), getKnee(), and setKnee().

◆ kneeHalf

float DanielRudrich::GainReductionComputer::kneeHalf

private

Definition at line 120 of file GainReductionComputer.h.

Referenced by applyCharacteristicToOverShoot(), GainReductionComputer(), and setKnee().

◆ makeUpGain

float DanielRudrich::GainReductionComputer::makeUpGain

private

Definition at line 125 of file GainReductionComputer.h.

Referenced by computeLinearGainFromSidechainSignal(), GainReductionComputer(), getCharacteristicSample(), getMakeUpGain(), and setMakeUpGain().

◆ maxGainReduction

std::atomic<float> DanielRudrich::GainReductionComputer::maxGainReduction {0}

private

Definition at line 128 of file GainReductionComputer.h.

Referenced by computeGainInDecibelsFromSidechainSignal(), and getMaxGainReductionInDecibels().

◆ maxInputLevel

std::atomic<float> DanielRudrich::GainReductionComputer::maxInputLevel {-std::numeric_limits<float>::infinity()}

private

Definition at line 127 of file GainReductionComputer.h.

Referenced by computeGainInDecibelsFromSidechainSignal(), and getMaxInputLevelInDecibels().

◆ releaseTime

float DanielRudrich::GainReductionComputer::releaseTime

private

Definition at line 123 of file GainReductionComputer.h.

Referenced by GainReductionComputer(), prepare(), and setReleaseTime().

◆ sampleRate

double DanielRudrich::GainReductionComputer::sampleRate

private

Definition at line 117 of file GainReductionComputer.h.

Referenced by GainReductionComputer(), prepare(), and timeToGain().

◆ slope

float DanielRudrich::GainReductionComputer::slope

private

Definition at line 124 of file GainReductionComputer.h.

Referenced by applyCharacteristicToOverShoot(), getCharacteristicSample(), and setRatio().

◆ state

float DanielRudrich::GainReductionComputer::state

private

Definition at line 131 of file GainReductionComputer.h.

Referenced by computeGainInDecibelsFromSidechainSignal(), and reset().

◆ threshold

float DanielRudrich::GainReductionComputer::threshold

private

Definition at line 121 of file GainReductionComputer.h.

Referenced by computeGainInDecibelsFromSidechainSignal(), GainReductionComputer(), getCharacteristicSample(), getThreshold(), and setThreshold().

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

Public Member Functions

Static Public Member Functions

Private Member Functions

Static Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ GainReductionComputer()

◆ ~GainReductionComputer()

Member Function Documentation

◆ applyCharacteristicToOverShoot() [1/2]

◆ applyCharacteristicToOverShoot() [2/2]

◆ computeGainInDecibelsFromSidechainSignal()

◆ computeLinearGainFromSidechainSignal()

◆ getCharacteristic()

◆ getCharacteristicSample() [1/2]

◆ getCharacteristicSample() [2/2]

◆ getKnee()

◆ getMakeUpGain()

◆ getMaxGainReductionInDecibels()

◆ getMaxInputLevelInDecibels()

◆ getThreshold()

◆ prepare()

◆ reset()

◆ setAttackTime()

◆ setKnee()

◆ setMakeUpGain()

◆ setRatio()

◆ setReleaseTime()

◆ setThreshold()

◆ timeToGain()

Member Data Documentation

◆ alphaAttack

◆ alphaRelease

◆ attackTime

◆ knee

◆ kneeHalf

◆ makeUpGain

◆ maxGainReduction

◆ maxInputLevel

◆ releaseTime

◆ sampleRate

◆ slope

◆ state

◆ threshold