updatePIController()

float fl::audio::AutoGain::updatePIController ( float targetGain, float dt )

private

Update PI controller toward target gain.

Parameters

targetGain	Desired gain
dt	Time step in seconds

Returns

Smoothed gain output

Definition at line 159 of file auto_gain.cpp.hpp.

                                                             {
    const float error = targetGain - mLastGain;
 
    // Bug 4 fix: Use absolute error threshold when gain is small to avoid
    // huge errorRatio from dividing by tiny mLastGain
    const bool largeError = (mLastGain > 0.1f)
        ? (fl::abs(error) / mLastGain > 0.2f)  // Relative: >20% of current gain
        : (fl::abs(error) > 0.1f);              // Absolute: >0.1 when gain is tiny
    const float tau = largeError ? mGainFollowFastTau : mGainFollowSlowTau;
 
    // Proportional term
    const float pTerm = mKp * error;
 
    // Bug 1 fix: PI target is where we WANT gain to be (not mLastGain + delta + delta)
    // targetGain + pTerm + integrator = the desired gain level
    const float piTarget = targetGain + pTerm + mIntegrator;
 
    // Smooth with exponential filter using adaptive tau
    float alpha = 1.0f;
    if (tau > 0.0f && dt > 0.0f) {
        alpha = 1.0f - fl::exp(-dt / tau);
    }
 
    const float unclamped = mLastGain + alpha * (piTarget - mLastGain);
 
    // Bug 2 fix: Back-calculation anti-windup — only accumulate integrator
    // when output is NOT clamped. Decay integrator when saturated (WLED: *= 0.91)
    const bool saturated = (unclamped > mConfig.maxGain) || (unclamped < mConfig.minGain);
    if (saturated) {
        mIntegrator *= 0.91f;
    } else {
        mIntegrator += mKi * error * dt;
    }
    // Clamp integrator magnitude to prevent runaway in pathological cases
    const float maxIntegral = 4.0f * mConfig.maxGain;
    mIntegrator = fl::max(-maxIntegral, fl::min(maxIntegral, mIntegrator));
 
    return unclamped;
}

References fl::abs(), fl::exp(), fl::max(), mConfig, mGainFollowFastTau, mGainFollowSlowTau, fl::min(), mIntegrator, mKi, mKp, and mLastGain.

Referenced by process().

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