fl::audio::AutoGain Class Reference

Detailed Description

AutoGain implements adaptive gain control using a PI (proportional-integral) controller with slow peak envelope tracking, inspired by WLED Sound Reactive.

The algorithm:

1. Track peak envelope of input RMS (fast attack ~10ms, slow decay ~3-7s)
2. Compute target gain = targetRMSLevel / peakEnvelope
3. PI controller smoothly drives actual gain toward target gain
4. Large errors use fast time constant, small errors use slow time constant
5. Integrator has anti-windup clamping

This design adapts to source-level differences (mic sensitivity, line-in voltage) without tracking musical dynamics, preventing cross-band coupling.

Usage:

AutoGain agc;
AutoGainConfig config;
config.preset = AGCPreset_Vivid;  // Faster response
agc.configure(config);
 
Sample sample = ...;
Sample amplified = agc.process(sample);

Definition at line 85 of file auto_gain.h.

#include <auto_gain.h>

Collaboration diagram for fl::audio::AutoGain:

Classes
struct	Stats
	Get current statistics (for monitoring/debugging) More...

Public Member Functions
	AutoGain () FL_NOEXCEPT
	AutoGain (const AutoGainConfig &config)
	~AutoGain () FL_NOEXCEPT
void	configure (const AutoGainConfig &config)
	Configure the auto gain controller.
float	getGain () const
	Get current gain multiplier.
const Stats &	getStats () const
Sample	process (const Sample &sample)
	Process audio sample with automatic gain adjustment.
void	reset ()
	Reset internal state.
void	setSampleRate (int sampleRate)
	Set sample rate for dt computation.

Private Member Functions
void	applyGain (const vector< i16 > &input, float gain, vector< i16 > &output)
	Apply gain to audio samples.
float	computeTargetGain ()
	Compute target gain from peak envelope.
void	resolvePreset ()
	Resolve preset enum into concrete PI tuning parameters.
float	updatePIController (float targetGain, float dt)
	Update PI controller toward target gain.

Private Attributes
AutoGainConfig	mConfig
float	mGainFollowFastTau = 0.38f
float	mGainFollowSlowTau = 12.3f
float	mIntegrator = 0.0f
	PI integrator state.
float	mKi = 1.7f
float	mKp = 0.6f
float	mLastGain = 1.0f
	Last smoothed gain output.
vector< i16 >	mOutputBuffer
	Working buffer (reused to avoid allocations)
float	mPeakDecayTau = 3.3f
AttackDecayFilter< float >	mPeakEnvelope {0.01f, 3.3f, 0.0f}
	Peak envelope tracker: fast attack (10ms), slow decay (preset-dependent)
int	mSampleRate = 44100
Stats	mStats

---

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

• fl/audio/auto_gain.h
• fl/audio/auto_gain.cpp.hpp