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

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

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

• /home/runner/work/dox/dox/fastled/src/fl/audio/auto_gain.h
• /home/runner/work/dox/dox/fastled/src/fl/audio/auto_gain.cpp.hpp