Overview

Automatic Gain Control gain calculator module

Type Definition

typedef struct _ModuleAGCCoreFract32
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    FLOAT32 targetLevel;                          // Target audio level
    FLOAT32 maxAttenuation;                       // Maximum attenuation of the AGC
    FLOAT32 maxGain;                              // Maximum gain of the AGC
    FLOAT32 ratio;                                // Slope of the output attenuation when the signal is above threshold
    FLOAT32 activationThreshold;                  // Activation threshold of the AGC. The AGC stops updating its gain when the instantaneous input level is below this value
    FLOAT32 smoothingTime;                        // Response time of the AGC. This controls the RMS smoothing interval and the time constant of the smoothly updating gain
    INT32 enableRecovery;                         // Boolean which enables the AGC's gain recovery. If enabled, the AGC slows returns 0 dB gain when the input is below the activation threshold
    FLOAT32 recoveryRate;                         // Rate at which the gain is adjusted when the input is below the activation threshold
    FLOAT32 currentGain;                          // Instantaneous gain of the smoothing operation.
    fract32 smoothingCoeffSampleFract32;          // Sample-by-sample smoothing coefficient for the output gain adjustment. Set via smoothingTime.
    fract32 smoothingCoeffBlockFract32;           // Block-by-block smoothing coefficient for the RMS measurement. Set via smoothingTime.
    fract32 targetGainFract32;                    // Target gain of the smoothing operation.
    fract32 energyFract32;                        // Smoothed energy measurement.
    fract32 oneOverNumSamplesFract32;             // 1 divided by the number of samples in the input pin. Used internally by the algorithm in order to save a divide operation.
    fract32 oneOverSlopeFract32;                  // Used by the processing function to compute the amount of cut/boost. Equal to 1-1/ratio.
    FLOAT32 oneOverSlope;                         // Used by the processing function to compute the amount of cut/boost. Equal to 1-1/ratio.
    FLOAT32 smoothingCoeffSample;                 // Sample-by-sample smoothing coefficient for the output gain adjustment. Set via smoothingTime.
    FLOAT32 smoothingCoeffBlock;                  // Block-by-block smoothing coefficient for the RMS measurement. Set via smoothingTime.
    FLOAT32 recoveryRateUp;                       // Recovery rate coefficient when increasing the gain (it is always >= 1)
    FLOAT32 recoveryRateDown;                     // Recovery rate coefficient when decreasing the gain (it is always <= 1)
    FLOAT32 targetGain;                           // Target gain of the smoothing operation.
    FLOAT32 energy;                               // Smoothed energy measurement.
    FLOAT32 oneOverNumSamples;                    // 1 divided by the number of samples in the input pin. Used internally by the algorithm in order to save a divide operation.
    fract32 targetLevelFract32;                   // Target audio level
    fract32 maxGainFract32;                       // Maximum gain of the AGC
    fract32 maxAttenuationFract32;                // Maximum attenuation of the AGC
    fract32 activationThresholdFract32;           // Activation threshold of the AGC. The AGC stops updating its gain when the instantaneous input level is below this value
    fract32 recoveryRateUpFract32;                // Recovery rate coefficient when increasing the gain (it is always >= 1)
    fract32 recoveryRateDownFract32;              // Recovery rate coefficient when decreasing the gain (it is always <= 1)
    fract32 currentGainFract32;                   // Instantaneous gain of the smoothing operation.
} ModuleAGCCoreFract32Class;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
targetLevel	float	parameter	0	-20	-50:0.1:50	dB
maxAttenuation	float	parameter	0	100	0:100	dB
maxGain	float	parameter	0	12	0:50	dB
ratio	float	parameter	0	10	1:100	dB/dB
activationThreshold	float	parameter	0	-50	-100:-20	dB
smoothingTime	float	parameter	0	100	1:5000	msec
enableRecovery	int	parameter	0	1	0:1
recoveryRate	float	parameter	0	2.4	1:20	dB/sec
currentGain	float	state	0	0	-12:12
smoothingCoeffSampleFract32	fract32	derived	0	0.0002083	Unrestricted
smoothingCoeffBlockFract32	fract32	derived	0	0.006644	Unrestricted
targetGainFract32	fract32	state	0	0	Unrestricted
energyFract32	fract32	state	0	0	Unrestricted
oneOverNumSamplesFract32	fract32	derived	0	0.03125	Unrestricted
oneOverSlopeFract32	fract32	derived	0	0.9	Unrestricted
oneOverSlope	float	derived	1	0.9	Unrestricted
smoothingCoeffSample	float	derived	1	0.0002083	Unrestricted
smoothingCoeffBlock	float	derived	1	0.006644	Unrestricted
recoveryRateUp	float	derived	1	1	Unrestricted
recoveryRateDown	float	derived	1	0.9998	Unrestricted
targetGain	float	state	1	0	Unrestricted
energy	float	state	1	0	Unrestricted
oneOverNumSamples	float	derived	1	0.03125	Unrestricted
targetLevelFract32	fract32	derived	1	-0.1563	Unrestricted
maxGainFract32	fract32	derived	1	0.09375	Unrestricted
maxAttenuationFract32	fract32	derived	1	0.7813	Unrestricted
activationThresholdFract32	fract32	derived	1	-0.3906	Unrestricted
recoveryRateUpFract32	fract32	derived	1	0.25	Unrestricted
recoveryRateDownFract32	fract32	derived	1	0.25	Unrestricted
currentGainFract32	fract32	state	1	0	Unrestricted

Pins

Input Pins

Name: in

Description: Audio input

Data type: fract32

Channel range: 1

Block size range: Unrestricted

Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out

Description: audio output

Data type: fract32

MATLAB Usage

File Name: agc_core_fract32_module.m

 M=agc_core_fract32_module(NAME)
 Audio Weaver modules which calculates the instantaneous gain needed
 by an automatic gain control AGC module.  This module is used in
 conjunction with the agc_multiplier_module. The input format for this 
 module is 1.31 and output format is 4.28.
    NAME - name of the module.

Documentation Hub [PUBLIC]

(8.D.2.2 ) AGCCoreFract32