AGCVariableAttackRelease

Overview

Peak follower with variable attack and release rates

Discussion

The AGCVariableAttackRelease module provides program-dependent peak following. This module has 2 attack time constants and 2 release time constants. When it is attacking, it will start by using the attackTimeInitial time constant. As the output level approaches the input level, it will smoothly vary to the attackTimeFinal time constant Likewise for release. This module also has an optional freeze pin. When the freeze pin is 1, then the state variable and the output values are frozen. When the freeze pin is deasserted, this module will continue operation from previous state.

Module Pack

Advanced

ClassID

classID = 1205

Type Definition

typedef struct _ModuleAGCVariableAttackRelease
{
ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
FLOAT32 attackTimeInitial;                    // Envelope detector initial attack time constant
FLOAT32 attackTimeFinal;                      // Envelope detector final attack time constant
FLOAT32 releaseTimeInitial;                   // Envelope detector initial release time constant
FLOAT32 releaseTimeFinal;                     // Envelope detector final release time constant
FLOAT32 attackCoefInitial;                    // Computed coefficient used for initial attack
FLOAT32 attackCoefFinal;                      // Computed coefficient used for final attack
FLOAT32 releaseCoefInitial;                   // Computed coefficient used for initial release
FLOAT32 releaseCoefFinal;                     // Computed coefficient used for final release
INT32 attackMode;                             // Internal variable to keep track of the last mode (1 = attack, 0 = release, -1 = not started)
FLOAT32 state;                                // Internal state variable. This is also the instantaneous output value.
FLOAT32 startLevel;                           // Internal state variable to keep track of the initial value of the attack or release phase
} ModuleAGCVariableAttackReleaseClass;

Variables

Properties

Name	Type	Usage	isHidden	Default Value	Range	Units
attackTimeInitial	float	parameter	0	0.01	0.001:100	msec
attackTimeFinal	float	parameter	0	0.01	0.001:100	msec
releaseTimeInitial	float	parameter	0	1	0.01:100	msec
releaseTimeFinal	float	parameter	0	50	0.01:1000	msec
attackCoefInitial	float	derived	1	0.8755	Unrestricted
attackCoefFinal	float	derived	1	0.8755	Unrestricted
releaseCoefInitial	float	derived	1	0.02062	Unrestricted
releaseCoefFinal	float	derived	1	0.0004166	Unrestricted
attackMode	int	state	1	-1	Unrestricted
state	float	state	1	0	Unrestricted
startLevel	float	state	1	0	Unrestricted

Pins

Input Pins


Name	in
Description	audio input
Data type	float
Channel range	1
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Real


Name	freeze
Description	freezes the output and state variables
Data type	int
Channel range	1
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Real

Output Pins


Name	out
Description	audio output
Data Type	float

Matlab Usage

File Name: agc_variable_attack_release_module.m 
 M=agc_variable_attack_release_module(NAME, FREEZEPIN) 
 Program dependent attack release envelope follower. The attack and  
 decay will smoothly vary between 2 user-specified values, depending 
 on the amplitude characteristics of the signal being processed. 
 Arguments: 
    NAME - name of the module. 
    FREEZEPIN - Optional boolean variable that specifies if the module has 
    a freeze pin. By default, FREEZEPIN = 0.