Overview

Multi-channel envelope detector with programmable attack and release times

Discussion

Envelope detector used in dynamics processor. The module accepts an N-channel buffer of amplitude and produces an output buffer the same size as the input. An envelope detector is applied to the input that has programmable attack and release times. The attack time applies when the current input value is larger than the state of the envelope detector. Similarly, the release time applies when the current input value is smaller than the state of the envelope detector.

Type Definition

typedef struct _ModuleAGCAttackRelease
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    FLOAT32 attackTime;                           // Speed at which the detector reacts to increasing levels.
    FLOAT32 releaseTime;                          // Speed at which the detector reacts to decreasing levels.
    FLOAT32 attackCoeff;                          // Internal coefficient realizing the attack time.
    FLOAT32 releaseCoeff;                         // Internal coefficient realizing the release time.
    FLOAT32* envStates;                           // Vector of sample-by-sample states of the envelope detectors; each column is the state for a channel.
} ModuleAGCAttackReleaseClass;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
attackTime	float	parameter	0	2	0.01:1000	msec
releaseTime	float	parameter	0	100	0.01:1000	msec
attackCoeff	float	derived	1	0.01036	Unrestricted
releaseCoeff	float	derived	1	0.0002083	Unrestricted
envStates	float*	state	1	[1 x 1]	Unrestricted

Pins

Input Pins

Name: in

Description: audio input

Data type: float

Channel range: Unrestricted

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_attack_release_module.m

 M=agc_attack_release_module(NAME)
 Envelope detector with programmable attack and release time constants.
 Arguments:
    NAME - name of the module.
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