AGCCompressorCore
Overview
Gain computer used to realize compressors
Discussion
This module accepts a mono input, takes the absolute value, computes an envelope follower (with settable attack and decay rates), and computes the appropriate gain based on threshold, gain, and slope parameters. The output has a linear gain factor. The computation is performed once per tick. If you have a multichannel input, then use the max_abs_module.m to compute the absolute value across multiple channels.
The envelope follower uses the maximum value of the input within the tick for its calculation. The output gain is smoothed with a one-pole smoother to reduce zipper noise.
Type Definition
typedef struct _ModuleAGCCompressorCore
{
ModuleInstanceDescriptor instance; // Common Audio Weaver module instance structure
FLOAT32 threshold; // Amplitude level at which the AGC Limiter Core reduces its output gain value.
FLOAT32 gain; // Value used to scale the output of the AGC Limiter Core.
FLOAT32 ratio; // Specifies the amount of attenuation (and gain) when above (or below) the threshold.
FLOAT32 attackTime; // Envelope detector attack time constant.
FLOAT32 attackTimeMin; // Minimum value of the attack time constant.
FLOAT32 decayTime; // Envelope detector decay time constant.
FLOAT32 decayTimeMin; // Minimum value of the decay time constant.
FLOAT32 currentGain; // Instantaneous gain applied at the end of the block.
FLOAT32 slope; // Internal parameter which holds the slope of the compression curve.
FLOAT32 sharpnessFactor; // Unused variable. Kept in for legacy support
FLOAT32 attackCoeff; // Internal derived coefficient based on the attackTime
FLOAT32 attackCoeffSmoothing; // Internal derived coefficient based on the attackTimeMin
FLOAT32 decayCoeff; // Internal derived coefficient based on decayTime
FLOAT32 decayCoeffSmoothing; // Internal derived coefficient based on decayTimeMin
FLOAT32 envState; // State of the envelope detector one-pole filter - runs at tick rate.
} ModuleAGCCompressorCoreClass;
Variables
Properties
Name | Type | Usage | isHidden | Default value | Range | Units |
threshold | float | parameter | 0 | -20 | -60:0 | dB |
gain | float | parameter | 0 | 1 | 0:100 | dB |
ratio | float | parameter | 0 | 4 | 1:100 | dB/dB |
attackTime | float | parameter | 0 | 20 | 20:100 | msec |
attackTimeMin | float | parameter | 0 | 20 | Unrestricted | |
decayTime | float | parameter | 0 | 100 | 20:1000 | msec |
decayTimeMin | float | parameter | 0 | 20 | Unrestricted | |
currentGain | float | state | 0 | 0 | -20:20 | |
slope | float | derived | 1 | 0.75 | 0:100 | dB/dB |
sharpnessFactor | float | derived | 1 | 0 | Unrestricted | |
attackCoeff | float | derived | 1 | 1 | Unrestricted | |
attackCoeffSmoothing | float | derived | 1 | 0.001041 | Unrestricted | |
decayCoeff | float | derived | 1 | 0.01324 | Unrestricted | |
decayCoeffSmoothing | float | derived | 1 | 0.0004166 | Unrestricted | |
envState | 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
Output Pins
Name: out
Description: audio output
Data type: float
MATLAB Usage
File Name: agc_compressor_core_module.m
M=agc_compressor_core_module(NAME)
Creates a gain computation part of a compressor. It is used in
conjunction with the AGCMultiplier to implement full compressor.
Arguments:
NAME - name of the module.