Ducker

Overview

Duck or reduce the audio level of the input

Discussion

The module has the parameter "manualTrigger" to trigger manually. when the trigger signal or manualTrigger is nonzero, the level of the input audio will be changed from 1.0 to duckLevelLinear smoothly, with the time constant determined by the attackTime parameter. duckLevelLinear is the linear value equivalent to the dB value of duckLevel. After the time 3*attackTime + holdTime, the gain of the input audio changed to 1.0 smoothly, with the time constant determined by the releaseTime parameter.

Type Definition

CODE

typedef struct _ModuleDucker
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    FLOAT32 duckLevel;                            // Level in dB at which the input will be attenuated when ducking is active.
    FLOAT32 attackTime;                           // Time constant in msec, which controls the ducking process.
    FLOAT32 holdTime;                             // Time constant in msec which controls how long the signal is attenuated for.
    FLOAT32 releaseTime;                          // Time constant in msec which controls how fast the gain is restored to 1.0.
    INT32 manualTrigger;                          // Boolean parameter to trigger manually.
    FLOAT32 duckLevelLinear;                      // Level in dB at which the input will be attenuated when ducking is active.
    FLOAT32 attackCoeff;                          // Internal coefficient realizing the attack time.
    FLOAT32 releaseCoeff;                         // Internal coefficient realizing the release time.
    INT32 timerPeriod;                            // The period of timer in terms of number of blocks.
    INT32 timerCount;                             // Instantaneous count of the timer.
    FLOAT32 currentGain;                          // Instantaneous gain applied by the module.
    FLOAT32 targetGain;                           // Target gain applied by the module.
    FLOAT32 smoothingCoeff;                       // Internal coefficient realizing the smoothing time.
} ModuleDuckerClass;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
duckLevel	float	parameter	0	-20	-60:0	dB
attackTime	float	parameter	0	20	0.01:1000	msec
holdTime	float	parameter	0	1000	0.01:1000	msec
releaseTime	float	parameter	0	100	0.01:1000	msec
manualTrigger	int	parameter	0	0	0:1
duckLevelLinear	float	derived	1	0.1	Unrestricted
attackCoeff	float	derived	1	0.001041	Unrestricted
releaseCoeff	float	derived	1	0.0002083	Unrestricted
timerPeriod	int	derived	1	1590	Unrestricted
timerCount	int	state	1	0	Unrestricted
currentGain	float	state	1	1	Unrestricted
targetGain	float	state	1	1	Unrestricted
smoothingCoeff	float	state	1	1	Unrestricted

Pins

Input Pins

Name: trigger

Description: trigger signal

Data type: int

Channel range: 1

Block size range: 1

Sample rate range: Unrestricted

Complex support: Real

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: ducker_module.m

CODE

 M=ducker_module(NAME)
 Audio Weaver module to reduce the audio level of the input signal based on the 
 trigger input. The module has two input pins and one output pin.
 The first input pin is the trigger input of single channel and blockSize=1,
 contains a boolean value. The second input pin is the audio input contains 
 N channels and arbitary blockSize. The output pin contains same number of
 channels and blockSize as the input audio signal.
 
 Arguments:
    NAME - name of the module.