Overview

Mutes and unmutes to hide artifacts

Discussion

This module is used to hide pops and clicks during transitions. The module smoothly mutes, outputs silence, and then smoothly unmutes. You have full control over mute period, silence period, and unmuting period.

The .trigger variable is used to engage the entire process. Normally trigger=0 and the module passes the input unchanged. When you set trigger=1, then the module goes through the overall mute/silence/unmute cycle.

The module uses a raised cosine window for muting and unmuting. For memory efficiency the module uses a complex recursion to compute the gain profile for the raised cosine.

The constructor argument INITIALSTATE allows you to set the initial state of the trigger variable. By default, INITIALSTATE = 0 meaning that the module starts up unmuted. If you set INITIALSTATE = 1, then the module starts out muted.

Type Definition

typedef struct _ModuleMuteUnmute
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 trigger;                                // Begins the muting and unmuting process
    FLOAT32 muteTime;                             // Muting time, in msec
    FLOAT32 silenceTime;                          // Duration of the silence period, in msec
    FLOAT32 unmuteTime;                           // Unmuting time, in msec
    INT32 muteTimeSamples;                        // Muting time, in samples
    INT32 silenceTimeSamples;                     // Silence time, in samples
    INT32 unmuteTimeSamples;                      // Unmuting time, in samples
    FLOAT32 muteCoeffR;                           // One of two coefficients used to compute the muting profile
    FLOAT32 muteCoeffI;                           // One of two coefficients used to compute the muting profile
    FLOAT32 unmuteCoeffR;                         // One of two coefficients used to compute the unmuting profile
    FLOAT32 unmuteCoeffI;                         // One of two coefficients used to compute the unmuting profile
    FLOAT32 stateR;                               // One of two state variables which control the ramping profile
    FLOAT32 stateI;                               // One of two state variables which control the ramping profile
    INT32 sampleTime;                             // Counts the samples elapsed in the entire mute/silence/unmute cycle
} ModuleMuteUnmuteClass;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
trigger	int	state	0	0	0:1
muteTime	float	parameter	0	5	1:1000
silenceTime	float	parameter	0	100	0:10000
unmuteTime	float	parameter	0	50	1:1000
muteTimeSamples	int	derived	1	240	Unrestricted
silenceTimeSamples	int	derived	1	4800	Unrestricted
unmuteTimeSamples	int	derived	1	2400	Unrestricted
muteCoeffR	float	derived	1	0.9999	Unrestricted
muteCoeffI	float	derived	1	0.01309	Unrestricted
unmuteCoeffR	float	derived	1	1	Unrestricted
unmuteCoeffI	float	derived	1	0.001309	Unrestricted
stateR	float	state	1	0	Unrestricted
stateI	float	state	1	0	Unrestricted
sampleTime	int	state	1	0	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

Scratch Pins

Channel count: 1

Block size: 32

Sample rate: 48000

MATLAB Usage

File Name: mute_unmute_module.m

 M=mute_unmute_module(NAME, INITIALSTATE)
 Creates a module which mutes, remains silent, and then unmutes
 after a period of time.  This is used to hide artifacts.  The
 module has programmable mute, unmute, and silence periods.  The
 muting and unmuting is performed using raised cosine windows.
 Arguments:
    NAME - name of the module.
    INITIALSTATE - optional argument which specifies the default state
      of the trigger variable.  By default, INITIALSTATE = 0 meaning that
      the module comes up unmuted.