Overview

General purpose scaler with separate gains per channel

Discussion

Scaler (or gain) module for floating-point signals. Compared to the general purpose scaler, this module takes equal time for fadein and fadeout as decided by fadingTime. This module has a single gain (masterGain) which is applied all channels plus a separate per channel gain (trimGain). For each channel, masterGain and trimGain[n] is combined to form the target gain value.

The gains are intrepreted as either linear or dB values based on the isDB module variable. By default, isDB=1 and the gains are treated as dB values. If you set isDB=0 then the gains are treated as linear values. When in dB, targetGain = masterGain + trimGain[n]. When in linear mode, targetGain = masterGain * trimGain[n].

The module can also switch between smoothed and unsmoothed gain changes. You enable smoothing by setting the parameter fadingTime to a non-zero value. If fadingTime=0 then no smoothing is performed. fadingTime is the time in which the target gain is achieved. The module is slightly more efficient when no smoothing occurs.

The module argument NUMCHANNELS sets the initial number of channels. This allows you to configure the module for the proper number of channels before the system is built. After the system is built, NUMCHANNELS is no longer used and the number of channels is determined from the input wire.

Type Definition

typedef struct _ModuleScalerNSymmetricFading
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    FLOAT32 masterGain;                           // Overall gain to apply.
    FLOAT32 fadingTime;                           // Time in which the target gain has to be reached (0 = unsmoothed).
    INT32 isDB;                                   // Selects between linear (=0) and dB (=1) operation
    FLOAT32* trimGain;                            // Array of trim gains, one per channel
    FLOAT32* targetGain;                          // Computed target gains in linear units
    FLOAT32* currentGain;                         // Instanteous gains. These ramp towards targetGain
    FLOAT32* factor;                              // The factor to be multiplied for implementing the exponential ramp up or ramp down
    INT32* numSamples;                            // Number of samples over which smoothing has to be applied
    FLOAT32* prevGain;                            // Previous gains
} ModuleScalerNSymmetricFadingClass;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
masterGain	float	parameter	0	0	-24:24	dB
fadingTime	float	parameter	0	10	0:1000	msec
isDB	int	parameter	0	1	0:1
trimGain	float*	parameter	0	[1 x 1]	-24:24	dB
targetGain	float*	derived	1	[1 x 1]	Unrestricted
currentGain	float*	state	1	[1 x 1]	Unrestricted
factor	float*	derived	1	[1 x 1]	Unrestricted
numSamples	int*	derived	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 and Complex

Output Pins

Name: out

Description: audio output

Data type: float

MATLAB Usage

File Name: scalern_symmetric_fading_module.m

 M = scalern_symmetric_fading_module(NAME, NUMCHANNELS)
 Scaler module with a separate gain per channel.
 Compared to the general purpose scaler, this scaler takes equal time for fadeIn or FadeOut.
 The module can be configured for linear or dB operation as well as
 smoothed and unsmoothed gain changes. Arguments:
    NAME - name of the module.
    NUMCHANNELS - default number of channels.  Default = 1.  This is
        used to draw the initial inspector.  The actual number of
        channels processed by the module is determined by pin
        propagation.