Overview

Linear multichannel smoothly varying scaler with control pin

Discussion

Scales all input channels by the gain values taken from the first input pin. Changes to the gain parameter are exponentially smoothed (first order IIR) by the smoothingTime parameter on the block basis. Internally, currentGain represents the instantaneous smoothed gain that is applied. The module starts with a current gain equal to 0 and then slews towards the gain specified on the control input. The module supports multiple input and output pins and the number of pins is specified by the second argument NUMPINS. By default, NUMPINS = 1. All audio inputs and outputs are in fract32 format. The processing function is implemented using a fractional multiply by the smoothed gain followed by a fixed bit right-shift at the end.

The module argument DATATYPE specifies the data type of the control input. DATATYPE = 0 (the default) indicates that the control pin will be fractional with Q9.23 format. Alternatively, if DATATYPE = 1 then the control input is a floating-point value.

The control input can have any block size and any number of channels. The module uses the first sample value of the control pin at the target gain; all other values are ignored.

Type Definition

typedef struct _ModuleScalerControlBlockSmoothedFract32
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    FLOAT32 smoothingTime;                        // Time constant of the smoothing process
    INT32 dataType;                               // Specifies data type at input control pin (0=Q9.31, 1=float)
    fract32 currentGain;                          // Instantaneous gain applied by the module. This is also the starting gain of the module.
    fract32 smoothingCoeff;                       // Smoothing coefficient
} ModuleScalerControlBlockSmoothedFract32Class;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
smoothingTime	float	parameter	0	10	0:1000	msec
dataType	int	const	0	0	Unrestricted
currentGain	fract32	state	1	0	Unrestricted	linear
smoothingCoeff	fract32	derived	1	0.002081	Unrestricted

Pins

Input Pins

Name: g

Description: gain input

Data type: fract32

Channel range: 1

Block size range: Unrestricted

Sample rate range: Unrestricted

Complex support: Real

Name: in1

Description: audio input

Data type: fract32

Channel range: Unrestricted

Block size range: Unrestricted

Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out1

Description: audio output

Data type: fract32

MATLAB Usage

File Name: scaler_control_block_smoothed_fract32_module.m

 M=scaler_control_block_smoothed_fract32_module(NAME, NUMPINS, DATATYPE)
 The scaler operates on fractional 32-bit values. The scaler
 accepts multichannel input and scales all channels by the same
 value.  The input and output audio signals are in standard fract32
 format (Q1.31).  Arguments:
    NAME - name of the module.
    NUMPINS - number of input and output audio pins (default = 1)
    DATATYPE - data type of the control signal.  You can select
      between Q9.23 (DATATYPE = 0, the default) or floating-point
      (DATATYPE = 1)
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