ScalerSmoothedFract32
Overview
Linear multichannel smoothly varying scaler
Discussion
Scales all input channels by a single gain value. Changes to the gain parameter are exponentially smoothed (first order IIR) at the sample rate, with the time constant determined by the smoothingTime parameter. This module is controlled by varying the gain variable. Internally, currentGain represents the instantaneous smoothed gain that is applied. currentGain exponentially approaches gain with a time constant equal to smoothingTime.
The module's prebuild function initializes the currentGain equal to the gain. Thus, the module begins in a converged state. The module supports fract32 data types. The processing function is implemented using a fractional multiply (smoothed) followed by a fixed bit shift of the result. The number of bits to shift is based on .gain.range. You should set .gain.range near the expected operating values. Otherwise, if .gain.range is too large, you will lose some bits of precision in the final result. Note also that .gain.range must be set prior to building the system since the computation of the bit shift occurs in the prebuild function.
Type Definition
typedef struct _ModuleScalerSmoothedFract32
{
ModuleInstanceDescriptor instance; // Common Audio Weaver module instance structure
FLOAT32 gain; // Target gain
FLOAT32 smoothingTime; // Time constant of the smoothing process
fract32 targetGain; // Desired (or target) of the fractional portion of the overall scaling. This is also the starting gain of the module.
fract32 currentGain; // Instantaneous gain applied by the module. This is also the starting gain of the module.
fract32 smoothingCoeff; // Smoothing coefficient
INT32 postShift; // Number of bits to shift after the fractional multiply. This is based on gain.range.
FLOAT32 twoPowMinusPostShift; // 2^(-postShift). Used by to streamline the operation of the set function
} ModuleScalerSmoothedFract32Class;
Variables
Properties
Name | Type | Usage | isHidden | Default value | Range | Units |
gain | float | parameter | 0 | 1 | -10:10 | linear |
smoothingTime | float | parameter | 0 | 10 | 0:1000 | msec |
targetGain | fract32 | derived | 1 | 0.0625 | Unrestricted | |
currentGain | fract32 | state | 1 | 0.0625 | -10:10 | linear |
smoothingCoeff | fract32 | derived | 1 | 0.002081 | Unrestricted | |
postShift | int | derived | 1 | 4 | Unrestricted | |
twoPowMinusPostShift | float | derived | 1 | 0.0625 | Unrestricted |
Pins
Input Pins
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_smoothed_fract32_module.m
M=scaler_smoothed_fract32_module(NAME, NUMPINS)
Creates a smoothly varying scaler module with a single input
and single output pin. This module operates on fract32
data signals. Arguments:
NAME - name of the module.
NUMPINS - Number of pins