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Overview

2nd order smoothly updating IIR filter

Discussion

Smoothly varying 5 coefficient biquad filter. The module is designed to operate on multiple channels and applies the same coefficients across all channels. The state array is allocated to contain 4*numChannels values. The frequency response of the module is determined by the values of the 5 coefficients, and the coefficients come directly from the MATLAB second order representation. The leading a0 coefficient is not supplied and is assumed to equal 1.0.

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The rate of smoothing is controlled by the .smoothingTime instance variable.

Type Definition

Code Block
typedef struct _ModuleBiquadSmoothedFract32
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 updateActive;                           // Specifies whether the filter coefficients are updating (=1) or fixed (=0)
    FLOAT32 smoothingTime;                        // Time constant of the smoothing process
    fract32 smoothingCoeff;                       // Smoothing coefficient. This is computed based on the smoothingTime, sample rate, and block size of the module
    INT32 postShift;                              // Number of bits to shift
    INT32 currentPostShift;                       // Current post shift
    FLOAT32* coeffs;                              // Desired coefficients
    fract32* coeffsFract32;                       // Desired coefficients in fract32
    fract32* current_coeffsFract32;               // Instantaneous coefficients
    fract32* state;                               // State variables. 4 per channel.
} ModuleBiquadSmoothedFract32Class;

Variables

Properties

Name

Type

Usage

isHidden

Default value

Range

Units

updateActive

int

parameter

0

1

0:1

smoothingTime

float

parameter

0

10

0:1000

msec

smoothingCoeff

fract32

derived

1

0.06449

Unrestricted

postShift

int

derived

1

1

Unrestricted

currentPostShift

int

state

1

1

Unrestricted

coeffs

float*

parameter

0

[5 x 1]

-10:10

linear

coeffsFract32

fract32*

derived

1

[5 x 1]

Unrestricted

current_coeffsFract32

fract32*

state

0

[5 x 1]

Unrestricted

state

fract32*

state

1

[4 x 1]

Unrestricted

Pins

Input Pins

Name: in

Description: audio input

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Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out

Description: audio output

Data type: fract32

MATLAB Usage

File Name: biquad_smoothed_fract32_module.m

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