Overview

2nd order IIR filter

Discussion

Standard second order 5 multiply recursive 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 2*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. The order of the coefficients must be [b0 b1 b2 a1 a2]. The module implements the difference equation: $y[n]=b_0x[n]+b_1x[n-1]+b_2x[n-2]-a_1y[n-1]-a_2y[n-2].$

Type Definition

typedef struct _ModuleBiquad
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    FLOAT32 b0;                                   // First numerator coefficient.
    FLOAT32 b1;                                   // Second numerator coefficient.
    FLOAT32 b2;                                   // Third numerator coefficient.
    FLOAT32 a1;                                   // Second denominator coefficient.
    FLOAT32 a2;                                   // Third denominator coefficient.
    FLOAT32* state;                               // State variables. 2 per channel.
} ModuleBiquadClass;

Variables

Properties

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

MATLAB Usage

File Name: biquad_module.m

 M=biquad_module(NAME)
 Creates a second order IIR filter (biquad) for use with Audio
 Weaver.

 Arguments:
     NAME - name of the module.