biquad-filter's Introduction

Biquad Filter library

The Biquad Filter is a JavaScript library that implements a cascade of biquad filters

This library implements a biquad filter with the possibility of use a cascade of biquad filters where you can specify the coefficients:

                       1 + b1*z^-1 + b2*z^-2
One biquad:   H1(z) = -----------------------
                       1 + a1*z^-1 + a2*z^-2

Cascade of biquads:   H(z) = g · H1(z) · H2(z) · ... · Hn(z)
where g is the global gain of the cascade of biquads and n is the number of biquad filters.

Example

A working demo for this module can be found here and in the examples folder.

Coefficients format

The input format of the coefficients for the library is a JavaScript Array with all the coefficients:

For one biquad filter:

[g, b1, b2, a1, a2]

For two or more biquad filters:

[g, b1_1, b2_1, a1_1, a2_1, b1_2, b2_2, a1_2, a2_2, ... , b1_n, b2_n, a1_n, a2_n ]

where n is the number of biquad filters and g is the global gain of the cascade of biquads.

API

The binauralFIR object exposes the following API:

Method	Description
`biquadFilter.setCoefficients(coef)`	Set the coefficients of the filter.
`biquadFilter.process(inputBuffer, outputBuffer)`	Calculate the output of the cascade biquad filter for an inputBuffer. The inputBuffer and the outputBuffer are Arrays with the same length.

License

This module is released under the BSD-3-Clause license.

Acknowledgments

This code has been developed from both Acoustic And Cognitive Spaces and Analysis of Musical Practices IRCAM research teams. It is also part of the WAVE project (http://wave.ircam.fr), funded by ANR (The French National Research Agency), ContInt program, 2012-2015.

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