# biquad-coeffs-webaudio-v1

> WebAudio formulae for audio EQ biquad filter coefficients

Latest version **1.2.0** (published 2016-10-02) · MIT license · 0 weekly downloads

## Install

```sh
npm install biquad-coeffs-webaudio-v1
pnpm add biquad-coeffs-webaudio-v1
yarn add biquad-coeffs-webaudio-v1
bun add biquad-coeffs-webaudio-v1
```

## Health

**Score 15/100 (F)** — status: abandoned.

Positive: no vulnerabilities.

Warnings: low downloads; no types; no esm support.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 1.2.0 |
| Published | 2016-10-02 |
| First published | 2016-09-29 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | CommonJS |
| Dependencies | 0 |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 17 |
| Author | Nao Yonamine |
| Maintainers | mohayonao |
| Keywords | biquad, coeffs, webaudio, dsp, filter |

## Links

- npm: https://www.npmjs.com/package/biquad-coeffs-webaudio-v1
- Repository: https://github.com/mohayonao/biquad-coeffs
- Homepage: https://github.com/mohayonao/biquad-coeffs/
- Issues: https://github.com/mohayonao/biquad-coeffs/issues
- npm.io page: https://npm.io/package/biquad-coeffs-webaudio-v1

## Recent versions

- 1.2.0 (latest) — 2016-10-02
- 1.0.0 — 2016-09-29

## README

# biquad-coeffs-webaudio-v1
[![Build Status](https://img.shields.io/travis/mohayonao/biquad-coeffs.svg?style=flat-square)](https://travis-ci.org/mohayonao/biquad-coeffs)
[![NPM Version](https://img.shields.io/npm/v/biquad-coeffs-webaudio-v1.svg?style=flat-square)](https://www.npmjs.org/package/biquad-coeffs-webaudio-v1)
[![License](https://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat-square)](http://mohayonao.mit-license.org/)

> WebAudio formulae for audio EQ biquad filter coefficients
> - https://www.w3.org/TR/webaudio/

## Installation

```
$ npm install --save biquad-coeffs-webaudio-v1
```

## API
  - `[filterType](freq, q, gain): number[]`
    - `filterType: string`
      - "lowpass"
      - "highpass"
      - "bandpass"
      - "notch"
      - "allpass"
      - "peaking"
      - "lowshelf"
      - "highshelf"
    - `freq: number` filter cutoff or center frequency
      - This parameter should be normalized (0..1).
      - `normalizedFrequency = frequency / sampleRate`
    - `q: number` filter Q (resonance)
      - This parameter is NOT used by "lowshelf" or "highshelf".
    - `gain: number` filter gain
      - This parameter is used by "peaking", "lowshelf" or "highshelf".
    - returns coeffs `[ b0, b1, b2, a1, a2 ]` (a0 = 1)

## Usage

DSP

```js
const coeffs = require("biquad-coeffs-webaudio-v1");

const [ b0, b1, b2, a1, a2 ] = coeffs.lowpass(1200/44100, 6);
const signal = new Float32Array(2048).map(Math.random);

let x0, x1 = 0, x2 = 0;
let y0, y1 = 0, y2 = 0;

for (let i = 0; i < signal.length; i++) {
  x0 = signal[i];
  y0 = (b0 * x0) + (b1 * x1) + (b2 * x2) - (a1 * y1) - (a2 * y2);

  signal[i] = y0;

  x2 = x1;
  x1 = x0;
  y2 = y1;
  y1 = y0;
}
```

Web Audio API

```js
const coeffs = require("biquad-coeffs-webaudio-v1");

const [ b0, b1, b2, a1, a2 ] = coeffs.lowpass(1200/audioContext.sampleRate, 6);
const audioContext = new AudioContext();
const oscillator = audioContext.createOscillator();
const filter = audioContext.createIIRFilter([ b0, b1, b2 ], [ 1, a1, a2 ]);

oscillator.type = "sawtooth";
oscillator.frequency.value = 880;
oscillator.start(audioContext.currentTime);
oscillator.stop(audioContext.currentTime + 2);
oscillator.connect(filter);

filter.connect(audioContext.destination);
```

## License

MIT

---
_Source: https://npm.io/package/biquad-coeffs-webaudio-v1 · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._