@audio/filter-biquad

import { highpass, lowpass, bandpass, notch, allpass } from '@audio/filter-biquad'

Hz/Q-parameterized wrappers over the shared @audio/biquad kernel — one call per filter shape, coefficients recomputed only when fc/Q/fs/order actually change, state cached on the params object.

lowpass(buffer, { fc: 2000, fs: 44100 })                // 2nd-order (default) — no registration needed
highpass(buffer, { fc: 80, fs: 44100 })                  // rumble filter
bandpass(buffer, { fc: 1000, Q: 5, fs: 44100 })          // narrow band
notch(buffer, { fc: 50, Q: 30, fs: 44100 })              // remove 50 Hz mains hum
allpass.first(buffer, { a: 0.5 })                        // 1st-order, coefficient a
allpass.second(buffer, { fc: 1000, Q: 1, fs: 44100 })    // 2nd-order, center fc, quality Q

lowpass/highpass default to a 2nd-order RBJ biquad ($-12\,\text{dB/oct}$). For 4th-order-and-up Butterworth cascades, register a designer once — kept out of the default import so the common 2nd-order case stays dependency-free:

import butterworth from 'digital-filter/iir/butterworth.js'

lowpass.useButterworth(butterworth)                       // once, before any order > 2 call
lowpass(buffer, { fc: 2000, order: 4, fs: 44100 })        // 4th-order Butterworth, -24 dB/oct

Pass the same params object on every call to persist state across blocks:

let params = { fc: 1000, fs: 44100 }
for (let buf of stream) lowpass(buf, params)

Use when: building an audio-facing biquad filter (Hz/Q, not raw SOS coefficients); bypass this and use @audio/biquad directly when you already have coefficients or need cascade/analysis primitives.

Part of @audio/filter — the filter family umbrella. This README is generated from the umbrella docs.

MIT © audiojs