Class Equalizer

A parametric equalizer with up to eight bands, processed in series in WebAssembly (RBJ biquad filters).

Extends Effector.

Without options it starts as a flat 5-band EQ:

| Band | Type | Frequency | Q | |---|---|---|---| | 0 | lowshelf | 80 Hz | 0.7071 | | 1 | peaking | 250 Hz | 1 | | 2 | peaking | 1000 Hz | 1 | | 3 | peaking | 4000 Hz | 1 | | 4 | highshelf | 10000 Hz | 0.7071 |

Band types

| Type | Uses gain | Q means | |---|---|---| | "peaking" | Yes | Bandwidth (higher = narrower) | | "lowshelf" / "highshelf" | Yes | Slope of the shelf (0.7071 = no overshoot) | | "lowpass" / "highpass" | No | Resonance at the cutoff (0.7071 = Butterworth) | | "notch" / "bandpass" | No | Bandwidth |

Example

import { Equalizer } from "@fluex/fluexgl-dsp";

// Default 5-band EQ, with a few changes.
const eq = new Equalizer();

eq.setBand(0, { gain: 3 });                 // +3 dB low shelf at 80 Hz
eq.setBand(2, { frequency: 800, gain: -4 }); // -4 dB around 800 Hz

channel.addEffect(eq);

// Or define the bands yourself:
const telephone = new Equalizer({
    bands: [
        { type: "highpass", frequency: 300, q: 0.7071 },
        { type: "peaking", frequency: 1500, gain: 6, q: 1.5 },
        { type: "lowpass", frequency: 3400, q: 0.7071 }
    ]
});

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Constructor

new Equalizer(options?: Partial<EqualizerOptions>): Equalizer;

Arguments

• options?: Partial<EqualizerOptions> bands replaces the default bands (at most 8 are used). Missing band fields fall back to the default band at the same index.

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Properties

static MAX_BANDS: number

Maximum number of bands: 8.

label: string | null

Defaults to "Equalizer".

name: string

Defaults to "Equalizer".

bands: EqualizerBand[]

The current bands. Change them with setBand(), addBand() or removeBand(), not directly, so the processor is updated. See EqualizerBand.

outputGain: number

Gain (dB) after the bands, between -24 and 24. Defaults to 0.

strictMode: StrictMode

Defaults to StrictMode.Disabled.

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Methods

initializeOnAttachment(context: AudioContext): Promise<void>

Creates the EqualizerProcessor AudioWorklet node. Because parameterData only accepts numbers, the bands are passed as flattened keys (band0Type, band0Frequency, ...).

returnOptionsAsObject(): EqualizerOptions

Returns a snapshot of the bands and output gain.

getBand(index: number): EqualizerBand | null

Returns a copy of a band, or null when it does not exist.

setBand(index: number, band: Partial<EqualizerBand>): boolean

Changes an existing band. Only the given fields change. Values are clamped: frequency 10 to 24000 Hz, gain -24 to 24 dB, Q 0.1 to 24. The filter state is kept, so changing a band while audio plays does not click. Returns false when the index does not exist.

Arguments

• index: number, band: Partial<EqualizerBand>

Returns

• boolean - true when the value was sent to the processor (or applied to the audio node), false when the effect is not attached yet. The value is stored either way and used on attachment.

addBand(band: Partial<EqualizerBand>): number

Adds a band at the end (defaults: peaking, 1000 Hz, 0 dB, Q 1, enabled). Returns its index, or -1 when all eight bands are in use.

removeBand(index: number): boolean

Removes a band. The bands after it move up one position.

flatten(): void

Sets the gain of every band to 0 dB.

setOutputGain(outputGain: number): boolean

Sets the gain after the bands (dB), clamped between -24 and 24.

Arguments

• outputGain: number

Returns

• boolean - true when the value was sent to the processor (or applied to the audio node), false when the effect is not attached yet. The value is stored either way and used on attachment.

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Events

Inherited from Effector. The EqualizerProcessor processor sends processor-wasm-instantiated when its WebAssembly module is ready, and an incoming-processor-message for every parameter change.

Requirements

Runs on an AudioWorklet backed by WebAssembly. Attach it only after await pipeline.initializeDpsPipeline(), on the AudioDevice returned by resolveDefaultAudioOutputDevice(). Requires a worklet and WASM build from FluexGL-DSP-WebAssembly 0.4.9 or newer, which registers EqualizerProcessor.