Class Compressor

A dynamic range compressor, built on the native Web Audio DynamicsCompressorNode. Reduces the level of the signal above the threshold, after which a makeup gain can bring the overall level back up.

Extends Effector. Unlike most effects, Compressor does not use an AudioWorklet, so it does not require WebAssembly and can be used before the DSP pipeline is initialized.

input -> DynamicsCompressorNode -> makeup gain -> output

Example

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

const compressor = new Compressor({
    threshold: -18,
    ratio: 4,
    attack: 0.005,
    release: 0.2,
    makeupGain: 4
});

channel.addEffect(compressor);

// Later, for example in a meter:
console.log(compressor.reduction); // e.g. -3.2 (dB)

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Constructor

new Compressor(options?: Partial<CompressorOptions>): Compressor;

Arguments

• options?: Partial<CompressorOptions> Optional compressor configuration. Every field is optional, falls back to the class defaults below, and is clamped to its valid range.

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Properties

label: string | null

Custom label for this effector. Defaults to "Compressor".

name: string

Internal name for this effector. Defaults to "Compressor".

threshold: number

Level (dB) above which compression starts. Between -100 and 0. Defaults to -24.

knee: number

Range (dB) above the threshold over which the curve smoothly transitions to the full ratio. Between 0 and 40. Defaults to 30.

ratio: number

Amount of dB input change for 1 dB of output change. Between 1 and 20. Defaults to 4.

attack: number

Time (seconds) to reduce the gain by 10 dB. Between 0 and 1. Defaults to 0.003.

release: number

Time (seconds) to increase the gain by 10 dB. Between 0 and 1. Defaults to 0.25.

makeupGain: number

Gain (dB) applied after compression. Between -24 and 24. Defaults to 0.

compressorNode: DynamicsCompressorNode | null

The native compressor node. null until the effect is attached.

makeupGainNode: GainNode | null

The gain node that applies makeupGain. null until the effect is attached.

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Methods

initializeOnAttachment(context: AudioContext): Promise<void>

Creates the DynamicsCompressorNode and makeup GainNode with the current option values. When the effect is attached again on the same AudioContext, the existing nodes are reused.

Arguments

• context: AudioContext
  The audio context used to create the nodes.

Returns

• Promise<void>

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returnOptionsAsObject(): CompressorOptions

Returns a plain object snapshot of the current option values.

Returns

• CompressorOptions

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setThreshold(threshold: number): boolean

setKnee(knee: number): boolean

setRatio(ratio: number): boolean

setAttack(attack: number): boolean

setRelease(release: number): boolean

setMakeupGain(makeupGain: number): boolean

Update the corresponding option. The value is clamped to its valid range (see Properties) and applied with a short ramp (10 ms time constant) to avoid clicks.

Arguments

• value: number

Returns

• boolean - true when the value was applied to the audio node. false when the effect is not attached yet; the value is stored and used once the effect is attached.

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Getters and setters

get reduction(): number

Current gain reduction in dB (0 or negative). Useful for metering. 0 while the effect is not attached.

get inputNode(): AudioNode | null

Returns compressorNode. See Effector.

get outputNode(): AudioNode | null

Returns makeupGainNode. See Effector.

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Events

Compressor does not use an AudioWorklet processor, so it does not dispatch the processor events of Effector.

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Notes

Native or WebAssembly?

The native DynamicsCompressorNode runs in the browser's audio engine on the audio thread, costs very little, and its parameters change without clicks. A WebAssembly implementation would only add value for features the native node does not offer, such as a sidechain input, a configurable lookahead, or identical behavior across browsers.

Automatic makeup gain

The Web Audio specification adds a small automatic makeup gain inside every DynamicsCompressorNode, based on the threshold, knee and ratio. Compressor keeps this behavior. If you need a strict output ceiling, use Limiter, which compensates for it.