audio-param-shim

Shimmed AudioParams

audio-param-shim lets you create objects that work almost exactly like AudioParams, except it doesn't actually touch any web audio stuff. Instead, one can subscribe for value changes and then do whatever one wants with that value.

All value scheduling methods are inherited from pseudo-audio-param by @mohayonao.

Features

• Create AudioParam shims with custom names and default, min and max values
• Scheduling values as you would on an AudioParam, such as with exponentialRampToValueAtTime(value, time)
• Subscribe to (and unsubscribe from) value changes so that you can act upon them

Missing features

• Using AudioNodes to modulate the parameter value

Use case

I'm working on an audio library that does it's own version of a built-in Web Audio API functionality. I do, however, want it to be completely interchangable. This means exposing an AudioParam API to the developer, hence this library.

When not to use

If you want an extension that works directly on AudioNodes.

Installation

npm i -S audio-param-shim

Usage

import createAudioParam from 'custom-audio-param'

// Create a NoiseParam class
const NoiseParam = createAudioParam('noise', 0.25, 0, 1)

// Create a param instance and change its value
const ctx = new AudioContext()
const noise = new NoiseParam(ctx)

noise.value = 0.4 // -> 0.4
noise.value = 4   // -> 1
noise.value = -1  // -> 0

// Change the value exponentially over 3 seconds and change the
// amount of noise accordingly
let noiseAmplitude = noise.value
// Use noiseAmplitude in a ScriptProcessorNode or something...

noise.subscribe(newValue => noiseAmplitude = newValue)
noise.exponentialRampToValueAtTime(0.9, ctx.currentTime + 3)

API

Top-level functions

createAudioParam(name, defaultValue, minValue, maxValue)

Returns a AudioParamShim class that looks and acts just like an AudioParam instance, except it doesn't actually touch any web audio stuff. Instead, one can subscribe for value changes and then do whatever one wants with that value.

Argument	Type	Description
name	String	The parameter's name
defaultValue	Number	The parameter's default value
minValue	Number	The parameter's minimum value
maxValue	Number	The parameter's maximum value

AudioParamShim API

Properties

Property	Type	Description
defaultValue (readonly)	Number	The parameter's default value
maxValue (readonly)	Number	The parameter's max value
minValue (readonly)	Number	The parameter's min value
name (readonly)	String	The parameter's name
value	Number	The parameter's value

Methods

subscribe(fn)

Subscribes to value changes.

Argument	Type	Description
fn	Function	A callback function

unsubscribe(fn)

Unsubscribes from value changes.

Argument	Type	Description
fn	Function	A callback function

Credits

• @mohayonao for creating pseudo-audio-param

See also

• mohayonao/pseudo-audio-param
• mohayonao/audio-param-transform
• mmckegg/custom-audio-node