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

audio-param-shim