The read-only parameters
property of the AudioWorkletNode
interface returns the associated AudioParamMap
— that is, a Map
-like collection of AudioParam
objects. They are instantiated during creation of the underlying AudioWorkletProcessor
according to its parameterDescriptors
static getter.
Syntax
audioWorkletNodeInstance.parameters
Value
The AudioParamMap
object containing AudioParam
instances. They can be automated in the same way as with default AudioNode
s, and their calculated values can be used in the process
method of your AudioWorkletProcessor
.
Examples
To demonstrate creation and usage of custom AudioParam
s, we'll expand the example from AudioWorkletNode
page. There we've created a simple node which outputs white noise. Here, additionally, we'll create a custom gain parameter, so we can directly change volume of the output (although you could use GainNode
to achieve this as well).
First, we need to define a custom AudioWorkletProcessor
, and register it. Note that this should be done in a separate file.
We expand the processor by adding a static parameterDescriptors
getter. It will be used internally by the AudioWorkletNode
constructor to populate its parameters
with instantiated AudioParam
objects.
// white-noise-processor.js class WhiteNoiseProcessor extends AudioWorkletProcessor { static get parameterDescriptors () { return [{ name: 'customGain', defaultValue: 1, minValue: 0, maxValue: 1, automationRate: 'a-rate' }] } process (inputs, outputs, parameters) { const output = outputs[0] output.forEach(channel => { for (let i = 0; i < channel.length; i++) { channel[i] = (Math.random() * 2 - 1) * (parameters['customGain'].length > 1 ? parameters['customGain'][i] : parameters['customGain'][0]) // note: a parameter contains an array of 128 values (one value for each of 128 samples), // however it may contain a single value which is to be used for all 128 samples // if no automation is scheduled for the moment. } }) return true } } registerProcessor('white-noise-processor', WhiteNoiseProcessor)
Next, in our main scripts file we'll load the processor, create an instance of AudioWorkletNode
passing it the name of the processor, and connect the node to an audio graph.
const audioContext = new AudioContext() await audioContext.audioWorklet.addModule('white-noise-processor.js') const whiteNoiseNode = new AudioWorkletNode(audioContext, 'white-noise-processor') whiteNoiseNode.connect(audioContext.destination)
Now we can change the gain on the node like this:
const gainParam = whiteNoiseNode.parameters.get('customGain') gainParam.setValueAtTime(0, audioContext.currentTime) gainParam.linearRampToValueAtTime(0.5, audioContext.currentTime + 0.5)
Specifications
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'parameters' in that specification. |
Working Draft |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
parameters | Chrome Full support 66 | Edge Full support 79 | Firefox Full support 76 | IE No support No | Opera Full support Yes | Safari No support No | WebView Android Full support 66 | Chrome Android Full support 66 | Firefox Android No support No | Opera Android Full support Yes | Safari iOS No support No | Samsung Internet Android Full support 9.0 |
Legend
- Full support
- Full support
- No support
- No support