AudioWorkletNode: parameters property
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2021.
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
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.
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 |
---|
Web Audio API # dom-audioworkletnode-parameters |
Browser compatibility
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