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AudioParamDescriptor

files/en-us/web/api/audioparamdescriptor/index.md

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{{APIRef("Web Audio API")}}

The AudioParamDescriptor dictionary of the Web Audio API specifies properties for {{domxref("AudioParam")}} objects.

It is used to create custom AudioParams on an {{domxref("AudioWorkletNode")}}. If the underlying {{domxref("AudioWorkletProcessor")}} has a {{domxref("AudioWorkletProcessor.parameterDescriptors", "parameterDescriptors")}} static getter, then the returned array of objects based on this dictionary is used internally by AudioWorkletNode constructor to populate its {{domxref("AudioWorkletNode.parameters", "parameters")}} property accordingly.

Instance properties

  • name
    • : The string which represents the name of the AudioParam. Under this name the AudioParam will be available in the {{domxref("AudioWorkletNode.parameters", "parameters")}} property of the node, and under this name the {{domxref("AudioWorkletProcessor.process")}} method will acquire the calculated values of this AudioParam.
  • automationRate {{optional_inline}}
    • : Either "a-rate", or "k-rate" string which represents an automation rate of this AudioParam. Defaults to "a-rate".
  • minValue {{optional_inline}}
    • : A float which represents minimum value of the AudioParam. Defaults to -3.4028235e38.
  • maxValue {{optional_inline}}
    • : A float which represents maximum value of the AudioParam. Defaults to 3.4028235e38.
  • defaultValue {{optional_inline}}
    • : A float which represents initial value of the AudioParam. Defaults to 0.

Examples

The code fragment below shows a descriptor of this type being returned by a static {{domxref("AudioWorkletProcessor.parameterDescriptors", "parameterDescriptors")}} method defined in a custom AudioWorkletProcessor (this is part of the more complete example in AudioWorkletNode.parameters).

js
// white-noise-processor.js
class WhiteNoiseProcessor extends AudioWorkletProcessor {
  static get parameterDescriptors() {
    return [
      {
        name: "customGain",
        defaultValue: 1,
        minValue: 0,
        maxValue: 1,
        automationRate: "a-rate",
      },
    ];
  }

  // …
}

Specifications

{{Specifications}}

See also