tone
Version:
A Web Audio framework for making interactive music in the browser.
90 lines • 3.09 kB
JavaScript
import { gainToDb } from "../../core/type/Conversions";
import { optionsFromArguments } from "../../core/util/Defaults";
import { MeterBase } from "./MeterBase";
import { warn } from "../../core/util/Debug";
import { Analyser } from "./Analyser";
/**
* Meter gets the [RMS](https://en.wikipedia.org/wiki/Root_mean_square)
* of an input signal. It can also get the raw value of the input signal.
*
* @example
* const meter = new Tone.Meter();
* const mic = new Tone.UserMedia();
* mic.open();
* // connect mic to the meter
* mic.connect(meter);
* // the current level of the mic
* setInterval(() => console.log(meter.getValue()), 100);
* @category Component
*/
export class Meter extends MeterBase {
constructor() {
super(optionsFromArguments(Meter.getDefaults(), arguments, ["smoothing"]));
this.name = "Meter";
/**
* The previous frame's value
*/
this._rms = 0;
const options = optionsFromArguments(Meter.getDefaults(), arguments, ["smoothing"]);
this.input = this.output = this._analyser = new Analyser({
context: this.context,
size: 256,
type: "waveform",
channels: options.channels,
});
this.smoothing = options.smoothing,
this.normalRange = options.normalRange;
}
static getDefaults() {
return Object.assign(MeterBase.getDefaults(), {
smoothing: 0.8,
normalRange: false,
channels: 1,
});
}
/**
* Use [[getValue]] instead. For the previous getValue behavior, use DCMeter.
* @deprecated
*/
getLevel() {
warn("'getLevel' has been changed to 'getValue'");
return this.getValue();
}
/**
* Get the current value of the incoming signal.
* Output is in decibels when [[normalRange]] is `false`.
* If [[channels]] = 1, then the output is a single number
* representing the value of the input signal. When [[channels]] > 1,
* then each channel is returned as a value in a number array.
*/
getValue() {
const aValues = this._analyser.getValue();
const channelValues = this.channels === 1 ? [aValues] : aValues;
const vals = channelValues.map(values => {
const totalSquared = values.reduce((total, current) => total + current * current, 0);
const rms = Math.sqrt(totalSquared / values.length);
// the rms can only fall at the rate of the smoothing
// but can jump up instantly
this._rms = Math.max(rms, this._rms * this.smoothing);
return this.normalRange ? this._rms : gainToDb(this._rms);
});
if (this.channels === 1) {
return vals[0];
}
else {
return vals;
}
}
/**
* The number of channels of analysis.
*/
get channels() {
return this._analyser.channels;
}
dispose() {
super.dispose();
this._analyser.dispose();
return this;
}
}
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