tone
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A Web Audio framework for making interactive music in the browser.
88 lines • 4.09 kB
JavaScript
import { PhaseShiftAllpass } from "../component/filter/PhaseShiftAllpass.js";
import { optionsFromArguments } from "../core/util/Defaults.js";
import { Effect } from "../effect/Effect.js";
import { Add } from "../signal/Add.js";
import { Multiply } from "../signal/Multiply.js";
import { Negate } from "../signal/Negate.js";
import { Signal } from "../signal/Signal.js";
import { Oscillator } from "../source/oscillator/Oscillator.js";
import { ToneOscillatorNode } from "../source/oscillator/ToneOscillatorNode.js";
/**
* FrequencyShifter can be used to shift all frequencies of a signal by a fixed amount.
* The amount can be changed at audio rate and the effect is applied in real time.
* The frequency shifting is implemented with a technique called single side band modulation using a ring modulator.
* Note: Contrary to pitch shifting, all frequencies are shifted by the same amount,
* destroying the harmonic relationship between them. This leads to the classic ring modulator timbre distortion.
* The algorithm will produces some aliasing towards the high end, especially if your source material
* contains a lot of high frequencies. Unfortunatelly the webaudio API does not support resampling
* buffers in real time, so it is not possible to fix it properly. Depending on the use case it might
* be an option to low pass filter your input before frequency shifting it to get ride of the aliasing.
* You can find a very detailed description of the algorithm here: https://larzeitlin.github.io/RMFS/
*
* @example
* const input = new Tone.Oscillator(230, "sawtooth").start();
* const shift = new Tone.FrequencyShifter(42).toDestination();
* input.connect(shift);
* @category Effect
*/
export class FrequencyShifter extends Effect {
constructor() {
const options = optionsFromArguments(FrequencyShifter.getDefaults(), arguments, ["frequency"]);
super(options);
this.name = "FrequencyShifter";
this.frequency = new Signal({
context: this.context,
units: "frequency",
value: options.frequency,
minValue: -this.context.sampleRate / 2,
maxValue: this.context.sampleRate / 2,
});
this._sine = new ToneOscillatorNode({
context: this.context,
type: "sine",
});
this._cosine = new Oscillator({
context: this.context,
phase: -90,
type: "sine",
});
this._sineMultiply = new Multiply({ context: this.context });
this._cosineMultiply = new Multiply({ context: this.context });
this._negate = new Negate({ context: this.context });
this._add = new Add({ context: this.context });
this._phaseShifter = new PhaseShiftAllpass({ context: this.context });
this.effectSend.connect(this._phaseShifter);
// connect the carrier frequency signal to the two oscillators
this.frequency.fan(this._sine.frequency, this._cosine.frequency);
this._phaseShifter.offset90.connect(this._cosineMultiply);
this._cosine.connect(this._cosineMultiply.factor);
this._phaseShifter.connect(this._sineMultiply);
this._sine.connect(this._sineMultiply.factor);
this._sineMultiply.connect(this._negate);
this._cosineMultiply.connect(this._add);
this._negate.connect(this._add.addend);
this._add.connect(this.effectReturn);
// start the oscillators at the same time
const now = this.immediate();
this._sine.start(now);
this._cosine.start(now);
}
static getDefaults() {
return Object.assign(Effect.getDefaults(), {
frequency: 0,
});
}
dispose() {
super.dispose();
this.frequency.dispose();
this._add.dispose();
this._cosine.dispose();
this._cosineMultiply.dispose();
this._negate.dispose();
this._phaseShifter.dispose();
this._sine.dispose();
this._sineMultiply.dispose();
return this;
}
}
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