tone/build/esm/effect/Chebyshev.js

A Web Audio framework for making interactive music in the browser.

import { Effect } from "./Effect.js";
import { optionsFromArguments } from "../core/util/Defaults.js";
import { WaveShaper } from "../signal/WaveShaper.js";
import { assert } from "../core/util/Debug.js";
/**
 * Chebyshev is a waveshaper which is good
 * for making different types of distortion sounds.
 * Note that odd orders sound very different from even ones,
 * and order = 1 is no change.
 * Read more at [music.columbia.edu](http://music.columbia.edu/cmc/musicandcomputers/chapter4/04_06.php).
 * @example
 * // create a new cheby
 * const cheby = new Tone.Chebyshev(50).toDestination();
 * // create a monosynth connected to our cheby
 * const synth = new Tone.MonoSynth().connect(cheby);
 * synth.triggerAttackRelease("C2", 0.4);
 * @category Effect
 */
export class Chebyshev extends Effect {
    constructor() {
        const options = optionsFromArguments(Chebyshev.getDefaults(), arguments, ["order"]);
        super(options);
        this.name = "Chebyshev";
        this._shaper = new WaveShaper({
            context: this.context,
            length: 4096,
        });
        this._order = options.order;
        this.connectEffect(this._shaper);
        this.order = options.order;
        this.oversample = options.oversample;
    }
    static getDefaults() {
        return Object.assign(Effect.getDefaults(), {
            order: 1,
            oversample: "none",
        });
    }
    /**
     * get the coefficient for that degree
     * @param  x the x value
     * @param  degree
     * @param  memo memoize the computed value. this speeds up computation greatly.
     */
    _getCoefficient(x, degree, memo) {
        if (memo.has(degree)) {
            return memo.get(degree);
        }
        else if (degree === 0) {
            memo.set(degree, 0);
        }
        else if (degree === 1) {
            memo.set(degree, x);
        }
        else {
            memo.set(degree, 2 * x * this._getCoefficient(x, degree - 1, memo) -
                this._getCoefficient(x, degree - 2, memo));
        }
        return memo.get(degree);
    }
    /**
     * The order of the Chebyshev polynomial which creates the equation which is applied to the incoming
     * signal through a Tone.WaveShaper. Must be an integer. The equations are in the form:
     * ```
     * order 2: 2x^2 + 1
     * order 3: 4x^3 + 3x
     * ```
     * @min 1
     * @max 100
     */
    get order() {
        return this._order;
    }
    set order(order) {
        assert(Number.isInteger(order), "'order' must be an integer");
        this._order = order;
        this._shaper.setMap((x) => {
            return this._getCoefficient(x, order, new Map());
        });
    }
    /**
     * The oversampling of the effect. Can either be "none", "2x" or "4x".
     */
    get oversample() {
        return this._shaper.oversample;
    }
    set oversample(oversampling) {
        this._shaper.oversample = oversampling;
    }
    dispose() {
        super.dispose();
        this._shaper.dispose();
        return this;
    }
}
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