Tone.js/Tone/effect/StereoFeedbackEffect.ts

import { StereoEffect, StereoEffectOptions } from "./StereoEffect";
import { NormalRange } from "../core/type/Units";
import { Signal } from "../signal/Signal";
import { Gain } from "../core/context/Gain";
import { readOnly } from "../core/util/Interface";
import { Split } from "../component/channel/Split";
import { Merge } from "../component/channel/Merge";

export interface StereoFeedbackEffectOptions extends StereoEffectOptions {
	feedback: NormalRange;
}

/**
 * Just like a stereo feedback effect, but the feedback is routed from left to right
 * and right to left instead of on the same channel.
 * ```
 * +--------------------------------+ feedbackL <-----------------------------------+
 * |                                                                                |
 * +-->                          +----->        +---->                          +---+
 *      feedbackMerge +--> split        (EFFECT)       merge +--> feedbackSplit
 * +-->                          +----->        +---->                          +---+
 * |                                                                                |
 * +--------------------------------+ feedbackR <-----------------------------------+
 * ```
 */
export class StereoFeedbackEffect<Options extends StereoFeedbackEffectOptions> extends StereoEffect<Options> {
	
	/**
	 * The amount of feedback from the output
	 * back into the input of the effect (routed
	 * across left and right channels).
	 */
	readonly feedback: Signal<"normalRange">;

	/**
	 * the left side feedback
	 */
	protected _feedbackL: Gain;

	/**
	 * the right side feedback
	 */
	protected _feedbackR: Gain;

	/**
	 * Split the channels for feedback
	 */
	protected _feedbackSplit: Split;

	/**
	 * Merge the channels for feedback
	 */
	protected _feedbackMerge: Merge;

	constructor(options: StereoFeedbackEffectOptions) {

		super(options);

		this.feedback = new Signal({
			context: this.context,
			value: options.feedback, 
			units: "normalRange"
		});
		this._feedbackL = new Gain({ context: this.context });
		this._feedbackR = new Gain({ context: this.context });

		this._feedbackSplit = new Split({ context: this.context, channels: 2 });
		this._feedbackMerge = new Merge({ context: this.context, channels: 2 });

		this._merge.connect(this._feedbackSplit);
		this._feedbackMerge.connect(this._split);
		
		// the left output connected to the left input
		this._feedbackSplit.connect(this._feedbackL, 0, 0);
		this._feedbackL.connect(this._feedbackMerge, 0, 0);

		// the right output connected to the right input
		this._feedbackSplit.connect(this._feedbackR, 1, 0);
		this._feedbackR.connect(this._feedbackMerge, 0, 1);
		
		// the feedback control
		this.feedback.fan(this._feedbackL.gain, this._feedbackR.gain);
		readOnly(this, ["feedback"]);
	}

	static getDefaults(): StereoFeedbackEffectOptions {
		return Object.assign(StereoEffect.getDefaults(), {
			feedback: 0.5,
		});
	}

	dispose(): this {
		super.dispose();
		this.feedback.dispose();
		this._feedbackL.dispose();
		this._feedbackR.dispose();
		this._feedbackSplit.dispose();
		this._feedbackMerge.dispose();
		return this;
	}
}