Tone.js/Tone/source/Noise.ts

import { ToneAudioBuffer } from "../core/context/ToneAudioBuffer";
import { Positive, Time } from "../core/type/Units";
import { optionsFromArguments } from "../core/util/Defaults";
import { Source, SourceOptions } from "../source/Source";
import { ToneBufferSource } from "./buffer/BufferSource";

type NoiseType = "white" | "brown" | "pink";

interface NoiseOptions extends SourceOptions {
	type: NoiseType;
	playbackRate: Positive;
}

/**
 * Noise is a noise generator. It uses looped noise buffers to save on performance.
 * Noise supports the noise types: "pink", "white", and "brown". Read more about
 * colors of noise on [Wikipedia](https://en.wikipedia.org/wiki/Colors_of_noise).
 *
 * @param type the noise type (white|pink|brown)
 * @example
 * //initialize the noise and start
 * var noise = new Noise("pink").start();
 *
 * //make an autofilter to shape the noise
 * var autoFilter = new Tone.AutoFilter({
 * 	"frequency" : "8m",
 * 	"min" : 800,
 * 	"max" : 15000
 * }).connect(Tone.Master);
 *
 * //connect the noise
 * noise.connect(autoFilter);
 * //start the autofilter LFO
 * autoFilter.start()
 */
export class Noise extends Source<NoiseOptions> {

	name = "Noise";

	/**
	 * Private reference to the source
	 */
	private _source: ToneBufferSource | null = null;

	/**
	 * private reference to the type
	 */
	private _type!: NoiseType;

	/**
	 *  The playback rate of the noise. Affects
	 *  the "frequency" of the noise.
	 */
	private _playbackRate: Positive;

	constructor(options?: NoiseType | Partial<NoiseOptions>);
	constructor() {
		super(optionsFromArguments(Noise.getDefaults(), arguments, ["type"]));
		const options = optionsFromArguments(Noise.getDefaults(), arguments, ["type"]);

		this._playbackRate = options.playbackRate;
		this.type = options.type;
	}

	static getDefaults(): NoiseOptions {
		return Object.assign(Source.getDefaults(), {
			playbackRate: 1,
			type: "white" as NoiseType,
		});
	}

	/**
	 * The type of the noise. Can be "white", "brown", or "pink".
	 * @example
	 * noise.type = "white";
	 */
	get type(): NoiseType {
		return this._type;
	}
	set type(type: NoiseType) {
		this.assert(type in _noiseBuffers, "Noise: invalid type: " + type);
		if (this._type !== type) {
			this._type = type;
			// if it's playing, stop and restart it
			if (this.state === "started") {
				const now = this.now();
				this._stop(now);
				this._start(now);
			}
		}
	}

	/**
	 *  The playback rate of the noise. Affects
	 *  the "frequency" of the noise.
	 */
	get playbackRate(): Positive {
		return this._playbackRate;
	}
	set playbackRate(rate: Positive) {
		this._playbackRate = rate;
		if (this._source) {
			this._source.playbackRate.value = rate;
		}
	}

	/**
	 *  internal start method
	 */
	protected _start(time?: Time): void {
		const buffer = _noiseBuffers[this._type];
		this._source = new ToneBufferSource(buffer).connect(this.output);
		this._source.loop = true;
		this._source.playbackRate.value = this._playbackRate;
		this._source.start(this.toSeconds(time), Math.random() * (buffer.duration - 0.001));
	}

	/**
	 *  internal stop method
	 *
	 *  @param {Time} time
	 *  @private
	 */
	protected _stop(time?: Time): void {
		if (this._source) {
			this._source.stop(this.toSeconds(time));
			this._source = null;
		}
	}

	/**
	 * Restarts the noise.
	 * @param  time When to restart the noise.
	 */
	restart(time?: Time): this {
		// TODO could be optimized by cancelling the buffer source 'stop'
		// stop and restart
		this._stop(time);
		this._start(time);
		return this;
	}

	/**
	 *  Clean up.
	 */
	dispose(): this {
		super.dispose();
		if (this._source) {
			this._source.disconnect();
		}
		return this;
	}
}

///////////////////////////////////////////////////////////////////////////
// THE NOISE BUFFERS
///////////////////////////////////////////////////////////////////////////

// Noise buffer stats
const BUFFER_LENGTH = 44100 * 5;
const NUM_CHANNELS = 2;

/**
 * The cached noise buffers
 */
interface NoiseCache {
	[key: string]: ToneAudioBuffer | null;
}

/**
 * Cache the noise buffers
 */
const _noiseCache: NoiseCache = {
	brown: null,
	pink: null,
	white: null,
};

/**
 * The noise arrays. Generated on initialization.
 * borrowed heavily from https://github.com/zacharydenton/noise.js
 * (c) 2013 Zach Denton (MIT)
 */
const _noiseBuffers = {
	get brown(): ToneAudioBuffer {
		if (!_noiseCache.brown) {
			const buffer: Float32Array[] = [];
			for (let channelNum = 0; channelNum < NUM_CHANNELS; channelNum++) {
				const channel = new Float32Array(BUFFER_LENGTH);
				buffer[channelNum] = channel;
				let lastOut = 0.0;
				for (let i = 0; i < BUFFER_LENGTH; i++) {
					const white = Math.random() * 2 - 1;
					channel[i] = (lastOut + (0.02 * white)) / 1.02;
					lastOut = channel[i];
					channel[i] *= 3.5; // (roughly) compensate for gain
				}
			}
			_noiseCache.brown = new ToneAudioBuffer().fromArray(buffer);
		}
		return _noiseCache.brown;
	},

	get pink(): ToneAudioBuffer {
		if (!_noiseCache.pink) {
			const buffer: Float32Array[] = [];
			for (let channelNum = 0; channelNum < NUM_CHANNELS; channelNum++) {
				const channel = new Float32Array(BUFFER_LENGTH);
				buffer[channelNum] = channel;
				// tslint:disable-next-line: one-variable-per-declaration
				let b0, b1, b2, b3, b4, b5, b6;
				b0 = b1 = b2 = b3 = b4 = b5 = b6 = 0.0;
				for (let i = 0; i < BUFFER_LENGTH; i++) {
					const white = Math.random() * 2 - 1;
					b0 = 0.99886 * b0 + white * 0.0555179;
					b1 = 0.99332 * b1 + white * 0.0750759;
					b2 = 0.96900 * b2 + white * 0.1538520;
					b3 = 0.86650 * b3 + white * 0.3104856;
					b4 = 0.55000 * b4 + white * 0.5329522;
					b5 = -0.7616 * b5 - white * 0.0168980;
					channel[i] = b0 + b1 + b2 + b3 + b4 + b5 + b6 + white * 0.5362;
					channel[i] *= 0.11; // (roughly) compensate for gain
					b6 = white * 0.115926;
				}
			}
			_noiseCache.pink = new ToneAudioBuffer().fromArray(buffer);
		}
		return _noiseCache.pink;
	},

	get white(): ToneAudioBuffer {
		if (!_noiseCache.white) {
			const buffer: Float32Array[] = [];
			for (let channelNum = 0; channelNum < NUM_CHANNELS; channelNum++) {
				const channel = new Float32Array(BUFFER_LENGTH);
				buffer[channelNum] = channel;
				for (let i = 0; i < BUFFER_LENGTH; i++) {
					channel[i] = Math.random() * 2 - 1;
				}
			}
			_noiseCache.white = new ToneAudioBuffer().fromArray(buffer);
		}
		return _noiseCache.white;
	},
};