alawmulaw

alawmulaw

Copyright (c) 2018 Rafael da Silva Rocha.
https://github.com/rochars/alawmulaw

A-Law and mu-Law codecs in JavaScript.

Install

npm install alawmulaw

Use

Node

Require from 'alawmulaw'

const alawmulaw = require('alawmulaw');

// Encode all the samples in a file
// Only 16-bit samples are supported
let aLawSamples = alawmulaw.alaw.encode(pcmSamples);

ES module

Import from alawmulaw.js:

import * as alawmulaw from './dist/alawmulaw.js';
let aLawSamples = alawmulaw.alaw.encode(pcmSamples);

Browser

Use the compiled file in the /dist folder:

<script src="./dist/alawmulaw.min.js"></script>
<script>
    // A-Law
    samples = alawmulaw.alaw.encode(samples);
    samples = alawmulaw.alaw.decode(samples);
    sample = alawmulaw.alaw.encodeSample(sample);
    sample = alawmulaw.alaw.decodeSample(sample);

    // mu-Law
    samples = alawmulaw.mulaw.encode(samples);
    samples = alawmulaw.mulaw.decode(samples);
    sample = alawmulaw.mulaw.encodeSample(sample);
    sample = alawmulaw.mulaw.decodeSample(sample);
</script>

Or get it from the jsDelivr CDN:

<script src="https://cdn.jsdelivr.net/npm/alawmulaw"></script>

Or get it from unpkg:

<script src="https://unpkg.com/alawmulaw"></script>

Or as a ES6 module in modern browsers from jspm:

<script type="module">
  import * as alawmulaw from 'https://dev.jspm.io/alawmulaw';
  // ...
</script>

API

alawmulaw.alaw

/**
 * Encode a 16-bit linear PCM sample as 8-bit A-Law.
 * @param {number} sample A 16-bit PCM sample
 * @return {number}
 */
export function encodeSample(sample) {}

/**
 * Decode a 8-bit A-Law sample as 16-bit PCM.
 * @param {number} aLawSample The 8-bit A-Law sample
 * @return {number}
 */
export function decodeSample(aLawSample) {}

/**
 * Encode 16-bit linear PCM samples as 8-bit A-Law samples.
 * @param {!Int16Array} samples A array of 16-bit PCM samples.
 * @return {!Uint8Array}
 */
export function encode(samples) {}

/**
 * Decode 8-bit A-Law samples into 16-bit linear PCM samples.
 * @param {!Uint8Array} samples A array of 8-bit A-Law samples.
 * @return {!Int16Array}
 */
export function decode(samples) {}

alawmulaw.mulaw

/**
 * Encode a 16-bit linear PCM sample as 8-bit mu-Law.
 * @param {number} sample A 16-bit PCM sample
 * @return {number}
 */
export function encodeSample(sample) {}

/**
 * Decode a 8-bit mu-Law sample as 16-bit PCM.
 * @param {number} muLawSample The 8-bit mu-Law sample
 * @return {number}
 */
export function decodeSample(muLawSample) {}

/**
 * Encode 16-bit linear PCM samples into 8-bit mu-Law samples.
 * @param {!Int16Array} samples A array of 16-bit PCM samples.
 * @return {!Uint8Array}
 */
export function encode(samples) {}

/**
 * Decode 8-bit mu-Law samples into 16-bit PCM samples.
 * @param {!Uint8Array} samples A array of 8-bit mu-Law samples.
 * @return {!Int16Array}
 */
export function decode(samples) {}

Distribution

This library is a ES module also distributed as a CommonJS module, UMD module and a compiled script for browsers. It works out of the box in Node when installed with npm install alawmulaw. It includes a TypeScript definition file.

If you use the Closure Compiler, this package includes a externs file: ./externs.js.

If you are using this lib in a browser:

You may load both ./dist/alawmulaw.umd.js and ./dist/alawmulaw.min.js in the browser with <script> tags. Ideally you should use alawmulaw.min.js. You can load it via the https://unpkg.com and https://www.jsdelivr.com/ CDNs:

unpkg:

<script src="https://unpkg.com/alawmulaw"></script>

jsDelivr:

<script src="https://cdn.jsdelivr.net/npm/alawmulaw"></script>

If you are using this lib as a dependency:

• The CommonJS dist is ./dist/alawmulaw.cjs.js. It is the dist file used by Node. It is served in the "main" field of package.json and is the source you are running when you npm install alawmulaw. It is not compiled or minified.

• The UMD module is ./dist/alawmulaw.umd.js. It is transpiled to ES5 and compatible with Node, AMD and browsers. It is served in the "browser" field of package.json.

• The browser-only dist is ./dist/alawmulaw.min.js. It is transpiled to ES5 and compiled. It is used in the "unpkg" and "jsdelivr" fields of package.json.

• The ES6 dist is ./dist/alawmulaw.js, served as "es2015" in package.json. It is not compiled/minified.

• ./main.js is served as "module" in package.json. This should be the entry point for bundlers.

If your module bundler is using "browser" as the entry point your dist should work the same but will be a larger file.

References

https://github.com/torvalds/linux/blob/master/sound/core/oss/mulaw.c
https://github.com/deftio/companders
http://dystopiancode.blogspot.com.br/2012/02/pcm-law-and-u-law-companding-algorithms.html

LICENSE

Copyright (c) 2018 Rafael da Silva Rocha.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.