alawmulaw

alawmulaw

Copyright (c) 2018-2019 Rafael da Silva Rocha.
https://github.com/rochars/alawmulaw

A-Law and mu-Law codecs in JavaScript.

Install

npm install alawmulaw

Use

Browser

Use the alawmulaw.js file in the /dist folder:

<script src="alawmulaw.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>

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);

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) {}

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) 2018-2019 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.

Changelog

6.0.0 - 2019-12-31

• New package structure:
  • dist file is "./dist/alawmulaw.js", a UMD served as "main"
  • ES6 source is "./index.js", served as "module"
• Fix: clip mulaw samples after add bias (https://github.com/rochars/alawmulaw/issues/2)