ac3.js

AC3.js

JavaScript AC-3 (ATSC A/52) decoder for the Aurora.js audio framework.

Installation

yarn add ac3.js

Usage

Simple

import {AC3SimpleDecoder} from 'ac3.js';
import fs from 'fs';

// This example loads an AC-3 audio file and writes the PCM data to file.
// The output file is in PCM signed 16-bit interleaved format.

// Initialize input and output stream
const inputStream = fs.createReadStream('example.ac3');
const outputStream = fs.createWriteStream('example.pcm');

// Initialize simple decoder
const simpleDecoder = new AC3SimpleDecoder(inputStream);

// Write PCM data to output stream (data is an Uint8Array)
simpleDecoder.on('data', (data) => {
    outputStream.write(data);
});

Aurora.js

import {AC3Decoder, AC3Demuxer} from 'ac3.js';
import AV from 'av';

// This example loads an AC-3 audio file and plays it.
// - In Node.js this should play the audio using the speaker module.
// - In the browser this should play the audio using the Web Audio API.

// Register demuxer and decoder
AV.Demuxer.register(AC3Demuxer);
AV.Decoder.register('ac3', AC3Decoder);

// Initialize player
const player = AV.Player.fromURL('https://example.org/example.ac3');

player.on('format', (format) => console.log('format', format));
player.on('duration', (duration) => console.log('duration', duration));
player.on('progress', (progress) => console.log('progress', progress));
player.on('ready', () => console.log('ready'));
player.on('end', () => console.log('end'));
player.on('error', (error) => console.error(error));

// Start the player
player.play();

For detailed information on how to use Aurora.js, check out the documentation.

Authors

• Danielle Huisman
• Karl Koscher

License

AC3.js is available under the terms of the MIT license.

Progress

Syntax implementation

• syncframe
  • syncinfo
  • bsi
  • audblk
  • auxdata
  • errorcheck

Decoding implementation

• Input Bit Stream
• Synchronization
• Error Detection
• Unpack BSI
• Unpack Side Information
• Decode Exponents
• Bit Allocation
• Process Mantissas
• Decoupling
• Rematrixing
• Inverse Transform
• Window, Overlap/Add
• Downmixing
• PCM Output Buffer
• Output PCM

Roadmap

• Support all downmixing modes
• Support Enhanced AC-3 (E-AC-3)
• Error detection
• Unit tests