gapless-meta

This library is designed to extract metadata from audiofiles to allow for gapless playback (for example, in browser-based media players), but also extracts some other standard metadata.

Audio file support

The following audio formats are supported, and are part of the test suite:

• MP3 files
  • Encoded by LAME or libavformat (Lavf)
  • With or without ID3v2 tags.

Installation

npm install @synesthesia-project/gapless-meta

Usage

import getMetadata from '@synesthesia-project/gapless-meta';

const buffer = ... // (some ArrayBuffer)
const metadata = getMetadata(buffer.buffer);
console.log(metadata);

Output:

{
  version: '1',
  layer: '3',
  bitrate: 128,
  mode: 'joint_stereo',
  sampleRate: 44100,
  samplesPerFrame: 1152,
  vbrInfo: {
    isCBR: true,
    numberOfFrames: 185,
  },
  lameInfo: {
    encoder: 'LAME3.100',
    paddingStart: 576,
    paddingEnd: 1058
  }
}

(For extensive examples of usage, see the tests).

TODO

• MP3
  • CRC Verification
  • Support APEv2 tags at start of audio files
  • Support more encoders
  • Support MPEG Layer 1
• MP4 AAC Support

Inspiration

This library is inspired and informed by a number of documents, blog posts and specifications, including:

• https://github.com/jquense/mpeg-frame-parser
• https://dalecurtis.github.io/llama-demo/index.html#creating-gapless-content
• https://www.codeproject.com/Articles/8295/MPEG-Audio-Frame-Header
• http://gabriel.mp3-tech.org/mp3infotag.html#delays
• http://www.id3.org/