Read MP3 ID3 Info

mp3-id3.js

var fs = require('fs'),
    _ = require('underscore'),
    directory = 'mp3s/',
    files = fs.readdirSync(directory),
    genres = [
        'Blues','Classic Rock','Country','Dance','Disco','Funk','Grunge','Hip-Hop','Jazz','Metal',
        'New Age','Oldies','Other','Pop','R&B','Rap','Reggae','Rock','Techno','Industrial',
        'Alternative','Ska','Death Metal','Pranks','Soundtrack','Euro-Techno','Ambient','Trip-Hop',
        'Vocal','Jazz+Funk','Fusion','Trance','Classical','Instrumental','Acid','House','Game',
        'Sound Clip','Gospel','Noise','AlternRock','Bass','Soul','Punk','Space','Meditative',
        'Instrumental Pop','Instrumental Rock','Ethnic','Gothic','Darkwave','Techno-Industrial',
        'Electronic','Pop-Folk','Eurodance','Dream','Southern Rock','Comedy','Cult','Gangsta',
        'Top 40','Christian Rap','Pop/Funk','Jungle','Native American','Cabaret','New Wave',
        'Psychadelic','Rave','Showtunes','Trailer','Lo-Fi','Tribal','Acid Punk','Acid Jazz','Polka',
        'Retro','Musical','Rock & Roll','Hard Rock','Folk','Folk-Rock','National Folk','Swing',
        'Fast Fusion','Bebob','Latin','Revival','Celtic','Bluegrass','Avantgarde','Gothic Rock',
        'Progressive Rock','Psychedelic Rock','Symphonic Rock','Slow Rock','Big Band','Chorus',
        'Easy Listening','Acoustic','Humour','Speech','Chanson','Opera','Chamber Music','Sonata',
        'Symphony','Booty Bass','Primus','Porn Groove','Satire','Slow Jam','Club','Tango','Samba',
        'Folklore','Ballad','Power Ballad','Rhythmic Soul','Freestyle','Duet','Punk Rock','Drum Solo',
        'Acapella','Euro-House','Dance Hall'
    ];

for (var i = 0; i < files.length; i++) {
    var path = directory + files[i],
        stats = fs.statSync(path),
        tags = readTags(fs.readFileSync(path)),
        metadata = {};

    metadata.id = _.uniqueId();
    metadata.path = path;
    metadata.artist = tags.artist;
    metadata.title = tags.title;
    metadata.album = tags.album;
    metadata.genre = tags.genre;
    metadata.year = tags.year;
    metadata.size = roundNumber(stats.size / 1000000, 1) + 'mb';

    console.log(metadata);
}

function roundNumber (num, length) {
    return parseFloat(Math.round(num * Math.pow(10, length)) / Math.pow(10, length));
}

function findZero (buffer, start, end) {
    var i = start;
    while (buffer[i] !== 0) {
        if (i >= end) {
            return end;
        }
        i++;
    }
    return i;
}

function readTags (buffer) {
    var offset = buffer.length - 128,
        header = buffer.toString('binary', offset, offset + 3),
        tags   = {};

    if ('TAG' !== header) {
        return tags;
    }

    // Skip header
    offset += 3;

    // Title
    tags.title = buffer.toString('ascii', offset, findZero(buffer, offset, offset + 30));
    offset += 30;

    // Artist
    tags.artist = buffer.toString('ascii', offset, findZero(buffer, offset, offset + 30));
    offset += 30;

    // Album
    tags.album = buffer.toString('ascii', offset, findZero(buffer, offset, offset + 30));
    offset += 30;

    // Year
    tags.year = buffer.toString('ascii', offset, findZero(buffer, offset, offset + 4));
    offset += 4;

    // Genre
    tags.genre = genres[buffer[buffer.length - 1]];

    return tags;
}