server.js

var y = require('youtube-dl')
var ffmpeg = require('liquid-ffmpeg')
var fs = require('fs')
var http = require('http')
var url = require('url')
var through = require('through2')
var request = require('request')
var options = require('./options.json')

var stream;
var data;
var child;
var video;
http.createServer(audio).listen(8000, 'localhost');
console.log('Server listening on port 8000');

function audio(a, b) {
    data = url.parse(a.url, true).query;
    video = y(data.i);

    if (data.s != 0) {
        request({
            url: "http://gdata.youtube.com/feeds/api/videos/" + data.i + "?v=2&alt=jsonc",
            json: true
        }, function(error, response, p) {
            p = parseInt(options.bitrate + "000") / 8 * p["data"]["duration"];
            b.writeHead(200, {
                'Transfer-Encoding': 'binary',
                "Connection": "keep-alive",
                "Content-Type": "audio/mpeg",
                'Content-Length': p,
                "Accept-Ranges": "bytes"
            });
        });
    }

    stream = b.file ? fs.createWriteStream(b.file):through();

    new ffmpeg({source: video, timeout: 6000}).toFormat('mp3').withAudioBitrate(options.bitrate).writeToStream(stream);

    stream.pipe(b);
};