How to convert bitrate of audio files in javascript?

Question

firstly, I have to say sorry for my bad English :)

Anyway, I'm going to develop a simple website that users can upload their audio files and play others' files. I planed to use Node.js, and HTML5 built-in audio tag to play the files. I have never used the audio tag, so I wondered if the tag really works fine, so today I lightly wrote a simple code and played a mp3 file and I got a problem, which is that the mp3 file wasn't be played using the tag. I realized the audio tag cannot play audio files above bitrate 128kbps. so now, I need a way of auto-converting from more than 128kbps to 128kbps, in javascript(using Node.js).

I've never used Node.js, so I never know how to do this. The things I want to know are that it is possible and it is easy.

Anyone give me how or where to find the solution please.

Thanks to read my bad-English question anyway.

Good luck :)

Answer 1

You can do this easily by spawning something like SoX, ffmpeg, etc. Here's an example using SoX (on Debian/Ubuntu you'll need to make sure libsox-fmt-mp3 or libsox-fmt-all is installed for mp3 support):

var spawn = require('child_process').spawn;

require('http').createServer(function(req, res) {
  if (req.url === '/audio') {
    res.statusCode = 200;
    var cp = spawn('sox', ['/path/to/input.mp3', '-C', '128', '-']);
    return cp.stdout.pipe(res);
  }
  res.statusCode = 404;
  res.end();
}).listen(8000);