File Converters. How Do They Work?

how do file converters work? IE: Making a web application that will convert mp3 to ogg nearly instantly. This has always interested me.

Solution 1:

The server has a program installed that does the conversion. The file is accepted, run (possibly with exec('mp3-to-ogg tmpfile.mp3'); or similar), and passed back to be downloaded. It's quite simple, really, just as long as you have the program installed somewhere on the server where it can be run.