The term MP4 is most often associated with video, while the term MP3 is almost universally recognized to be about music. How can then one convert MP4 to MP3, and what can be the reason to do so?
A decade ago, audio compression was the biggest thing in multimedia applications. There was a time when the only kind of audio you could possibly download from the internet was minuscule midi files. And that was about the limit of what you could carry from one computer to another, because all the removable medium you had in those days was the measly floppy disk. But then came the MP3.
Now, the same thing has happened with video. With the help of modern video compression technologies, it has become possible to put small yet high-quality video files on hand-held,portable personal video players. And the commonest type of file used by these is the MP4.
However, not all MP4 files contain video. The MP4 file format is able to contain video, but nothing says that it has to contain video. It may just contain an audio stream, and that would play perfectly well in any capable MP4 player. In fact, the hugely popular online music store iTunes sells its music in MP4 format. You shall notice that iTunes files have the .m4a extension. This is Apple's way of indicating that these are MP4 files with only an audio stream in them, and no video.
But not everyone owns an iPod or some other MP4 player. MP3 players have been with us for a decade or more, and MP4 players haven't yet been able to beat them in numbers. So when you want to listen that catchy tune you caught on your friend's iPod, but own only a couple-of-years-old MP3 player, you need a tool that can convert MP4 to MP3.
The good news is that the audio stream inside MP4 files is nothing other than the good old MP3, merely inserted in a different package. So it is really trivial to extract this stream and save it as a different file that can be played on your old player.
