using a codec?

Dows anybody know of a resource (book or online) that shows how to make use of an already-existing codec?

From some of the applications I've seen, it looks like you can write a program that works with any Windows compatible codec... I mean there seems to be an interface standard between Windows applications and Windows codecs. Is that true, or do I have to write a custom interface for each codec?

I'm thinking about writing an audio application, and it would be cool I could make it work with MP3, WMA, OGG, etc., without worrying about encoding / decoding the various formats.

Have any of you done anything like this?

I've poked-around on MSDN, and have only found stuff on using the Windows Media Player... Do I need the Media SDK???

Do any of you own this book: Fundamentals of Programming the Microsoft Windows Media Platform?

If you use DirectShow to work with your audio files, then you wont have to worry about codecs. Your application will automatically be able to use any codecs which are installed. You will need the Media SDK to write DirectShow applications (DirectShow is no longer part of DirectX).