What users need to know is that there are hundreds of codecs out there.  They facilitate the handling of hundreds of media types, including audio and video compression apps., streaming media types like Flash, video conferring software, speech capture software, and screen capture software.

Formats like WMA, RealAudio, RealVideo, DivX, and Xvid all require a specialized codec to work with a given program.  In the case of Windows Movie Maker, Microsoft has made specialized codecs to enable play of all of these.

What's a Codec Anyway?

Codecs are computer programs that are essential to your PC’s media players.  They enable large media files to be easily shrunk and played.  Hence they make accommodating movie and music files easier.  Codecs take the raw file and, utilizing a mathematical coder, they shrink the large file down for faster downloads. Once the downloads are complete, the decoders go to work opening the file.

So how do you know which codecs your PC needs?

A fresh-off-the-line PC will come with commonly used codecs, pre-installed.   Namely these are the ones needed to play WMV files, audio CDs, AVI files and WAV files. But even a new PC will need a few new codecs to access all of the most popular  media.

If you are trying to access a file and your PC doesn’t have the correct codec, Movie Maker will usually give you an error message with a four-number code that corresponds to a specific codec. You can visit http://www.fourcc.org/fcccodec.htm to find the missing decoder by its four-number index.

Automatically download the codec you need

You can enable automatic downloads of needed codecs while in Movie Maker. Microsoft’s support page instructs you how to set up the automatic download so you don’t have to keep looking for individual codecs whenever you receive an error. By default, automatic download is not enabled in Movie Maker.

1. Click Start, click Programs or All Programs, and then click Windows Movie Maker.


2. On the Tools menu, click Options.


3. Click the General tab.


4. Check the box for “Download codecs automatically.”