Troubleshoot codecs

Once upon a time, computers and multimedia files didn’t get along particularly well: bleeps and pixellated images aside, your average PC didn’t ever do much with video or audio. Today, of course, things have changed: we’re all used to streaming videos almost instantly from the web, listening to music and opening all manner of multimedia files, and most of the time these files will simply play with no extra effort needed. But then, every once in a while, something goes wrong.

Usually this problem occurs after downloading a video file and opening it: Windows Media Player launches as usual, but then refuses to play the file. Annoyingly, there’s often very little information given about what’s gone wrong, but this is almost always a problem with codecs (an abbreviation for coder/decoder) ­ the tiny bits of software that decode each type of multimedia file.

In this latest in our series of ‘back to basics’ features, which are intended as an introduction for novices and refresher courses for more experienced readers, we’ll explain how to find out which codecs are installed on your PC, how to add more, how to disable them when they go wrong, and how to work out which are needed to play any given multimedia file.

Spot the problem
There are several warning signs of a problem with codecs. Most obviously, when opening a video or audio file in, for example, Windows Media Player, you might see a warning dialogue box stating that ‘Windows Media Player cannot play the file’.

When attempting to open a video file you may, alternatively, find that only the sound plays, with Media Player displaying a placeholder image where the video should be. Finally, video or audio files may stutter, ‘tear’ or appear discoloured.

Any of these problems can be a symptom of a faulty or missing codec, alt hough bear in mind that other system errors can also be at fault. If one type of video file appears stuttering and in garish colours, for example, it’s likely to be a codec problem, but if all video files appear this way then you should first check your graphics card drivers or even the physical connection to your monitor.

Windows relies on a variety of codecs from a range of different manufacturers to play a range of multimedia files, and these codecs are buried deep in the system itself: most live inside the \Windows\system32 folder.