Without the appropriate codec , you'll be prohibited from playing AV files. In this case, GOM Player Codec Finder will guide you to the exact codec you need to install and where you can download the codec.
If you download AV files from the internet, you can't always play them. Sometimes you just see a black screen, or sometimes you just hear the sound of a file.
In this case, you have to install appropriate codec.
Automatic Codec Finder
The Codec Finder window will pop up when there are codec problems.
Search Result will be shown on a new internet page. Once you've found it, simply download and install to watch the AV files.
If Codec Finder cannot find the appropriate codec, check your file first. It may be a damaged or a fake file.