The file h264decfilter.ax is part of the ArcSoft H.264 Decoder (Filter) from Arcsoft. H.264 is a video compression format standard. An ax file is a filter that is used by a codec (coder-decoder). A codec is a program that translates digital data, like video, into a format your computer recognizes.
If you get an error with this file, you may not be able to view videos that use the H.264/MPEG-4 AVC video format. Fixing this file may require reinstalling the codex, but first you might try cleaning your registry.
The registry is a database that acts as an information desk for your operating system. When you start a program, Windows checks the registry to find out where all the files that belong to that program are located on your drive, and how to use those files.
If there is a mistake in the registry, the program may not run. SpyZooka deals with those mistakes. SpyZooka finds and fixes every error in your registry, getting your system running smoothly again.