ClassID, Filetype and Subtype

All plugin types that support media must identify unique classID, filetype, and subtype.

These are all four character codes, or 'fourCCs'.

Identifier	Purpose
filetype	Identifies the plugin's associated file type(s). Plugins create lists of filetypes they support.
subtype	Differentiates between files of the same filetype. Identifies the codec or compression to be used.
classID	With the new editing mode system starting in CS4, the classID is far less important. It is used as part of the identification for exporters in the Editing Mode XML. And plugins may share information with most other plugins running in the same process using the ClassData Functions.