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.