Part-ID
A 32-bit field that defines the feature as being either brand-specific or universal.
Overview
The second field is the part-ID, which defines the feature as being either brand-specific or universal. Brand-specific features are particular to a specific brand. Universal features are can be found in any file type that uses the profile atom. Universal features have a part-ID of four ASCII spaces (0x20202020). Brand-specific features have a part-ID that is one of the Compatible_Brand codes for that file type, as specified in the file type atom ('ftyp'). For example, the part-ID for QuickTime-specific features is 'qt '. All features described in this documentation, however, are universal.