Chunk types that are used only in a certain form type use a lowercase chunk ID. A lowercase chunk ID has specific meaning only within the context of a specific form type. After a form designer is allocated a registered form type, the designer can choose lowercase chunk types to use within that form. See Registering Multimedia Formats for information on registering form types.
For example, a chunk with ID 'scln' inside one form type might contain the "number of scan lines." Inside some other form type, a chunk with ID 'scln' might mean "secondary lambda number."