Defining and Registering RIFF Forms

The form-type code for a RIFF form must be unique. To guarantee this uniqueness, you must register any new form types before release. To register form types, and to get a current list of registered RIFF forms, request a Multimedia Developer Registration Kit from the following group:

Microsoft Corporation
Multimedia Systems Group
Product Marketing
One Microsoft Way
Redmond, WA 98052-6399

Like RIFF forms, RIFX forms must also be registered. Registering a RIFF form does not automatically register the RIFX counterpart. No RIFX form types are currently defined.

When you document the RIFF form, you should use the notation described in “Notation for Representing RIFF Files,” later in this chapter.

Registered Form and Chunk Types

By convention, the form-type code for registered form types contains only digits and uppercase letters. Form-type codes that are all uppercase denote a registered, unique form type. Use lowercase letters for temporary or prototype chunk types.

Certain chunk types are also globally unique and must also be registered before use. These registered chunk types are not specific to a certain form type; they can be used in any form. If a registered chunk type can be used to store your data, you should use the registered chunk type rather than define your own chunk type containing the same type of information.

For example, a chunk with chunk ID “INAM” always contains the name or title of a file. Also, within all RIFF files, filenames or titles are contained within chunks with ID “INAM” and have a standard data format.

Unregistered (Form-Specific) Chunk Types

Chunks 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 the Multimedia Developers Registration Kit for details.

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.”