A RIFF form is a chunk with a 'RIFF' chunk ID. The term also refers to a file format that follows the RIFF framework. The following is the current list of registered RIFF forms. Each is described in Multimedia File Formats.
Form Type
Using the notation for representing a chunk, a RIFF form looks like the following:
RIFF ( <formType> <ck>... )
The first four bytes of a RIFF form make up a chunk ID with values 'R', 'I', 'F', 'F'. The ckSize field is required, but for simplicity it is omitted from the notation.
The first ULONG of chunk data in the 'RIFF' chunk (shown above as <formType>) is a four-character code value identifying the data representation, or form type, of the file. Following the form-type code is a series of subchunks. Which subchunks are present depends on the form type. The definition of a particular RIFF form typically includes the following: