The IOProc is expected to return the standard presentation format header length when header translation is specified. The following are examples of some structures that the preceding parameters might use. These are the standard presentation format header structures.

• MMIMAGEHEADER, includes structure length, content, size, color type and other information, including space for a 256-color palette.

• MMAUDIOHEADER, includes structure length, content, samples per second, and sample size.

• MMMIDIHEADER, contains all pertinent information about the MIDI.

• MMMOVIEHEADER contains information about the movie.

• MMVIDEOHEADER contains information about the digital video data.