The Multimedia extensions support a tagged file structure called the Resource Interchange File Format (RIFF). There are two RIFF file formats currently defined for audio files:
| RIFF File Format | File Extension | Description |
| RMID | .RMI | MIDI audio file |
| WAVE | .WAV | Waveform audio file |
The WAVE file format supports a number of different digital audio data formats. All multimedia computers support PCM (pulse code modulated) data formats of 8-bit mono at sample rates of 11.025 kHz and 22.05 kHz.
In addition to RMID files, the MCI MIDI sequencer plays standard MIDI files in the format defined by the International MIDI Association in the “Standard MIDI Files 1.0” specification. See “Further Reading” at the end of this chapter for information on how to obtain this specification. RMID files are standard MIDI files with a RIFF header.
For more information on RIFF files and the RMID and WAVE file formats, see the file formats chapter in the Programmer's Reference.
The multimedia file I/O services include functions for working with RIFF files. For information on using these functions, see Chapter 10, “Multimedia File I/O Services.”