XMF(eXtensible Music Format) is a family of music-related file formats created and administered by the MIDI Manufacturer's Association. XMF is based on the idea of containing one or more existing files – such as Standard MIDI Files, DLS instrument files, WAV or other digital audio files, etc. – to create a collection of all the resources needed to present a musical piece, an interactive web page soundtrack, or any other piece of media using pre-produced sound elements.
XMF is designed to keep file sizes as small as possible, in order to be useful on systems ranging from small-footprint mobile devices like cell phones to desktop/laptop computers to high-power web servers. It also has no maximum file size, so it could be used to store very large collections if desired. To support international music data commerce, the meta-data that travels with the resources can be International, keyed to the user's language and the country in which playback is happening – so in an XMF album, the liner notes could change language depending on who's listening.
XMF File Types
XMF Type 0 and XMF Type 1 Files (RP-031) contain Standard MIDI Files that can use General MIDI instruments (provided by a player), and custom DLS instruments (provided in the XMF File). The MIDI files and the DLS files are bound together in the XMF file, rather than traveling separately where they can get lost. Type 0 and Type 1 are identical, except that in Type 0 the MIDI data may be streamed.
XMF Type 2 Files are also called Mobile XMF Files (RP-042). Mobile XMF (Type 2) was developed specifically for mobile phones, and supports SP-MIDI format SMF files as well as Mobile DLS content. It uses the new version 2 Meta File Format specification, which enables MIME Type support.
XMF Type 3 Files are also called Audio Clips for Mobile XMF Files (RP-045). XMF Type 3 makes XMF a rich recorded music format by allowing digital audio clips to be placed on the MIDI timeline (not just MIDI instruments). The audio clips can use various codecs (if registered with MMA/AMEI), and the files can include ID3 metadata (like MP3). Additionally, if Mobile Phone Control messages are included (see RP-046), XMF Type 3 content can use MIDI to control LEDs, vibras, and other non-audio output devices.
XMF Type 4 files are called Interactive XMF (iXMF) files. Interactive XMF is the world's first open format for interactive audio content.