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[[Category: Formats With {{{Header}}} Headers]] [[Category: Formats With {{{Content}}} Content]] [[Category: Formats With {{{Instruments}}} Instruments]]
id's Music Format
Developer: id Software
Header: {{{Header}}}
Content: {{{Content}}}
Instruments: {{{Instruments}}}
Target Output
Output - Digital Audio - No.png Output - MIDI - No.png Output - FM Synthesis - No.png Output - PSG - No.png
Released: 1991/11/??
First Game: Catacomb 3-D (DOS)
  • *.imf
  • *.wlf
  • *.adlib

The id music format (name verified by John Romero) is an AdLib audio structure developed by Jason Blochowiak. It was designed to be an optimized MIDI-like format that would be played via FM Synthesis on an AdLib card. In fact, the format is actually very similar to to the AdLib command syntax because it stores the raw data that needs to be sent to the OPL chip. The Winamp plugin AdPlug gives the most accurate playback of IMF.

IMF was originally created to be used in Commander Keen IV: Secret of the Oracle (DOS), but due to contractual obligations, the first published game to use IMF was Catacomb 3-D (DOS). It was almost released in the game Keen Dreams (DOS), but due to space constraints all music was removed from the game in order to fit on a single floppy disk.

There are two types of IMF. The first series of games to use IMF format are in what is now called Type-0. Type-0 IMF doesn't include any header information and is sent straight to the OPL chip. Later games use Type-1 which has a short header that includes the length of the song, and allows for meta data in a footer.

IMF has one design flaw. Different games play IMF files at different speeds, but the playback rate is not part of the IMF header. Because of this, extra precautions must be made when playing back IMF files. Bio Menace, Catacomb 3-D, Commander Keen, and Monster Bash all play at 560 Hz, but Cosmo's Cosmic Adventures, Wolfenstein 3-D, and games using the Wolf 3D engine (Spear of Destiny, Blake Stone 1 & 2, Operation Body Count, and Corridor 7) all run at 700 Hz. Duke Nukem II is unique and runs at 280 Hz. To fix this problem, the Wolf 3D games are given the *.WLF extension and Duke Nukem II delays are simply doubled in the file to match the 560 Hz tempo. This flaw can easily be fixed by creating a file header which included the necessary playback rate, but both the files and players would have to be updated.


Players That Support IMF


Games That Use IMF