MOD (file format)
From Free net encyclopedia
MOD is a computer file format used to represent music, and was the first module file format. MOD files use the ".MOD" file extension. A MOD file contains a set of instruments in the form of samples, a number of patterns indicating how and when the samples are to be played, and a list of what patterns to play in what order.
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History
The first version of the format was created by Karsten Obarski for use in the Soundtracker tracker released for the Amiga computer in 1987[1]. The format has since been supported by hundreds of playback programs and dozens of other trackers including ProTracker and NoiseTracker.
The original version of the MOD format featured four channels of simultaneous audio playback, corresponding to the Amiga hardware capabilities of the time, and up to 15 instruments.
Later variations of the format have extended this to up to 32 channels and 31 instruments.
The format was designed to be directly playable on the Amiga without additional processing: for example, samples are stored in 8-bit PCM format ready to be played on the Amiga DAC, and pattern data is not packed. Playback required very little CPU time on an Amiga, and many games used MOD files for their background music.
Format overview
A pattern is typically represented in a sequencer user interface as a table with one column per channel (hence 4 columns in the original SoundTracker) and up to 64 rows. Each row lasts 0.02 seconds times the current speed setting.
A cell in the table can cause something to happen on its column's channel when its row's time is reached:
- Start an instrument playing a new note in this channel at a given volume and with an optional special effect applied
- Change the volume or special effect being applied to the current note
- Do nothing; any existing note playing in this channel will continue to play
An instrument is a single sample along with an optional indication of which portion of the sample can be repeated to hold a sustained note.
In a MOD file the minimum time frame is 0.02 seconds, because the original software used the VSync of the monitor running at 50 Hz (for PAL) or 60 Hz (for NTSC) for timing.
Other MOD formats
MOD is also the file format used on many camcoders, such as the JVC Everio, and the Panasonic D-Snap SD-card camcorders.
See also
Software
- Soundtracker is available for UNIX systems with X11
- Unix Amiga Delitracker Emulator plays most of the Amiga music formats on UNIX platforms (open source).
External Amiga-related links
- Details on MOD file format
- Amiga Music Preservation - Tens of thousands of Amiga music modules to download
- Exotica - Lots of music modules, dedicated to "unusual" tracker formats from the Amiga
- Aminet's MOD Archive - AmiNet archive's mod file section - no longer updated but was the hub of the modscene for years.
- MOD Archive - A site for Amiga music modules. Also includes the Altered Perception mod archive.
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