MDI
| Ad Lib MIDI | |||||
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| Developer: | Ad Lib, Inc. | ||||
| Header: | SMF | ||||
| Content: | Notational | ||||
| Instruments: | Internal | ||||
Target Output
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| Released: | 1989-05-08 | ||||
| First Game: | AdLib (DOS) | ||||
| Extensions |
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The MDI format was created by Ad Lib, Inc. to upgrade from MUS (AdLib) format. It uses the MIDI structure but designed to work with OPL2 sound chip that allow it to store instrument data and change modes.
Because the format is so similar to MIDI, some MIDI players are able to play the files, though they won't utilize the instrument data or set the song into the correct mode, so the song won't sound correct. The players which can play MDI files correctly are listed below.
There don't appear to be any MDI players that support looping. This is needed to make proper recordings.
Contents
Players
- AdPlug - DOS, foobar2000, UNIX, Winamp, XMMS
- MIDI Play - DOS
- Multi Media Machine - DOS
Editors
- MIDIPLEX - Windows 32
Converters
MDI to ?
- MIDIPLEX - Windows 32 - CMF, MIDI, MUS (AdLib), SND (AdLib)
? to MDI
- MIDIPLEX - Windows 32 - CMF, MUS (AdLib), SND (AdLib)
- ROL to MIDI - DOS - ROL
Games
| Released | Title | Sample |
|---|---|---|
| 1990-09-20 | AdLib (DOS) | |
| 1990-??-?? | Golden Axe (DOS) | |
| 1991-??-?? | Dark Ages (DOS) | |
| 1991-??-?? | Dragonflight (DOS) | |
| 1991-??-?? | Prehistorik (DOS) | |
| 1992-0?-?? | Clik Clak (DOS) | |
| 1992-??-?? | Amberstar (DOS) | |
| 1992-??-?? | Galactix (DOS) | |
| 1992-??-?? | Starfire (DOS) | |
| 1993-??-?? | Ultimuh MCMLXVII (DOS) | |
| 1994-08-23 | Microsoft Space Simulator (DOS) |
How to Obtain
MDI files usually have to be manually extracted from game files, a process that is different for pretty much every game that uses them.
Technical
- All MDI files begin with "MThd" MIDI header and contain "MTrk" at the start of the MIDI track.
- The End Of Track "FF 2F 00" event is located at the end of file, but not included in the track.
- Events 0xD# (channel aftertouch) are used to control channel volume.
- Velocity parameter (with Note On and Note Off events) is also used to change current channel volume. It actually doesn't belong to the specified note.
- Some Note Off events may have note parameter equal to 0 (see example). This event just stops last played note on specified channel. Even if there is no played note on channel, it used to change channel volume.
- Program Change events are not used in the track.
Sequencer-Specific Event Format
These events are used to control OPL-compatible chip.
| Delta-ticks | Event | Length | AdLib ID | Opcode | Data |
|---|---|---|---|---|---|
| 00 | FF 7F | XX | 00 00 3F | XX XX | XX .. XX |
Possible Opcodes
| Opcode | Meaning | Byte # | Description |
|---|---|---|---|
| 00 01 | Patch (instrument change) | 1 | Voice / channel number for instrument |
| 2 - 29 | 28 byte array of parameters (see structure below) | ||
| 00 02 | Card mode | 1 | 0 = melodic, 1 = percussive |
| 00 03 | Pitch bend sensitivity | 1 | 1 - 12 inclusive |
Instrument Structure
Instrument parameters are expressed with the structure, which is identical to the structure for an instrument inside a BNK file:
| Data type | Name | Description |
|---|---|---|
| MDI_OPLREGS | oplModulator | Register values for the Modulator operator (op 0) |
| MDI_OPLREGS | oplCarrier | Register values for the Carrier operator (op 1) |
| UINT8 | iModWaveSel | Modulator wave select (OPL base register 0xE0) |
| UINT8 | iCarWaveSel | Carrier wave select (OPL base register 0xE0) |
The MDI_OPLREGS structure is defined as:
| Data type | Name | Description | OPL base register |
|---|---|---|---|
| UINT8 | ksl | Key scaling level | 0x40 (bits 6-7) |
| UINT8 | multiple | Frequency multiplier | 0x20 (bits 0-3) |
| UINT8 | feedback | Feedback [op 0 only, op 1 ignored] | 0xC0 (bits 1-3) |
| UINT8 | attack | Attack rate | 0x60 (upper four bits) |
| UINT8 | sustain | Sustain level | 0x80 (upper four bits) |
| UINT8 | eg | Envelope gain (nonzero value is on) | 0x20 (bit 5) |
| UINT8 | decay | Decay rate | 0x60 (lower four bits) |
| UINT8 | releaseRate | Release rate | 0x80 (lower four bits) |
| UINT8 | totalLevel | Total output level | 0x40 (bit 0-5) |
| UINT8 | am | Amplitude modulation (Tremolo) | 0x20 (bit 7) |
| UINT8 | vib | Frequency Vibrato | 0x20 (bit 6) |
| UINT8 | ksr | Key scaling/envelope rate | 0x20 (bit 4) |
| UINT8 | con | Connector [op 0 only, op 1 ignored] | 0xC0 (bit 0, inverted) |
Channel Utilization
The channel utilization is the same as in the MUS format, except the music can be composed in both melodic and percussive modes, since the format supports mode switching during playback.
Default Timbre
Player should load default timbre if it isn't loaded by sequencer-specific event before.
Links
- shikadi.net/moddingwiki/MDI_Format - ModdingWiki.
- cd.textfiles.com/soundsensations/MISCPROG/ZIPFILES/AD-PROG.ZIP - Source code (part of the Ad Lib Programmer's Manual).
- swag.outpostbbs.net/SOUND/0066.PAS - MDI2MUS by Colin Buckley (incomplete program source).
