GENMIDI.OP2 OPL2 sound bank: Lua parsing library

GENMIDI.OP2 is a sound bank file used by players based on DMX sound library to play MIDI files with General MIDI instruments using OPL2 sound chip (which was commonly installed on popular AdLib and Sound Blaster sound cards).

Major users of DMX sound library include:

  • Original Doom game engine (and games based on it: Heretic, Hexen, Strife, Chex Quest)
  • Raptor: Call of the Shadows

File extension

op2

KS implementation details

License: CC0-1.0
Minimal Kaitai Struct required: 0.9

References

This page hosts a formal specification of GENMIDI.OP2 OPL2 sound bank using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Lua source code to parse GENMIDI.OP2 OPL2 sound bank

genmidi_op2.lua

-- This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
--
-- This file is compatible with Lua 5.3

local class = require("class")
require("kaitaistruct")
local str_decode = require("string_decode")

-- 
-- GENMIDI.OP2 is a sound bank file used by players based on DMX sound
-- library to play MIDI files with General MIDI instruments using OPL2
-- sound chip (which was commonly installed on popular AdLib and Sound
-- Blaster sound cards).
-- 
-- Major users of DMX sound library include:
-- 
-- * Original Doom game engine (and games based on it: Heretic, Hexen, Strife, Chex Quest)
-- * Raptor: Call of the Shadows
-- See also: Source (http://www.fit.vutbr.cz/~arnost/muslib/op2_form.zip)
-- See also: Source (http://doom.wikia.com/wiki/GENMIDI)
-- See also: Source (http://www.shikadi.net/moddingwiki/OP2_Bank_Format)
GenmidiOp2 = class.class(KaitaiStruct)

function GenmidiOp2:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function GenmidiOp2:_read()
  self.magic = self._io:read_bytes(8)
  if not(self.magic == "\035\079\080\076\095\073\073\035") then
    error("not equal, expected " ..  "\035\079\080\076\095\073\073\035" .. ", but got " .. self.magic)
  end
  self.instruments = {}
  for i = 0, 175 - 1 do
    self.instruments[i + 1] = GenmidiOp2.InstrumentEntry(self._io, self, self._root)
  end
  self.instrument_names = {}
  for i = 0, 175 - 1 do
    self.instrument_names[i + 1] = str_decode.decode(KaitaiStream.bytes_terminate(KaitaiStream.bytes_strip_right(self._io:read_bytes(32), 0), 0, false), "ASCII")
  end
end


GenmidiOp2.InstrumentEntry = class.class(KaitaiStruct)

function GenmidiOp2.InstrumentEntry:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function GenmidiOp2.InstrumentEntry:_read()
  self.flags = self._io:read_u2le()
  self.finetune = self._io:read_u1()
  self.note = self._io:read_u1()
  self.instruments = {}
  for i = 0, 2 - 1 do
    self.instruments[i + 1] = GenmidiOp2.Instrument(self._io, self, self._root)
  end
end

-- 
-- MIDI note for fixed instruments, 0 otherwise.

GenmidiOp2.Instrument = class.class(KaitaiStruct)

function GenmidiOp2.Instrument:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function GenmidiOp2.Instrument:_read()
  self.op1 = GenmidiOp2.OpSettings(self._io, self, self._root)
  self.feedback = self._io:read_u1()
  self.op2 = GenmidiOp2.OpSettings(self._io, self, self._root)
  self.unused = self._io:read_u1()
  self.base_note = self._io:read_s2le()
end

-- 
-- Feedback/AM-FM (both operators).
-- 
-- Base note offset.

-- 
-- OPL2 settings for one operator (carrier or modulator)
GenmidiOp2.OpSettings = class.class(KaitaiStruct)

function GenmidiOp2.OpSettings:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function GenmidiOp2.OpSettings:_read()
  self.trem_vibr = self._io:read_u1()
  self.att_dec = self._io:read_u1()
  self.sust_rel = self._io:read_u1()
  self.wave = self._io:read_u1()
  self.scale = self._io:read_u1()
  self.level = self._io:read_u1()
end

-- 
-- Tremolo/vibrato/sustain/KSR/multi.
-- 
-- Attack rate/decay rate.
-- 
-- Sustain level/release rate.
-- 
-- Waveform select.
-- 
-- Key scale level.
-- 
-- Output level.