research/opl/genmidi/genmidi-dumper

#!/usr/bin/env ruby

NUM_INSTRUMENTS = 175

# Layout of GENMIDI lump data:

LMP_AM_VIB_OFFSET          = 0
LMP_ATTACK_DECAY_OFFSET    = 1
LMP_SUSTAIN_RELEASE_OFFSET = 2
LMP_WAVE_SELECT_OFFSET     = 3
LMP_KSL_OFFSET             = 4
LMP_OUTPUT_LEVEL_OFFSET    = 5

LMP_OPERATOR2_OFFSET = 7
LMP_OPERATOR_LENGTH = 6
LMP_FEEDBACK_OFFSET = 6

# Layout of SBI format files:

SBI_HEADER = "2OP\032"
SBI_AM_VIB_OFFSET          = 0
SBI_KSL_LEVEL_OFFSET       = 2
SBI_ATTACK_DECAY_OFFSET    = 4
SBI_SUSTAIN_RELEASE_OFFSET = 6
SBI_WAVE_SELECT_OFFSET     = 8
SBI_CONNECTION_OFFSET      = 10

class Instrument
    FIXED_PITCH  = 0x0001
    DOUBLE_VOICE = 0x0004
    attr_reader :voice1_data, :voice2_data, :feedback, :flags
    attr_reader :fine_tuning, :fixed_note
    attr_accessor :name

    def initialize(data)
        header = data[0,4]

        @flags = data[0] | (data[1] << 8)
        @fine_tuning = data[2] - 128
        @fixed_note = data[3]
        @voice1_data = data[4,13]
        @voice2_data = data[20,13]
    end

    def fixed_pitch
        (@flags & FIXED_PITCH) != 0
    end

    def double_voice
        (@flags & DOUBLE_VOICE) != 0
    end
end

def read_instrument(file)
    data = file.read(36)

    Instrument.new(data)
end

def read_name(file)
    data = file.read(32)
    data.strip
end

def read_instruments(filename)
    instruments = []

    File.open(filename) do |file|
        header = file.read(8)

        if header != "#OPL_II#"
            raise "Header not found!"
        end

        NUM_INSTRUMENTS.times do
            instrument = read_instrument(file)
            instruments.push(instrument)
        end

        NUM_INSTRUMENTS.times do |i|
            name = read_name(file)
            instruments[i].name = name
        end
    end

    instruments
end

def data_to_s(data)

    stringified = []

    data.each_byte do |val|
        stringified.push(sprintf("%02x", val))
    end

    stringified.join(",")
end

def display_instruments(instruments)
    for instrument in instruments
        print instrument.name
        padding = 25 - instrument.name.length
        print " " * padding

        print "(#{instrument.fine_tuning},#{instrument.flags}) "

        print data_to_s(instrument.voice1_data)
        print "|"
        print data_to_s(instrument.voice2_data)
        print "\n"
    end
end

def lmp_voice_to_sbi(voice_data)
    operator_data = [
        voice_data[0, LMP_OPERATOR_LENGTH],
        voice_data[LMP_OPERATOR2_OFFSET, LMP_OPERATOR_LENGTH]
    ]

    result = "\0" * 11

    for op in [0, 1]
        op_data = operator_data[op]

        result[SBI_AM_VIB_OFFSET + op] = op_data[LMP_AM_VIB_OFFSET]
        result[SBI_KSL_LEVEL_OFFSET + op] = (op_data[LMP_KSL_OFFSET] \
                                           | op_data[LMP_OUTPUT_LEVEL_OFFSET])
        result[SBI_ATTACK_DECAY_OFFSET + op] = op_data[LMP_ATTACK_DECAY_OFFSET]
        result[SBI_SUSTAIN_RELEASE_OFFSET + op] = op_data[LMP_SUSTAIN_RELEASE_OFFSET]
        result[SBI_WAVE_SELECT_OFFSET + op] = op_data[LMP_WAVE_SELECT_OFFSET]
    end

    result[SBI_CONNECTION_OFFSET] = voice_data[LMP_FEEDBACK_OFFSET]

    result
end

def pad_name(name, length)
    name = name[0, length]

    result = "\0" * length
    result[0, name.length] = name

    result
end

def lmp_instrument_to_sbi(instrument)
    # Build header

    result = SBI_HEADER

    name = pad_name(instrument.name, 32)
    
    # fine tuning:

    if instrument.fine_tuning != 0
        name[28] = 64 + instrument.fine_tuning
    end
    if (instrument.flags & Instrument::FIXED_PITCH) != 0
        name[31] = instrument.fixed_note
    end

    result += name

    # Voice data

    result += lmp_voice_to_sbi(instrument.voice1_data)
    result += lmp_voice_to_sbi(instrument.voice2_data)
    result += "\0\0"

    result
end

# Write an SBI format file.

def write_sbi(filename, instruments, start_instrument)
    File.open(filename, "w") do |file|
        start_instrument.times do
            file.write "\0" * 60
        end

        for instrument in instruments
            data = lmp_instrument_to_sbi(instrument)
            file.write(data)
        end
    end
end

if ARGV.length < 2
    puts "Usage: genmidi-dumper [ -sbi | -txt ] <filename>"
    exit(0)
end

instruments = read_instruments(ARGV[1])

if ARGV[0] == "-sbi"
    write_sbi("std.o3", instruments[0, 128], 0)
    write_sbi("drums.o3", instruments[128, instruments.length], 35)
elsif ARGV[0] == "-txt"
    display_instruments(instruments)
end