195 lines
4.7 KiB
Python
195 lines
4.7 KiB
Python
#!/usr/bin/env python3
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# SPDX-License-Identifier: BSD-3-Clause
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#
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# Module for interacting with Doom GENMIDI lumps.
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#
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from instrument import Instrument, NullInstrument
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import struct
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import sys
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GENMIDI_HEADER = "#OPL_II#"
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NUM_INSTRUMENTS = 175
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INSTR_DATA_LEN = 36
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INSTR_NAME_LEN = 32
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FLAG_FIXED_PITCH = 0x0001
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FLAG_TWO_VOICE = 0x0004
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KSL_MASK = 0xC0
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VOLUME_MASK = 0x3F
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# Order of fields in GENMIDI data structures.
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GENMIDI_FIELDS = [
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"m_am_vibrato_eg",
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"m_attack_decay",
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"m_sustain_release",
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"m_waveform",
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"m_ksl",
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"m_volume",
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"feedback_fm",
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"c_am_vibrato_eg",
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"c_attack_decay",
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"c_sustain_release",
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"c_waveform",
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"c_ksl",
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"c_volume",
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"null",
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"note_offset",
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]
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# Encode a single voice of an instrument to binary.
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def encode_voice(data, offset):
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result = dict(data)
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result["m_ksl"] = data["m_ksl_volume"] & KSL_MASK
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result["m_volume"] = data["m_ksl_volume"] & VOLUME_MASK
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result["c_ksl"] = data["c_ksl_volume"] & KSL_MASK
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result["c_volume"] = data["c_ksl_volume"] & VOLUME_MASK
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result["null"] = 0
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result["note_offset"] = offset
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return struct.pack(
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"<BBBBBBBBBBBBBBh", *map(lambda key: result[key], GENMIDI_FIELDS)
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)
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# Encode an instrument to binary.
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def encode_instrument(instrument):
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flags = 0
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instr1_data = encode_voice(instrument.voice1, instrument.offset1)
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if instrument.voice2 is not None:
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flags |= FLAG_TWO_VOICE
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instr2_data = encode_voice(instrument.voice2, instrument.offset2)
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else:
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instr2_data = encode_voice(NullInstrument.voice1, 0)
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if instrument.fixed_note is not None:
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flags |= FLAG_FIXED_PITCH
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fixed_note = instrument.fixed_note
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else:
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fixed_note = 0
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header = struct.pack("<hBB", flags, 128, fixed_note)
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return header + instr1_data + instr2_data
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def encode_instruments(instruments):
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result = []
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for instrument in instruments:
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result.append(encode_instrument(instrument))
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return b"".join(result)
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def encode_instrument_names(instruments):
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result = []
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for instrument in instruments:
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instr_name = instrument.voice1["name"].encode("ascii")
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result.append(struct.pack("32s", instr_name))
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return b"".join(result)
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def write(filename, instruments):
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header = struct.pack(
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"%is" % len(GENMIDI_HEADER), GENMIDI_HEADER.encode("ascii")
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)
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with open(filename, "wb") as f:
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f.write(header)
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f.write(encode_instruments(instruments))
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f.write(encode_instrument_names(instruments))
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def decode_voice(data, name):
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fields = struct.unpack("<BBBBBBBBBBBBBBh", data)
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result = {}
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for i in range(len(GENMIDI_FIELDS)):
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result[GENMIDI_FIELDS[i]] = fields[i]
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result["m_ksl_volume"] = result["m_ksl"] | result["m_volume"]
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result["c_ksl_volume"] = result["c_ksl"] | result["c_volume"]
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result["name"] = name.decode("ascii").rstrip("\0")
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return result
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def decode_instrument(data, name):
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flags, finetune, fixed_note = struct.unpack("<hBB", data[0:4])
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voice1 = decode_voice(data[4:20], name)
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offset1 = voice1["note_offset"]
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# Second voice?
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if (flags & FLAG_TWO_VOICE) != 0:
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voice2 = decode_voice(data[20:], name)
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offset2 = voice2["note_offset"]
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else:
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voice2 = None
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offset2 = 0
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# Null out fixed_note if the fixed pitch flag isn't set:
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if (flags & FLAG_FIXED_PITCH) == 0:
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fixed_note = None
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return Instrument(
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voice1, voice2, off1=offset1, off2=offset2, note=fixed_note
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)
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def read(filename):
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with open(filename, "rb") as f:
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data = f.read()
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# Check header:
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header = data[0 : len(GENMIDI_HEADER)]
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if header.decode("ascii") != GENMIDI_HEADER:
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raise Exception("Incorrect header for GENMIDI lump")
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body = data[len(GENMIDI_HEADER) :]
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instr_data = body[0 : NUM_INSTRUMENTS * INSTR_DATA_LEN]
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instr_names = body[NUM_INSTRUMENTS * INSTR_DATA_LEN :]
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result = []
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for i in range(NUM_INSTRUMENTS):
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data = instr_data[i * INSTR_DATA_LEN : (i + 1) * INSTR_DATA_LEN]
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name = instr_names[i * INSTR_NAME_LEN : (i + 1) * INSTR_NAME_LEN]
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result.append(decode_instrument(data, name))
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return result
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if __name__ == "__main__":
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for filename in sys.argv[1:]:
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instruments = read(filename)
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for i in range(len(instruments)):
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instrument = instruments[i]
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fixed_note = instrument.fixed_note
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if fixed_note is not None:
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print("%i (fixed note: %i):" % (i, fixed_note))
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else:
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print("%i:" % i)
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print("\tVoice 1: %s" % instrument.voice1)
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if instrument.voice2 is not None:
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print("\tVoice 2: %s" % instrument.voice2)
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