genmidi: Split off GENMIDI code into separate file.

Split out code for handling the GENMIDI format into a separate genmidi.py
file. Add routine to load the contents of a GENMIDI lump.

lumps/genmidi/genmidi.py

@@ -0,0 +1,214 @@
+#!/usr/bin/env python
+#
+# Copyright (c) 2011, 2012
+# Contributors to the Freedoom project.  All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#  * Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+#  * Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#  * Neither the name of the freedoom project nor the names of its
+#    contributors may be used to endorse or promote products derived from
+#    this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+# IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
+# OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+# ----------------------------------------------------------------------
+#
+# Module for interacting with Doom GENMIDI lumps.
+#
+
+from instrument import Instrument, NullInstrument
+import struct
+import sys
+
+GENMIDI_HEADER = "#OPL_II#"
+NUM_INSTRUMENTS = 175
+INSTR_DATA_LEN = 36
+INSTR_NAME_LEN = 32
+
+FLAG_FIXED_PITCH = 0x0001
+FLAG_TWO_VOICE   = 0x0004
+
+KSL_MASK = 0xc0
+VOLUME_MASK = 0x3f
+
+# Order of fields in GENMIDI data structures.
+
+GENMIDI_FIELDS = [
+	"m_am_vibrato_eg",
+	"m_attack_decay",
+	"m_sustain_release",
+	"m_waveform",
+	"m_ksl",
+	"m_volume",
+	"feedback_fm",
+	"c_am_vibrato_eg",
+	"c_attack_decay",
+	"c_sustain_release",
+	"c_waveform",
+	"c_ksl",
+	"c_volume",
+	"null",
+	"note_offset"
+]
+
+# Encode a single voice of an instrument to binary.
+
+def encode_voice(data, offset):
+	result = dict(data)
+
+	result["m_ksl"] = data["m_ksl_volume"] & KSL_MASK
+	result["m_volume"] = data["m_ksl_volume"] & VOLUME_MASK
+	result["c_ksl"] = data["c_ksl_volume"] & KSL_MASK
+	result["c_volume"] = data["c_ksl_volume"] & VOLUME_MASK
+
+	result["null"] = 0
+	result["note_offset"] = offset
+
+	return struct.pack("<BBBBBBBBBBBBBBh",
+	                   *map(lambda key: result[key], GENMIDI_FIELDS))
+
+# Encode an instrument to binary.
+
+def encode_instrument(instrument):
+	flags = 0
+
+	instr1_data = encode_voice(instrument.voice1, instrument.offset1)
+
+	if instrument.voice2 is not None:
+		flags |= FLAG_TWO_VOICE
+		instr2_data = encode_voice(instrument.voice2,
+		                           instrument.offset2)
+	else:
+		instr2_data = encode_voice(NullInstrument.voice1, 0)
+
+	if instrument.fixed_note is not None:
+		flags |= FLAG_FIXED_PITCH
+		fixed_note = instrument.fixed_note
+	else:
+		fixed_note = 0
+
+	header = struct.pack("<hBB", flags, 128, fixed_note)
+
+	return header + instr1_data + instr2_data
+
+def encode_instruments(instruments):
+	result = []
+
+	for instrument in instruments:
+		result.append(encode_instrument(instrument))
+
+	return b"".join(result)
+
+def encode_instrument_names(instruments):
+	result = []
+
+	for instrument in instruments:
+		result.append(struct.pack("32s", instrument.voice1["name"]))
+
+	return b"".join(result)
+
+def write(filename, instruments):
+	header = struct.pack("%is" % len(GENMIDI_HEADER), GENMIDI_HEADER)
+
+	f = open(filename, 'w')
+
+	f.write(header)
+	f.write(encode_instruments(instruments))
+	f.write(encode_instrument_names(instruments))
+
+	f.close()
+
+def decode_voice(data):
+
+	fields = struct.unpack("<BBBBBBBBBBBBBBh", data)
+
+	result = {}
+	for i in range(len(GENMIDI_FIELDS)):
+		result[GENMIDI_FIELDS[i]] = fields[i]
+
+	result["m_ksl_volume"] = result["m_ksl"] | result["m_volume"]
+	result["c_ksl_volume"] = result["c_ksl"] | result["c_volume"]
+
+	return result
+
+def decode_instrument(data, name):
+	flags, finetune, fixed_note = struct.unpack("<hBB", data[0:4])
+
+	voice1 = decode_voice(data[4:20])
+	offset1 = voice1["note_offset"]
+
+	# Second voice?
+
+	if (flags & FLAG_TWO_VOICE) != 0:
+		voice2 = decode_voice(data[20:])
+		offset2 = voice2["note_offset"]
+	else:
+		voice2 = None
+		offset2 = 0
+
+	# Null out fixed_note if the fixed pitch flag isn't set:
+
+	if (flags & FLAG_FIXED_PITCH) == 0:
+		fixed_note = None
+
+	return Instrument(voice1, voice2,
+	                  off1=offset1, off2=offset2,
+	                  note=fixed_note)
+
+def read(filename):
+	f = open(filename)
+	data = f.read()
+	f.close()
+
+	# Check header:
+
+	header = data[0:len(GENMIDI_HEADER)]
+	if header != GENMIDI_HEADER:
+		raise Exception("Incorrect header for GENMIDI lump")
+
+	body = data[len(GENMIDI_HEADER):]
+	instr_data = body[0:NUM_INSTRUMENTS * INSTR_DATA_LEN]
+	instr_names = body[NUM_INSTRUMENTS * INSTR_DATA_LEN:]
+	result = []
+
+	for i in range(NUM_INSTRUMENTS):
+		data = instr_data[i * INSTR_DATA_LEN:(i+1) * INSTR_DATA_LEN]
+		name = instr_names[i * INSTR_NAME_LEN:(i+1) * INSTR_NAME_LEN]
+
+		result.append(decode_instrument(data, name))
+
+	return result
+
+if __name__ == "__main__":
+	for filename in sys.argv[1:]:
+		instruments = read(filename)
+		for i in range(len(instruments)):
+			instrument = instruments[i]
+			fixed_note = instrument.fixed_note
+
+			if fixed_note is not None:
+				print "%i (fixed note: %i):" % (i, fixed_note)
+			else:
+				print "%i:" % i
+
+			print "\tVoice 1: %s" % instrument.voice1
+			if instrument.voice2 is not None:
+				print "\tVoice 2: %s" % instrument.voice2
+