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Message from discussion Python classes for MIDI

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More options Dec 6 2001, 7:41 am
Newsgroups: alt.sources
From: Will Ware <ww...@alum.mit.edu>
Date: Thu, 06 Dec 2001 07:43:42 -0500
Local: Thurs, Dec 6 2001 7:43 am
Subject: Re: Python classes for MIDI
#!/usr/bin/env python

"""
midi.py -- MIDI classes and parser in Python
Placed into the public domain in December 2001 by Will Ware

Python MIDI classes: meaningful data structures that represent MIDI events
and other objects. You can read MIDI files to create such objects, or
generate a collection of objects and use them to write a MIDI file.

import sys, string, types, exceptions

debugflag = 0

def showstr(str, n=16):
for x in str[:n]:
print ('%02x' % ord(x)),
print

def getNumber(str, length):
# MIDI uses big-endian for everything
sum = 0
for i in range(length):
sum = (sum << 8) + ord(str[i])
return sum, str[length:]

def getVariableLengthNumber(str):
sum = 0
i = 0
while 1:
x = ord(str[i])
i = i + 1
sum = (sum << 7) + (x & 0x7F)
if not (x & 0x80):
return sum, str[i:]

def putNumber(num, length):
# MIDI uses big-endian for everything
lst = [ ]
for i in range(length):
n = 8 * (length - 1 - i)
lst.append(chr((num >> n) & 0xFF))
return string.join(lst, "")

def putVariableLengthNumber(x):
lst = [ ]
while 1:
y, x = x & 0x7F, x >> 7
lst.append(chr(y + 0x80))
if x == 0:
break
lst.reverse()
lst[-1] = chr(ord(lst[-1]) & 0x7f)
return string.join(lst, "")

class EnumException(exceptions.Exception):
pass

class Enumeration:
def __init__(self, enumList):
lookup = { }
reverseLookup = { }
i = 0
uniqueNames = [ ]
uniqueValues = [ ]
for x in enumList:
if type(x) == types.TupleType:
x, i = x
if type(x) != types.StringType:
raise EnumException, "enum name is not a string: " + x
if type(i) != types.IntType:
raise EnumException, "enum value is not an integer: " + i
if x in uniqueNames:
raise EnumException, "enum name is not unique: " + x
if i in uniqueValues:
raise EnumException, "enum value is not unique for " + x
uniqueNames.append(x)
uniqueValues.append(i)
lookup[x] = i
reverseLookup[i] = x
i = i + 1
self.lookup = lookup
self.reverseLookup = reverseLookup
lst = [ ]
for k in self.lookup.keys():
lst.append((k, self.lookup[k]))
for k in other.lookup.keys():
lst.append((k, other.lookup[k]))
return Enumeration(lst)
def hasattr(self, attr):
return self.lookup.has_key(attr)
def has_value(self, attr):
return self.reverseLookup.has_key(attr)
def __getattr__(self, attr):
if not self.lookup.has_key(attr):
raise AttributeError
return self.lookup[attr]
def whatis(self, value):
return self.reverseLookup[value]

channelVoiceMessages = Enumeration([("NOTE_OFF", 0x80),
("NOTE_ON", 0x90),
("POLYPHONIC_KEY_PRESSURE", 0xA0),
("CONTROLLER_CHANGE", 0xB0),
("PROGRAM_CHANGE", 0xC0),
("CHANNEL_KEY_PRESSURE", 0xD0),
("PITCH_BEND", 0xE0)])

channelModeMessages = Enumeration([("ALL_SOUND_OFF", 0x78),
("RESET_ALL_CONTROLLERS", 0x79),
("LOCAL_CONTROL", 0x7A),
("ALL_NOTES_OFF", 0x7B),
("OMNI_MODE_OFF", 0x7C),
("OMNI_MODE_ON", 0x7D),
("MONO_MODE_ON", 0x7E),
("POLY_MODE_ON", 0x7F)])

metaEvents = Enumeration([("SEQUENCE_NUMBER", 0x00),
("TEXT_EVENT", 0x01),
("SEQUENCE_TRACK_NAME", 0x03),
("INSTRUMENT_NAME", 0x04),
("LYRIC", 0x05),
("MARKER", 0x06),
("CUE_POINT", 0x07),
("MIDI_CHANNEL_PREFIX", 0x20),
("MIDI_PORT", 0x21),
("END_OF_TRACK", 0x2F),
("SET_TEMPO", 0x51),
("SMTPE_OFFSET", 0x54),
("TIME_SIGNATURE", 0x58),
("KEY_SIGNATURE", 0x59),
("SEQUENCER_SPECIFIC_META_EVENT", 0x7F)])

# runningStatus appears to want to be an attribute of a MidiTrack. But
# it doesn't seem to do any harm to implement it as a global.
runningStatus = None

class MidiEvent:

def __init__(self, track):
self.track = track
self.time = None
self.channel = self.pitch = self.velocity = self.data = None

def __cmp__(self, other):
# assert self.time != None and other.time != None
return cmp(self.time, other.time)

def __repr__(self):
r = ("<MidiEvent %s, t=%s, track=%s, channel=%s" %
(self.type,
repr(self.time),
self.track.index,
repr(self.channel)))
for attrib in ["pitch", "data", "velocity"]:
if getattr(self, attrib) != None:
r = r + ", " + attrib + "=" + repr(getattr(self, attrib))
return r + ">"

global runningStatus
self.time = time
# do we need to use running status?
if not (ord(str[0]) & 0x80):
str = runningStatus + str
runningStatus = x = str[0]
x = ord(x)
y = x & 0xF0
z = ord(str[1])

if channelVoiceMessages.has_value(y):
self.channel = (x & 0x0F) + 1
self.type = channelVoiceMessages.whatis(y)
if (self.type == "PROGRAM_CHANGE" or
self.type == "CHANNEL_KEY_PRESSURE"):
self.data = z
return str[2:]
else:
self.pitch = z
self.velocity = ord(str[2])
channel = self.track.channels[self.channel - 1]
if (self.type == "NOTE_OFF" or
(self.velocity == 0 and self.type == "NOTE_ON")):
channel.noteOff(self.pitch, self.time)
elif self.type == "NOTE_ON":
channel.noteOn(self.pitch, self.time, self.velocity)
return str[3:]

elif y == 0xB0 and channelModeMessages.has_value(z):
self.channel = (x & 0x0F) + 1
self.type = channelModeMessages.whatis(z)
if self.type == "LOCAL_CONTROL":
self.data = (ord(str[2]) == 0x7F)
elif self.type == "MONO_MODE_ON":
self.data = ord(str[2])
return str[3:]

elif x == 0xF0 or x == 0xF7:
self.type = {0xF0: "F0_SYSEX_EVENT",
0xF7: "F7_SYSEX_EVENT"}[x]
length, str = getVariableLengthNumber(str[1:])
self.data = str[:length]
return str[length:]

elif x == 0xFF:
if not metaEvents.has_value(z):
print "Unknown meta event: FF %02X" % z
sys.stdout.flush()
raise "Unknown midi event type"
self.type = metaEvents.whatis(z)
length, str = getVariableLengthNumber(str[2:])
self.data = str[:length]
return str[length:]

raise "Unknown midi event type"

def write(self):
sysex_event_dict = {"F0_SYSEX_EVENT": 0xF0,
"F7_SYSEX_EVENT": 0xF7}
if channelVoiceMessages.hasattr(self.type):
x = chr((self.channel - 1) +
getattr(channelVoiceMessages, self.type))
if (self.type != "PROGRAM_CHANGE" and
self.type != "CHANNEL_KEY_PRESSURE"):
data = chr(self.pitch) + chr(self.velocity)
else:
data = chr(self.data)
return x + data

elif channelModeMessages.hasattr(self.type):
x = getattr(channelModeMessages, self.type)
x = (chr(0xB0 + (self.channel - 1)) +
chr(x) +
chr(self.data))
return x

elif sysex_event_dict.has_key(self.type):
str = chr(sysex_event_dict[self.type])
str = str + putVariableLengthNumber(len(self.data))
return str + self.data

elif metaEvents.hasattr(self.type):
str = chr(0xFF) + chr(getattr(metaEvents, self.type))
str = str + putVariableLengthNumber(len(self.data))
return str + self.data

else:
raise "unknown midi event type: " + self.type

"""
register_note() is a hook that can be overloaded from a script that
imports this module. Here is how you might do that, if you wanted to
store the notes as tuples in a list. Including the distinction
between track and channel offers more flexibility in assigning voices.

import midi
notelist = [ ]
def register_note(t, c, p, v, t1, t2):
notelist.append((t, c, p, v, t1, t2))
midi.register_note = register_note
"""

def register_note(track_index, channel_index, pitch, velocity,
keyDownTime, keyUpTime):
pass

class MidiChannel:

"""A channel (together with a track) provides the continuity connecting
a NOTE_ON event with its corresponding NOTE_OFF event. Together, those
define the beginning and ending times for a Note."""

def __init__(self, track, index):
self.index = index
self.track = track
self.pitches = { }

def __repr__(self):
return "<MIDI channel %d>" % self.index

def noteOn(self, pitch, time, velocity):
self.pitches[pitch] = (time, velocity)

def noteOff(self, pitch, time):
if self.pitches.has_key(pitch):
keyDownTime, velocity = self.pitches[pitch]
register_note(self.track.index, self.index, pitch, velocity,
keyDownTime, time)
del self.pitches[pitch]
# The case where the pitch isn't in the dictionary is illegal,
# I think, but we probably better just ignore it.

class DeltaTime(MidiEvent):

type = "DeltaTime"

self.time, newstr = getVariableLengthNumber(oldstr)
return self.time, newstr

def write(self):
str = putVariableLengthNumber(self.time)
return str

class MidiTrack:

def __init__(self, index):
self.index = index
self.events = [ ]
self.channels = [ ]
self.length = 0
for i in range(16):
self.channels.append(MidiChannel(self, i+1))

time = 0
assert str[:4] == "MTrk"
length, str = getNumber(str[4:], 4)
self.length = length
mystr = str[:length]
remainder = str[length:]
while mystr:
delta_t = DeltaTime(self)
time = time + dt
self.events.append(delta_t)
e = MidiEvent(self)
self.events.append(e)
return remainder

def write(self):
time = self.events[0].time
# build str using MidiEvents
str = ""
for e in self.events:
str = str + e.write()
return "MTrk" + putNumber(len(str), 4) + str

def __repr__(self):
r = "<MidiTrack %d -- %d events\n" % (self.index, len(self.events))
for e in self.events:
r = r + "    " + `e` + "\n"
return r + "  >"

class MidiFile:

def __init__(self):
self.file = None
self.format = 1
self.tracks = [ ]
self.ticksPerQuarterNote = None
self.ticksPerSecond = None

def open(self, filename, attrib="rb"):
if filename == None:
if attrib in ["r", "rb"]:
self.file = sys.stdin
else:
self.file = sys.stdout
else:
self.file = open(filename, attrib)

def __repr__(self):
r = "<MidiFile %d tracks\n" % len(self.tracks)
for t in self.tracks:
r = r + "  " + `t` + "\n"
return r + ">"

def close(self):
self.file.close()

assert str[:4] == "MThd"
length, str = getNumber(str[4:], 4)
assert length == 6
format, str = getNumber(str, 2)
self.format = format
assert format == 0 or format == 1   # dunno how to handle 2
numTracks, str = getNumber(str, 2)
division, str = getNumber(str, 2)
if division & 0x8000:
framesPerSecond = -((division >> 8) | -128)
ticksPerFrame = division & 0xFF
assert ticksPerFrame == 24 or ticksPerFrame == 25 or \
ticksPerFrame == 29 or ticksPerFrame == 30
if ticksPerFrame == 29: ticksPerFrame = 30  # drop frame
self.ticksPerSecond = ticksPerFrame * framesPerSecond
else:
self.ticksPerQuarterNote = division & 0x7FFF
for i in range(numTracks):
trk = MidiTrack(i)
self.tracks.append(trk)

def write(self):
self.file.write(self.writestr())

def writestr(self):
division = self.ticksPerQuarterNote
# Don't handle ticksPerSecond yet, too confusing
assert (division & 0x8000) == 0
str = "MThd" + putNumber(6, 4) + putNumber(self.format, 2)
str = str + putNumber(len(self.tracks), 2)
str = str + putNumber(division, 2)
for trk in self.tracks:
str = str + trk.write()
return str

def main(argv):
global debugflag
import getopt
infile = None
outfile = None
printflag = 0
optlist, args = getopt.getopt(argv[1:], "i:o:pd")
for (option, value) in optlist:
if option == '-i':
infile = value
elif option == '-o':
outfile = value
elif option == '-p':
printflag = 1
elif option == '-d':
debugflag = 1

m = MidiFile()
m.open(infile)
m.close()

if printflag:
print m
else:
m.open(outfile, "wb")
m.write()
m.close()

if __name__ == "__main__":
main(sys.argv)