midiparser.py

# Placed into Public Domain in June 2006 by Sean D. Spencer

# Sean D. Spencer
# sean_don4@lycos.com
# 2/19/2006
# Last Revision: 4/19/2007

# MIDI Parsing Library for Python.

import sys

TRUE = -1
FALSE = 0

class format:
    SingleTrack = 0
    MultipleTracksSync = 1
    MultipleTracksAsync = 2

class voice:
    NoteOff = 0x80
    NoteOn = 0x90
    PolyphonicKeyPressure = 0xA0 # note aftertouch
    ControllerChange = 0xB0
    ProgramChange = 0xC0
    ChannelPressure = 0xD0
    PitchBend = 0xE0

class meta:
    FileMetaEvent = 0xFF
    SMPTEOffsetMetaEvent = 0x54
    SystemExclusive = 0xF0
    SystemExclusivePacket = 0xF7
    SequenceNumber = 0x00
    TextMetaEvent = 0x01
    CopyrightMetaEvent = 0x02
    TrackName = 0x03
    InstrumentName = 0x04
    Lyric = 0x05
    Marker = 0x06
    CuePoint = 0x07
    ChannelPrefix = 0x20
    MidiPort = 0x21
    EndTrack = 0x2F
    SetTempo = 0x51
    TimeSignature = 0x58
    KeySignature = 0x59
    SequencerSpecificMetaEvent = 0x7F

class EventNote:
    def __init__(self):
	self.note_no = None
	self.velocity = None

class EventValue:
    def __init__(self):
	self.type = None
	self.value = None

class EventAmount:
    def __init__(self):
	self.amount = None

class MetaEventKeySignature:
    def __init__(self):
	self.fifths = None
	self.mode = None

class MetaEventTimeSignature:
    def __init__(self):
	self.numerator = None
	self.log_denominator = None
	self.midi_clocks = None
	self.thirty_seconds = None

class MetaEventText:
    def __init__(self):
	self.length = None
	self.text = None

class MetaEventSMPTEOffset:
    def __init__(self):
	self.hour = None
	self.minute = None
	self.second = None
	self.frame = None
	self.sub_frame = None

class MetaValues:
    def __init__(self):
	self.length = None
	self.values = None

def getNumber(theString, length):
    # MIDI uses big-endian for everything
    sum = 0
    #print "Length: " + str(length) + "  strlen: " + str(len(theString))
    for i in range(length):
        #sum = (sum *256) + int(str[i])
	sum = (sum << 8) + ord(theString[i])
    return sum, theString[length:]

def getVariableLengthNumber(str):
    sum = 0
    i = 0
    while 1:
        x = ord(str[i])
        i = i + 1
	# sum = (sum * 127) + (x (mask) 127) # mask off the 7th bit
        sum = (sum << 7) + (x & 0x7F)
	# Is 7th bit clear?
        if not (x & 0x80):
            return sum, str[i:]

def getValues(str, n=16):
    temp = []
    for x in str[:n]:
	temp.append(repr(ord(x)))
    return temp

class File:
    def __init__(self, file):
        self.file = file
        self.format = None
	self.num_tracks = None
	self.division = None
        self.tracks = []

	self.file = open(self.file, 'rb')
	str = self.file.read()
	self.file.close()

	self.read(str)

    def read(self, str):
	assert str[:4] == "MThd"
	str = str[4:]

	length, str = getNumber(str, 4)
	assert length == 6

	self.format, str = getNumber(str, 2)

	self.num_tracks, str = getNumber(str, 2)
	self.division, str = getNumber(str, 2)

	for i in range(self.num_tracks):
	    track = Track(i+1)
	    str = track.read(str)
	    self.tracks.append(track)

class Track:
    def __init__(self, index):
	self.number = index
	self.length = None
	self.events = []

    def read(self, str):
	self.length, str = getNumber(str[4:], 4)
	track_str = str[:self.length]

	prev_absolute = 0
	prev_status = 0

	i = 0
	while track_str:
	    event = Event(self.number, i+1)
	    track_str = event.read(prev_absolute, prev_status, track_str)

	    prev_absolute += event.delta
	    prev_status = event.status
	    self.events.append(event)
	    i += 1

	return str[self.length:]

class Event:
    def __init__(self, track, index):
	self.number = index
	self.type = None
	self.delta = None
	self.absolute = None
	self.status = None
	self.channel = None

    def read(self, prev_time, prev_status, str):
	self.delta, str = getVariableLengthNumber(str)
	self.absolute = prev_time + self.delta

	# use running status?
	if not (ord(str[0]) & 0x80):
	    # squeeze a duplication of the running status into the data string
	    str = prev_status + str

	self.status = str[0]
	self.channel = ord(self.status) & 0xF

	# increment one byte, past the status
	str = str[1:]

	has_channel = has_meta = TRUE

	# handle voice events
	channel_msg = ord(self.status) & 0xF0
	if channel_msg == voice.NoteOn or \
		channel_msg == voice.NoteOff or \
		channel_msg == voice.PolyphonicKeyPressure:
	    self.detail = EventNote()
	    self.detail.note_no = ord(str[0])
	    self.detail.velocity = ord(str[1])
	    str = str[2:]

	elif channel_msg == voice.ControllerChange:
	    self.detail = EventValue()
	    self.detail.type = ord(str[0])
	    self.detail.value = ord(str[1])
	    str = str[2:]

	elif channel_msg == voice.ProgramChange or \
		channel_msg == voice.ChannelPressure:

	    self.detail = EventAmount()
	    self.detail.amount = ord(str[0])
	    str = str[1:]

	elif channel_msg == voice.PitchBend:
	    # Pitch bend uses high accuracy 14 bit unsigned integer.
	    self.detail = EventAmount()
	    self.detail.amount = (ord(str[0]) << 7) | ord(str[1])
	    str = str[2:]

	else: has_channel = FALSE

	# handle meta events
	meta_msg = ord(self.status)
	if meta_msg == meta.FileMetaEvent:

	    meta_msg = type = ord(str[0])
	    length, str = getVariableLengthNumber(str[1:])

	    if type == meta.SetTempo or \
		    type == meta.ChannelPrefix:

		self.detail = EventAmount()
		self.detail.tempo, str  = getNumber(str, length)

	    elif type == meta.KeySignature:
		self.detail = MetaEventKeySignature()
		self.detail.fifths = ord(str[0])

		if ord(str[1]): self.detail.mode = "minor"
		else: self.detail.mode = "major"

		str = str[length:]

	    elif type == meta.TimeSignature:
		self.detail = MetaEventTimeSignature()
		self.detail.numerator = ord(str[0])
		self.detail.log_denominator = ord(str[1])
		self.detail.midi_clocks = ord(str[2])
		self.detail.thirty_seconds = ord(str[3])
		str = str[length:]

	    elif type == meta.TrackName or \
		    type == meta.TextMetaEvent or \
		    type == meta.Lyric or \
		    type == meta.CuePoint or \
		    type == meta.CopyrightMetaEvent:

		self.detail = MetaEventText()
		self.detail.length = length
		self.detail.text = str[:length]
		str = str[length:]

	    elif type == meta.SMPTEOffsetMetaEvent:
		self.detail = MetaEventSMPTEOffset()
		self.detail.hour = ord(str[0])
		self.detail.minute = ord(str[1])
		self.detail.second = ord(str[2])
		self.detail.frame = ord(str[3])
		self.detail.sub_frame = ord(str[4])
		str = str[length:]

	    elif type == meta.EndTrack:
		str = str[length:] # pass on to next track

	    else: has_meta = FALSE

	elif meta_msg == meta.SystemExclusive or \
		meta_msg == meta.SystemExclusivePacket:
	    self.detail = MetaValues()
	    self.detail.length, str = getVariableLengthNumber(str)
	    self.detail.values = getValues(str, self.detail.length)
	    str = str[self.detail.length:]

	else: has_meta = FALSE

	if has_channel:
	    self.type = channel_msg
	elif has_meta:
	    self.type = meta_msg
	else:
	    #raise "Unknown event."
            self.type = None
	return str