def process_track_chunk(data):
log.info("Parsing Track Chunk...")
events = []
running_status = None
while len(data) > 0:
data, delta = variable_length_field(data)
prefix = data[:8]
if prefix == F0_SYSEX_EVENT_PREFIX or prefix == F7_SYSEX_EVENT_PREFIX:
data, event = process_sysex_event(prefix, data[8:])
events.append((delta, event))
elif prefix == META_EVENT_PREFIX:
data, event = process_meta_event(data[8:])
events.append((delta, event))
else:
data, event, running_status = process_midi_event(data, running_status)
events.append((delta, event))
if events[-1][1]["sub_type"] != "End of Track":
raise Exception("End of Track event missing")
return {
"type": TRACK,
"events": events
}
def test_variable_length_decoding_of_0_returns_correct_result(self):
input = BitArray("0x00")
remainder, extracted = variable_length_field(input)
self.assertEqual(extracted, 0)
self.assertEqual(remainder, BitArray())
def test_variable_length_decoding_of_268435455_with_excess_data_returns_correct_result_and_correct_remainder(
self):
input = BitArray("0xFFFFFF7F12304FABC")
remainder, extracted = variable_length_field(input)
self.assertEqual(extracted, 268435455)
self.assertEqual(remainder, BitArray("0x12304FABC"))
def process_sysex_event(prefix, data):
data, length = variable_length_field(data)
if prefix == F0_SYSEX_EVENT_PREFIX:
subtype = "F0"
elif prefix == F7_SYSEX_EVENT_PREFIX:
subtype = "F7"
else:
raise Exception(
"Tried to process Sysex event but invalid prefix {} found.\nExiting..."
.format(prefix))
event = {"type": "SYSEX", "sub_type": subtype, "data": data[:8 * length]}
return data[:8 * length], event
def process_meta_event(data):
type = data[:8].hex
data, length = variable_length_field(data[8:])
event_data = data[:length * 8]
remainder = data[length * 8:]
event = {"type": META, "sub_type": "Unknown", "data": event_data}
# TODO make sure that these comparisons are case correct/case-insensitive
if type == "00":
# This is an optional event, which must occur only at the start of a track, before any non-zero delta-time.
#
# For Format 2 MIDI files, this is used to identify each track.If omitted, the sequences are numbered
# sequentially in the order the tracks appear.
#
# For Format 1 files, this event should occur on the first track only.
event["sub_type"] = "Sequence Number"
event["sequence_number"] = event_data[:length * 8].bytes
elif type == "01":
event["sub_type"] = "Text Event"
event["text"] = event_data[:length * 8].bytes
elif type == "02":
event["sub_type"] = "Copyright Notice"
event["text"] = event_data[:length * 8].bytes
elif type == "03":
event["sub_type"] = "Sequence/Track Name"
event["text"] = event_data[:length * 8].bytes
elif type == "04":
event["sub_type"] = "Instrument Name"
event["text"] = event_data[:length * 8].bytes
elif type == "05":
event["sub_type"] = "Lyric"
event["text"] = event_data[:length * 8].bytes
elif type == "06":
event["sub_type"] = "Marker"
event["text"] = event_data[:length * 8].bytes
elif type == "07":
event["sub_type"] = "Cue Point"
event["text"] = event_data[:length * 8].bytes
elif type == "20":
# MIDI Channel Prefix
# Associate all following meta-events and sysex-events with the specified MIDI channel, until the next
# <midi_event> (which must contain MIDI channel information).
if length != 1:
log.error("Channel Prefix Event has the wrong length!\nExiting...")
exit(1)
event["sub_type"] = "MIDI Channel Prefix"
event["channel"] = event_data[:8].hex
elif type == "21":
# MIDI Prefix Port
if length != 1:
print("MIDI Prefix Port event has the wrong length!\nExiting...")
exit(1)
event["sub_type"] = "MIDI Prefix Port"
event["device"] = event_data[:8]
elif type == "2f":
print("End of Track")
# This event is not optional.
# It is used to give the track a clearly defined length, which is essential information if the track is looped
# or concatenated with another track
if length:
print("End of Track event should not have any length!\nExiting...")
exit(1)
event["sub_type"] = "End of Track"
elif type == "51":
# Set Tempo
# This sets the tempo in microseconds per quarter note. This means a change in the unit-length of a delta-time
# tick. (note 1)
# If not specified, the default tempo is 120 beats/minute, which is equivalent to tttttt=500000
if length != 3:
print("Set Tempo event has the wrong length!\nExiting...")
exit(1)
event["sub_type"] = "Set Tempo"
event["new_tempo"] = event_data[:8 * 3]
elif type == "54":
# SMTPE Offset
# This (optional) event specifies the SMTPE time at which the track is to start.
# This event must occur before any non-zero delta-times, and before any MIDI events.
# In a format 1 MIDI file, this event must be on the first track (the tempo map).
if length != 5:
print("SMTPE Offset event has the wrong length!\nExiting...")
exit(1)
event["sub_type"] = "SMTPE Offset"
event["hours"] = event_data[:8]
event["minutes"] = event_data[8:16]
event["seconds"] = event_data[16:24]
event["frames"] = event_data[24:32]
event["fractional_frames"] = event_data[32:40]
elif type == "58":
# Time Signature
if length != 4:
print("Time Signature event has the wrong length!\nExiting...")
exit(1)
event["sub_type"] = "Time Signature"
event["numerator"] = event_data[:8].int
event["denominator"] = event_data[8:16].int
# MIDI clocks per metronome click
event["clocks_per_tick"] = event_data[16:24].int
# number of 1/32 notes per 24 MIDI clocks (8 is standard)
event["32nd_notes_per_24_clocks"] = event_data[24:32].int
elif type == "59":
# Key Signature
# Key Signature, expressed as the number of sharps or flats, and a major/minor flag.
# 0 represents a key of C, negative numbers represent 'flats', while positive numbers represent 'sharps'.
if length != 2:
print("Key Signature event has the wrong length!\nExiting...")
exit(1)
event["sub_type"] = "Key Signature"
event["sharps_flats"] = event_data[:8].int
event["major_minor"] = event_data[8:16].int
elif type == "7F":
# This is the MIDI-file equivalent of the System Exclusive Message.
# A manufacturer may incorporate sequencer-specific directives into a MIDI file using this event.
# consists of <id> + <data>, length is length of both of these fields combined
# <id> is either one or three bytes, and is the Manufacturer ID
# This value is the same as is used for MIDI System Exclusive messages
# <data> 8-bit binary data
event["sub_type"] = "Sequencer-Specific Meta-event"
event["data"] = event_data[:length * 8]
else:
log.warning("Unrecognised Meta event: {}".format(type))
return remainder, event