这个真的是费了好大好大好的的劲才弄出来。。。

格式

头区块 (Head Chunk)

MThd + +

头区块字符长度 一般为 6

轨道区块 (Track Chunk)

Track Chunk = MTrk + +

区块字符长度 是 4 byte 的无符号长整型

= + ( | | )

时间戳 为用 VLQ 表示的相对于上一个数据点的时间变化量 (delta time)

= \xFF + + +

类型 为 1 byte 的字节，对照表在下文

数据长度 为用 VLQ 表示的数据块的字符数

例子

比如下面这段 bwv806a.mid 的前 200 字节：

MThd\x00\x00\x00\x06\x00\x01\x00\x04\x00\xf0MTrk\x00\x00\x00G\x00\xff\x03\x08untitled\x00\xffT\x05`\x00\x03\x00\x00\x00\xffX\x04\x0c\x03\x0c\x08\x00\xffY\x02\x00\x00\x00\xffQ\x03\x06EO\x83\x97h\xffQ\x03\x07\xa1 \x82h\xffQ\x03\t\xa3\x1b\x82h\xffQ\x03\x0c\xe5\x0e\x00\xff/\x00MTrk\x00\x00\n\xd9\x00\xff!\x01\x00\x00\xff\x03\x1bEnglish Suite 1, 1. Prelude\x00\xc0\x00\x00\xb0\x07d\x00\n@\x90p\x90Qk\x81pLkxIk\x82hEk`Q\x00\x18PkHL\x00\x00E\x00\x00I\x00\x18P\x00\x18Nk`N\x00\x18Lk`L\x00\x18Nk`N\x00\x18

翻译后如下：

MThd

\x00\x00\x00\x06

\x00\x01 \x00\x04 \x00\xf0

0, 0, Header, 1, 4, 240

MTrk

\x00\x00\x00 G # length of track

1, 0, Start_track

\x00 \xff \x03 \x08 untitled

1, 0, Title_t, "untitled" # Time0, METAEVENT, Type3, len8, data

\x00 \xff T \x05 `\x00\x03\x00\x00

1, 0, SMPTE_offset, 96, 0, 3, 0, 0

\x00 \xff X \x04 \x0c\x03\x0c\x08

1, 0, Time_signature, 12, 3, 12, 8

\x00 \xff Y \x02 \x00\x00

1, 0, Key_signature, 0, "major"

\x00 \xff Q \x03 \x06EO

1, 0, Tempo, 410959

\x83\x97 h \xff Q \x03 \x07\xa1 # 注意这里结尾\xa1后还有一个空白字符 ' '

1, 52200, Tempo, 500000

\x82 h \xff Q \x03 \ t \xa3

1, 52560, Tempo, 631579

\x1b\x82 h \xff Q \x03 \x0c\xe5\x0e

1, 52920, Tempo, 845070

\x00 \xff / \x00

1, 52920, End_track

MTrk

\x00\x00 \n \xd9

2, 0, Start_track

\x00 \xff ! \x01 \x00

2, 0, MIDI_port, 0

\x00 \xff \x03 \x1b English Suite 1, 1. Prelude

2, 0, Title_t, "English Suite 1, 1. Prelude"

\x00 \xc0 \x00

2, 0, Program_c, 0, 0

\x00 \xb0 \x07 d

2, 0, Control_c, 0, 7, 100

\x00 \n @

2, 0, Control_c, 0, 10, 64

\x90 p \x90 Q k

2, 2160, Note_on_c, 0, 81, 107

\x81 p LkxIk

2, 2400, Note_on_c, 0, 76, 107

\x82 h Ek

2, 2520, Note_on_c, 0, 73, 107

.......

程序

from struct import unpack

import time

def read_vlq(f):

result = ''

buffer = unpack('B', f.read(1))[0]

length = 1

while buffer > 127:

print(buffer)

result += '{0:{fill}{n}b}'.format(buffer-128, fill='0', n=7)

buffer = unpack('B', f.read(1))[0]

length += 1

result += '{0:{fill}{n}b}'.format(buffer, fill='0', n=7)

return int(result, 2), length

def parse_event(evt, param):

if 128 <= evt <= 143:

print('Note Off event.')

elif 144 <= evt <= 159:

print('Note On event.', unpack('>BB', param))

elif 176 <= evt <= 191:

print('Control Change.')

elif 192 <= evt <= 207:

print('Program Change.')

with open('bwv806a.mid', 'rb') as f:

print(f.read(200))

# HEADER

if f.read(4) != b'MThd':

raise Exception('not a midi file!')

print(f.read(4))

header_info = f.read(6)

print(unpack('>hhh', header_info))

''' ================================== '''

while True:

track_head = f.read(4)

if track_head != b'MTrk':

if track_head != b'':

print(f.read(20))

raise Exception('not a midi file!')

else:

break

# length of track

len_of_track = unpack('>L', f.read(4))[0]

# print('len_of_track ', len_of_track)

counter = 0

t = 0

last_event = None

while True:

delta_t, len_ = read_vlq(f)

counter += len_

t += delta_t

# print('T ', t, end='')

event_code = f.read(1)

event_type = unpack('>B', event_code)[0]

counter += 1

# print(' event_type ', event_type, end='')

if event_type == 255:

meta_type = f.read(1)

counter += 1

# print(' - meta_type ', meta_type, end='')

data_len, len_= read_vlq(f)

counter += len_

data = f.read(data_len)

counter += data_len

# print(' - ', data)

elif event_type <= 127:

parse_event(last_event, event_code+f.read(1))

counter += 1

else:

if 128 <= event_type <= 143:

# print(' Note Off event.', end='')

parse_event(event_type, f.read(2))

counter += 2

elif 144 <= event_type <= 159:

# print(' Note On event.', end='')

parse_event(event_type, f.read(2))

counter += 2

elif 176 <= event_type <= 191:

# print(' Control Change.', end='')

parse_event(event_type, f.read(2))

counter += 2

elif 192 <= event_type <= 207:

# print(' Program Change.', end='')

parse_event(event_type, f.read(1))

counter += 1

last_event = event_type

# print(counter)

if counter == len_of_track:

break

参考资料：