MIDIProtocol
craig@ccrma.stanford.edu
21January2016
Bytes
MIDIprotocolandMIDIfilesarebasedonbytes
Bytes
•  Bytesare8-digitbinarydigits(states)
•
00000000—11111111
TotalnumberofconfiguraGonsofthe8digits:
bit=BinarydigIT
28=256
•  RepresenGngasanunsignedinteger:
0—255
•  RepresenGngasa2’scomplimentsignedinteger(sGll256states):
0—127,-128—-1
PosiGonalnotaGonofnumbers
hSps://en.wikipedia.org/wiki/PosiGonal_notaGon
•  Whatdoes“365”mean?
PosiGonalnotaGonofnumbers
hSps://en.wikipedia.org/wiki/PosiGonal_notaGon
•  Whatdoes“365”mean?
365=300+60+5
365=3x100+6x10+5x1
365=3x102+6x101+5x100
3 6 5
DigitposiGon:
2
1
0
BinaryNumbers
Whatisthebinarynumber10110indecimalposiGonalnotaGon(base-10)?
101102
1x24+0x23+1x22+1x21+0x20
16+0+4+2+0
2210
HexadecimalNumbers
•  Hexadecimaluses16astheposiGonalbase.
•  DigitsrepresenGng“10”through“15”aretheleSers“A”through“F”
A16=1010
B16=1110
C16=1210
D16=1310
E16=1410
F16=1510`
HexvsBinaryvsDecimal
•  Computersoperateinternallywithbinary(on/offstates)
•  ConverGng011010102todecimalisnon-trivial(addlotsofpowersoftwo)
•  ConverGng011010102tohexadecimalistrivial(memorize16conversions)because
everyfourbinarydigitsrepresentonehexdigit(“nibble”).
011010102:
011010102
01101010
4+28+2
6A
6A16
011010102
64+32+8+2
10610
UsefulConversiontoKnow
111111112=FF16=25510
2’scomplimentinterpretaGon:
=-110
011111112=7F16=12710
100000002=8016=12810
Note:FFhand0xFFarealternatewaysofindicaGnghex.
OtherPosiGonalBases
hSp://wiki.ccarh.org/images/9/92/Hexadecimal_numbers.pdf
Tallymarks(base-1):
24
Sexagesimal(Base-60)
hSps://en.wikipedia.org/wiki/Sexagesimal
Developed~5000yearsagobySumerians
(c.1800–1600BCE)
Minutes/Seconds:
1;24,51,10=1+24/601+51/602+10/603
=1.41421296≈√2
12’3’’+16’42”=20’12”
MIDIBytes
MIDIData/CommandBytes
0—127
Databytes
128—255
Commandbytes
10000000
2—011111112
80h—FFh
000000002—01111111
2
7-BITS
00h—7Fh
MIDICommands
Command
nibble
8_
9_
A_
B_
Note-off
Note-on
Apertouch
XY
C_
D_
E_
F_
ConGnuouscontroller
Channel
nibble
Patchchange
ChannelPressure
Pitchbend
Systemmessages
MIDICommandParameters
=databyte(numberbetween0and127)
Note-off
Note-on
Apertouch
ConGnuous
controller
8_
9_
A_
B_
C_
D_
E_
F_
velocity
Patch
change
key
velocity
Channel
pressure
key
pressure
Pitchbend
controller
value
System
messages
key
instrument
pressure
LSB
MSB
(usually0exceptsysex)
RunningStatus
REGULARMESSAGING:
903C48913E52913E00903C 00
RUNNINGSTATUS(removerepeatedcommandbytes):
903C48913E523E00903C00
ReconstrucGngregularmessages
903C48913E52 (91) 3E00903C00
AlternateNote-OffCommands
8_commandsarefornote-offmessages:
803C64
=turnoffnote60(0x3C,middleC)
Withareleasevelocityof100(64h)
Butalsoacommonnote-offshorthand:
903C00
=turnoffnote60(0x3C,middleC)
Withundefinedreleasevelocity
•  Sosopestsoundingnotehasdatabyteof01,not00.
Cinmidi
hSp://wiki.ccarh.org/wiki/Cinmidi
“Console-InMIDI”:DisplayincomingMIDImessagesinterminalwithGmestamps.
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0
30
128
7
23
109
25
98
4
102
28
109
Style:
Timing:
Message format:
Format:
Command-line:
Input Port:
Cpu Speed:
0x90
0x80
0x90
0x80
0x90
0x90
0x80
0x90
0x80
0x80
0x90
0x80
default
delta milliseconds
delta-time, MIDI command-byte, MIDI parameter-byte(s)
asciimidi 1.0
cinmidi -o invention13-28.txt -p 1
1:
1000 MHz
64 88
45 64
69 88
64 64
57 87
72 91
69 64
71 91
72 64
71 64
64 104
57 64
;
;
;
;
;
;
;
;
;
;
;
;
NOTE chan:1 key:E4 vel:88
NOTEOFF chan: 1 key:A2 vel:
NOTE chan:1 key:A4 vel:88
NOTEOFF chan: 1 key:E4 vel:
NOTE chan:1 key:A3 vel:87
NOTE chan:1 key:C5 vel:91
NOTEOFF chan: 1 key:A4 vel:
NOTE chan:1 key:B4 vel:91
NOTEOFF chan: 1 key:C5 vel:
NOTEOFF chan: 1 key:B4 vel:
NOTE chan:1 key:E4 vel:104
NOTEOFF chan: 1 key:A3 vel:
64
64
64
64
64
64