# Logiciels > Solutions d'entreprise > BPM >  [FMODex] Rcuperer le "bpm" d'un fichier midi

## remax_ren

Bonjour,
Je cherche avec FmodEx, que j'utilise pour mon projet (plus prcisment, j'utilise nativeFmodEx, qui permet l'utilisation de la lib Fmod en java),  rcuprer des infos sur un fichier midi.
Plus prcisment, le bpm (beats per minute).
J'ai eu beau chercher dans les exemples, j'ai rien trouv.
Je connais pas trop la structure des fichiers midi, mais je suppose que cette info (ou d'autres infos relatives au tempo) est stocke quelque part dans le fichier. Une piste tempo peut etre.

Si vous avez des infos la dessus, je suis preneur.
Merci d'avance!

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## Rmi Coquet

Un incontournable: *Maximum Midi* - Writing Music Applications In C

Un petit bout d'autre chose, dans lequel tu trouveras dj quelques bases simplistes:

Standard MIDI File Format
Dustin Caldwell
The standard MIDI file format is a very strange beast. When viewed as a
whole, it can be quite overwhelming. Of course, no matter how you look at it,
describing a piece of music in enough detail to be able to reproduce it
accurately is no small task. So, while complicated, the structure of the midi
file format is fairly intuitive when understood. 
I must insert a disclaimer here that I am by no means an expert with
midi nor midi files. I recently obtained a Gravis UltraSound board for my PC,
and upon hearing a few midi files (.MID) thought, "Gee, I'd like to be able to
make my own .MID files." Well, many aggravating hours later, I discovered that
this was no trivial task. But, I couldn't let a stupid file format stop me.
(besides, I once told my wife that computers aren't really that hard to use,
and I'd hate to be a hypocrite) So if any errors are found in this
information, please let me know and I will fix it. Also, this document's scope
does not extend to EVERY type of midi command and EVERY possible file
configuration. It is a basic guide that should enable the reader (with a
moderate investment in time) to generate a quality midi file.
1. Overview
A midi (.MID) file contains basically 2 things, Header chunks and Track
chunks. Section 2 explains the header chunks, and Section 3 explains the track
chunks. A midi file contains ONE header chunk describing the file format,
etc., and any number of track chunks. A track may be thought of in the same
way as a track on a multi-track tape deck. You may assign one track to each
voice, each staff, each instrument or whatever you want. 
2. Header Chunk
The header chunk appears at the beginning of the file, and describes the
file in three ways. The header chunk always looks like:
4D 54 68 64 00 00 00 06 ff ff nn nn dd dd
The ascii equivalent of the first 4 bytes is MThd. After MThd comes the 4-byte
size of the header. This will always be 00 00 00 06, because the actual header
information will always be 6 bytes. 
ff ff is the file format. There are 3 formats:
0 - single-track 
1 - multiple tracks, synchronous
2 - multiple tracks, asynchronous
Single track is fairly self-explanatory - one track only. Synchronous multiple
tracks means that the tracks will all be vertically synchronous, or in other
words, they all start at the same time, and so can represent different parts
in one song. Asynchronous multiple tracks do not necessarily start at the same
time, and can be completely asynchronous. 
nn nn is the number of tracks in the midi file.
dd dd is the number of delta-time ticks per quarter note. (More about this
later)

3. Track Chunks
The remainder of the file after the header chunk consists of track chunks.
Each track has one header and may contain as many midi commands as you like.
The header for a track is very similar to the one for the file:
4D 54 72 6B xx xx xx xx
As with the header, the first 4 bytes has an ascii equivalent. This one is
MTrk. The 4 bytes after MTrk give the length of the track (not including the
track header) in bytes. 
Following the header are midi events. These events are identical to the
actual data sent and received by MIDI ports on a synth with one addition. A
midi event is preceded by a delta-time. A delta time is the number of ticks
after which the midi event is to be executed. The number of ticks per quarter
note was defined previously in the file header chunk. This delta-time is a
variable-length encoded value. This format, while confusing, allows large
numbers to use as many bytes as they need, without requiring small numbers to
waste bytes by filling with zeros. The number is converted into 7-bit bytes,
and the most-significant bit of each byte is 1 except for the last byte of the
number, which has a msb of 0. This allows the number to be read one byte at a
time, and when you see a msb of 0, you know that it was the last (least
significant) byte of the number. According to the MIDI spec, the entire delta-
time should be at most 4 bytes long. 
Following the delta-time is a midi event. Each midi event (except a
running midi event) has a command byte which will always have a msb of 1 (the
value will be >= 128). A list of most of these commands is in appendix A. Each
command has different parameters and lengths, but the data that follows the
command will have a msb of 0 (less than 128). The exception to this is a meta-
event, which may contain data with a msb of 1. However, meta-events require a
length parameter which alleviates confusion. 
One subtlety which can cause confusion is running mode. This is where
the actual midi command is omitted, and the last midi command issued is
assumed. This means that the midi event will consist of a delta-time and the
parameters that would go to the command if it were included. 
4. Conclusion
If this explanation has only served to confuse the issue more, the
appendices contain examples which may help clarify the issue. Also, 2
utilities and a graphic file should have been included with this document: 
DEC.EXE - This utility converts a binary file (like .MID) to a tab-delimited
text file containing the decimal equivalents of each byte.
REC.EXE - This utility converts a tab-delimited text file of decimal values
into a binary file in which each byte corresponds to one of the decimal
values.
MIDINOTE.PS - This is the postscript form of a page showing note numbers with
a keyboard and with the standard grand staff.
Appendix A
1. MIDI Event Commands
Each command byte has 2 parts. The left nybble (4 bits) contains the actual
command, and the right nybble contains the midi channel number on which the
command will be executed. There are 16 midi channels, and 8 midi commands (the
command nybble must have a msb of 1).
In the following table, x indicates the midi channel number. Note that all
data bytes will be <128 (msb set to 0).
Hex Binary Data Description
8x 1000xxxx nn vv Note off (key is released)
nn=note number
vv=velocity
9x 1001xxxx nn vv Note on (key is pressed)
nn=note number
vv=velocity
Ax 1010xxxx nn vv Key after-touch
nn=note number
vv=velocity
Bx 1011xxxx cc vv Control Change
cc=controller number
vv=new value
Cx 1100xxxx pp Program (patch) change
pp=new program number
Dx 1101xxxx cc Channel after-touch
cc=channel number
Ex 1110xxxx bb tt Pitch wheel change (2000H is normal or no
change)
bb=bottom (least sig) 7 bits of value
tt=top (most sig) 7 bits of value
The following table lists meta-events which have no midi channel number. They
are of the format:
FF xx nn dd
All meta-events start with FF followed by the command (xx), the length, or
number of bytes that will contain data (nn), and the actual data (dd).
Hex Binary Data Description
00 00000000 nn ssss Sets the track's sequence number.
nn=02 (length of 2-byte sequence number)
ssss=sequence number
01 00000001 nn tt .. Text event- any text you want.
nn=length in bytes of text
tt=text characters
02 00000010 nn tt .. Same as text event, but used for
copyright info.
nn tt=same as text event
03 00000011 nn tt .. Sequence or Track name
nn tt=same as text event
04 00000100 nn tt .. Track instrument name
nn tt=same as text event
05 00000101 nn tt .. Lyric
nn tt=same as text event
06 00000110 nn tt .. Marker
nn tt=same as text event
07 00000111 nn tt .. Cue point
nn tt=same as text event
2F 00101111 00 This event must come at the end of each
track
51 01010001 03 tttttt Set tempo
tttttt=microseconds/quarter note
58 01011000 04 nn dd ccbb Time Signature
nn=numerator of time sig.
dd=denominator of time sig. 2=quarter
3=eighth, etc.
cc=number of ticks in metronome click
bb=number of 32nd notes to the quarter
note
59 01011001 02 sf mi Key signature
sf=sharps/flats (-7=7 flats, 0=key of C,
7=7 sharps)
mi=major/minor (0=major, 1=minor)
7F 01111111 xx dd .. Sequencer specific information
xx=number of bytes to be sent
dd=data 
The following table lists system messages which control the entire system.
These have no midi channel number. (these will generally only apply to
controlling a midi keyboard, etc.)
Hex Binary Data Description
F8 11111000 Timing clock used when synchronization is
required.
FA 11111010 Start current sequence
FB 11111011 Continue a stopped sequence where left
off
FC 11111100 Stop a sequence

The following table lists the numbers corresponding to notes for use in note 
on and note off commands.

Octave|| Note Numbers
# ||
|| C | C# | D | D# | E | F | F# | G | G# | A | A# | B
-----------------------------------------------------------------------------
0 || 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11
1 || 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23
2 || 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35
3 || 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47
4 || 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59
5 || 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71
6 || 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83
7 || 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95
8 || 96 | 97 | 98 | 99 | 100 | 101 | 102 | 103 | 104 | 105 | 106 | 107
9 || 108 | 109 | 110 | 111 | 112 | 113 | 114 | 115 | 116 | 117 | 118 | 119
10 || 120 | 121 | 122 | 123 | 124 | 125 | 126 | 127 |

BIBLIOGRAPHY
"MIDI Systems and Control" Francis Rumsey 1990 Focal Press
"MIDI and Sound Book for the Atari ST" Bernd Enders and Wolfgang Klemme
1989 M&T Publishing, Inc.
MIDI file specs and general MIDI specs were also obtained by sending e-mail
to LISTSERV@AUVM.AMERICAN.EDU with the phrase GET MIDISPEC PACKAGE
in the message.

------------------------------- DEC.CPP ------------------------------------


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## remax_ren

merci, a fait de la doc  potasser.
Je posterai ici mes avances (si il y en a!)

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## Invit

Salut Remax,
Tu as ta rponse dans la doc ci-dessus comme suit :



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Delta-time ticks, si ma mmoire est bonne , est une constante.  
M'enfin ce n'est pas trs grave car il faut fouiner un peu. 
En premier lieu, procure toi un sequencer midi : Sonar LE 2004 ou Cubase LE sont fournis en bundle avec des synths et installables sans dongle donc si tu n'en as pas encore , procure t'en un ou va chez un pote qui en est quip.

2. Produire une srie de midifiles vides ou copies depuis une dj existante en modifiant seulement le tempo. P.ex. :
-monMorceau_90.mid
-monMorceau_100.mid
-monMorceau_120.mid

3. dans ton code : ouvre le fichier .mid en binary (obligatoire)
4. charge tout le header chunk dans un buffer ou bien va lire les bytes 13 et 14
5. Pour chaque dclinaison de fichier mid , regarde comment est cod le tempo dans les bytes 13 et 14 
On peut le faire plus vite avec un dumper hexa

Attention les bytes de poids fort et faible  peuvent tre inverss (Intel) ou non (Motorola) 

Aprs avoir vrifi les trois fichiers il faut retrouver la valeur du ratio 'Delta ticks' 
Ou plus simplement reproduire le tempo qui t'interresse aprs avoir vrifi au dumper hexa comment le sequencer le code aux bytes 13 et 14 du fichier mid donc

D'aprs mes souvenirs, le comptage des intervalles d'vnements midi s'appuient aussi sur ce delta tick qui est assez horrible  encoder mais pour le tempo , c'est _relativement_ simple.

Bon courage

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## Invit

Serait-il possible d'ouvrir un forum midi qui ne soit pas trop mlang aux formats soundtrackers.

Midi est quand mme trs diffrent des soundtrackers (genre mod, st3,...) et a une vie autrement excitante : systmes professionnels. 
Soundtracker a toujours t aussi gnial que minimal. Aucun de ces formats n'a jamais vraiment march chez les pros du spectacle alors que midi est incontournable.

Les outils midi ont une philosophie trs diffrente.

Cherchez Keykit sur google par exemple..

En language de prog midi , il y a aussi CAL chez roland (sonar) et toute une famille de logiciels trs utilisables chez les professionnels alors qu'une squence soundtracker est quasiment inexploitable ailleurs tant qu'on ne la convertit pas.   D'autre part, les musiciens soundtracker ont quand mme trs peu de dbouchs et les logiciels restent trs frustes.  Un musicien est quasiment oblig de migrer vers le midi dont les logiciels sont extrmement matures

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## LittleWhite

> Serait-il possible d'ouvrir un forum midi qui ne soit pas trop mlang aux formats soundtrackers.
> 
> Midi est quand mme trs diffrent des soundtrackers (genre mod, st3,...) et a une vie autrement excitante : systmes professionnels. 
> Soundtracker a toujours t aussi gnial que minimal. Aucun de ces formats n'a jamais vraiment march chez les pros du spectacle alors que midi est incontournable.
> 
> Les outils midi ont une philosophie trs diffrente.
> 
> Cherchez Keykit sur google par exemple..
> 
> En language de prog midi , il y a aussi CAL chez roland (sonar) et toute une famille de logiciels trs utilisables chez les professionnels alors qu'une squence soundtracker est quasiment inexploitable ailleurs tant qu'on ne la convertit pas.   D'autre part, les musiciens soundtracker ont quand mme trs peu de dbouchs et les logiciels restent trs frustes.  Un musicien est quasiment oblig de migrer vers le midi dont les logiciels sont extrmement matures


Un nouveau forum ? Pour la programmation avec bibliothque sonore, non je ne pense pas. Nous avons un message par semaine sur le FMOD ( et encore moins ). Deux ou trois sur Midi...
Je ne pense pas que ce soit assez pour sous catgoris encore plus.

Sinon, les fichiers track .mod .xm ... et autre beaut de ce genre, sont du mme niveau que le .midi, mais pour une utilisation diffrente.
Je ne vais pas refaire une guerre, mais les .mod est tout a ( Atari / Amiga ) tait trs utilis et trs performant. 
Le midi aussi, mais c'est surtout pour de la communication entre priphrique ( et stockage si possible ).
Le midi devrait avanc de nos jours, mais toujours pas de nouvelle norme.

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