ojn file format information so far

file format breakdown

OJN file documentation

LITTLE ENDIAN

HEADER

INT       genre
FLOAT     bpm
short     easy-leve
short     med-level
short     hard-level
short     0 (always)
int[3]    event count (one for each diff)
int[3]    note counts (one for each diff)
int[3]    measure count
int[3]    package count (?)
short     old-encode-version
short     old-song-id
byte[20]  old_genre
int       bmp size
int       file version
byte[64]  title
byte[32]  artist
byte[32]  noter
byte[32]  ojm file
int       cover size
int       easy duration
int       med duration
int       hard duration
int       note-offset easy
int       note-offset med
int       note-offset hard
int       cover-offset


EVENTS

int       measure
short     chanel #
short     events count


BPM/Measure EVENT

float     v


NOTE EVENT

short     value
int       volume_pan
int       type

Notes on Channel number:

Chanel 0     Time signature
Given as a percentage of a full measure as a float

Chanel 1     BPM change 
BPM values are given as a float

Chanel 2-8   Note events 1-7

Chanel 9+    Autoplay events


Notes on note events:

short unknown1?
int volume_pan ?
int type (ignore 0)
float volume (1-15, 0 = MAX)
float pan (LEFT 1-8 center 8-15 right, 0=8)

if type mod 8 > 3 value+1000?

case (type mod 4)
0 = none
1 = unused
2 = hold
3 = release

notes from open2jam

***** Notes Section *****
Before diving into the notes section is important to define some terms:

events: The notes section doesn't just contain the notes, it also has the bpm
changes of the music (and other things that I got yet to found out), so I will
just call them events.

beat: Ever noticed those horizontal lines in between the notes during the music
? Those are the beats, and for all the notes before the first line we call them
beat 0, after the first we call them beat 1 and so on.

package: These are the blocks that form a note section, each package contain
one or more events inside. Each package correspond to a specifically beat in a
specific channel(see below). The number of packages in each section is in
the package_count variable in the header section.

Each package has a mini-header as follows:
struct package_header {
	 long32 beat;
	short16 channel;
	short16 events;
};

beat: This is the beat in which the package will appear.
channel: This determine the package type, so far a got these:
channel type
0       fractional measure
1       BPM change
2       note on 1st lane
3       note on 2nd lane
4       note on 3rd lane
5       note on 4th lane(middle button)
6       note on 5th lane
7       note on 6th lane
8       note on 7th lane
9 ~ ?   auto-play samples (?)

Each event has, as far as I know, 4 bytes, when the channel is 0 or 1
these 4 bytes are a float.

channel 0: represents how much of the measure to use, that is a value of 0.75 would make 
this measure only 75% the size of a normal measure( where the 'normal' size depends 
on the screen resolution and the hi-speed).

channel 1: is a BPM change, the number contains the new BPM to be used from that point on.

channel 2 ~ 8: the 4 bytes are divided like this:
struct note_event {
	short value;
	char unk;
	char type;
};
value: when value is 0 the event is ignored ( see below why), 
otherwise its the OJM sample reference(see below).

unk: It's usually 0, on V3 it has some values, but none on Red Sign, I'm
clueless.

type: 0 when it's is a normal note, 2 when it is the start of a long note,
and 3 at the end of a long note.

channel 9 ~ ?: 
These seems to be directions to auto-play samples, so far I think
they are divided in the same way the notes are, value also reference a sample on
the OJM, the OJM seems to have a distinct numbers for each sample but starts from 0,
interesting enough, the range of numbers for value seems to be equal but +1, 
also, in some songs, V3 for example, there are some with type = 4, and on the OJM
there are repeated reference numbers for these, I'm guessing that when type = 0
the value references a sample W###( as seen on notetool) and when type = 4 it's
a M### sample, now what difference it makes using one over another ? I don't know.

There also seems to have type = 2 and type = 3 for these channels, and in pairs like
if it was a long note, but I don't know how that would change the way the sample is
played.. perhaps the sample is looped over the interval ?. I don't know either.



As you could see, each package can have more than one event, in these cases,
the position of the event inside the beat is determined dividing the ocurrence
by the number of events. Example: if you got a package with 16 events, the 8th
event will be at the middle of the beat(8/16=0.5), that's probably why we have
those 'ignored events'(value = 0), they are there for padding the real events
in the right position inside the beat.


Well that's pretty much all, I still got to find out how the speed affect the
notes position, but I'm almost sure it simple changes the beat size, and the
beat size is probably scaled by the screen size.