Schema

This page gives a top-down view of how a memon file is structured

Root

{
    "version": "x.y.z",
    "metadata": {},
    "timing": {},
    "data": {}
}

This is the root / top level structure of a memon file.

It’s a json object with the following keys :

version
- string, required
- Indicates the schema version this memon file uses, follows semver. If a memon file does not have this key it’s probably following the pre-semver format
metadata
- object, optional
- Contains the metadata object
timing
- object, optional
- Contains the default / fallback timing object
- See Multiple Timing Objects for more details on the behavior this should have
data
- object, required
- Contains the data object

{
    "title": "",
    "artist": "",
    "audio": "",
    "jacket": "",
    "preview": {},
}

Contains information that applies to the whole set of charts

title
- string, optional
- Song title
artist
- string, optional
audio
- string, optional
- Path to the music file, relative to the memon file.
jacket
- string, optional
- Relative path to the jacket / album cover / album art to be shown in music select for example. usually a square image.
preview
- object or string, optional
- Contains either a preview object or a path to a bms-style preview file

{
    "start": 0.0,
    "duration": 0.0,
}

Describes the part of the music file that’s meant to be played on loop when previewing this song at the music select screen

start
- number or string, required
- In seconds, start of the loop
- Positive
- Strings allowed for easier decimal representation preservation
duration
- number or string, required
- In seconds, duration of the loop
- Strictly positive
- Strings allowed for easier decimal representation preservation

{
    "offset": 0,
    "resolution": 240,
    "bpms": [],
    "hakus": []
}

Describes the relationship between seconds in the audio file and symbolic time (time measured in beats)

offset
- number or string, optional
- If the key is missing, defaults to 0
- In seconds, time at which the first beat occurs in the music file.
  
  For instance, if the first beat occurs at 0.15 seconds in the audio file, the offset should be the number literal 0.15, or the string "0.15" if the tools used can’t keep a clean decimal representation when using json number literals.
resolution
- integer, optional
- Greater than 0, always an integer
- If the key is missing, defaults to 240
- Number of ticks in a beat for the bpm events defined in this timing object, if some bpm events define a beat using a single integer, this is the implicit fraction denominator to use to convert the integer number of ticks to a fractional number of beats.
bpms
- array, optional
- If the key is missing, defaults to
```
[{"beat": 0, "bpm": 120}]
```
- Array of BPM events
hakus
- array, optional
- If the key is missing, default to the regular background bounce pattern
- HAKUs (named after the HAKU command in .eve files) describe how the background animation should bounce along with the music, most songs just leave a default regular patterns that makes the background bounce on every beat, but some songs use these commands as a gimmick. In that sense they are similar to beat lines in BMS

Timing objects can appear in multiple places in a memon file. The section Multiple Timing Objects explains how to deal with them.

{
    "beat": 0,
    "bpm": 120
}

Defines a change in tempo measured in beats per minutes happening at a specific symbolic time (measured in beats)

beat
- symbolic time, required
- Beat at which the tempo changes
bpm
- number or string
- Song tempo at the given beat, in Beats per Minute.
- Striclty positive
- Strings allowed for easier decimal representation preservation

{
    "BSC": {},
    "ADV": {},
    "...": {},
    "My cool chart": {}
}

The data object maps difficulty names to chart objects.

Keys in this object are not fixed, they can be any string.

By convention, "BSC", "ADV" and "EXT" are to be understood as the usual 3 levels found in jubeat. Other values are “edits” or bonus charts.

When sorting, difficulties may be presented in that order :

BSC ➔ ADV ➔ EXT ➔ (everything else in alphabetical order)

{
    "level": 10.3,
    "resolution": 240,
    "timing": {},
    "notes": []
}

level
- number or string, optional
- Chart level, can be an integer or a decimal value, or even a string holding a decimal number
resolution
- integer, optional
- Greater than 0, always an integer
- If the key is missing, defaults to 240
- Number of ticks in a beat for all the notes in the chart, see Symbolic Time
timing
- Timing object, optional
- Chart-specific timing information
- See Multiple Timing Objects for more details on the behavior this should have
notes
- array, required
- Array of tap notes and long notes that make up the chart

{
    "n": 0,
    "t": 3600,
}

A classic note.

{
    "n": 0,
    "t": 3600,
    "l": 10000,
    "p": 5
}

A classic long note, with a tail

n : same as in a tap note
t : same as in a tap note
l
- Symbolic Time, required
- If a number, strictly positive
- If an array, l[0] and l[1] cannot both be zero at the same time
- Long note duration in ticks or beats
p
- number, required
- Integer between 0 and 5 inclusive
- Tail starting position in 6-notation :
  
  For every given button on the controller, there are 6 possible starting positions for long note tails.
  
  For example if the long note is held here :
```
□□□□
□□□□
□■□□
□□□□
```
  the long note’s tail can start on any of the six squares marked with an × :
```
□×□□
□×□□
×■××
□×□□
```
  6-notation labels these 6 possibilities this way :
  - 0, 1, 2 : horizontal tails from left to right
  - 3, 4, 5 : vertical tails from top to bottom
  If we replace ×s with the numbers we get :
```
□3□□
□4□□
0■12
□5□□
```
  For example, "p": 0 produces the following long note :
```
□□□□
□□□□
▷■□□
□□□□
```
  and "p": 3 gives :
```
□▽□□
□|□□
□■□□
□□□□
```

Either an integer like 0 or an array like [0, 2, 3].

Represents a time point (or a duration) measured in beats

integer greater or equal to 0
Time measured in ticks :

Ticks are fractions of the beat. Using ticks implies a resolution is defined somewhere else in the file. The resolution defines how many ticks are in a beat. In other words if the resolution is 240, a tick lasts for 1/240th of a beat.

For more info about measuring time in ticks, see bmson’s docs (their docs refers to ticks as pulses).