OTO Compatibility

Project OutFox is working on a new OTO notesloader that supports the .osu (Osu) chart format, which is the standard format used in conjunction with the kb and taiko game types. The following page contains details on the .osu parsing options that Project OutFox currently supports. This is a living document - it will be updated as time allows and we add the support or features within.

This documentation exists as a mental ’layout’ for me to learn about the format and how best to parse it for the way OutFox needs. It will be updated in a few segments - There may be errors, but do let me know so i can update and clarify them, thanks for joining me on this ride! - (Squirrel)

We are calling it the OTO parser as we chose to follow the Osu Tatakae Ouendan name.

.osu is a format containing information about Osu beatmaps, which confusingly contain charts for other game modes as well. We use the term chart around the Scrolling Rhythm Game genre, because we do not use specific co-ordinates like on a map. The Osu Tatakae Ouendan mode uses both x and y mapping for the circles, curves and spinners etc, so this is why a lot of players who play the game call the other modes’ charts beatmaps, because of the original game.

Although catch, taiko and mania do not use co-ordinate systems, similar to almost all the other modes in OutFox, they inherit the beatmap definition by players of the game.

Throughout this page, we will be using the chart term, as we do not support the Osu Tatakae Ouendan (Mode=0) mode, as we have no way of mapping the circles/hit objects to the screen at this time.

.osu files are constructed using sections which contain content within to describe and give information about the map or chart detailed within. Each file will only contain one set of data; it is not like SSC or DTX which can contain several charts.

Most beatmap artists will include different difficulty levels to what they have created, usually with different mode support in some cases. This allows access to different skill levels and more availability to players, as not everyone is highly competitive or have the means to play one specific mode.

The .osu file format describes how notes are arranged and how the game is meant to behave if/when a player takes a specific action. It is usually a simple plain text file with the command lines made up of key:value pairs.

Please note! There are 3 layouts to the pairs, which will be explained further down in the page, so if you are parsing this file, do take note about the spaces around the pairs.

The format consists of 8 different sections which detail specifics about the chart. We will be going through in detail on the most commonly used commands and features of this format on this page. We will not be supporting editing or creating this format; The support in OutFox is parse (read) only.

Status: ✅ Supported

Usage Example:

osu file format v14 

This value is at the very beginning of the file, and sets the version of the specification that the file uses. As of January 2022, This is Version 14.

This variable is used in OutFox just to check for the supported version (charts under version 5 are not supported).

An example of the layout of this section is below. There are several items not included on most charts, but we will cover all of the values you may see in a file so to avoid confusion. Like with the other loader support pages, it is better to be complete than omit things. The commands for this section are done as Command: Value. Do note the space!

This section covers settings and options for the chart and game-play screen. As OutFox has a very different setup and internal system, most of the options in this section do not apply. It’s here primarily for completeness and to explain what bits do.

[General]
AudioFilename: audio.mp3
AudioLeadIn: 0
PreviewTime: 35841
Countdown: 0
SampleSet: Soft
StackLeniency: 0.8
Mode: 3
LetterboxInBreaks: 0
CountdownOffset: 0
SpecialStyle: 0
WidescreenStoryboard: 1

Status: ✅ Supported

Usage Example:

AudioFilename: song.mp3 

This entry in the list tells the game what music file to use for the chart. It will be case sensitive on Linux/Mac so bear this in mind if you have a chart which cannot find it’s music file, this will be the issue.

This variable is equivalent to the #MUSIC entry on SM/SSC files.

#MUSIC:song.mp3;

Status: ❌ Ignored (Unsupported)

Usage Example:

AudioLeadIn: 0

This entry in the list tells the game the number of milliseconds of silence to add before the first sample of the music that plays. It is used for effects or to prepare players for the beginning of the chart, however with how OutFox does timing, this would act more as an offset, and our clock system does not work in milliseconds.

At this time we do not plan on supporting this variable.

This variable has no equivalent SM/SSC value.

Status: ✅ Supported

Usage Example:

PreviewTime: 35841

This value tells the game the time in milliseconds to play the preview section of the song in the music wheel. There is no separate option for a preview file in this format, so it uses a time offset based on the music file detailed in the AudioFilename entry.

Unlike SM/SSC there is no #SAMPLELENGTH in this format that tells the game to loop or reset the point of playback. It will fall back to the default 15 second length when parsing.

To make this variable compatible with OutFox it needs to be divided by 1000 to get the seconds value, as per the #SAMPLESTART SM/SSC variable.

#SAMPLESTART:35.841;

Status: ❌ Ignored (Unsupported)

Usage Example:

Countdown: 0

The countdown happens before the beginning of the first hit object or note, allowing the option to ‘ready’ the player before the song starts. This option allows the chart author to set 4 different speed values. Most modern day charts set this to 0 (disabled).

• 0 = Set the countdown to be disabled, so the chart will begin as soon as everything loads.

• 1 = Set the countdown to be normal, thus adding a 3, 2, 1…GO! option that happens before the music plays. This only happens if there is an offset before the beginning from what the documentation says, so it is not always guaranteed.

• 2 = Sets a half speed countdown; one that is half the speed of 1.

• 3 = Sets a double speed countdown; one that is double the speed of 1.

At this time we do not plan on supporting this variable.

This variable has no equivalent SM/SSC value.

Status: ❌ Ignored (Unsupported)

Usage Example:

SampleSet: Normal

This variable allows for the chart artist to specify a selection of sound samples to be used when setting a hit object. These sounds play when an object (note) is hit, much like keysounds in BMS or DTX modes.

The definition seems to imply that there are 3 base types that can be set for the whole song, and one can also change this variable in the [HitObjects] and the [TimingPoints] sections described further down.

OutFox will honour specific hitsounds as keysounds in modes that support them, but at this time we do not have a custom sound sample pack for this command. If you wish to have this supported, do let us know for consideration!

• Normal = Set the sound sample packs to normal.

• Soft = Set the sound sample packs to softer less distracting sounds.

• Drum = Set the sound sample packs to drum based sounds.

At this time we do not plan on supporting this variable.

This variable has no equivalent SM/SSC value.

Status: ❌ Ignored (Unsupported)

Usage Example:

StackLeniency: 0.7

StackLeniency is used in the Osu Tatakae Ouendan mode to ‘stack’ circles upon one another if they are in the same place (or within a few osupixels) as one previously drawn on the screen.

There is some confusion as to what this modifier actually does, and it seems this is a multiplier in time, most likely from 0-1 seconds, so the closer to 1.0 the more likely you will have a stack of circles, (which will have a number within to show the number of circles one needs to hit).

As the stack leniency heads towards 0 there is less chance of the ‘multitap’ circles forming on the notefield so this I believe is what the variable is for.

OutFox does not support the Osu Tatakae Ouendan mode, so this variable is ignored.

If there is anyone out there with a better/more comprehensive explanation of this variable, I’d love to have it so we can update it here. This is just my rough guess on seeing it in game - Squirrel

This variable has no equivalent SM/SSC value.

Status: ✅ Supported

Usage Example:

Mode: 1

This command sets the game mode the chart (or map) is for.

• 0 = Sets the mode to circles, the basic Osu Tatakae Ouendan mode. The file is a beatmap with correct co-ordinates. Status:❌ Unsupported

• 1 = Sets the mode to taiko, a drum based game. The file is a note chart with adapted variables, drumrolls and denden multihit notes. These charts will be selectable in the Outfox taiko gamemode. Status:✅ Supported

• 2 = Sets the mode to catch, a vertical item drop game. The file is a item chart with adapted variables. Status:❌ Unsupported

• 3 = Sets the mode to mania, a vertical scrolling note game. The file is a note chart with adapted variables and holds. These charts will be selectable in the Outfox kb gamemode. Status:✅ Supported

This variable has no equivalent SM/SSC value.

Status: ❌ Ignored (Unsupported)

Usage Example:

LetterboxInBreaks: 0

This command controls an [Effect], such as a background or a video. Setting this to 1 will add a cinematic ’letterbox’ (black bars) within the edges of the screen.

At this time we do not plan on supporting this variable.

This variable has no equivalent SM/SSC value.

Status: ❌ Ignored (Unsupported)

Usage Example:

UseSkinSprites: 0

This command controls a [Storyboard] setting, which sets whether or not the storyboard script can use the image files for the skin in use.

OutFox does not plan to implement the [Storyboard] feature as we have a modding system built in already, so this setting is ignored.

This variable has no equivalent SM/SSC value.

Status: ❌ Ignored (Unsupported)

Usage Example:

OverlayPosition: NoChange

This command affects the readability of hit circles in Osu Tatakae Ouendan mode. It allows the chart author to control how the overlays (the circle animations or hit animations) are drawn. This can make the ’numbers’ within the circle easier to see, as well as making stacks work slightly better for those with colour issues.

• NoChange = Sets the mode to the default.

• Below = Sets the mode to draw the effects below the numbers. This makes the value easier to read.

• Above = Sets the draw above the numbers. Can affect how easy it is to read, but does look cool.

At this time we do not plan on supporting this variable.

This variable has no equivalent SM/SSC value.

Status: ❌ Ignored (Unsupported)

Usage Example:

SkinPreference: Ice

This command allows the chart author to select a custom ‘skin’ (theme) to use when the chart is played. This allows for a new level of immersion if your charts are based on a subject type or theme.

At this time we do not plan on supporting this variable.

This variable has no equivalent SM/SSC value.

Status: ❌ Ignored (Unsupported)

Usage Example:

EpilepsyWarning: 0

This command controls an option to show a setting to warn about flashing colours or lights before the song plays.

This variable has no equivalent SM/SSC value.

Status: ❌ Ignored (Unsupported)

Usage Example:

CountdownOffset: 28

This command sets the time (in beats) that the countdown starts before the first hit object or note.

This variable has no equivalent SM/SSC value.

Status: ❌ Ignored (Unsupported)

Usage Example:

SpecialStyle: 0

This command sets a different key layout named ‘N+1’ for mania mode. This option is not used as apparently this can be set within the options of the actual game. Setting this requires compatible noteskins / skins to be available, and a suitable mode layout or it can render the song unplayable on the client due to missing assets.

This is not available in Outfox as keys can be assigned as required by the player.

This variable has no equivalent SM/SSC value.

Status: ❌ Ignored (Unsupported)

Usage Example:

WidescreenStoryboard: 0

This option sets the [Storyboard] as available to be viewed as widescreen on systems that support it or not. The default is 4:3 for normal play, due to the osupixels 640x480 setup

This variable has no equivalent SM/SSC value.

This section contains entries for the editor of Osu so won’t be used or processed in OutFox.

This section details the main song metadata used in the chart or beatmap that is used when caching, being used in the music wheel, saving scores, and online profiles.

OutFox does not have some of those features yet as they are being built, but almost all of this section is used in some way within our caching, scoring and music wheel system.

The commands for this section are done as Command:Value. Do note the lack of spaces!

[Metadata]
Title:My Great Song
TitleUnicode:私の素晴らしい歌
Artist:OutFox Sound Team
ArtistUnicode:「OutFox」音楽
Creator:Squirrel
Version:OutFox Easy Mod File 2021
Source:Serenity Volume 2
Tags:japanese j-pop modfile
BeatmapID:0123456789
BeatmapSetID:0987654

Status: ✅ Supported

Usage Example:

Title:My Great Song 

This entry in the list tells the game what the song title is for this chart in roman form.

On OutFox this entry is usually the transliterated (translation) of the title, so we will be parsing this as that entry. If there is no TitleUnicode entry it will use this as the title.

This variable is equivalent to the #TITLETRANSLIT entry on SM/SSC files.

#TITLETRANSLIT:My Great Song;

Status: ✅ Supported

Usage Example:

TitleUnicode:私の素晴らしい歌

This entry in the list tells the game what the song title is for this chart in utf8.

On OutFox this entry is usually the original title, so we will be parsing this as that entry.

This variable is equivalent to the #TITLE entry on SM/SSC files.

#TITLE:私の素晴らしい歌;

Status: ✅ Supported

Usage Example:

Artist:OutFox Sound Team 

This entry in the list tells the game what the song artist is for this chart in roman form.

On OutFox this entry is usually the transliterated (translation) of the artist name, so we will be parsing this as that entry. If there is no ArtistUnicode entry it will use this as the artist name.

This variable is equivalent to the #ARTISTTRANSLIT entry on SM/SSC files.

#ARTISTTRANSLIT:OutFox Sound Team;

Status: ✅ Supported

Usage Example:

ArtistUnicode:「OutFox」音楽

This entry in the list tells the game what the song artist name is for this chart in utf8.

On OutFox this entry is usually the original artist name, so we will be parsing this as that entry.

This variable is equivalent to the #ARTIST entry on SM/SSC files.

#ARTIST:「OutFox」音楽;

Status: ✅ Supported

Usage Example:

Creator:Squirrel

This entry in the list tells the game the creator or author of the beatmap or chart.

On OutFox this entry is referred to as the chart credit, and is used as a given entry on the music wheel.

This variable is equivalent to the #CREDIT entry on SM/SSC files.

#CREDIT:Squirrel;

Status: ✅ Supported

Usage Example:

Version:OutFox Easy Mod File 2021

This entry in the list allows a chart author to name a difficulty ‘version’ for the particular .osu file within a collection for one song. It is usually used for descriptive difficulty information, or to ’theme’ difficulties, for example (spring easy, summer hard, autumn extreme, winter death).

Other authors use this field to also add the number of keys the chart has in mania mode, for example [3k], [6k], [10k] would let people know it uses 3 columns, 6 columns and 10 columns respectively before the difficulty name.

There is no specific detail given for this entry, other than it being used within the online portion of the game for difficulty and to give information on the music wheel when choosing a song. It is better to give some detail about the difficulty in the entry given, as you can risk not being ranked, and upsetting players.

On OutFox this entry is used for the ‘multi-chart per folder’ setup some packs have in the new kbx mode. This gives you seamless loading capabilities without having to split up multi-song chart packs.

This variable has no equivalent SM/SSC value.

Status: ✅ Supported

Usage Example:

Source:Serenity Volume 2

This entry in the list identifies the source of the song, or the original media it was produced for (in the case of anime openings/themes etc). It can also be used as the pack source if the song was created specifically for games, as our example.

On OutFox this entry is likely going to be parsed as the ‘subtitle’ entry until we fit another option for this information.

Status: ✅ Supported

Usage Example:

Tags:japanese j-pop modfile

This command adds a selection of words that the chart can be searched by on the online system, and within the music wheel. They are simply space separated, and act like tags on a youtube video or instagram post, allowing players to find the chart.

It is important you put useful or meaningful tags in this section that reflect the chart so it can be found!

OutFox supports this function for chart searching in supported wheels.

Status: ❌ Ignored (Unsupported)

Usage Example:

BeatmapID:0123456789
BeatmapSetID:0987654

The BeatmapID is used as an identifier for the ‘Difficulty ID’ according to the official documentation, with the BeatmapSetID being used as the identification of the chart or beatmap itself.

The use of these is mainly for the upload content system so the web side can catalogue and add the entries to the database. Without these one would not be able to tie scores or combos to the charts played. These identifiers also are likely used for ranking and high scoring/music wheels internally for the client.

OutFox has it’s own unique hashing system and database system planned which will be used as the IDs in this format are not compatible.

This variable has no equivalent SM/SSC value.

This section details the main difficulty setup that the chart or beatmap will use. There are several values which change depending on the mode type, as well as the sizes of the circles and other settings.

OutFox will not be using many of these as they are for circles mode primarily, but the taiko and mania mode changes will be detailed here.

The commands for this section are done as Command:Value. Do note the lack of spaces!

Status: ❌ Ignored (Unsupported)

Usage Example:

HPDrainRate:7.2

HP Drain Rate, usually shortened to HP, sets the rate of health increase or decrease depending on how a note is hit. This is usually a set amount of time before or after, which we call a timing window. The closer to the notes actual time it is hit, the high the ‘category’ or ‘judgment’ the game records for that hit.

It allows for a recovery (health is added to the life bar) on a GOOD hit or better. The scale is from 0.0 to 10.0, with lower values giving more health returns. A higher value lowers the health return gained on the note.

In reflection, the drain of this value, which is given when a note is hit badly is different to the value. so a lower value affects the health bar less on a bad hit, and a higher value punishes the player more.

In circles and catch this value can also modify the passive rate of drain. These modes have a constant drain on the life-bar. If the life bar drains to 0 the player counts as failing the chart.

In OutFox we do not have a life draining mechanism at this time, so this value isn’t supported. If catch mode is ever implemented this mechanism will of course be required.

This variable has no equivalent SM/SSC value.

Status: ✅ Supported (mania only)

Usage Example:

CircleSize:3.2
CircleSize:4

Circle Size (CS) is a variable that lives a double life in the beatmaps or charts. In circles it defines the size of the hit objects, within the range of 1 to 10. Higher values helpfully make the circles smaller. In the community it is seen that the majority of the beatmaps use between 2.5 and 4.0. This is followed by 4.0 to 5.7, with values outside of these ranges almost never being used, mainly due to them being too small on some devices to hit, or just too big to make an efficient beatmap that flows with effects (Sliders/spinners overlapping etc due to scale).

If the chart is above 7, it is likely that one of the Osu games mods, Hard Rock is being used. Outside of this, it is very unlikely to be used. The sliders in the editor do not permit for values outside of 2.0 to 7.0, so one needs to manually edit this value in the .osu file.

The other life this value leads, is within the catch mode. In this mode, the Circle Size defines the size of the fruit and the catcher sprites. It works as above, higher numbers make the fruit and catch smaller. This mode usually has values between 2 and 7, which is commonly seen as 3-4.

If the value is set to the highest value, 10, the hit objects will be the same size as the cursor that is shown on the screen to show the location of the mouse/pointer/pen/touch etc.

This value is also ‘seen’ in the taiko mode, however, it does nothing. It is also ignored in the OutFox taiko mode.

However, if the mode is mania, this value becomes something completely different. In the editor it is an automatic switch to a variable called 'KeyCount'. As this mode is a vertical scrolling game, this value is the number of ‘keys’ (on a keyboard or controller) you will be using to play that particular chart. This is also the same as the ‘column count’ we have in OutFox.

The .osu file does not reflect the KeyCount word. It remains as CircleSize. The difference is, the mode uses whole numbers, so there will be no CircleSize:4.3.

The values used for this version of CircleSize you will see 3 to 10. This is contrary to what the official documentation says, it is not 1 to 9.

OutFox computes these column amounts as CircleSize - 1 as our columns begin at 0. The new kb mode will support all key modes from 1 to 10, with 2 player support.

This variable has no equivalent SM/SSC value.

Status: ✅ Supported

Usage Example:

OverallDifficulty:1.3

Status: ❌ Ignored (Unsupported)

Usage Example:

ApproachRate:4.8

Status: ❌ Ignored (Unsupported)

Usage Example:

SliderMultiplier:3.7

Status: ❌ Ignored (Unsupported)

Usage Example:

SliderTickRate:7.2

Written and Maintained with ♡ by Squirrel, containing information with thanks from the Osu! Wiki and members of the international Taikojira and Mania! communities.