BMS/osu 5K to 10K Decalcomanie Tool

Development: CircusGalop & 윾이 & Codex

Korean documentation: README_KO.md

Double-click dist\BMS_Decalcomanie_Tool.exe, run_decalcomanie_tool.bat, or BMS_Decalcomanie_Tool.pyw, add BMS or osu!mania files, then click Convert to 10K decalcomanie.

The original files are not overwritten. By default, converted files are written beside each source file so existing relative BMS #WAVxx paths and osu AudioFilename paths still work. If you choose another output folder, make sure the referenced sound files are available from that folder too.

The GUI also has Copy selected osu decal notes to clipboard for selected .osu files. It copies only mirrored HitObject rows. Open random chart generator creates direct BMS or osu!mania files, copies generated osu!mania HitObject rows, or inserts a generated section into an existing .osu file. BMS output uses visible lanes in order from 11-15 then 21-25, with long-note lanes 51-55 then 61-65; osu output uses Mode: 3 and sets CircleSize to the key count.

BMS conversion rule

• Keep original 5K lanes 11-15.
• Copy the same note object IDs to the opposite side in reverse order:
  • 11 -> 25
  • 12 -> 24
  • 13 -> 23
  • 14 -> 22
  • 15 -> 21
• Copy long-note lanes when enabled:
  • 51 -> 65
  • 52 -> 64
  • 53 -> 63
  • 54 -> 62
  • 55 -> 61
• Set #PLAYER 3 by default so the output is treated as double play.
• Replace or add the BMS key extension command as #10K.
• Do not copy or rename sound files. The output reuses the existing #WAVxx key-sound definitions and note IDs.

osu!mania conversion rule

• Accept .osu files with Mode: 3 and CircleSize: 5.
• Set CircleSize:10.
• Move the original 5K columns into the left half of the 10K field.
• Copy each hit object to the right half in reverse order.
• Preserve the rest of each hit-object line, including hold end times and hit-sample fields.
• Keep AudioFilename unchanged and append [10K Decal] to the difficulty Version.
• The clipboard action emits the same mirrored hit objects without the .osu file sections, for manual text editing under [HitObjects].

CLI

python bms_decalcomanie_converter.py "path\to\chart.bms"
python bms_decalcomanie_converter.py "path\to\chart.osu"
python bms_decalcomanie_converter.py "path\to\folder" -o "path\to\output"

Random chart generator

The generator checks each selected key lane at a fixed beat interval and can write either BMS or osu!mania based on the output extension.

• Key count: lane count from 1 to 10.

• BMS key extension command: 4K-8K outputs #4K through #8K, 9K outputs no key extension command, and 10K outputs #10K.

• Generation count: how many beat-interval positions to roll. For example, 256 at 0.25 beat interval makes 16 measures of 16th-note positions.

• Minimum notes/beat: when greater than 0, that many randomly chosen empty lanes per generated position cannot roll 3a. If too many lanes are being held by long notes, enough 2b keeps are forced into 1b ends so the next position can still create the minimum.

• Maximum notes/beat: default 10. When the number of empty lanes is greater than this value, the excess randomly chosen empty lanes are forced to 3a.

• If 2a long-note starts would leave too few free lanes for the next position, the excess 2a starts are randomly converted into 1a single notes.

• Empty lane:

  • 1a: create a single note, default weight 25
  • 2a: start a long note, default weight 50
  • 3a: create no note, default weight 25

• Holding long note:

  • 1b: end the long note, default weight 25
  • 2b: keep holding, default weight 75

Beat interval is in beats and must divide one 4-beat measure exactly, such as 1, 0.5, 0.25, or 1/8. The generator writes a silent WAV named _random_note_silence.wav beside the output if it does not already exist. BMS uses it as a key-sound; osu uses it as AudioFilename.

Use Generate random clipboard when you want raw .osu HitObject rows for manual text editing under [HitObjects]. Clipboard/file start time (ms) offsets the generated section before copying.

The osu! client does not reliably paste raw HitObject text as editor objects. For editor-section workflows, choose a target .osu file and click Apply random section to osu file. It inserts the generated rows at Clipboard/file start time (ms), sorts the [HitObjects] section by time, checks that CircleSize matches Key count, and writes a one-time .osu.bak backup beside the target file.

python bms_decalcomanie_converter.py --random-output "path\to\random_10k.bms" --bpm 150 --beat-interval 0.25 --measures 16
python bms_decalcomanie_converter.py --random-output "path\to\random_10k.osu" --bpm 150 --beat-interval 0.25 --measures 16
python bms_decalcomanie_converter.py --random-output "path\to\random_7k.osu" --keys 7 --generate-count 128
python bms_decalcomanie_converter.py --random-output "path\to\random_10k.osu" --keys 10 --generate-count 256 --min-notes-per-beat 2
python bms_decalcomanie_converter.py --random-output "path\to\random_10k.osu" --keys 10 --generate-count 256 --max-notes-per-beat 4

Build EXE

build_exe.bat

The EXE is written to dist\BMS_Decalcomanie_Tool.exe.

Options:

• --no-player-3: leave #PLAYER unchanged.
• --no-ln: do not mirror long-note channels.
• --mirror-invisible: also mirror invisible channels 31-35 to 45-41.
• --overwrite: overwrite the default output filename.
• --random-output: create a direct random BMS or osu!mania file.
• --keys: random output key count, 1-10.
• --generate-count: number of beat-interval positions to generate. Alias: --note-count.
• --min-notes-per-beat: minimum notes to force per generated beat position.
• --max-notes-per-beat: maximum empty lanes allowed to roll non-3a per generated beat position. Default: 10.
• --weight-single, --weight-ln-start, --weight-empty, --weight-ln-end, --weight-ln-keep: random generator weights.
• --seed: repeat a random generator result.
• --random-overwrite: allow overwriting an existing random output file.