Back

Reference Bpm Manipulation

Contents

• 1 Summary
  • 1.1 Zero Offset Reference Bpm Line (Z-Line)
• 2 Caveats
• 3 Details

Summary

For example, if you have a map that looks like below

 ...
 //Storyboard Layer 4 (Overlay)
 //Storyboard Sound Samples

 [TimingPoints]
 -23,240,4,2,0,50,1,0
 6697,240,4,2,0,50,1,0
 15817,240,4,2,0,50,1,0
 17737,-166.666666666667,4,2,0,50,0,0
 18457,240,4,2,0,25,1,0

 ...

 174702,240,4,2,0,50,1,0
 202782,240,4,2,0,50,1,0
 240222,428.571428571429,4,2,0,50,1,0
 281364,480,4,2,0,50,1,0
 329364,240,4,2,0,50,1,0

 [HitObjects]
 448,192,17737,5,0,0:0:0:0:

 ...

You found out that the map is on reference BPM 200, you would like to change it to 100.

Zero Offset Reference Bpm Line (Z-Line)

(Had the idea of calling it Z-Line because it should be at the end and also it's zero offset.)

Simply add a line of offset 0 (Note: 600 because 60,000/100 = 600)

0,600,4,2,0,50,1,0

at the end, so:

 ...
 174702,240,4,2,0,50,1,0
 202782,240,4,2,0,50,1,0
 240222,428.571428571429,4,2,0,50,1,0
 281364,480,4,2,0,50,1,0
 329364,240,4,2,0,50,1,0
 0,600,4,2,0,50,1,0 < --- HERE

 [HitObjects]
 448,192,17737,5,0,0:0:0:0:

 ...

You would notice that the reference would change. This works for any bpm, not for all offsets though.

You may need to move the offset to the negatives in some rare occasions.

Caveats

This works because osu!'s algorithm assumes a sorted TimingPoint .osu file.

• Saving the map will move the Z-Line back to the start, take note of that.
• This manipulation doesn't seem to be compatible with NaN Fake Note Generation during osu! upload. (Require verification)
• During upload, osu will attempt shift Z-Line during package creation. Spam saving the original .osu file may be required to retain its position. (To find out if there's a more consistent way to upload these files).

Details

I wrote a small article speculating on why it works.

osu! reference BPM