How to adjust sync

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Tips on adjusting sync

(TODO)

If you want a more detailed discussion, then keep reading this article.

How do offset settings affect gameplay?

In the case you didn't already know, rhythm games are all about producing correct inputs (say, pressing buttons) at the correct timings.

Every rhythm games use 'delta values' to grade players' inputs. 'Delta values' are the values measured for each note, which is the difference between the time the player hit the note and the time the player should hit the note (i.e. the moment the note crosses the judge line).

The signs of delta values depend on which way the timestamp values are subtracted, and thus are arbitrary.
For ease of discussion, let's assume that delta = hit time - correct time. In this case:

• Delta = 0 means that the note is hit at the exactly correct moment.
• Delta < 0 means that the note has been hit too early.
• Delta > 0 means that the note has been hit too late.

In the perfect world, this is end of the story. The note crosses the judgement line while being perfectly synced with the music, and when the player hits the note at that moment, the delta will be zero. Unfortunately, we are not living in a perfect world, and there are various delays involved that hinders accurate measurements of timings.

There are three significant and measurable delays that need to be accounted for a rhythm game.

Input Delay

Time between a player's input and the moment that the event's timestamp is being created.

Audio Delay

Time between audio (especially keysounds/hitsounds when it's present) being written on the buffer and the moment it's being (physically) played.

Video Delay

Time between notes' positions being determined and the moment notes are being (physically) displayed.

In practice, three delay values are not independent, as players can't distinguish between "large input delay + small audio/video delay" and "small input delay + large audio/video delay". Therefore, two offset settings are sufficient.
Many rhythm games let players adjust following two parameters as offset settings:

Input Offset

This is a straightforward way of adjusting delays: the game adds (or subtracts) this value from the measured delta value to adjust it.

Audio-Video Offset

Many rhythm games compensates difference between audio delay and video delay, by artifically shifting notes' positions. This value dictates how much notes should shift.

Some rhythm games force players themselves to account for input delay. For rhythm games with keysounds, this might seem natural as it's the only way to keep background music and keysound in sync.
However, I still think that not providing a method to adjust input offsets limits players' preferences, and providing one (+ an option to disable keysounds) would help players like me to play various rhythm games in a more consistent manner.
Moreover, intentionally not providing input offset option for a game with only hitsounds is... just a super lame move.

Having said that, the two offset values I mentioned are not the only ways to compensate for delays, and even for the two offset values, the names, magnitudes, and signs can be set arbitrarily. Therefore, even when instructions are provided, players would be easily confused by what each setting would do.
Some rhythm games, such as Crypt of the NecroDancer and (surprisingly) Fortnite Festival provide a way to calibrate offsets interactively, but it's pretty hard to get audio-video offsets right.

Hence, I've devised two methods of measuring delays in a more consistent way.

Audio-only delta

The average delta value when the game is being played blindfolded (without any visual cue).
As playing blindfolded is usually not easy, playing without looking at the judgement line could be an (incomplete) alternative.

This measures the sum of input delay and audio delay.

Video-only delta

The average delta value while the game is being muted (being played without any audio cue).
On arcade machines where muting the game is very hard, you could try using headsets while listening to noises.

This measures the sum of input delay and video delay.

I've collected various rhythm games' offset settings and how would they affect audio-only/video-only deltas.

The tool at the top of this page generates guides based on this table.