Tool-assisted game movies
When human skills are just not enough

Desync Help TAS

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It happens quite often, especially on newer emulators. You carefully construct your TAS and when you check your progress, the movie goes off at some point and does something wrong.

Most desyncs are a result of inconsistent savestates, when an emulator or savestate error causes you to start using a wrong savestate. Once that happens, your movie starts to go down the wrong track. If you notice this happening, recreate your savestates at the most recent point where the movie plays as intended.

While you are making a movie, make it a habit to periodically play through your whole movie to verify that it syncs, and always make a backup of the working copy.

If your run desyncs, no one can help you recover the lost work. It is up to you to be careful.

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There are a number of causes of inconsistent savestates:

Emulator problems

PCSX, Mupen64, and FBA-rr

  • In general, these emulators have some desync issues. Be careful.


  • Wiimote recording is prone to frequent desyncs, and will fail to playback if you do not restart Dolphin each time you wish to start recording or playback of a movie.


  • Official version of Snes9x 1.43/1.51/1.52 has some desync issues. Use snes9x-rerecording instead. (The improved Snes9x can play and record movies in both Final and WIP timing.)
  • Snes9x 1.43/1.51 has trouble with sound. Games with timing to music or sound might desync. Some state saving/loading patterns during music changes might cause trouble as well. Using the improved version, disabling sound emulation entirely or using Fake Mute mode may prevent it from happening.
    • SNES9x 1.52 improved sound emulation logic overall, and the issue above has probably been fixed. If you don't need some advanced TAS features (such as Lua scripting), you should use SNES9x Rerecording 1.52.

Visual Boy Advance

  • VBA v20 has some emulation problems with SGB games. You may try recording with other versions instead. (The timing of GBx games is mostly different in v20.)
  • VBA versions prior to v21 have a bug that may automatically disable the GBA Lag Reduction setting. If this happens, you may try to hex-edit the GBA Lag Reduction flag stored inside your desynced movie according to the VBM format description.


  • Stopping emulation when executing very long instruction sequences without any (conditional) jump instructions (and also some other instructions) can lead to a desync. Fortunately, such sequences are extremely rare.
  • Savestating while the joystick is being polled will cause a desync in versions before r11.4. If you enable joystick (it isn't enabled by default), use r11.4 or newer.
  • Certain forms of self-modifying code may very rarely produce desyncs if pipeline flushing is not enabled.

Savestate problems

Other problems

You have external codes on (ex. Game Genie codes)

Be very careful that you don't have external codes on. It is easy to miss. If your movie requires external codes to play back correctly, TASVideos cannot accept your movie.

You changed the settings by accident

If this happens, try to rectify what you can. Do not continue with inconsistent settings.

Replay is not quite deterministic

If you discover that different ways of playing the movie yield different results, it could mean an emulation issue with that game, and it is recommended you stop TASing it until the problem is diagnosed and fixed.

Game suddenly resets

Some versions of some emulators may have a bug that inserts spurious resets in some conditions, resulting in a movie that suddenly resets the game. This can be fixed by editing the movie file to remove the spurious reset.

TODO: update info.

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DesyncHelpTAS last edited by ThunderAxe31 on 2017-09-18 17:21:19
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