1. Capture settings that survive late rounds

  • Hardware encoder. NVENC, AMD AMF or Apple VideoToolbox. BTD6's late-round simulation is CPU-bound (why), and a CPU encoder fights it for the same cores.
  • 30 fps, not 60. Past round 150 the game cannot hold 60 anyway, and recording at 60 doubles the number of repeated frames you'll have to remove.
  • Record the whole run in one file. Pausing the recorder between rounds creates seams; it is easier to cut later.
  • Leave the game at 1× or 3× consistently. LagCut reads the speed button to keep pacing correct, and a timelapse with mixed in-game speeds looks like it is ramping even after editing.

2. Remove lag frames before anything else

This is the step most timelapse tutorials skip, and it is why their late rounds look like a slideshow. Every time the game stalled, your recorder wrote the previous frame again (how that happens). If you set the clip to 1000% speed, those repeated frames are still there, flashing past, while real frames between them are skipped. Strip the repeats first, then set the pace, and the game appears to run smoothly at whatever rate it was really drawing. Two ways to do it:

  • ffmpeg: ffmpeg -i run.mp4 -vf "mpdecimate,setpts=N/FRAME_RATE/TB" -an -fps_mode cfr -r 30 clean.mp4. The full guide explains the flags.
  • LagCut: drop the clip in, it finds repeated frames and pause menus and exports a clean MP4 at 1× or 3×. Browser-based, nothing uploaded, first 30 seconds of a file, so use it for the late-round highlight and ffmpeg for the whole run.

3. Pick the pace

A full CHIMPS run is 40 to 60 minutes of real time. For a 60-second timelapse that is roughly 50×; for a two-minute one, 25×. Set it on the cleaned clip. In most editors this is a speed/duration setting; in ffmpeg it is setpts=PTS/50. Two refinements that make a timelapse watchable: hold at 1× for the first two or three seconds so viewers see the map, and slow back to real time for the final round or the boss kill.

4. Add audio

Game audio cannot be sped up 50× and stay listenable, and any frame removal breaks sync anyway, so timelapses use music. Export the video without audio (LagCut does this by default; in ffmpeg use -an) and lay a track under it in your editor. If you want a few seconds of real game sound at the end, cut it from the original recording at the matching timecode.

Checklist

  1. Record at 30 fps with a hardware encoder, one file, consistent in-game speed.
  2. Trim to the run (LosslessCut is free and does this without re-encoding).
  3. Remove repeated frames and pause menus.
  4. Speed up the cleaned clip to your target length.
  5. Score it with music; optionally slow to 1× for the finale.

Questions people ask

Why does my BTD6 timelapse stutter in late rounds?

The source recording has lag-frozen (repeated) frames from when the game stalled. Speeding up does not remove them. Strip them first with ffmpeg mpdecimate or LagCut, then speed up.

What speed should a BTD6 timelapse be?

For a 45-minute CHIMPS run, 25× gives about two minutes and 50× about one minute. Hold real time for the first few seconds and the final round.

Should I record BTD6 at 60 fps?

Not for timelapses. Late rounds will not hold 60, and recording at 60 only produces more repeated frames to remove. 30 fps is enough once sped up.