21 Jan 2025
An artist friend took videos of her art creation process and asked for assistance converting them into per-artwork timelapse recordings. Let’s document the steps for my future self!
For the given recordings, finding the cut points for the first and last steps could easily be done manually.1
Install commandline video editing tool FFmpeg.
After viewing a recording and making note of the timestamps around a specific artwork’s creation (in this example, 00:25:16 to 00:42:34):
# Trim into new file, remove audio
ffmpeg -i INPUT.mp4 -ss 00:25:16 -to 00:42:34 -c:v copy -c:a copy -an ARTWORK_A.mp4
# Speed it up into a 4x timelapse, update framerate=60fps, rotate 90 degrees
ffmpeg -i ARTWORK_A.mp4 -vf "setpts=PTS/4,fps=60,transpose=2" ARTWORK_A_4x.mp4
# Trim out region with inactivity (00:03:39 to 00:04:17)
ffmpeg -i ARTWORK_A_4x.mp4 -vf "select='not(between(t,219,257))',setpts=N/FRAME_RATE/TB" ARTWORK_A_4x_trimmed.mp4
This recording happened to be filmed vertically but needed to be flipped to horizontal; if that flip isn’t necessary, exclude the transpose=2 argument from the second processing step. (For whatever reason, doing
this transpose is realllllly slow. Wasn’t worth investigating here, but be warned.)
The region with inactivity was found manually (within ARTWORK_A_4x.mp4), and then converted into seconds. It could alternatively be found and excluded as part of the first step.
Note that these steps generate intermediate videos ARTWORK_A.mp4 and ARTWORK_A_4x.mp4 as well as output video ARTWORK_A_4x_trimmed.mp4. That was intentional, to give the friend the
different types of output for other use-cases. If those intermediate videos aren’t desired, the various steps can be combined.