Clever compass mechanism is clever (DCS Spitfire video)

[-0303-]

Just noticed the four downwards sticky pins and suddenly grasped their purpose (or so I believe). The compass "sticks" at any  significant bank or pitch preventing compass accumulating spin momentum. Real (glider) compasses I've seen, spins on turning (a glider turns all day long...) and keeps oscillating after straightening out. It's unreadable while turning and 30 sec or more after.

But whenever the Spitfire turns (banks) the P8 compass sticks", doesn't gain spin momentum, it then unlocks at straight and level, making for a more sedate settling. Made a video, external view and compass splitscreen (two DCS Replay recordings, frames synchronized).

Video
White cross is north. Compass is free on takeoff, sticks on ascending left turn, unsticks at level [1:37], sticks (flips twice) while rolling. Sticks/unsticks intermittent right descending turn before landing. Funny it doesn't stick at -43 bank, but giving benefit of doubt to modelers, it's more complicated than angles, there's also acceleration.

Note, pitch and bank are very readable center of video for comparison (after YT gets focused at 15s).

Note to self (and interested) making the video

Command line FFmpeg is a  very versatile free open-source Swiss knife software for video editing. One would think GUI packaging of FFmpeg like "Handbrake" would include menued templates for common things like splitscreen. It doesn't. FFmpeg is the simplest, if not only, free tool I found for this. It's  akin to linux or dos scripting, powerful, terse, complicated, incomprehensible... Anyway, found templates online to adapt.

Recorded DCS Replay with Xbox Game Bar [Win + G]. Used click "Fly" scene-shift to synchronize, that's why they're staggered. Obviously couldn't click "Fly" at the exact same millisecond both videos but single stepping MPC-HC video player to scene-shift and then go "MPC-HC -> Navigate -> Go to..."  gives the current video frame (and millisecond). 43 - 36 = 7 frames. Also, Right-click MPC-HC time display "High Precision" gives milliseconds.

Found (adapted) command online:
ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "[0:v]null [left];[1:v]tpad=7:start_mode=add [right];[left][right]vstack" Spitfire_compass.mp4

The relevant part is "vstack", stack vertical and "tpad=xx", delay XX frames. I'm sure this includes redundant syntax. Just:

ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex vstack video3.mp4

will vertical stack videos ("hstack" horisontal) but what's the correct syntax to add "tpad" delay? I copied and adapted something that works including redundant syntax.

Edited June 5 by -0303-