Play videos at the same time in sync

I have multiple videos of the same content from different angles, the audio is roughly the same.

With a batch file I can start multiple instances of MPC-HC at the same time to play these different videos, but that results just in start loading the videos at the same time, but since the loading time is different and varies a bit each time (so /start ms is no solution), they don't play exactly at the same time in sync.

How do you play multiple videos at the same time in sync?

Not possible with a batch script. Best you can do is set volume to 0 for all instances except one. Then small video sync issues will be less obvious.

For full control you need to write an application that uses the MPC-HC API:
https://github.com/clsid2/mpc-hc/blob/develop/src/mpc-hc/MpcApi.h

When I set the volume to 0 for all instances except one, MPC-HC starts with volume 0 the next time.

How do you prevent MPC-HC from remembering the volume setting, or set the volume to 100 by default at normal startup (without command line parameters)?

You can avoid that issue by closing the instances with volume 100 last.