If it’s twice as wide as you want, just resize it. More important is that you probably ending up with both planes, left and right being identical, meaning it will not have 3D effect. Just tested it myself with latest version of ffmpeg. Still no official MVC support it seems…

https://www.videohelp.com/software/BD3D2MK3D

How about this tool? As far as I’m aware plain FFmpeg can’t decode MVC (or am I wrong?)

deleted by creator

https://f-droid.org/en/packages/at.bitfire.nophonespam/