You either have to use libav, or a more recent FFmpeg, or manually turn off threaded decoding in VLC preferences.
Whatn FFmpeg version I should build VLC with for threading to work, can I simply grab the latest 4.x?
Could it be that bug #898428 could be avoided with latest FFmpeg? Thanks! [0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=898428