Hi,
it dos not seem to me as 2.78 bug. It was actually okay until I manually installed LAV filters version 0.78 (because i wanted to play AV1 files).
Version 2.78 BSplayer codec manager installs only LAV filters version 0.72 that can't handle AV1.
more info here:
https://forum.bsplayer.com/bug-repor...1-support.html