When I watching video in PiP mode, I found the subtitle is missing and it is still not shown even infuse is switched into normal window or full-screen mode. Though I could turn off and on subtitles to workaround. It seems to be a bug in public beta 6.
This may at least be partly a bug or limitation of the macOS PiP implementation. I have an extension to let me use PiP for videos in Safari which I use for Netflix, Hulu, etc and their subs never work in PiP
The lack of subtitles in PiP is an iOS/macOS limitation. The bug in Infuse where switching back from PiP doesn’t automatically re-enable the subtitles has been present in the iOS version for as long as I can remember - I’m not surprised it’s also in the macOS version. This would be a nice fix.
The iina player can play the same video with the subtitle in PiP. But I do not know how it works.