I don’t know the exact version off hand, I’d have to look around. But Plex’s implementation of Exoplayer has modifications to fit in with the rest of Plex’s features. Just updating the core Exoplayer code won’t work. It needs to be made to work with the rest of the app.
I could be wrong as I’m not a developer, but AFAIK, the implementation of ass/ssa for Exoplayer only deals with files stored locally on the device. It doesn’t help with streaming, like what Plex does. There isn’t a native ass/ssa support when streaming.
