There's no way to show subtitles on AVI files (.srt, same name as file on same folder) when connected by DLNA. I've tried with several AVI files, even with several DLNA different brand servers, and of course, those avi + srt works on PC or via USB.
But MKV works flawlessly. You can alternate subs and audio streams right from the remote.
This could be a perfect BDplayer if the AVI files could show srt files too.
BDP5180 1.54 firmware.