Plex Android & Android TV clients, including the Amazon Fire Stick, direct play PGS, VOBSUB, and SRT subtitles, including when the video or audio is transcoding.
Enabling ASS subtitles currently results in a video transcode.
However, Plex is adding support for ASS subtitles. There is a preview build (pre-beta) available for testing (Nvidia SHIELD/Android app SSA/ASS format anime subtitles + transcoding problems).
