How can I avoid transcoding for the Fire Stick?



I am very new to Plex and transcoding in general, so please bear with me.

I am trying to avoid transcoding when I watch on my Fire Stick because I’m not using a dedicated server as my Plex server.
My TV is capable of 1080p, the fire stick is set to 1080p 60Hz, and Plex is using the defaults (as far as I can tell), with the H264 Maximum set to 5.0 (Recommended).

I’m watching with subtitles (which I know can often require transcoding), but I tested various movies/shows without the subtitles and still saw some require transcoding. I can’t find a pattern indicating when transcoding is necessary. If possible, I’d like the know the Codec I can use, the maximum resolution, the bit depth, the audio quality, what style subtitles, etc. to avoid transcoding entirely.

Here are my test cases. They all required transcoding when the subtitles were on and the results were mixed when the subtitles were off.

As you can see, the only common feature on the three that didn’t need transcoding was H264, but there were two using H264 that still needed transcoding.

I’d appreciate any insight and recommendations.


I can't seem to edit my original post, but I wanted to add that all the videos are in MKV format.


Subs will need to be converted to UTF-8
Audio with need to be converted to AC3 5.1 or AAC 2.0
HEVC is a crapshoot as is 10 bit. Plex hasn't learned to play nice with these guys. You may have to encode HEVC in an MP4 file and if you do that you'll need sidecar subs in UTF-8. Best to just avoid HEVC for a few years.