First of all thank you for bringing Plex to the new Apple TV - it's a very slick product! I knew little about Plex previously, but upon seeing the Apple TV app I thought I'd give this whole digital library thing a shot. I started by ripping a handful of my own Blu-rays using MakeMKV.
The Problem: Unfortunately, I discovered that of the six movies I ripped last night, some play back at Unlimited 1080p perfectly (Jurassic World, Avengers: Age of Ultron, 1989 Batman), while others suffer from dropped frames and pixelation until I downgrade the quality to "20Mbps, 1080p" (Mad Max: Fury Road, Ghostbusters, Ghostbusters II). As I'm unwilling to rip my entire collection of 101 blu-rays if it means any degradation in playback quality, this is unfortunately a deal-breaker unless I can get the issue resolved.
I've so far had no luck in identifying why some movies work flawlessly and others do not. The first thing I did is check the files locally on my server, but they were visually perfect there. I thought perhaps those problematic films had a higher bitrate than the others, but I checked the files and Jurassic World had the highest bitrate of them all yet plays to the Apple TV without a hitch (Age of Ultron wasn't far behind). Then I thought perhaps there was a commonality with the audio formats each disc used, but that was also not true. And playback is completely consistent: I can fire up Fury Road and see dropped frames in the very few seconds of the movie - skip ahead to anywhere in the film and see visual glitches every 10 seconds or so - but then switch to Jurassic World or Age of Ultron and get perfect playback every time.
So it would appear the issue is not a bottleneck with my server or my network. I am truly stumped. Here are my details:
tvOS software version 9.0
Plex app version 1.0 (or whatever you're calling the initial release).
Plex Media Server Version 0.9.12.18.1520-6833552, operating on a late-2012 Mac Mini with Quad-Core 2.6Ghz i7, 16GB RAM, Fusion Drive, OS X El Capitan 10.11.1
All six movie files were ripped personally from my Blu-Ray collection with MakeMKV v1.9.7
Thank you so much for your assistance. I really hope to see this issue resolved as I'm totally sold on Plex at this point otherwise.