TL;DR make sure the settings on the device you are casting from is set to original. The Chromecast will use the casting devices quality settings
I figured out what was causing my initial problem, so I will explain the issue and solution in case anyone else runs into the same problem…
The initial problem was that we had 2 Chromecasts on 2 different TVs and the same file would direct play on one Chromecast but then transcode when played on the other. I searched through the logs to try and understand why this was and could see that the Chromecast would load an “augmented profile” instead of the Chromecast.xml profile that is the Resources folder of Plex. The augmented profile that was being used had set the maxResolution to SD, meaning that the video would begin transcoding.
Turns out, my girlfriend was casting from her Android device to one TV, and I was casting to the other from my Android device. The difference was that she hadn’t changed the “Quality over WiFi” setting to original within the Android application. It appears the Chromecast uses the quality settings from the devices that casts it and not the best quality settings available for the Chromecast (which I had assumed it would).
I have no idea if this is common knowledge or common sense, but 3 days of investigating lead me to this conclusion. I also tested the theory by casting from the web player after changing the quality settings and it’s the same behaviour. FML!
Also, to try and answer my own questions:
How are profiles loaded?
No idea
How can I tell if profiles are being picked up correctly?
You can see in the Plex Media Server.log file if a profile is being used
What determines a match between a device and a profile?
■■■■ knows
What is an “Augmented Profile” and how is it created?
I believe an “augmented profile” is the profile that casting devices sends to the Chromecast/server so that it can decide if the file needs to be transcoded
mic drop
