I recently set up my Plex Media Server on a Raspberry Pi (running Ubuntu MATE) connected to my local network. When I start casting to my Chromecast (same network), I encounter some problems. If I initiate the cast from the Pi server itself (web interface), the quality is perfect, no problems at all, but when I initiate a cast of the same file using the Plex Android app, the quality is atrocious and can barely stream at all. Why is this? Clearly there is no issue with the file itself since it can cast fine in some circumstances. There is no Original Quality option that I can find in the Quality settings on the Android app, so I've set everything to 20mbps or Maximum, but according to Plex documentation this shouldn't matter, as casting should automatically use original quality. Any help would be greatly appreciated.
It's what the client application is capable of that determines whether a file is directly played or must be transcoded.
So is the issue with the Android app or the Chromecast? If it's the app, how do I change it? The app settings indicate that it should play at original quality if the file is 20Mbps/1080p or less, but it's clearly not doing that. If it's the Chromecast, why does it successfully cast when initiated from the web interface?
You are confusing the terms quality, transcoding, and application capability.