I have a couple of MP4 movies that when I try to play via Plex I get a playback error “This server is not powerful enough to convert video.” The movies are around 2.5GB in size. Funny thing is, the exact same files play just fine via Emby. I have both Emby and Plex connected to the same movie DB which resides on my Synology 918+. Any idea what is going on? Probably a setting somewhere I missed? I have around 300 movies so its not like I cant play anything at all.
I may have discovered the problem. In Settings/Plex Web/Quality I had “Automatically adjust quality (Beta)” checked. Unchecking this option seems to allow either of the two movies to play without error. Checking again and trying to play the movies brings up the original error. I know this says Beta so perhaps this will be addressed sometime in the future.
Using that option causes the stream to get transcoded. That’s the only way that feature will work. Turning off that feature allows the stream to direct play (if possible), which sounds like it is.
As the error indicated, your Synology is not powerful enough to perform the transcoding. There is no fix for that.