I've run into an issue after building a new server on Ubuntu 16.04 that seems to crop up when 4-5 transcodes are in progress and a new transcode session is attempted. From the Plex web perspective, the loading screen appears and spins, with no error returned. The logs below seem to indicate that the transcoder process is having issues initalizing. A full log of the relevant session is attached as well. I can also provide the log from startup, starting of other streams, up til the failure as well if needed.
Apr 26, 2016 01:41:36 [0x7f45bbbfa700] ERROR - [Transcoder] [AVFilterGraph @ 0x36618e0] Error initializing threading.
Apr 26, 2016 01:41:36 [0x7f45a9fff700] ERROR - [Transcoder] [AVFilterGraph @ 0x36618e0] Error creating filter 'scale'
Apr 26, 2016 01:41:36 [0x7f45b1fff700] ? - [Transcoder] Error configuring filters.
Apr 26, 2016 01:41:36 [0x7f45aebff700] ? - [Transcoder]
Apr 26, 2016 01:41:36 [0x7f45c0bff700] ERROR - Failed to start session successfully
Initially I was experiencing the issue with a Plex install inside a 16.04 container on LXC. To rule the container\LXC out, I installed Plex onto a normal 16.04 install on the server and encounted the same issue. After reinstalling 14.04 on bare metal, transcoding again works as expected, and I am able to spin up 15+ transcoding streams with no issues. Transcoding also functions normally in a 14.04 container on a 16.04 host. I don't see anything in the syslogs of the server itself to indicate any other issues at the time of the problem. For reference, the source files being transcoded are all rather large (20-30G).
Anyone running into this issue or have any suggestions?