I installed Media Center on a Raspberry Pi 3 B running the latest distribution of Raspbian (as of a week or so ago). I followed the "new" installation guide, thought not straight through since I initially picked up old directions. Media Center version is 23.0.102. When I run Media Center manually thread priorities look OK. But when I start it as a service thread priorities are not working.
Starting via the VNC viewer start menu gives:
pi@raspberrypi:~ $ ps -T -eo user,pid,tid,class,rtprio,ni,pri,comm | grep mediacenter23
pi 3412 3412 TS - 0 19 mediacenter23
pi 3412 7193 RR 46 - 86 mediacenter23
pi 3412 7194 RR 46 - 86 mediacenter23
pi 3412 7203 RR 50 - 90 mediacenter23
pi 3412 7205 RR 50 - 90 mediacenter23
pi 3412 7207 RR 50 - 90 mediacenter23
pi 3412 7211 RR 50 - 90 mediacenter23
Stopping the manually initiated task and starting system service shows:
pi@raspberrypi:~ $ sudo systemctl start jriver.service
pi@raspberrypi:~ $ ps -T -eo user,pid,tid,class,rtprio,ni,pri,comm | grep mediacenter23
pi 7357 7357 TS - 0 19 mediacenter23
pi 7357 7560 TS - 0 19 mediacenter23
pi 7357 7572 TS - 0 19 mediacenter23
pi 7357 7576 TS - 0 19 mediacenter23
pi 7357 7580 TS - 0 19 mediacenter23
pi 7357 7584 TS - 0 19 mediacenter23
pi 7357 7586 TS - 0 19 mediacenter23
pi 7357 7588 TS - 0 19 mediacenter23
pi 7357 7996 TS - 0 19 mediacenter23
pi 7357 7998 TS - 0 19 mediacenter23
pi 7357 8000 TS - 0 19 mediacenter23
pi 7357 8004 TS - 0 19 mediacenter23
pi 7357 8008 TS - 0 19 mediacenter23
The same thing happens when the service is started at bootup.
I tried some of the ideas in the installation guide posts (changing @audio to pi in limits.conf, etc.) but nothing helped.