Try to do my best in explaining.
I tried to play a movie (.mkv ripped from Blu-Ray) from the beginning, then I set >>16x and I leave it alone while position is getting increased.
Immediately free RAM tends to decrease to zero, and depending on video content location, the behavior is pretty different:
1. content stored on Plex server, plugin "PlexKodiConnect" on Kodi player -> memory goes to "0" and the whole thing freezes (oom-killer message in dmesg), then kodi restarts after a while (watchdog?) and all features are recovered;
2. content locally stored on USB, browsed through "movies", going backwards through "../../" until I see "files/mydisk/.../path_to_moviefile.mkv" -> memory decreases to a few MB (~50) faster than in case number 1, but it never goes to "0". When I resume "play" memory is not freed and constant square artifacts are shown on video frames. Pressing "stop" frees used memory. In this case, if I "play" content before memory going down to critical level, the play is smooth, even if used memory does not decrease until "stop" is pressed.
My environment is:
kodi 17.0 Git:a10c504
OpenELEC 0.8.9
Titan skin 3.7.23
CPU: Pentium N3700 @ 1.6 GHz
RAM: 3855 MB, free 3101 MB
Resolution: 1920 x 1080 @ 60 Hz