After multiple start/stop playback of any kind of source (I tested on regular avi file & rtsp source) I see a memory usage increasion (via ProcessExplorer, TaskManager).
E.g. when I start playback at first time - I see 116 Mb. After a lot of stop/play commands (tested manually by pressing "s"/space keys aprox. 5 minutes) value of used memory increased by ~10 Mb.
Tested on 2.2.2 & 3.0.0-git 30-03-2016 win32.
My OS is Windows 7 Pro 64 bit.