VideoCapture (file, ffmpeg) memleak?

Recently I observed that VideoCapture slowly uses more and more mem.
For example:
AVC1 movie, 1920x1080p (= 6 MB/frame),

capt >> frame; // VideoCapture capt; Mat frame; for all frames

Every abt. 20,000 frames it suddenly consumes abt. 100kB+/- more.

OK, that’s not much today, still something seems to be leaking?

(I ripped the code to the above line)