Too big originally:
-rw-r--r-- 1 miro miro 33074956 2016-01-18 23:12 Screen_160118_2307_g0n.mkv
-rw-r--r-- 1 miro miro  9988065 2016-01-18 23:43 Screen_160118_2341_g0n.mkv
-rw-r--r-- 1 miro miro  2974186 2016-01-18 23:44 Screen_160118_2344_g0n.mkv

After simple FFmpeg recode:
-rw-r--r-- 1 miro miro 14716956 2016-01-19 00:11 Screen_160118_2307_g0nr.mkv
-rw-r--r-- 1 miro miro  4835777 2016-01-19 00:12 Screen_160118_2341_g0nr.mkv
-rw-r--r-- 1 miro miro  1202539 2016-01-19 00:12 Screen_160118_2344_g0nr.mkv
(and these latter renamed to, and replaced the former.