4k video on a cell phone can good! By default 35mbps is too low for any motion to stay sharp. Most 4k cell phone video looks worse then full HD. Now you can hack your phone to more than triple the bitrate.

First root your phone
http://www.droidviews.com/root-att-and-verizon-galaxy-s5-without-voiding...

LG G3 Hack
http://www.droidviews.com/jishnus-camera-mod-for-lg-g3/

Note 3 Hack
http://forum.xda-developers.com/showthread.php?p=49598931