on real time.
but on android 4.x and on nexus 5 not support this function.
I can not use programs: hangon, slype etc for video call but only cellular protocol for video call
example galaxy s2 with android 3.x have video call, but s2 with 4.x not have video call native
i solve many problem with xposed of XDA ma not find solutions for enable native video call for nexus 5