The control goes back and forth is delaying the frames when the loop back is triggered. I used H.264 codec 1280 x720 and 30 fps
Tests
Mac Pro - 2011
version 10.11.6
2GHz Intel Core I7
8GB 1333
AMD Radeon HD 6490 256 MB M
and
I MAC 2011
2,7 GHz intel core I5
8GB 1333
AMD Raedon HD 6770 M 512 MB