Poor Facetime Video

Hi all,

I have 2 Mac Pros (late 2013) running El Capitan (latest). I added a web cam to each (Logitech HD Pro Webcam C920) and I made a video call from one to the other using Facetime. The video quality varied per call, but was usually unacceptable - and never equal to 720P quality. When I watch the modem and router, it is clear that the call is going through the router only - not out over the modem. In such a case I would expect the video quality to be quite good.

When I do the same thing using Safari running the Google Hangouts plug-in, the is video quality is way better. It is also clear that the call is going out over the ISP modem, and must be switched through the router for each machine.

The webcam shows very high quality video when using the recording function of the Qujicktime player.

What is the matter with Facetime? Is there some reason it might not like calls being switched locally through a router? I have never tested it out over the Ethernet.

Facetime has such a simple interface; there is really nothing I can adjust. Is this just bad software, poor Apple network, etc.?