(Too late to edit - a small error there. The Logitech cam was of course connected to a USB port on the Pi. The two HDMI connections in question were two ports o

(Too late to edit - a small error there. The Logitech cam was of course connected to a USB port on the Pi. The two HDMI connections in question were two ports on the TV, one with the Pi as source, the other with the normal cable box as input)