Unless you’re pushing the limits of the supported screen size, there typically is some idle time in the TMDS links in an HDMI cable. What I’d wager she’s seeing

Unless you’re pushing the limits of the supported screen size, there typically is some idle time in the TMDS links in an HDMI cable. What I’d wager she’s seeing is the transition from idle time back to transmitting on the links. There’s some kind of sync mechanism in HDMI, too, but I don’t recall what it is. Or possibly data islanding?