How to determine that the TV is displaying HDMI with a Raspberry connected to it, and not other ports or air?

Question

HDMI

A RASPBERRY is connected to the TV via HDMI, it transmits certain content to the TV. How do I determine that someone has not switched the image from the connected raspberry to another port or TV broadcast? How can I do that?
It is necessary that if there is a switch to another port, the malinka sends us a message to the mail through the web server installed on its web server .

Answer 1

Poke the OSD button on the remote, then the box will show the channel or input from which it broadcasts.

Answer 2

Very dumb, but working. Take some kind of sensor that recognizes the brightness / color, attach it to the lower right pixel of the TV - stupidly "drop" on the screen - not physically to the pixel of course, isolate. In the video stream, add a rigidly fixed and well-known information to this same pixel - for example, fill it with red. Calibrate the sensor, remember the value when the flow is on. As soon as the value deviated strongly, then the channel was switched.
You can try the same thing through the audio channel.