[rsync]

I don't own a smart TV and I, too, am skeptical that your grandparent is correct that TV makers are surreptitiously using other devices as network bridges with HDMI, etc.

BUT ... since we're talking about it ... are the network lines on HDMI reserved for that purpose such that you could create an "HDMI condom" ? I have USB condoms that I use to charge phones with, etc., and wonder if the same concept works with HDMI ...

[nitrogen]

It looks like HDMI uses separate pins from the video signal for Ethernet and Audio Return Channel. I originally thought it was using a shared packetized bus for HEC, but it's actually kind of clever -- differential mode signal on those two pins is HEC, common mode signal is ARC.

HEAC utilizes two lines from the connector: the previously unused Reserved pin (called HEAC+) and the Hot Plug Detect pin (called HEAC−).

- https://en.wikipedia.org/wiki/HDMI#HDMI_Ethernet_and_Audio_R...

So if you don't need ARC, it should be possible to make a simple filter that blocks both HEC and ARC. Older HDMI cables that might not connect the Reserved pin might also block HEC+ARC. And it also seems like you can get ARC-only by disconnecting the Reserved pin.

I'd guess HEC is most commonly going to be used in situations where you'd also want ARC -- to provide network access from an A/V receiver to a smart TV, and then get the audio back into the receiver.

[karlding]

HDMI Enhanced Audio Return Channel (eARC) uses the two Ethernet pins.