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I learned recently that most HDMI cables support ethernet capability, and from what I gather their typical usage is specially adapted for home theatre setups, and usually not used at all.

I will be threading an HDMI cable through a wall soon, and I want to minimize the number of cables going through a small hole if at all possible. One end of the cable will go to my PC (steam setup), the other end will be cut, then reassembled onto a breakout adapter, then to a TV.

I would also like to connect ethernet from my TV to a network switch (not my PC). So to save on cables I would ideally like a pair of devices: One takes ethernet from the switch and HDMI from my PC and outputs HDMI w/ Ethernet. The other takes HDMI w/ Ethernet and outputs HDMI and an ethernet plug.

Does such a pair of devices exist? I tried looking online and all I can find is the exact opposite, devices that mangle HDMI into a pair of dedicated ethernet cables and back.

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  • That breakout adapter is going to be bad for signal integrity. You might find that it works for the early versions of HDMI with low clock speeds and not for the later versions with higher clock speeds. So in 2022 when you upgrade to an 8HD projector with holographic smell-o-vision, you might need to punch a larger hole in the wall. Could you use mini or micro instead of cutting the cable? – pericynthion Nov 1 '17 at 23:27
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No, there are no passive adapters to allow Ethernet to be added to an HDMI cable.

HDMI Ethernet Channel (HEC) is 100 Mbps data connection that shares two wires on the HEAC channel. Handshaking is involved to enable this. It is not a simple pass through connection. What you want, a passive adapter cable, does not exist. You need two devices that support HEAC. Conceivably, you can find or make an active HDMI compliant device that allows you to pass through normal ethernet connections, but that seems like a rocket launcher for a fly.

Details:

HEAC uses pins 14/19 and is used for hot plug detect, Audio return and Ethernet. It uses a specific PHY to separate the functions and is only available on HDMI High Speed and High Speed with Ethernet cables. It is defined in the HDMI 1.4 spec.

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Pins 14/17/19 are in a new shielded group (E)

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