4 ms·

Hang on - HDMI can do Ethernet? That was news to me.

by jsmeaton 7y ago

lightedman 7y ago
Yup, been in the spec for a while. Video cards try to install drivers for it now days. I always stop that garbage.
kuzimoto 7y ago
There are virtually no devices that actually support it, at least as of about a year ago.
gregmac 7y ago
I was trying to find an "HDMI condom" (equivalent to the usb ones [1]) but came up dry. Does such a thing exist yet, or is there just no market? Is it possible to use something such as an HDMI splitter to accomplish the same thing, or can those pass Ethernet as well, and how would you be able to tell? [1] https://int3.cc/products/usbcondoms https://int3.cc/products/usbcondoms
- wh1t3n01s3 7y ago
  You could maybe try an old hdmi splitter not compatible with latest dhcp (that supports ethernet)
dillonmckay 7y ago
Some network switches actually used HDMI to connect between switches.
- ThePowerOfFuet 7y ago
  Only the cable, not the protocol.
  - SlowRobotAhead 7y ago
    Correct, it wasn’t carrying HDMI signal, rather leveraging a much higher quality cable and terminals, correctly twisted pairs for long distance, high quality shielding (or double), etc. For any faults, HDMI is a typically good cable.
myself248 7y ago
Yes, almost every HDMI cable now brags that it includes ethernet, which is carried on a formerly-unused* pair within the HDMI connector. Many older cables didn't connect it, or grounded one of the pins (*because it had been used as a plug-detect pin), but since devices started actually using it, cable vendors started wiring it. The extra pair doesn't make the cable much stiffer, but leaving it out had made them ever so slightly more flexible. Many devices don't support it, but some newer video cards install an Ethernet device when you load the driver, so they do. And some TVs do, of course. So if such a card and such a TV are connected with such a cable, voila! An connection you might not even realize is there. Your formerly-isolated TV is no longer isolated, assuming the video card driver installer did something like enable bridging to that ethernet interface. There are a few ways to avoid it. First, don't install that driver if your video card prompts for it, or disable the device. Second, use a cable tester to verify that you're using a cable which doesn't connect the pins, which is gonna get harder if you need a newer cable that's tested to a higher bandwidth spec. Or third, open up the cable and bite the wires in half. It's tricky to know which pins those are; I plan to do it with an inductive "toner" probe connected to a breakout adapter. (Unrelated: Some Ethernet switches used HDMI cables to connect each other for "stacking". This is just because the connectors are cheap, the cables are cheap, and they have a lot of high-bandwidth pairs. The switch makers could run more-or-less full backplane speeds over a short HDMI cable more cheaply than they could over a custom stacking cable. But the signals on the wires are not HDMI, they're more-or-less Ethernet on whatever inter-switch-chip format, probably QSFP or something, that needs a bunch of length-matched pairs.)

Hang on - HDMI can do Ethernet? That was news to me.

lightedman 7y ago

Yup, been in the spec for a while. Video cards try to install drivers for it now days. I always stop that garbage.

kuzimoto 7y ago

There are virtually no devices that actually support it, at least as of about a year ago.

gregmac 7y ago

I was trying to find an "HDMI condom" (equivalent to the usb ones [1]) but came up dry. Does such a thing exist yet, or is there just no market? Is it possible to use something such as an HDMI splitter to accomplish the same thing, or can those pass Ethernet as well, and how would you be able to tell? [1] https://int3.cc/products/usbcondoms https://int3.cc/products/usbcondoms

wh1t3n01s3 7y ago
You could maybe try an old hdmi splitter not compatible with latest dhcp (that supports ethernet)

dillonmckay 7y ago

Some network switches actually used HDMI to connect between switches.

ThePowerOfFuet 7y ago
Only the cable, not the protocol.
- SlowRobotAhead 7y ago
  Correct, it wasn’t carrying HDMI signal, rather leveraging a much higher quality cable and terminals, correctly twisted pairs for long distance, high quality shielding (or double), etc. For any faults, HDMI is a typically good cable.

myself248 7y ago

Yes, almost every HDMI cable now brags that it includes ethernet, which is carried on a formerly-unused* pair within the HDMI connector. Many older cables didn't connect it, or grounded one of the pins (*because it had been used as a plug-detect pin), but since devices started actually using it, cable vendors started wiring it. The extra pair doesn't make the cable much stiffer, but leaving it out had made them ever so slightly more flexible. Many devices don't support it, but some newer video cards install an Ethernet device when you load the driver, so they do. And some TVs do, of course. So if such a card and such a TV are connected with such a cable, voila! An connection you might not even realize is there. Your formerly-isolated TV is no longer isolated, assuming the video card driver installer did something like enable bridging to that ethernet interface. There are a few ways to avoid it. First, don't install that driver if your video card prompts for it, or disable the device. Second, use a cable tester to verify that you're using a cable which doesn't connect the pins, which is gonna get harder if you need a newer cable that's tested to a higher bandwidth spec. Or third, open up the cable and bite the wires in half. It's tricky to know which pins those are; I plan to do it with an inductive "toner" probe connected to a breakout adapter. (Unrelated: Some Ethernet switches used HDMI cables to connect each other for "stacking". This is just because the connectors are cheap, the cables are cheap, and they have a lot of high-bandwidth pairs. The switch makers could run more-or-less full backplane speeds over a short HDMI cable more cheaply than they could over a custom stacking cable. But the signals on the wires are not HDMI, they're more-or-less Ethernet on whatever inter-switch-chip format, probably QSFP or something, that needs a bunch of length-matched pairs.)