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I would like to plug a mouse and keyboard into a monitor and have the HDMI cable carry the signal back to the laptop along with the video. Do HDMI cables an ports support this functionality?

The laptop—an Acer Aspire V5-571P-6828 running Windows 10—has an HDMI port but no other video ports, so a DisplayPort is not an option.

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    I'm curious too because amzn.to/3mfnkbv sure seems like there are special HDMI cables that handle USB and mic/speaker too. See section "How to Get Keyboard and Mouse Work" (sic).
    – Ryan
    Oct 23, 2020 at 13:18
  • +1 upvote, check out my experience of this here: superuser.com/a/1698155/21353 Jan 8, 2022 at 13:25
  • HDMI cables in fact do have enough wires exactly for stuff like this (well, originally for Audio Return Channel and Ethernet). However, your laptop wouldn’t support that.
    – Daniel B
    Jan 8, 2022 at 14:30

2 Answers 2

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No, HDMI cables don't support this functionality.

HDMI does have a backchannel (CEC) which in principle could be used to carry mouse and keyboard signals, but I don't know of any hardware which actually uses it for that. You may be able to use it that way in hardware you built yourself, but it's extremely unlikely your monitor supports it.

Monitors sometimes have an integrated USB hub for mouse and keyboard, and require an USB cable back to the computers.

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  • +1 upvote, CEC might explain my experience using a KVM which seems to support USB over HDMI (unofficially or by some other proprietary method). superuser.com/a/1698155/21353 Jan 8, 2022 at 13:25
  • @therobyouknow The "breakout" at the end of the proprietary cable in your picture very likely means they just bundled the USB wires with the HDMI wires inside that cable. Unless you can use your KVM switch with a standard, third-party HDMI cable, it's a one-off solution with no relation to the HDMI standard.
    – dirkt
    Jan 8, 2022 at 18:41
  • HDMI does have a backchannel (CEC) which in principle could be used to carry mouse and keyboard signals: the bandwidth is very low (417 bits per second), probably not enough. Theoretically, another option would be Ethernet-over-HDMI (HEC/HEAC) combined with USB-over-Ethernet/USB-over-IP, but I don't know if anyone has ever done that Dec 27, 2023 at 19:42
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Unofficially it seems, from this CKLau KVM switch that I have purchased. No affiliation.

Update

Yes, this does work for this device: USB mouse and keyboard data is carried along with HDMI from the KVM's HDMI output to the device where it has a breakout of HDMI and USB plugs that plug into the device.

The keyboard and mouse plug separately into USB inputs at the KVM.

Presumably the implementation in the KVM to carry USB data could be making use of of the CEC as this other answer here mentions: https://superuser.com/a/1155529/21353 Either that or an unofficial proprietary out-of-band method.

In conclusion, I'm not keen on this device for what seems to be a 'hack' / shortcut.

Also because on a separate note it does not carry the monitor's EDID information to communicate the display capabilities to the end device. I see 800x600 default Windows display but when plugging same device into a HDMI cable directly between it and the monitor, the native 1920x1080 resolution of the monitor is made use of.

So I wouldn't recommend KVMs that unofficially support USB over HDMI.

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