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Hello! There are adapters (basically repeater pairs) that take an HDMI signal (from a regular HDMI output), via a short HDMI cable into an HDMI-style input. In the other end ...
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  1. #1
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    Linux driver for HDMI over ethernet port


    Hello!

    There are adapters (basically repeater pairs) that take an HDMI signal (from a regular HDMI output), via a short HDMI cable into an HDMI-style input. In the other end of the adapter, you connect a possibly much longer ethernet cable to the input of the second adapter. In the other end of the second adapter you plug a short HDMI cable to the target port:

    SourceHDMIport -> HDMIcable -> Adapter1Input -> Adapter1Output -> LONG TP CABLE -> Adapter2Input -> Adapter2Output -> HDMIcable -> TargetHDMIport

    This makes it possible to use regular networking cables to create a very long (>100m) HDMI connection , whereas a regular HDMI cable may not work at half that length, and is much more expensive.

    Speaking of digital signals, you can also do ethernet over a USB port / cable.

    Question:

    Can HDMI video be sent directly through a 100Mb/s ethernet adapter (skipping the first adapter in the diagram)? Is there a driver for that?

    Additional, off-topic, questions:

    2. Can I use my HDMI port as an ethernet jack?

    3. Why are HDMI cables so crappy and expensive (lower production volume?)?

    4. Why not use the same cable for everything (and, like USB, use new backwards-compatible specifications as needed)? Why do different digital specifications need different connectors (apart from serial/parallel)?

    5. Imagine the mother of all digital cables. What would it look like? How many pins does it need to have?
    Last edited by salantrax; 10-16-2013 at 07:23 PM. Reason: comma Chameleon

  2. #2
    Super Moderator Roxoff's Avatar
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    It is unlikely that you'll be able to send HDMI over ethernet directly. The HDMI signal is encoded in hardware, and you need special stuff to decode it. HDMI includes digital signal protection to prevent anyone taking the hi-def video/audio signal and ripping off Hollywood by copying it to their hard disk. So, while it's not actually going to be impossible to take the HDMI signal and convert it to packetised ethernet, I suspect it's quite difficult to do.

    You probably want to stick to DVI anyway - these can do a higher resolution than HDMI and are also a digital signal (albeit with no sound included). HDMI is intended to do up to 1080p, which is starting to look a little crap for PCs these days.

    So to answer your other questions:

    2. Why would you want to? We have ethernet for that... Seriously, with all the protection ladled onto HDMI, you're better off sticking with a network port

    3. crappy and expensive? They are if you buy them from the high street. The last HDMI lead I bought cost about 1.50 from Amazon or somewhere similar. As the standard is digital, you don't need gold contacts or heavy duty cables to reduce analogue signal loss.

    4. To an extent we've been headed this way for most peripherals with USB. It's not really suited to everything, though - and display output does have to be absolutely immediate.

    5. It'd have a usb plug on each end... I have one here
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    Quote Originally Posted by Roxoff View Post
    It is unlikely that you'll be able to send HDMI over ethernet directly. The HDMI signal is encoded in hardware, and you need special stuff to decode it. HDMI includes digital signal protection to prevent anyone taking the hi-def video/audio signal and ripping off Hollywood by copying it to their hard disk.
    Magic. Got it.

    Seriously, this makes sense. (I thought HDMI was basically a (n open) protocol.) I suspect this is why my open video drivers often don't support HDMI output. (With the exception of the opentegra drivers for a Tegra2 device.) This ends the dream of HDMI as a universal digital interface.

    Quote Originally Posted by Roxoff View Post
    You probably want to stick to DVI anyway - these can do a higher resolution than HDMI and are also a digital signal (albeit with no sound included). HDMI is intended to do up to 1080p, which is starting to look a little crap for PCs these days.
    Actually, I think HDMI supports much higher resolutions than that... It's just that it is marketed as a home media interface, and therefore PC drivers don't concern themselves with higher resolutions than most TV's can display. Also, a lot of modern laptops (and even desktops) unfortunately doesn't support DVI. [Edit: HDMI 1.4 seems to support at least 40962160].


    Quote Originally Posted by Roxoff View Post
    3. crappy and expensive? They are if you buy them from the high street. The last HDMI lead I bought cost about 1.50 from Amazon or somewhere similar.
    A clear exaggeration from my side, I agree. I haven't bought a lot of them, and I realize now that there are cheap ones to be found.

    Quote Originally Posted by Roxoff View Post
    [USB is] not really suited to everything, though - and display output does have to be absolutely immediate.
    Too slow. Got it.

    Quote Originally Posted by Roxoff View Post
    5. It'd have a usb plug on each end... I have one here
    [strikethrough]But imagine a broadened USB interface. Like, 10 pins. 10 Gbps. Parallel capable. Aggregatable.[/strikethrough]

    There should be 1 digital interface only! xkcd.com/927/

    Thank you for your informed answer.
    Last edited by salantrax; 10-16-2013 at 07:12 PM.

  4. #4
    Super Moderator Roxoff's Avatar
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    Quote Originally Posted by salantrax View Post
    Actually, I think HDMI supports much higher resolutions than that... It's just that it is marketed as a home media interface, and therefore PC drivers don't concern themselves with higher resolutions than most TV's can display. Also, a lot of modern laptops (and even desktops) unfortunately doesn't support DVI. [Edit: HDMI 1.4 seems to support at least 40962160].
    I haven't read the specs on what HDMI is capable of, I'm only aware that my FM2 mainboard does VGA and HDMI, and I also know the current limitations on resolution that computer HDMI ports impose. To run our higher res monitors at work we need to use DVI. I'd be really pleased if my own computer was capable of higher res - the 1080p 'standard' has held back display resolution improvements for years.
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