HDMI over ethernet

Discussion in 'General Electronics Chat' started by dadane, Jan 5, 2015.

  1. dadane

    Thread Starter New Member

    Jan 5, 2015
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    I have no knowledge of the spec for HDMI so was hoping someone here might.

    As far as I can tell all video and audio data is transmitted using the four differential TDMS 0/1/2/CLK signal pairs. So is it possible to distribute using only these signals or will the receiving device refuse to accept it if, say, the DDC channel is missing. Basically, am I snookered by DRM?

    HDMI cables don't come cheap, and the point of this exercise is to do it the cheapest possible way, so I thought I'd find out if this is a dead duck before I start chopping.

    PS. Yes, I know I can buy devices to do this but where is the fun in that :) Plus they are about 5 times the price here they are in the US or UK.

    PPS. The runs are quite short but probably not short enough, so I do realise that a TX driver and RX buffer may be required. I'll cross that bridge when I come to it (maybe come up with something to utilise the batch of RS485 line drivers currently gathering dust and cobwebs in the shed.)
     
  2. Brownout

    Well-Known Member

    Jan 10, 2012
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    I bought a 6' HDMI cable at Best Buys for about 12 dollar. Got to be cheaper online.
     
  3. dadane

    Thread Starter New Member

    Jan 5, 2015
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    Trying to get about 20' - 30' through one floor and two walls. Laying in a CAT6 cable anyway because a) I've got some spare and b) I'm in the middle of wiring up mains and RF on that route so might as well build in redundancy. Not sure a prefab cable will help. Thanks, Dave.
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    You theoretically should be able to use normal ethernet cable (or two to get around the drm issues), but frankly I´d rather buy the ready made cable then do all the hassle with wiring the tiny connectors to an unwieldy cable.
     
  5. Brownout

    Well-Known Member

    Jan 10, 2012
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    So, you're saying between your video device and the display device, there is 20 - 30 feet and walls, floors, etc??? It sounds like you have something else in mind, like streaming from one video device to a different one ( Machine to machine ) In that case, you can use a protocol that embeds MPEG video in IP packets. You can also look into the new wireless streaming devices.
     
  6. dadane

    Thread Starter New Member

    Jan 5, 2015
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    No, I'm not going to mess around even attempting to solder an HDMI connector, just chop one end off and go to stripboard.

    I had no idea you buy a 20' HDMI cable. Where?
     
  7. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Well, I am not sure which stores are available in the middle of the pacific ocean, but where I live I can buy just with the first google hit a 10 meter cable (30 ft i guess) for less than $10.
     
  8. dadane

    Thread Starter New Member

    Jan 5, 2015
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    I have a Sat decoder, DVD player, legacy VCR, and a PC dedicated to AVIs/streaming in a central location. These are currently distributed to other rooms and outbuilding using analogue AV which keeps everything in sound synch but also allows one TV to be on broadcast, one online, one on DVD, etc. simultaneously. I'm just looking at modifying the set up and joining the 21st century.
     
  9. dadane

    Thread Starter New Member

    Jan 5, 2015
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    10m will do it for this particular extension, I have a 25m to do next and I have no intention of digging up my driveway to force an HDMI connector through the existing underground trunking. They are not available here at the moment at that price: awaiting shipment (according to my trade connections). Anyway, we are getting off thread: Can you redistribute HDMI signals using only the TDMS data to an HDMI compliant receiving device?

    PS. Suggest you look at Google Earth a little more carefully... .-)
     
  10. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    That should depend on your source of video signal. For example a blue-ray disc will likely be DRM protected and won't let you run full resolution without compliant cables and devices, but other sources like PC games and ripped discs should work fine.
    Either way, if you run two cat6 cables instead of one you should have no issues.

    Actually with just one cable you are missing the DDC channel and the hdmi might not work at all, many systems use this to check for a presence of a monitor or other receiver so that they set up the resolution and start sending data. Also you are missing a ground which might turn disastrous over long runs due to different earth potentials.
     
  11. dadane

    Thread Starter New Member

    Jan 5, 2015
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    On MEN mains here. It's a horrendous 'on the cheap' distribution system but it does make equipotential bonding easy.

    The DDC situation is what I really want to know about. How does this apply to standard (non-BR) DVD for instance?
     
  12. Brownout

    Well-Known Member

    Jan 10, 2012
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  13. dadane

    Thread Starter New Member

    Jan 5, 2015
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    I'm a hardcore VLC addict already thanks. I want more though... I want it synched in multiple rooms in HD (already got it in analogue) and I want to find the cheapest way of doing it without buying any off-the-shelf hardware. I've just spent a day routing cables so that everything is hidden, installing a PC at the top off the kitchen wall next to the brand new slimline TV may be effective but falls slightly short of the mark from both an interior design and energy efficiency viewpoint.
     
  14. crutschow

    Expert

    Mar 14, 2008
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    Going to stripboard will likely kill the signal. The high frequency HDMI digital signals much be matched very closly in propagation delay so the bits won't get scrambled. Even a slight difference between two wire lengths can cause problems.
    Also the impedance mismatch from the stripboard would likely cause troublesome signal reflections.

    Can't you order cables on the internet from UK or USA suppliers?
     
  15. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    I was assisting in an office move. Two if the conference room tables had VGA connectors for laptop presentations direct to the wall mount TV. The electricians cut the cable to snake it through the wall, and spliced it back together.

    That ruined the signal. They had to come back, drill (and repair) bigger holes to fit the connectors through and snake a replacement $$ cable. Where a cable splice messed up the signal, I can imagine what bringing it to strip board will do.
     
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