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HDMI into DVI?

Discussion in 'LCD & LED LCD TVs' started by NickXX, Mar 5, 2005.

  1. NickXX

    NickXX
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    Hi all,

    I've got a Tosh 27wl46 which has DVI input, but is not HDMI capable. When I bought the tv, I wasn't too fussed about the Sky HiDef coming out next year, as I have the tv hooked up to my PC. However, if I did change my mind, would there be any way of displaying the hidef signal on this tv? Surely it would be possible for some sort of convertor to take the HDMI HiDef signal and decrypt it into DVI, or is it not this simple?

    Many thanks in advance!

    Nick
     
  2. loz

    loz
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    HDMI into DVI is straightforward.
    However, HDCP will be still be required to watch Sky. This can use HDMI or DVI, so if your DVI connection doesn't support it, converting HDMI to DVI won't help.
     
  3. ianh64

    ianh64
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    Nick

    Don't confuse HDMI and HDCP. For Sky HD and blu-ray/HD-DVD when it comes, a HDCP compliant digital input will be mandatory for viewing material with the copy protected flag set, ie most films or big series'. A source that uses HDCP will encrypt the signal so that only a display that can decrypt HDCP will beable to unscramble the picture. Each source and display has its own secret key and only a device with a valid secret key can participate in the encryption/decryption process. Since the encryption also changes every few frames it would take an enormous amount of power to decrypt a video signal in real time and recalculctre the decryption every few seconds. If a display secret key is compromised, then it can be made revoked by viewing material that includes a revocation list. ie broadcast, DVD, blu-ray/HD-DVD etc. You can draw your own conclusions on whether there will be an economical device that will beable to reliably hack HDCP.

    HDMI and DVI are however quite similar, such that a simple cable or converter is all that is required to make the video side of HDMI and DVI electrically compatible. However as far as data is concerned, it is all very much up in the air. For a start, HDCP is implicit in the HDMI specification, so a DVI display must be HDCP compliant. In addition, DVI is PC orientated whilst HDMI is video orientated so DVI will only officially accept 8 bit RGB data whilst HDMI will do RGB, YUV, 10 bit data etc etc. In addition, digital signal leves between PC and Video, so if a display that expects PC orientated gets video signal levels, then you will loose dynamic range - blacks will be grey and whites will not be full white. Add to this display resolutions and video timings must also be available on both source and display, you can end up with a very limited available range.

    So best advice is to actually connect the source and display that you want to use. Unfortunately in your case it will not be possible, but whilst the display may not be HDMI compliant, it may be HDCP compliant so you may get something.
     
  4. NickXX

    NickXX
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    Hi guys,

    Thanks for the responses! I think that what I meant was could I convert HDCP into DVI, so Ian has cleared it up for me. I've also just realised why it can't be converted to DVI too. I was basically wondering if I could get a box which could decode HDCP into an RGB or DVI picture to go straight to the TV, but I guess this would compromise the whole point of HDCP (as you'd be able to link the source to a recorder of some sort)! Doh!

    Thanks for clearing it up, looks like I'll have to make do without HiDef Sky :)

    Many thanks!

    Nick
     
  5. ianh64

    ianh64
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    There is a box available to sort of do this. MAW was going to buy one (see plasma forum) but im not sure if he did in the end when it was pointed out that it could be potentially 'disabled' at any time - there is some question of its legality.
     
  6. NickXX

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    I can't see how Sky could profitably launch such a system if so few people are going to be able to use it. A box which fed out DVI would be great, but the fact that it could be disabled is quite disconcerting. However, in reality I suppose it would be a very similar piece of hardware to what is present within HDCP enabled tvs - just made external, so I imagine it'd be legal to use if you were going to just feed the output into your TV, but illegal if you started to record the output signal.
     

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