1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Say it ain't so.

Discussion in 'Projectors, Screens & Video Processors' started by LTJ, Aug 7, 2004.

  1. LTJ

    LTJ
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Well I've recently discovered the joy of pixel matching and this has initiated my plans to build/obtain a HTPC system. Now I thought that when using a sky box plus modified to SDI out-put into the pc and using the pc's dvd all I had to do was take the DVI out-put on my graphics card and feed into a PJ which had a DVI input, thus hoping that the signal was kept in the digital format all the way through.
    Now talking to a chap at Musical Images this afternoon he informed me that dvd's on a PC would not out-put a digital signal through the DVI output on the graphics card. The only signal out would be analogue!
    He further explained only DVI outputs on standalone DVD players would stay digital. Is this the case.
    Is anyone using DVI on a PJ ?
     
  2. Claude

    Claude
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Good question LTJ. I was planning on using the DVI output on my All-in-wonder' ati graphics card as my digitial source so I am also interested in knowing the answer to this one.
     
  3. Beastie Boy

    Beastie Boy
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    The guy is talking crap.

    Yes, you will get a digital video output from the DVI interface of your graphics card.

    It sounds as though he would rather sell you a DVD player.

    Cheers, Beastie.
     
  4. LTJ

    LTJ
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Beastie boy either he misunderstood or as you say "he's talking crap". He was though very adamant that this was the case due to copy-right laws. In other words HDMI are about to make things very akward with regards to this matter. You know I can measurevoltage, amperage and resistance but how do you measure a digital out-put ie a video card or a dvd player?
     
  5. hornydragon

    hornydragon
    Well-known Member

    Joined:
    Dec 19, 2001
    Messages:
    28,299
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    Somewhere near the M4 most of the time......
    Ratings:
    +1,215
    I think that HDCP is the issue, have a search theres loads on it and what is compatible with what.
     
  6. Claude

    Claude
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    LTJ,

    As an amateur electronic man I do have tequnique in mind that may hely you to distinquish the difference between a digital and an analogue output. Put your tongue onto the end of the cable and see whether there is a difference in the tingling effect! The analogue may turn your face into this :mad: whereas the digital may turn your face into this :eek:

    As for the DVI copyright stuff making it difficult, my understanding from geeking on this site is that many of the DVD manufacturers whom are incorporating a DVI output (i.e Samsung 945) are flying in the face of those very copyright laws. Not sure what my point is exactly!

    Could you tell me what HTPC stands for?
     
  7. FazerThou

    FazerThou
    Active Member

    Joined:
    Aug 23, 2003
    Messages:
    1,825
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    66
    Location:
    Bath
    Ratings:
    +143
    home theatre personnal computer
     
  8. LTJ

    LTJ
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Well thanks FazerThou. Anyhow looking into it a bit more it seems like a minefield of further confusion see
    http://www.datapro.net/dvi.html

    it would seem that there are 3 DVI formats
    1. DVI-D (Digital)
    2. DVI-A (Analog)
    3. DVI-I (Integrated Digital/Analog

    To muddy my waters further it would seem that DVI and HDMI can be interfaced see
    http://www.datapro.net/products/1163.html

    So I'm still confused.
    Q1 Will a graphics card (geforce 5600 in my case) out put digital if it has a DVI connector?
    Q2 Are DVI and HDMI the same signal just different connectors?
    Q3 If the answer to 2 is yes. Does that mean any pj with an HDMI input can be connected to a PC outputting via a DVI connector (digital or analogue still not sure)

    I've take on board horny dragon and beastie boys comments but I'm still not confident.
    Claude I tried your test method and I now have to drink my tea with a straw!
    Any definitive answers out there
     
  9. Miniholic

    Miniholic
    Well-known Member

    Joined:
    Apr 26, 2001
    Messages:
    3,046
    Products Owned:
    0
    Products Wanted:
    1
    Trophy Points:
    106
    Location:
    The Shire
    Ratings:
    +398
    HDMI has the capacity to carry audio too (the mags like comparing it to a digital scart), whereas DVI only carries video signals, but you can use an adaptor to interface between the two, but only for video use as far as I am aware.
     
  10. NinjaShredder

    NinjaShredder
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    HDMI allows higher resolutions (higher bandwidth data transfer) than DVI, but is backwards compatible with DVI. So something than outputs DVI can be easily converted to a HDMI connection. But a HDMI signal in a resolution higher than DVI allows cannot be converted to DVI.

    HDMI devices also are likely to support HDCP. Which I don't know much about.

    ATI's X800 card also says that it is HDMI compliant, and HDCP ready. This means that resolutions not allowed by DVI, but are allowed by HDMI can be transmitted. And I think WinDVD 6 mentioned HDCP. Conjecture: So if it was the case that there was some video content which must only be transmitted digitally if HDCP is included, then these things might support this.

    But as far as I know, PCs can easily ouput DVDs digitally, over a DVI-D cable, from their DVI-I port. But I do not have first hand experience of this, so cannot confirm this, as I haven't got my X800 with DVI conncetion yet.
     
  11. Beastie Boy

    Beastie Boy
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    If the hardware doesn't support HDCP (ie. a graphics card other than the X800), then it presumably it will not recognise (or look for) the relevent protection flag.
    So would the player still output a standard video signal over DVI even if there was HDCP protection? I'm assuming that the hardware needs to support the protection in order for it to be effective, in the same way that current DVD players support Macrovision and CSS used on todays DVDs.

    Cheers, Beastie.
     
  12. LTJ

    LTJ
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Hello Beastie Boy. This chap at musical images was very certain that although a DVI output was present yhe pC would only out-put in analogue. He said most people don't realise this fact. I know that DVI will output in analogue-oh well.
     
  13. Messiah

    Messiah
    Well-known Member

    Joined:
    Apr 22, 2002
    Messages:
    7,534
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Ratings:
    +339
    Well, if that's the case then I should not be getting any image from my HTPC as my projector only has a DVI-D (Digital DVI) connector. As it happens I get a stunning image, as many will concur.

    I also concur that, IMO, the guy at MI is talking cr4p. Having had quite a few dealings with them, and bought lots of kit from them, it does not surprise me :rolleyes:
     
  14. Joe Fernand

    Joe Fernand
    Distinguished Member AVForums Sponsor

    Joined:
    Jan 20, 2002
    Messages:
    24,423
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    The Borders
    Ratings:
    +2,592
    LTJ

    Its very easy to get misinformation on what is an emerging minefield.
    In its simplest form the vast majority of commercially available DVD discs (Movies, TV Shows, Music Vids etc) carry a digital 'Flag' that tells a DVD Player (or drive) equipped with Macrovision Copy Protection to switch on the Macrovision software to stop you making a copy of the disc.

    See http://www.macrovision.com/products/video/index.shtml

    That same digital 'Flag' has been adopted for use in the emerging and murky waters of Digital Video interconnectivity and if your DVD Player (or drive) is equipped with a suitable chip set your Digital Video signal has High-bandwidth Digital Copy Protection (HDCP) applied to it.

    See http://www.digital-cp.com/

    A Digital Video signal with HDCP applied will only 'talk' to a suitably equipped HDCP compatible Display Device (or other AV Product with Digital Video Inputs). Currently no units capable of Copying a Digital Video signal have been enabled with HDCP!

    The Digital feed from a (usually) Analogue only Digibox that's had an SDI module fitted is not Copy Protected in any way so if you have a PC with a suitable SDI Input card and a DVI equipped Graphics card then you can expect to connect the Digital Video output via DVI-D to pretty much any DVI-D or HDMI equipped Projector or Display.

    Whilst DVI Inputs may be HDCP enabled and all HDMI Inputs are HDCP enabled the HDCP 'gate' on the Projector or Display is only invoked if an HDCP signal is sensed - any Digital Video signals that are not carrying HDCP will pass through the DVI or HDMI Input unmolested.

    If the DVD Drive in your PC is not HDCP enabled then again you will have no hassles with the Digital Video output of your movies via DVI to DVI or HDMI Inputs.

    Please note that very few HDMI Inputs allow the range of accepted signal formats and resolutions you would expect a DVI input to accept - the HDMI spec allows the manufacturers to have a 'minimum' number of acceptable Input signals and these don't always correspond to the Native Resolution of the HDMI equipped Display device.

    See http://www.hdmi.org

    Best regards

    Joe
     
  15. Messiah

    Messiah
    Well-known Member

    Joined:
    Apr 22, 2002
    Messages:
    7,534
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Ratings:
    +339
    Wow, that's certainly conclusive. Nice one Joe :)

    LTJ - I think proven that some sales people are either talking from their rear end, don't know what they're on about or try to confuse punters for their own benefit. Or any combination of these :D
     
  16. Paul D

    Paul D
    Well-known Member

    Joined:
    Dec 27, 2000
    Messages:
    2,620
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Location:
    Manchester
    Ratings:
    +391
    I agree that you have been mis-informed.

    PCs with DVI VGA cards can output digital and analogue from the same DVI socket.
    Some come with a DVI to 15pin "D" VGA/or Component converter. This is so you can use a second analogue monitor or TV display.

    There is some truth to what he was saying though, but has nothing to do with HDCP.
    Some projectors could use either digital "or" analogue via their DVI input.(Benq?)
    The VGA card could detect what signal the projector was set to expect etc.
    This method is now being(or has been) fazed out.

    However when connected to a DVI-D display device, only the digital signal is sent.
    At least for now, there are no HDCP compliant VGA cards in use.(as far as i know)
    Therefore non HDCP DVI (and HDCP!)displays can be used without HDCP problems.
    The fact that ATI has one "ready" but not implemented, is for a reason.
    Imagine the backlash of all those people who use their PCs to watch DVDs via their non-HDCP LCD displays.
    Sat there looking at a blank screen, just because it's a computer LCD.
    They would never sell another card!!!
    HDMI VGA cards will have to be HDCP compliant though, meaning LCD computer displays will have to start making their display HDCP complaint.

    There are other issues about video levels with "PC" versus "Video" DVI being different. (PC=0-255 Video 16-235)
    Some displays only expect PC level DVI, some can be set for both.
    Some HDMI/DVI DVD player incorrectly use PC level DVI levels(Samsung?), some can be set for both!
    These differences won't stop the VGA outputting a digital DVI signal. It just means the black and white parts of the picture start and stop higher or lower.

    Apart from a few low cost DVD players, most will be HDCP compliant and only work with a HDCP compliant display.(Via HDMI/DVI etc)

    Anyway, the bottom line is that yes you can get totally digital DVI from your DVI VGA card to your DVI-D display.
    Matching the resolution from the VGA to the exact resolution of your display(1-1 mapping)is ideal, and as you have found gives amazing clarity/shaprness.

    Their are limits on cable length with DVI. Poor cables or long runs can lead to sparklies or astroids appearing in the image.(or no picture at all!)
    HDMI is better in this respect.

    Joe at www.tmfsolutions.co.uk is the man to speak to for cable and boosters/switchers etc.

    I'm running 1280x720@48hz/50hz/60hz via DVI from a NVidia5950Ultra VGA card with 1-1 mapping to my Marantz S3 projector. I'm running a 2m DVI cable to a Gefen 4x1 switcher, then a 10m DVI lead to the PJ without any sparklies etc.

    :thumbsup:

    EDIT: Wow, just as i was writing about asking Joe, he appeared! Spooky!
     

Share This Page

Loading...