DVI and HDMI

Discussion in 'LCD & LED LCD TVs Forum' started by chuckalicious, Nov 1, 2005.

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  1. chuckalicious

    chuckalicious
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    Okay, so from reading the FAQs, I now understand that DVI and HDMI will give exactly the same quality of image, the only difference being HDMI gives digital audio over the same cable.

    Now, for me, I'll always be outputting any audio, whether it be Sky (no DVI or HDMI anyway, and I aint paying for Sky HD) or DVD, through my surround amp, and only the video will go directly into the TV.

    So I'd like to get myself a 28-32" LCD, which is HD ready, and of course save as many pennies as possible. Now, I have seen THIS TV in the flesh and I was actually pretty impressed with it. Not seen an HD feed into it yet, but you can now get it in silver and the price is very reasonable indeed.

    From those specs do you think it does HD resolutions over the DVI as well as the component inputs?

    If I can use either component or HDMI-DVI from a DVD player to this display, I'll be very happy.

    Can anyone see any reason why I should get a display with HDMI over this one, assuming they could match or almost match the price?

    If HDMI to DVI does exactly the same thing, then this TV is future proof, or at least as future proof as any of the other HD ready TVs. Am I right?
     
  2. ianh64

    ianh64
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    That is a huge over simplification. HDMI has the potential to provide a much better picture than DVI.

    As far as digital goes, there are two DVI standards - DVI-PC and DVI-Video. Both are 8 bit for each R,G,B. The difference is that for DVI-PC digital 0,0,0 is black and 255,255,255 is full white. For DVI-Video, 16,16,16 is black and 235,235,235 is white. So for video use, there is a much smaller dynamic range for black..white/full colour.

    HDMI also supports both DVI-PC (full range) and DVI-Video (limited range) levels but it also supports YCbCr 4:4:4 and 4:2:2 at 8, 10 and 12 bits/pixel. A far greater dynamic range ie up to 256..3760 for luma and 256..3840 for chroma black..full range. HDMI is also more robust. It is a stricter standard but, being newer, it also makes use of newer technologies to better DV. For example standard HDMI cable lengths can be longer than standard DVI ones. Also, data structures within the data stream allow checks to be made on the integrity of the data. The moment a DVI device is incorporated in the chain, these data structures are removed and this integrity checking is not performed.

    As well as having the capability for audio, HDMI also passes control information to allow devices to talk to each other. So you could say press play on a DVD player and the TV and audio processor both select DVD input.

    Do on paper they look similar, but in reality they are very different even though HDMI is backward compatible with DVI. Take DVI out of the chain, HDMI is far more powerful.
     
  3. HCK

    HCK
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  4. ianh64

    ianh64
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    Well ecoustics.com obviously have not read the HDMI specification available from www.hdmi.org.

    They make the false assumption that DVI and HDMI use RGB and that analogue component uses YUV. They completely fail to mention that HDMI can also transmit YUV in the digital rather than analogue domain. It is the YUV formats that have a much higher dynamic range than the RGB formats used by DVI/HDMI. The YUV formats at 8, 10 and 12 bits are not part of the digital DVI specification so HDMI has the ability to provide greater image quality than DVI can.

    The article also says that the encoding schemes for DVI and HDMI are identical which is why DVI and HDMI can be connected together. They are not identical. HDMI is a superset of DVI. When HDMI detects a DVI device in the chain, it reverts to a DVI compliant mode. Only then are the encoding schemes compatible but you loose many of the benefits of HDMI such as YUV.

    Obviously though, whilst all this stuff it part of the HDMI specification, it needs to be implemented in both source and destination otherwise the lowest common denominator is used. In the case that YUV is not implemented by a piece of kit, 8 bit RGB will be used in which case, the image quality of DVI and HDMI should be the same.
     
  5. chuckalicious

    chuckalicious
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    So in other words buy one with an HDMI input if I want the best.

    So bloody complicated. Might even just stick with my CRT!!
     
  6. ianh64

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    To be honest, DVI was only an interim solution for digital video. If you intend to go the video (rather than PC) route, HDMI is definately the one to go for in the mid-long term. Its an evolving standard which will be expanded on in the future, but for display use, the standard in common use now is probably all that is required.
     
  7. bashtage

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    HDMI should start making its way on to PC video cards and LCD panels sometime next year. You can thank (or curse, depending) Microsoft and their apparent consessions to certain content providers (CableCard and HD-DVD mostly) which results in trusted video path. However, trusted video path will require a HDCP enabled output which supposedly is getting manus to switch to HDMI for PC's, at least at the higher end (although DVI-HDCP is also an options I suppose).
     
  8. HCK

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    I think the arguement really should be whether the capacity for HDMI is going to be used in the near furture ? DVI can stream up to 1Gbps, not even HD will reach that capacity. When the time comes for that capacity to be breached then I think we wont be using HD!!
     
  9. pingu

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    What about DisplayPort then? http://www.vesa.org/press/displayportaug.htm

    And doesn't the HDMI standard limit the resolutions it handles? So it may not be suitable for PCs?

    Great explanation ianh64 - I did wonder why the HDMI (YPbPr) output of my Denon 2910 was loads better than the HDMI (RGB) output. Now I know thanks :smashin:
     
  10. bashtage

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    HDMI has at least as much BW as DVI, and HDMI has both Single Link DVI (Type A HDMI)and Dual Link DVI (Type B) equivalent modes. so as far as I can tell, no. With the extra modes supported with HDMI, it could bring better fidelity to PC graphics as well as making hooking thing together easier.
     
  11. scott1527

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    sorry about hijacking the topic but i have a radeon 9700 pro with a dvi-i (i think its I)
    was thinking about getting a 5m dvi to hdmi lead to connect me puter and tv together. will this work and will it be better than the vga (which is pritty good)

    tv samsung le32r41bd
     
  12. Nom

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    No - the VGA input on the Samsung is far superior for PC use.

    The HDMI input overscans the image - so half of it vanishes off the sides, and what's left stops being mapped 1 : 1 so becomes a blurry mess.

    This is a "feature" of the Samsung though - normally you'd be right to use the HDMI instead :)
     
  13. scott1527

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    thing that puzzles me is how come vga to vga has lost detail? i.e in battlefield 2 the water has turned grey rather than shiney (if you know what i mean) the textures have also ermmm flattened out and arent crip. i would have thought the tv would be just as capable as my crt iiyama. or even come close to what i was seeing via crt screen. im using same cable and same video settings.

    i am a nooblet when it comes to connections. vga best optoin for pc use ? i also have a s-video.
     
  14. graviton

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    So why do most of the TVs implement overscan on HDMI even for DVI inputs. Is this the usual b******* of nobody being able to implement a standard properly ?
     
  15. Nom

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    Because you're supposed to use the HDMI input for video - so the overscan should be present.

    The only real solution is to overscan in every mode except the 1 : 1 mapping modes - I'm not sure if this is the approach that the LG takes, but it certainly appears so. Can anyone confirm ?
     
  16. gaz8080

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    A friend has just bought a Toshiba 32WL56 and wants to connect it to his PC. Is a DVI to HDMI cable the way to go? Or would VGA be just as good?
     
  17. Nom

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    It depends on the telly in question.
    You need to find out which input the Toshiba can do 1:1 mapping through (ie, display 1366x768 from the PC, exactly on it's 1366x768 screen, or whatever it's resolution happens to be) and then use it.
     

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