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1080p source on 1080i screen

Discussion in 'TVs' started by avinitski, Aug 26, 2005.

  1. avinitski

    avinitski
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    ive been playing some 1080p videos on my 1080i screen and they look fab, but how is the screen displaying it OK as it only supports 1080i?
     
  2. meansizzler

    meansizzler
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    The device which is ouputting the video, eg.PC, is ouputting at 1080i, well the graphics card is.....everything coming out of it will be 1080i, Most Ati an Nvidia cards which are less than than 2 years old have an option fof outputting at 1080i
     
  3. gizlaroc

    gizlaroc
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    Huh?

    What are you playing and on what screen?
     
  4. pjskel

    pjskel
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    Because the screen is taking the 1080p signal I presume from your PC, and is downconverting to 720p, then scaling to 768p - all assumed until told which TV and what source the signal is coming from.
     
  5. avinitski

    avinitski
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    ill try and explain a little clearer

    out putting a 1080p .wmv file from the pc through an x800xt GFX card on a DLP display capable of max 1080i

    if its downscaling then why?

    and yes im not too clued up on all of this...sorry!! lol
     
  6. Welwynnick

    Welwynnick
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    Very intruiging.
    What display is it?
    What connection do you use?
    Nick
     
  7. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    It sounds like you are not outputting 1080P at all. Sounds like the soruce material is 1080P but it is being rescaled by your graphics card and the actual resolution coming out is obviously one that is recognised by your display. What is your desktop resolution set to?

    Gordon
     
  8. avinitski

    avinitski
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    the display is an LG RE44SZ21R DLP

    connection is analog component cables (Y/Pb/Pr)

    and my desktop resolution is 1280x1024 but i have the DLP TV set to 1920x1080

    1080p/i .wmv files look outstanding

    so my GFX card is downscaling from 1080p > 1080i ?
     
  9. Stephen Neal

    Stephen Neal
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    If your desktop resolution is 1280x1024 then unless the video software is altering your resolution it is likely that your video is either being displayed at 1280x1024 anamorphic and your display is stretching it, or 1280x720 letterbox within a 1280x1024 frame and your display is zooming ?

    Either way I suspect your PC is scaling, and your display too.
     
  10. Welwynnick

    Welwynnick
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    The LG RE44SZ21R DLP has a 1024 x 576 display (difficult information to find, that. Came from Home Cinema Choice). If the GFX card is downscaling from 1080p to 1080i, then the TV is also downscaling from 1080i to 576p.
    You may be better of setting the GFX card to output 576p directly if you can.
     
  11. Stephen Neal

    Stephen Neal
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    Ah - that sounds like their Matterhorn (i.e. "PAL progressive 16:9") DLP based set. This is effectively a widescreen standard definition DLP device - though because it has a 576p native display it has a higher potential vertical resolution than a 576i display. However it is not capable of delivering the full resolution horizontally or vertically of a 1280x720 or a 1920x1080 HD signal - though I bet it still looks very good.

    I suspect a Powerstrip 1024x576/50Hz progressive mode would be the best way of driving it, if it accepts that as an input resolution, as you would then be able to 1:1 pixel match with Windows, and text and graphics will appear clearer on the display, and SD video will be perfectly line-matched. HD material will be scaled - but this is happening in the TV anyway.
     
  12. avinitski

    avinitski
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    but why would the manual and also the back of the TV say it accepts upto 1080i if it doesnt?
     
  13. Mr.D

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    Because it probably does accept 1080i through one or more input. It will however be downscaled to fit the smaller resolution of the actual panel in the display. (either deinterlaced to 1080p or more likely bobbed to 1920x540 and given a non-square rescale to fit the panel and give you the correct square pixel appearance).

    Like the man says doing all this at source and feeding 1024x576 into the display will probably give you the best image if 1:1 pixel mapping is possible.
     
  14. Stephen Neal

    Stephen Neal
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    Ah - there is a difference between accepting an input signal, and displaying it at full resolution. What your sets specs mean is that it will happily display a 1080i input signal - rather than refusing it. However it will scale the 1080i input signal to 576p for display, rather than displaying it at full resolution.

    This just the same as 1024x720 plasmas, 1366x768 LCDs etc. accepting 1920x1080 1080i inputs, it means they will display a 1080i signal, not that it will display them in full resolution.

    This can be confusing if you aren't careful - and one of the reasons they introduced the HD Ready spec - as 480p displays with 1080i/720p inputs were being sold as HD Ready, even though they weren't capable of displaying HD in HD. "HD Ready" now means a minimum of 720 lines of display resolution.
     
  15. avinitski

    avinitski
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    oh dear me i feel cheated! lol

    oh btw you people are giving me some great information here i really appreciate it! one of the joys of the net of course!

    anyway back on course....so what you peeps are saying is that no matter what signal i feed to the TV, be it 720p/1080i, the TV will downscale to 576p (1024x576) ?

    if thats the case its a total con how the manual and specs dont mention this!
     
  16. Stephen Neal

    Stephen Neal
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    Yep - because the DLP TV you have is based, like LCD and Plasma, on a fixed grid of display cells (in the case of DLP they are tiny little mirrors) it can only generate a picture at a fixed resolution (the "native" resolution of the display)

    The good news is that you have bought a 1024x576 display, which is a great match for UK TV and DVD (there is a 1:1 line mapping), so the set should deliver good pictures on UK standard def sources, as there will be no vertical scaling required.

    However, as you have surmised, because your display is a fixed resolution, all other sources at other resolutions (480i, 720p, 1080i) will be de-interlaced and/or scaled to 576p.

    This precise confusion - the difference between a set displaying a picture when fed an HD source, and displaying an HD source IN HD - is why the HD Ready standard (that requires a minimum of 720 lines native resolution) was created...
     
  17. avinitski

    avinitski
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    again brilliant information much appreciated

    im now using Powerstrip, as advised.

    i goto display profiles>configure>advanced timing options>custom resolutions then i select 1024x576p (HDTV PAL-derived) i select Add new resolution, then it says windows needs a reboot (sigh) i reboot but upon rebooting 1024x576 is not selectable within the display profiles

    could anyone help me here please?
    am i missing something?
     
  18. gizlaroc

    gizlaroc
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    What graphics card are you using?
     
  19. avinitski

    avinitski
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    x800XT
     
  20. gordymck

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    Gordon,

    Just the man to answer this puzzler...
    The product literature for Philips new 37PF9830 HD LCD Television states that the panel resolution is 1080p. However, the same documentation then goes on to state that it only has a maximum display resolution of 1080i.
    Why the contradiction?

    Does this mean the display will only process up to 1080i, and needs an external processor for 1080p? :confused:

    Please help, since the Philips info is as clear as mud :lease:
     
  21. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    The panel has 1920x1080 pixels. The hardware that drives the panel can only process 1080i signal. There are very few 1080P sources and the parts to deal with processing such a signal are probably rare and expensive.....

    Gordon
     
  22. gordymck

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    ... so my DVDO iScan HD+ should handle the processing of the 1080p signal, but I'm still unsure what the panel will do with it. Can you offer your best guess?

    Cheers.
     
  23. Kalos Geros

    Kalos Geros
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    This is all really weird since it is required from a progressive device (LCD) to run in interlaced mode (of which it is theoretically capable)...I suspect there is a weird logic integrated into this LCD device that supposes that 1080i will be the only 1080 mode available or teh spec sheet is wrong...the best bet is to try it somehow... :rolleyes:
     
  24. Stephen Neal

    Stephen Neal
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    I wouldn't be surprised if the display only expected to be fed 720p or 1080i, as they are the only formats currently available from broadcast and pre-recorded sources from set top boxes or standalone players. AFAIK there aren't any media players that replay material as 24p or 25p currently - though I'm happy to be proved wrong. Some scalers output 1080/50p or 60p to feed to the high-end projectors that support these inputs AIUI.

    PCs can produce 1080/50p or 1080/60p outputs - so there is a reason why displays would be expected to display this - though if the HDMI inputs are for broadcast rather than PC sources - 1080/50p or 60p aren't broadcast standards yet - this could explain it?
     
  25. Quickbeam

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    As I understand it most of the displays on sale today use v1.0 or v1.1 of the HDMI specification which does not support 1080p over a single connector. The newer v1.2 standard does, though I don't if there any displays on sale yet that actually support it.

    Displays that use DVI rather than HDMI are much more likely to support 1080p, such as the Westinghouse LVM-37W1 1080p LCD available in the US.

    Clearly from a buyer's point of view it is disappointing that you can't feed the Philips 37"/45" 1080p LCDs a native resolution signal. No doubt this issue will be addressed in next year's models.
     
  26. Welwynnick

    Welwynnick
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    All fixed pixel displays are progressive, so if an interlaced signal is input, it always has to be de-interlaced to progressive. For a long time, the highest res that a panel could physically accept was 720p or 1080i or one of the PC monitor resolutions like 1280x1024. More recent displays have been able to accept 1080p over VGA or component, but not over DVI or HDMI. The signal bandwidth is just too high for the available hardware. There are only one or two exceptions, and they are hardly available even in Japan or the US, yet.

    So it's quite normal for the best input to be 1080i - this is sadly typical of most of the new 1080p displays, even though it always has to be displayed at 1080p. But probably not very well: proper 1080i de-interlacing is too much to expect for any current display, so there's going to be some compromise for the time being.

    Nick
     
  27. Welwynnick

    Welwynnick
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    Any idea why that might be? Both DVI (single link) and HDMI (A connnector) are both supposed to support up to 165Mpps, which covers 1080p60 and only a little more. I heard the restrictions with some 1080p products that had HDMI conectors were down to poor performance HDCP decoder chips.
     
  28. Stephen Neal

    Stephen Neal
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    I thought this was the case until recently. However reading up on ALiS models it seems that they do indeed operate in an interlaced fashion instead. The 1024x1024 displays actually operate with a 1024i signal - which is very close to the original 1030i standard used in Japan, now tweaked to 1080i...
     
  29. Welwynnick

    Welwynnick
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    Yes, it does look like it, doesn't it?
    But I KEEP digging up what seem to be quite authoritative accounts of ALIS operation that always insist that it is NOT an interlaced display. Despite there being what two separately scanned fields that make up each frame.....
     

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