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720p/1080i question

Discussion in 'Projectors, Screens & Video Processors' started by dimitris x, Nov 25, 2004.

  1. dimitris x

    dimitris x
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    Hi and goodmorning all ,

    When we say that a pj plays 720p or 1080i , what does it mean ?
    We have a dvi dvdp , we select 720p/1080i , that means the dvdp
    upsamples the image from 720x576 or 1024x576 (anamorphic PAL) to
    1280x720 / 1920x1080.
    When our pj has a native resolution of 1280x720 then its ok.
    What happens if the pj has resolution of 852x480 ?
    Does the scaler of the pj downscales the image again at his native
    resolution (852x480) or projects the image at 1280x720 ? (the same goes for 1080i).
    My pj doesn't have a dvi , its 720p - 1080i ready , but i am thinking
    buying the yamakawa 375 which gives 720p-1080i through component , and i
    want to know if there is going to be any difference according the image quality.
    And something else , my current dvdp is a sony dvp-ns730p , which gives 525/625p
    what resolution is this (pixels) ?

    Thank you .
     
  2. KraGorn

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    Hi :hiya:

    Simple answer :) .. the projector always displays the image at its' own resolution, so if you feed it a signal smaller or larger it will rescale it as needed.

    So, on your projector the Yamakawa won't produce a better image than the Sony simply as a result of its' resizing to 720p .. and you'll certainly not want to use 1080i or any other interlaced signal as the de-interlacer in the projector is inferior to both those DVD players.

    Any difference in picture quality therefore will be basically down to the difference in their MPEG decoders and general signal handling, especially de-interlacing, and not due to the Yamakawa's scaler.

    AFAIK, 525p is another term for 576p, PAL resolution is 720x576 but I *think* there are only 525 lines used to display the image, the others are used for control purposes. 625p I'm not sure about.
     
  3. rscott4563

    rscott4563
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    Almost, 625 is actually Pal, though only 576 lines are used for picture information. NTSC is actually 525 though only 480 lines are active for the picture information.

    Cheers

    Ryan
     
  4. dimitris x

    dimitris x
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    thanx for the quick response.
    my question was that , because reading many pj tests,reviews,forums ,( lets say for infocus 4805 , benq 5120 ) projectors with the same resolution as mine , they say that the 720p projected image via dvi is very very good .
    so i am wondering how come is so good , if the projector takes this image which had been
    oversampled from the dvd , and then downscales it to its native resolution , so why they dont use 480p from the beginning............. :confused:
    I see no reason although i agree if u have a 1280x720p pj , but
    i see no reason for a 480p projector.
     
  5. KraGorn

    KraGorn
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    :suicide: .. of course!
     
  6. KraGorn

    KraGorn
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    My guess would be that it's because US HDTV is also often broadcast in 720p that they're mentioning this resolution .. 1080i being the other common HDTV format, also available in Europe.

    And of course HD-DVD, HiDef WMVs etc. are also commonly in 720p.
     
  7. dimitris x

    dimitris x
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    yes , hdtv is the only reason for this , and the best thing u can do is a 1280x720 pj.
    But the thing that made me curious was that they played 720p at a 480p projector
    using a dvd disk encoded at 720x576. :rolleyes:
     
  8. lochindaal

    lochindaal
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    Go to the DLP RPTV forum and look at the 2nd page of the Tosh in Comet thread. Krishna has posted a link to a good site that explains all in very simple English.

    There was probably a way I could have done a link but don't know how
     
  9. MikeK

    MikeK
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    If you have a DVI equipped upsampling DVD player playing an R1 disc, there's little point telling it to upscale and output a 720p signal into a 480p projector - the projector will always downscale any input back to 480p - so it's a pointless exercise (and will almost certainly result in a worse picture than just outputting 480p from the DVD player in the first place) - not that this will stop marketing bods encouraging this practice though. However, there may still be advantages to be gained by outputting 480p over DVI as opposed to component video, as this avoids the DA/AD conversion process as well.



    As to your issue, dimitris x, should you buy the Yamakawa (sounds like a motorbike :) ) DVD player?
    Depends on what PJ you have!
    I think you've already sussed that if you have a 480p projector, there's probably little point doing this - if you have a 720p projector, then it becomes a contest between the DVD player's scaler, and the scaler in the projector! Do understand though, that the higher the frequency of the signal you send over your component cables, the more important the quality of that cabling/connection becomes - 720p is a much higher frequency signal than 480p (approx 2.25x higher), any gain you might get from a better scaler (and I don't know if the Yamakawa scaler is better than your projector's scaler) might be offset by signal degradation in the cables.
    I don't want to get into a debate over the relative merits of this or that cable (I do believe that much of the esoteric cable market is blatant ripoff though), but I do accept that as the frequency increases, the cables can play a bigger part!
     
  10. dimitris x

    dimitris x
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    Since my projector is 852x480 , with no dvi outpout , and the result may be the same or worst , i see no reason buying this player.The cable thing is something i havent thought
    and i agree with you.
    Thank you a lot for all the responses.
     
  11. KraGorn

    KraGorn
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    I'm sure it was just so they could say what performance was like with 720p for HDTV reception .. since the projector uses its' scaler to size down as well as up, if the scaler was poor in performing this task then it could adversely affect the picture quality, even though down-scaling is a lot simpler to do than up-scaling.

    You're right to think that in itself re-sizing a DVD only to have it sized down again is pretty pointless. :)
     
  12. berserkgoose

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    Dimitris, The Yamakawa has a custom resolution option, I don't know all the details but if you could set this to 852 x 480 you may see improvement over the Sony.
     

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