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Sanyo Judder when panning

Discussion in 'Projectors, Screens & Video Processors' started by Timh, Mar 18, 2001.

  1. Timh

    Timh
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    I had a quick demo yesterday of the Sanyo plv-30.
    While watching A bug's life (r1) the picture juddered while panning across the image.
    Is this a common fault with lcd projectors, or maybe a problem with the disc?

    Cheers
    Tim

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  2. lmccauley

    lmccauley
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    Sounds like a classic case of 3:2 pulldown that you get with all 30fps (e.g. NTSC) versions of 24fps (e.g. film) sources.

    The following link explains it better than I ever could: http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html

    To avoid it you will need either a Progressive Scan DVD player like the Arcam DV27 or new Denon with a chip that recognises 3:2 pulldown (e.g. Sil503), or an external scaler that does the same (e.g. iScanPro).

    Cheers,
    Liam

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  3. JohnAd

    JohnAd
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    Liam

    As you say judder comes from converting 24fps film to 30fps, this effect is not removed by the products you mention. When they say they recognize 3:2 pulldown it is so they can reconstruct the correct progressive frame not remove the motion judder.

    To get rid of the motion judder you need an HTPC running at 72Hz.

    John

    [This message has been edited by JohnAd (edited 18-03-2001).]
     
  4. Timh

    Timh
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    Hi john
    Can you tell me what HTPC stands for?
    ta.

    Tim


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  5. jason t

    jason t
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    home theatre personal computer
     
  6. lmccauley

    lmccauley
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    JohnAd, you are quite correct; doing an inverse 3:2 pulldown in itself will not remove the juddering. Once again I learn something new from this forum [​IMG]

    You could use something like the Rock to de-interlace, scale to 800*600 and output at 72Hz. I assume the Sanyo can accept that (Chris/Gordon?).

    Cheers,
    Liam



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  7. Chris Frost

    Chris Frost
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    Timh,
    The cause of this judder is that you are seeing 50 or 60 still images a second. If the camera pans or someone moves across the screen quickly then you "see" a big difference in their position from frame to frame. You'll see exactly the same effect at the cinema.

    There is no fault with the equipment, you're simply seeing the limitation of motion picture technology based on film cameras shooting 24 still images a second.

    The sports world has struggled with this problem for years. Ordinary TV cameras take too few pictures a second for good slow motion replay. Special high speed cameras are used that shoot more frames per second to give smooth motion.

    Both John and Liams suggestions would help with certain aspects of this problem (called motion artefacts), but neither could reconstruct an image to fill in the missing information.

    Regards


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    Owl Video Systems Ltd
    www.owl-video.co.uk
     
  8. Ludae

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    Although such a scheme removes 3:2 judder, that fact that you would still be repeating images would cause judder and blur on motion, which is evident in the cinema at 48Hz typically.

    The simplest solution would be to display the source at its native frame rate, usually 24 or 25fps. Devices that could benefit from this are DLP, LCD, and ILA type projectors or panels. I am hoping that one day the manufacturers will realise this fact and design the necessary processing.

    TI's DLP DigitalCinema systems use the native frame rate and the results are obviously superior to the frame repeated images of cinema film projection in this respect.

    The other solution is to use motion-compensated frame rate up-conversion but that is altogether more complicated and expessive.


    [This message has been edited by Ludae (edited 18-03-2001).]
     
  9. Ludae

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    Motion-compensated frame rate conversion can also be used to provide super smooth slow motion from standard video rate material.
     
  10. Timh

    Timh
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    Thank's everybody, it's amazing what you can learn on this Forum.
    The more I know about projectors will help me in choosing one, one day.
    I personnaly think the Sanyo is great, and was well impressed with a demo at The www.hifishowrooms.co.uk showing Shakespear in Love on an 8ft screen.

    Cheers
    Tim

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  11. rory29

    rory29
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    hello all,
    i myself owe the sanyo machine and can
    say that i have never noticed any
    picture judders or have i had any problems
    player pal dvds i think for the cost its
    a good projector
    Rory
     
  12. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Judder seems to be one of those things that annoys some folk and doesn't others.

    There's an interesting thread going on about using 48hz refresh with D'ilA's over at AVSforum if anyone is interested.


    So, do you think I should try and get a Terranex Xantus for my wee Event Ludae?.. ;-)

    Gordon

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