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3:2 pulldown - Can someone please explain

Discussion in 'Projectors, Screens & Video Processors' started by tryingtimes, Apr 12, 2001.

  1. tryingtimes

    tryingtimes
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    I've heard this a few times and sometimes the context used does give me clues as to what it is but can someone explain it for me just to be sure. Or, of course, point me to a URL that explains it form me.

    Many thanks
    Alex
     
  2. tryingtimes

    tryingtimes
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    Thank you David J Perry and Stuart D Wright.

    Does this mean that, even in Progressive, one frame is on for 3/60ths of a second and the next on for 2/60ths of a second?

    Cheers
    Alex
     
  3. Guest

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    Yes, if the output rate is 60Hz progressive then usually a frame based 3:2 pulldown sequence is still used to compensate for the different between 24fps film and the 60fps progressive video output.

    Motion compensated frame rate conversion can eliminate the 3:2 requirement but such complex systems are not available for consumer level products yet.
     
  4. HT Dude

    HT Dude
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    Alex - most people running HCPCs set their computer to a multiple of 24fps. E.g. 72Hz, 96Hz or 120Hz. Obviosuly the projector has to be able to cope with it.
    Hence by avoiding juddery 3:2 pulldown (at 60Hz), motion is smoother.
     
  5. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    If you've a fixed output projector like a D'Ila,LCD or DLP there's also a chance that 48Hz could be the least juddery. There's an interesting thread about it over at AVS in the LCD/DLP d'ILA forum

    Gordon
     
  6. Stuart Wright

    Stuart Wright
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  7. Guest

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    Hi,

    if you were running PAL DVD's would you need to keep switching between 72 & 75Hz to get the best picture from a HCPC to a projector, and do most DLP and LCD projectors handle that switching without a problem?

    Thanks,

    Steve
     
  8. Paul D

    Paul D
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    Hi, i'am running a geforce card in a HCPC and in the option box that normally lets you set the refresh rate is missing. This is due to using it with a LCD projector no doubt. The "monitor" just shows as plug&play (no name). Can you get monitor drivers for projectors etc?...Paul
    PS it is set at 6ohz.
     
  9. Stuart Wright

    Stuart Wright
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    fulabeer, try picking a NEC 17 as the monitor. This should give you plenty of refresh rate options.
     
  10. tryingtimes

    tryingtimes
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    Ahh! I understand.
    So the point of having 3:2 pulldown detection is so that you can basically start again form the original 24 frames/second and scale up in multiples from that.

    Excellent - for some reason - looking at The progressive website it seemed as though there wasn't much point.

    Perhaps it needs an end paragraph to explain that, after this process you can take advantage of the flexible refresh rates on projectors to remove the uneven 3:2 frame lengths

    Thanks all
    Alex

    [ 18-04-2001: Message edited by: Alex Simon ]
     
  11. Guest

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    Well progressive PAL doesn't exist yet. They are working on the spec at the moment but it's becoming a very slow process. It will be 25fps and it's multiples.

    But in the meantime one of the Denon dvd players (Denon DVD-2800 in Austrialia) is believed to convert PAL to NTSC (a much cleaner conversion than NTSC->PAL as it's mainly downconverting rather than trying to up convert) and it can then output this progressively. Sounds like a good enough solution (it it's true) until progressive PAL comes along (if it ever does).
    Anyone confim if it can do this ?

    http://elec.denon.co.jp/europe/pdf/DVD28002.pdf
     
  12. Mr.D

    Mr.D
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    Yuck talk about throwing the baby out with the bath water. I've not read the pdf but if it is true its a bad compromise and totally unecessary to boot. I half suspect its actually referring to that age old colour frequency selection rather than a line/refresh rate conversion.

    The wonderful thing about going the HTPC route is that you don't have to wait for "progressive PAL players". You can get this already via the RGB output from an HTPC. Its not component but big deal who needs it.
     
  13. Guest

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    Well as DVD doesn't store PAL/NTSC colour (uses YUV instead) it must be refering to the line structure and refreshrate
     

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