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HD refresh rates

Discussion in 'Televisions' started by Rob100, Mar 5, 2005.

  1. Rob100

    Rob100
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    Hi all,

    Something I've been wondering about.

    Most (if not all) the HD demo's (MPEG 2 TS) and the T2 WMV DVD I have are produced at 24fps.

    I am currently playing these on my plasma (only an SD panel) with the refresh set to 72Hz and using re-clock to lock the video to the gfx card as I'm sure most people here do using their HTPC.

    I was reading in HCC the a european "HD Ready" standard has been put together which basically states the display is to accept a 50/60Hz signal at 720p or 1080i.

    Am I missing something or is this stupid? Will all NTSC/FILM sources have 3:2 pulldown applied to them to bring them up to 60Hz or will we have to put up with terrible jerky panning?

    Thanks,

    Rob.
     
  2. Dutch

    Dutch
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    Rob,

    I would presume that they telecine at 25fps and then apply 2:2 pulldown to give a full 50fps. I guess they would only show imported video material at native 60Hz.

    Steve
     
  3. Quickbeam

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    I think it is virtually certain now that Sky's film channels will be broadcast at 25 frames per second with 2:2 pulldown, run 4% fast.

    Sky's recently published HDTV FAQ states that "Any kind of screen or TV set could be connected to Sky's HD STB". The only way that you could view a 24fps movie via the SCART connection would be if the STB downconverted the output to 60Hz PAL/NTSC using 3:2 pulldown. I think it is pretty unlikely that the STB would be required to do that. Any channel that simulcasts in SD will have to broadcast at 50Hz anyway in order to be PAL compatible.

    I wonder how many of the currently available HD displays - including the fully compliant HDCP displays - will accept 720p or 1080p at 24Hz? I suspect that some will require the output to be upconverted to 60Hz, though we won't really know until Blu-ray and HD-DVD launch, which promise native 24p output.
     
  4. Rob100

    Rob100
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    I wasn't really thinking about Sky broadcasts, I was thinking more about hidef DVD etc.

    At the moment I tend to buy mainly R1 DVD's. I've never liked running at 75fps for PAL stuff (although reclock is happy it never looks quite right to me), but 72fps for NTSC looks fine and there's noticably less flicker on my display at 72hz than at 50hz - hence my preference for R1 DVD's.

    To me, the idea of watching R1 discs with 3:2 pulldown converting them to 60Hz (59.594) is crazy... I for one won't be investing in an "HD ready" kit until I get some definate answers.

    Rob.
     
  5. beeblebrox12

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    Haha, don't worry, hundreds of millions of people have been watching this for more than half a century without even the slightest idea it was crazy :) It's good thiugh that you and a dozen of other guys watching TV at 72Hz have finally enlightened us to the truth.
     
  6. Stephen Neal

    Stephen Neal
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    European HD outlets will carry 24fps films at 50i using 2:2 pulldown and 50p using frame repetition, both running the source material at 25fps with 4% speedup.

    They have to do this to allow downconversion in the broadcast chain - either to simulcast in SD, or to provide a decent quality SD output from the set top box to allow you to record HD channels onto SD DVD recorders or VHS machines.

    I suspect that HD-DVD and BlueRay players will either have the same regional issues as DVD - so will deliver 24fps with 3:2 pulldown for 60Hz regions, but 25 fps with 2:2 pulldown for 50Hz regions.

    (I doubt they will do the speed-up in the actual player, but during the mastering process. Whilst it is easy to speed-up the video - you just play out more or less frames per second - it is quite difficult to speed-up Dolby Digital and DTS soundtracks whilst keeping the sampling rate fixed at 48kHz for example, without decoding and recoding, which isn't practical AIUI?)
     
  7. StooMonster

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    Rob100, are you sure you plasma is actually displaying 72Hz? Many digital displays have fixed internal frame rates.

    StooMonster
     
  8. Rob100

    Rob100
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    That's what it reports when I go to the menu (to look at the signal). I have no reason to doubt that it isn't as pans etc are as smooth as can be expected.

    Rob.
     
  9. rscott4563

    rscott4563
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    What display are you using??

    Ryan
     
  10. rscott4563

    rscott4563
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    After a quick search I note you've previously mentioned having a 42" PW5 Panny. Is this still your display?

    If so then the status screen where it shows your signal is only showing the details of the incoming signal, not what your display is then doing with it before displaying it.

    I'm assuming your using an analogue input, probably RGBHV or YUV, I think Stoomonster tested the Panny a while back and found it didn't FRC at 48, 50 or 60Hz but I'm not sure he tested 72 or 75Hz but may he'll chip in. Its possible it is displaying the 72Hz without converting but without somesort of judder test it would be impossible to say for sure.

    Ryan :cool:
     
  11. Rob100

    Rob100
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    Yes still the Panny 42 PW5, using RGBHV input.

    Maybe this is why 75Hz never looks right on my display is there's some FRC going on.

    Happy to perform some tests... let me know what to do :)

    Rob
     
  12. St_ve

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    How many years is it going to take before 3:3 pulldown is the standard?
    I have been watching Praying Mantiss a high definition documentary which by the stunning picture quality was shot with a high definition camera.
    Have there been any movies made with the new camereras yet ?
     
  13. StooMonster

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    Yes, a while ago I found that Panny plasmas did not FRC 48, 50 or 60Hz but did every other MHz -- I even tested as high as 120Mhz input (the screen's limit).

    Anything else other than these refresh rates also made the image blur because the A>D convertors can't handle the bandwidth.

    I use a PC on my plasma for general surfing and game playing, and "snapped in" native resolution picture at 60MHz is fantastic and crisp (comparible to DVI on same screen); Rob100, you should compare the vertical and horizontal line patterns at 60Hz and against 72Hz and you'll see one is clear and the other blurred.

    Also discovered than Pioneer MXEs had fixed refresh rate of 72Hz and FRC everything to that, even DVI input that was fixed at 60Hz. And discovered that many LCD screens had fixed 60Hz refresh rates.

    People tell me that it's better (two years later) but I haven't had the chance to test myself.

    Rob100, try the excellent "judder tester" program; or with DVDO iScan HD the Judder Test Pattern (credited to me in the DVDO manual :) thanks Dale!) to check.

    Personally I reclock NTSC to 2:2 pulldown with DVDO iScan HD and use the 48MHz on Panny plasma and it looks fantastic; no judder at all. As plasmas are not CRTs, 48Hz versus 72Hz won't make any difference anyway, there's no "flicker" it's simply how often the pixel matrix is refreshed.

    StooMonster
     
  14. StooMonster

    StooMonster
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    May not be as noticeable on lower resolution screens, but definately apparent on the Panny 50 PW5.

    Note: all my Panny tests were on 50" PW5 at native resolution 1366x768.

    StooMonster
     
  15. Rob100

    Rob100
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    StooMonster,

    Where can I find this "Judder Tester" program? I did a quick google, but came up with nothing of interest. I don't have an iScan HD so can't try that.

    I have my display "snapped" in at 50Hz (@ 848x480), 59.94Hz and 72Hz (both @ 856x480). The only thing I have to adjust when switching between them is the "clock phase" in the PW5's menu to ensure a crisp image. In all cases once adjusted the picture is superb and there's no "shimmering" when viewing test patterns (alternate b/w pixels).

    I will try 48Hz later tonight as I'm off out in a mo. I will let you know how it compares with 72Hz playing film sources.

    Thanks,


    Rob.
     
  16. StooMonster

    StooMonster
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    JudderTest v1.1 software has a link here
    http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=318096
    Only available for Windows.

    When the white bar moves across screen it should be solid and smooth with no breakup. 1 pixel per MHz is smooth, but several pixels per MHz is best to see breakup.

    With this tester (or iScan HD) one can clearly see that only 48/50/60MHz work on Panny 50" PW5 anlogue VGA and 72/75/80/120MHz do not -- for DVI only 60MHz works.

    HTH

    StooMonster
     
  17. Rob100

    Rob100
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    Well you learn something every day! What a great program...

    I have to agree with StooMonster's tests. 48Hz is smooth and 72Hz isn't. I watched something last night at 48Hz (well as close to 2 x 23.976 as I could get (as reported by ReClock)) and it did look great, pans we definately smoother.

    Thanks for this info :smashin:

    So going back to my original post... what's going on with the "HD ready" displays etc only needing to support 50 and 60 Hz!

    Thanks again StooMoonster...

    Rob.
     
  18. Stephen Neal

    Stephen Neal
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    I guess it is because "HD Ready" displays are designed to connect to HD set top boxes and HD-DVD and BlueRay players.

    There is nobody broadcasting 24p material as 24p - only 50i/50p or 60i/60p is actually broadcast.

    I suspect, and this is only a guess, that BlueRay and HD-DVD recorders will output 24p sourced material as 50i/50p in Europe - as they will need to generate a PAL composite/S-video/RGB standard def signal simultaneously - which they couldn't do running at 24p/48i/48p.

    In the US and other 60Hz regions I suppose they COULD output 60i standard def (3:2 pulldown) and 24p or 48i HD - or 59.94 and 23.96?
     

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