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Vertical Refresh Rates for plasmas and LCDs - does your screen Frame Rate Convert?

Discussion in 'LCD & LED LCD TVs' started by StooMonster, Apr 20, 2004.

  1. StooMonster

    StooMonster
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    Simple definition
    Vertical Refresh Rate (VRR) is how many times a second the screen is redrawn with a new image -- e.g. 60Hz is 60 complete frames per second.

    Some displays say they can accept huge ranges of Vertical Refresh Rates -- e.g. Panasonic plasmas can accept and display video signals with VRR of 48Hz through 120Hz.

    But are they really displaying these rates?
    Modern analogue displays (CRT, RPTV, CRT-projectors) can display almost any available VRR with no problems and no Frame Rate Conversion.

    However, many digital displays (plasmas, LCDs, LCD-projectors) have an internal frame buffer which performs a Frame Rate Conversion. How this works is the display will sample the image at the frame buffer's own rate and do a Frame Rate Conversion on the source material. What this means is that it will introduce "motion judder" and/or "tearing artefacts". :(

    For example, if a screen has a fixed Internal Frame Buffer of 60Hz and it's fed a 50Hz signal (e.g. PAL) it will add additional frames to increase 50fps to 60fps, or if it's fed a 75Hz signal (e.g. PC or PAL with 3:3 pull down) it will drop frames to decrease 75fps to 60fps.

    How can I tell?
    Visible judder to tearing is a give away, especially visible on scrolling titles on television programmes. For example, if you are watching 50Hz PAL signal (e.g. Sky digital or DVD) and "credits" stutter and judder then it's quite likely your screen is Frame Rate Converting to 60Hz.

    Even better way to test: “judder tester”.

    A "judder tester" is a moving bar test pattern, intended to identify the frame rates at which a digital display will operate.

    There is a useful PC program called "judder test" that you can use (if you can plug PC into your display) which is available here, there is also a Microsoft MWP9 test pattern (hard to get hold of), and the DVDO iScan HD.

    These "judder testers" all consist of a vertical bar which moves slowly either back and forth or simply across the screen. The bar's motion is updated once in each VRR period (e.g. 50Hz), and it moves a fixed number of pixels horizontally in each VRR period.

    If the digital display is not performing any frame rate conversion -- i.e. it is actually displaying the output frame rate of the judder test -- the motion will be very smooth. However, if the digital display is performing any type of frame rate conversion there will be very noticeable stutter introduced in the smooth motion. Not just limited to "judder" either; there may also be other objectionable artefacts introduced depending on how the display actually performs the Frame Rate Conversion. These include tearing (top and bottom portion of the bar are horizontally misaligned) and image distortion.

    How did my tests go?

    Panasonic plasma has three level internal frame buffer: 48Hz, 50Hz, 60Hz. No Frame Rate Conversion on common sources (NTSC, PAL, DVI, NTSC 2:2 pulldown), but 3:3 pulldown is out (for NTSC 72Hz and PAL 75Hz).

    * American Panasonic screens may only support 60Hz.

    Pioneer MXE plasma has one internal frame buffer: 70Hz. PAL (50Hz) and NTSC (60Hz) and DVI input (60Hz) and 3:3 pulldown are internally converted to 70Hz and introduce judder at best, and tearing at worst.

    * New Pioneer screens claim 100Hz buffer, I'm interested to know what that means ... is it like Panasonic one where 50Hz signal is displayed twice, or have they changed Internal Frame Buffer to 100Hz up from 70Hz?

    Grundig 17” Widescreen LCD has one internal frame buffer: 60Hz. Explains why Sky digital has jerky picture in my bedroom.

    * I understand that most LCDs have 60Hz internal buffer, is this right?

    Dell 17" LCD monitor has two internal frame buffers: 60Hz and 75Hz. NTSC and PAL 3:3 or DVI @ 75Hz look great!

    What can you do if your screen has rubbish Frame Rate Conversion that judders or even worse tears?
    Check out DVDO iScan HD, it's got excellent Frame Rate Conversion feature that minimises the effects; and probably does it much better than internals of display. Even mad 60Hz DVI look almost acceptable with PAL for me.

    * Yes Gordon, sure the Lumagen scalers have the same feature. ;)

    So, what does your screen support?
    Post below and let us know, expand the knowledge base!

    Final note: sometimes US sourced screens only support 60Hz internal frame buffers whereas non US models of same screen support multiple refresh rates.

    StooMonster (see Acknowledgement in DVDO iScan HD manual)
     
  2. Eagerbeaver

    Eagerbeaver
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    I thought the 434/504 HDE Pioneers supported both 60Hz and 72Hz user selectable by the pure cinema function.
     
  3. SimonO

    SimonO
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    Pioneer literature states that on both the new 434/504HDE models the pure cinema feature runs PAL film based material at 75Hz...
     
  4. Eagerbeaver

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    Sorry, my typo. I meant 75Hz
     
  5. StooMonster

    StooMonster
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    Good job I didn't mention Pioneer HDE in my piece then wasn't it? ;)

    Now, have you tested this or just going by the literature, which is often not completely true. :)

    So, what does your screen support?
    Data and tests results obviously preferred to marketing collateral. :)

    StooMonster
     
  6. Eagerbeaver

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    Mine is currently packed away whilst decorating so I'll have to wait and see, unless someone else gets to test theirs.
     
  7. MattB

    MattB
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    My 433MXE tears/jerks horribly through the VGA and DVI inputs but looks smooth through the others (for PAL and NTSC). Has anyone found a 'magic rate' which is accepted and gives smooth motion with a PC source?

    I use a nvidia G4 Ti 4600 graphics card and wonder how much of the problem is at that end?
     
  8. SimonO

    SimonO
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    StooMonster, where are Pioneer claiming 100Hz frame buffer on new models..?
     
  9. Jasonjo

    Jasonjo
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    Stu,

    Nice post, I was wondering the other day if had found all of the internal rates supported on my Panny...

    Exactly what I found with my Panny PWD6 when using the 'judder test pattern' on my iScan HD.

    JJ
     
  10. StooMonster

    StooMonster
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    See above in first post, 70Hz is the internal frame buffer of MXE plasma. At least it was on the 50" one I tried. :)

    StooMonster
     
  11. StooMonster

    StooMonster
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    Note sure if it is Internal Frame Buffer, which is why I said "* New Pioneer screens claim 100Hz buffer, I'm interested to know what that means ... is it like Panasonic one where 50Hz signal is displayed twice, or have they changed Internal Frame Buffer to 100Hz up from 70Hz?"

    It was on some printed collateral I got from my local hi-fi retailer, will look up later; it says "100Hz progressive scan" whatever that means!

    Try GOOGLE "+pioneer +plasma +100Hz" (all three words required in any order) http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&q=+pioneer++plasma++100Hz&btnG=Search generates 19,600 results. So it must be mentioned quite frequently!

    StooMonster
     
  12. Jasonjo

    Jasonjo
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    Stu,

    Just seen your and OferLaOr's acknowledgements...

    Fame at last ;)

    JJ
     
  13. StooMonster

    StooMonster
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    Infamous more like.

    StooMonster
     
  14. Urotsukidoji

    Urotsukidoji
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    So the panasonic can't do PAL 75hz?
     
  15. kaspj

    kaspj
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    Thanks Stoo. Very useful follow-up to your previous comments on Panny refresh rates.

    *DVI card question removed - answered on Panny Series 7 thread

    JP.
     
  16. Jasonjo

    Jasonjo
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    Not without introducing judder...
     
  17. Urotsukidoji

    Urotsukidoji
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    Is the judder worse than pal at 60hz?
     
  18. Jasonjo

    Jasonjo
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    Yes IIRC. PAL @ 60Hz is actually pretty good....
     
  19. Urotsukidoji

    Urotsukidoji
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    I agree pal at 60hz is perfectly watchable. You get used to it very quickly.
     
  20. Jackass

    Jackass
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    Stoo,

    Is there any chance of you making a sticky with a definative list of all panels that accept native rez via DVI, VGA and whether or not they are HDCP compliant (DVI port only) and wether they frame rate convert the incoming signals on DVI and VGA?

    You seem to be the man for the task with all the knowledge and this would be a god send for making future purchases :)

    Steve.
     
  21. rscott4563

    rscott4563
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    I'd definitely second that, a sticky list would be great and very much appreciated..

    Ryan :smashin:
     
  22. GarethH

    GarethH
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    Do you still see the pulldown effect with NTSC on Plasmas then?
     
  23. StooMonster

    StooMonster
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    Depends what's doing your frame rate conversion, some good some bad.

    Do I notice it on my LCD television, not really too much ... except when there's movement, or scrolling text then it's horrible (regardless of the convertor).

    Not the best way to view PAL.

    And no it doesn't reduce "ringing" or "solarisation" viewing PAL at 60Hz either -- to anwer an email in a thread.

    Some people don't notice adding the extra frames, example is the Pioneer MXE that have 70Hz internal frame buffer they frame convert PAL and NTSC to 70Hz and add judder.

    The brain easily becomes accustomed to anything.

    Yes.

    Unless you have the likes of an DVDO iScan HD that plays NTSC movies at 48Hz with 2:2 pulldown and no judder ... hurrah! (Assuming your plasma has an internal frame buffer that allows 48Hz).

    StooMonster
     
  24. StooMonster

    StooMonster
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    When I wrote the first post in this thread I was hoping it would be a Sticky, and people would post details about the internal frame rates of the screens... guess testing it is beyond the skills or inclination of most. :blush:

    I thought it was down to Spectre or the moderators to make things sticky -- I don't know how to do it.

    StooMonster
     
  25. StooMonster

    StooMonster
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    Yes it is because the scaler is upping PAL to 75Hz, then the internal frame buffer is downing that to 60Hz and not necessarily picking the correct frames.

    This will look much more juddering than converting PAL to 60Hz, which is what you have to put up with if you want to use DVI (at the moment).

    StooMonster
     
  26. Eagerbeaver

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    So are we saying that even the MXE-1 screens will induce judder if the internal frame rate is 100Hz (or 2x50 or whatever).

    If so I'm starting to see little benefit of a MXE-1 over an HDE. They're just introducing a new set of problems or the old ones in a different way.
     
  27. rscott4563

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    The best way to get a sticky going with the required information would be to use this thread to gather the information as it comes in then get a mod to create a sticky and then post the required information yourself (and don't allow anyone else to post in it), from your own findings and from what ever useful information appears on this thread, as long as everyone is allowed to post you'll always get posts (such as questions and off topic stuff) other than just the information for the sticky.

    I'm unable to do any testing of my own at the moment as I'm without screen for a few weeks, though I have got hold of some judder tests and test patterns, but as you have already ran through all the tests for your own 5 series 50" Panny I doubt theres a lot I could add, though when I get the chance I will still have a go and see if there are any differences between the 5 & 6 series.

    Quick question, I've tried out the Judder tester on my LCD monitor and I get smooth flowing lines at 75Hz but I get lots of lost frames (100's), however if I set the monitor at 60Hz which is meant to be its native setting I get much less frame loss (2-4 in 2 mins) but a slightly jerky movement of the lines, the help file with the judder software isn't very enlightening, surely native refresh at native resolution should give me the smoothest but it doesn't, but with 75Hz where I assume lots of frames are being thrown away as it being down converted to 60Hz anyway, hence the lost frames, its actually at it smoothest??

    Oh and I'll be sure to pass your suggestion on to Lumagen :laugh:

    Ryan :smashin:
     
  28. rscott4563

    rscott4563
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    StooMonster

    I got my replacement Panny 6 series 50" a couple of days ago and so figured I'd run some tests to back up what you had already found.

    So I hooked up my PC to the plasma and ran the Judder Test software, now the really strange thing is, at 48Hz and 50Hz, I saw no judder whatsoever, just like you said, this was backed up by the software which reported back no lost frames.

    However when using 60Hz, there was a very very slight amount of judder still evident (very easy to miss though) and the software was reporting back lost frames, which one would assume meant that it was being internally converted to a different framerate???

    Whats going on why is 60Hz being reconverted, are you absolutely sure that with a 60Hz input you had no lost frames and smooth movement?

    I can't do any more testing at the moment as the plasma is all setup in the living room now and so I'll have to wait till I get my mini HTPC built or I borrow a laptop off someone with a VGA output (my Vaio needs an expensive adapter) before I can do some more conclusive testing.

    Ryan
     
  29. StooMonster

    StooMonster
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    Panny 5 50" is my screen, and there is definately no judder on 60Hz at native resolution.

    Which resolution are you feeding it? And with what graphics card? Also, I'm not sure how the software knows that frames have been dropped by screen, if you set it 75Mhz does it drop the number of frames you would expect?

    Perhaps you won't get judder around 59.94 MHz which is NTSC frequency.

    My Panny5 seems quite tollerant around the 48, 50 and 60 MHz ranges.

    Another give away with Pannies is the screen is blurred when not in one of these three zones. e.g. 60Hz is pin sharp where as 75Hz is blurred and 120Hz is really blurred but still smooth like 60Hz.

    StooMonster
     
  30. rscott4563

    rscott4563
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    I was using a Radeon 9700pro and I was running native resolution with 1:1, well when I say 1:1 it ended up as 1360x768 as even though I would tell powerstrip to output 1366 it would end up putting out 1360, I think this has been covered though with some graphics cards only doing multiples of 8, but I used test patterns to make sure it was 1:1.

    At 48 and 50 it was silky smooth and pin sharp, at 60Hz it was pin sharp but with a touch of judder.

    I didn't spend much time testing as I wanted to get it installed and setup asap, so didn't test the higher refresh rates, but will do more comprehensive testing when I get another PC to play with and hopefully I'll be able to get some testing done with the DVI board as well.
     

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