No judder with Blu-ray at 60hz - Samsung LEA656

Discussion in 'Projectors, Screens & Video Processors' started by Toadus, Feb 9, 2009.

  1. Toadus

    Toadus
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    Hi there.

    There has been some rather interesting discussion over in the Samsung LEA656 thread recently, (http://www.avforums.com/forums/lcd-...ntrast-usb-6ms-response-time-part-2-a-38.html) where owners can't seem to get their heads around how it's processing 24p material.

    In a nutshell, when playing 24p material such as Blu-ray, there does NOT appear to be any obvious signs of judder when the TV is refreshing at 24hz or at 60hz. The TV's technical specification descibes it as being 100hz including Motion Plus. I think we've already got the bottom of the "100hz" argument, that being, it's not a genuine 100hz as that's something that's only available in very new, high end PC monitors.

    Many owners, but not all, use a Sony PS3 to play Blu-rays. The PS3 gives you the option to disable 24p mode, which results in the TV displaying "60hz" in the display panel. If you do not turn 24p mode off, a Blu-ray will cause the TV's display panel to show 24hz. The strange thing is, in either mode, there's no obvious sign of judder, so what is the TV doing? :confused: Please bare in mind, I'm not in any instances here using or refering to 100hz Motion Plus, this is turned off.

    If anyone has any ideas what the TV might be doing to remove the judder, then I would appreciate the input. :) Is there anything I can test... ?
     
  2. SyStemDeMoN

    SyStemDeMoN
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    The LG I once owned did not show any judder when displaying 24hz content.

    Only reason I got rid of it was the really bad IR.
     
  3. Avi

    Avi
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    What size is the display ? Not all LE-A656 appear to process things in the same way according to Samsung.

    I'm not familiar with the Samsung but a couple of possibilities. It could be some from or progressive reprocessing (least likely) that is able to identify the source is film and recovers the original frames to refersh at multiple thereof i.e. 72hz, 120hz etc reducing 3:2 pull down judder. Or it may be using some form of frame interpolation. It's difficult to comment without seeing the image.

    When you say the TV display panels show 24hz or 60hz this sounds like the incoming signal freq not what the display refresh freq. Do you know what internal refresh rate the display uses with the various input freqs/material types ?

    IIRC there are some judder test patterns available to download.

    AVI
     
    Last edited: Feb 9, 2009
  4. Toadus

    Toadus
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    Hi Avi, thanks for the reply.

    I can't answer many of your questions I'm afraid.

    My set is a 40" model, but I'm fairly sure it's the same will the others. Bare in mind, the smallest 32" model is not a 100hz Motion Plus set.

    Yes, I believe that's the case with regard to the incoming signal, so seeing "24hz" or "60hz" may in fact mean nothing with regard to what the TV is actually doing...

    What do you mean about the internal refresh rate?

    EDIT: If you play a DVD, the TV displays "50hz" on the panel, and once again, no noticeable sign of judder. When playing a BD (24fps) and refreshing at 60hz, surely the 3:2 pulldown would make it very easy to see judder?
     
    Last edited: Feb 9, 2009
  5. Toadus

    Toadus
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    Moments ago, a user by the name of Lunar Wolf just posted this:

    "You've taken the manufacturers marketing spec of 100Hz and assumed it to be entirely accurate. Its not, the TV will only be operating in that mode while watching PAL format at 50Hz through doubling the frames or adding a new interpolated frames between the original. Basically manufacturers market the sets in Europe as '100Hz' as its historical due to PAL being our format not NTSC and the previous generations of European CRT's displaying Pal-50 frames twice to get '100Hz'.

    Now when a modern '100Hz' TV is sent a 60Hz signal it operates in 120Hz mode the same as their Japanese and US counter parts and does what it did with PAL, either repeating the same frame twice or making up a new one to go between the originals.

    When sent 24hz material it again works at 120Hz and displays the same frame 5 times, hence 5:5 pulldown, or may interpolate depending on how the user has it setup. "

    This is something which we've suspected all along, but don't know whether or not it's true... :lesson:
     
  6. Avi

    Avi
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    Internal refersh rate is the rate that the actual display panel is refreshed which may be different to the input freq. Most current LCD based displays will probably use a higher internal refresh rate and possibly frame interpolation to avoid the perception of smear/blur due sample and hold drive method. So 24hz or 60hz input may be driven at 120hz internal refresh.

    DVD film shouldn't exhibit any type of pulldown motion judder as the original 24fps is sped up to 25fps during the telecine process. This means 50hz DVD has an even 2:2 repeat rather than uneven 3:2 applied to 24 frame material output at 60hz.

    AVI
     
  7. NonPayingMember

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    If 24p and 60p look the same, then the Samsung is probably just taking 24p in and 3:2 it to 60p just the same as if the PS3 was doing the 3:2 to 60p. Net result both signals show the same amount of 3:2 judder so cannot be easily differentiated, and on a small display like this 3:2 judder can be very hard to spot.

    I had a quick glance at the linked thread and for some reason people are arguing over how it would get 100Hz from a 24p signal, which no TV would because it would be a horrible juddering nightmare! 100Hz is purely frame doubling 50Hz and barely adds anything to the quality of the image IMO. It's just another big number that manufacturers can stick on the box.
     
  8. Toadus

    Toadus
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    Avi - It seems you are going along the same lines as Lunar Wolf and many others. (120hz being used)

    Liam - You think it's likely that 3:2 pulldown is being used with 24p material, (at 60hz) but judder would be difficult to notice.

    Two likely answers... But which one is correct for this Samsung TV? :)
     
  9. Avi

    Avi
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    I haven't used these myself but they may help in comparisoin if you have a source capable of sending the output to the display-

    The zip file:

    http://www.w6rz.net/judder.zip

    contains four test streams.

    1) interlacejudder.ts - the moving bar advances 16 pixels horizontally each frame. However, since it's interlaced each field of the bar moves 8 pixels per field.

    2) pulldownjudder.ts - the moving bar advances 16 pixels horizontally each frame. However, 3:2 pulldown has been applied.

    3) progessivejudder.ts - the moving bar advances 16 pixels horizontally each frame. This is a [email protected] video bitstream.

    4) filmjudder.ts - the moving bar advances 16 pixels horizontally each frame. This is a [email protected] video bitstream.

    AVI
     
  10. Toadus

    Toadus
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    Avi, I have my PC hooked up to my Sammy TV. From the Windows OS, I can choose to refresh at either: 24, 25, 30, 50 or 60hz. I'm not sure if this will give the same test as when using the PS3 or not... ? :confused:

    What should I be looking for with those test thingies? :)
     
  11. Avi

    Avi
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    Compare the test material with a different native capture rate i.e 30 FPS to 24 FPS using 60hz. This should provide a comparison of the difference between motion as 30FPS material should not use 3:2 pull down unlike film being processed at 60hz.

    AVI
     
  12. choddo2006

    choddo2006
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    If the Samsung looks the same at both 1080p/24 and 1080p/60, my bet is that both are juddering. I don't think there are any TVs which detect & reverse 3:2 pulldown in a 1080p signal.

    Anyway;
    You want the PC outputting clean frames (can it output an interlaced signal? as you need that for the first two) and to see if it judders when the TV processes it.


    The key comparison you need to check is;
    Is pulldownjudder.ts output at 1080p/60 the same as filmjudder.ts output at 1080p/24 ?
    If they look the same then the Samsung is not displaying at a multiple of 24.
    If the latter looks smoother, then the Samsung IS displaying it correctly.

    Because;
    interlacejudder is 1080i/60 (output it at that if you can but output at 1080p/60 with the media player set to a bob interlace should give a similar effect) so you would expect this to be smooth at 60Hz

    pulldownjudder is a 24fps source with 3:2 pulldown forced into it so if you output at 1080p/60, you should see the judder

    progressivejudder is 1080p/30fps (output at 1080p/60 ideally) so you would expect this to be smooth at 60Hz. It might not look quite as smooth as the one above because it's jumping twice as far each 30th of a second, but it shouldn't judder.

    filmjudder is 1080p/24 (test output at both 1080p/24 and 1080p/60) - this in theory should be the same as the one above, when output at 1080p/24 so this is the comparison you need. At 1080p/60, unless the Samsung is really clever, it should be the same as pulldownjudder.ts
     
    Last edited: Feb 9, 2009
  13. Toadus

    Toadus
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    Thanks very much for the explanation. I will try this tonight, albeit a little over my head, but will do my best to notice and report the differences.

    EDIT: I think it might be able to output an interlaced signal. I will try my best...
     
    Last edited: Feb 10, 2009
  14. Toadus

    Toadus
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    Right. I've watched the filmjudder.ts file MANY times while refreshing at 60hz and also at 24hz. I've certainly picked up on the difference. When refreshing at 60hz, the moving bar would be perfectly smooth one moment, and then it would wobble / judder for a second or two, then go smooth again. Refreshing at 24hz displayed a consistent moving bar. I'm stumped as to why I haven't picked up on this when watching Blu-rays though!

    Let me see if I can work out what to do with the other .ts files! :)

    EDIT: Ooops. Ignore all of the above for the moment, I've just realised I had the 100hz Motion Plus active. (on low) This could seriously alter the results...
     
    Last edited: Feb 10, 2009
  15. Toadus

    Toadus
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    Some interesting results. With 100hz Motion Plus turned off, the results above still stand, but I did note that it was more difficult to see the judder at 60hz. This then led me to experiement a little... :) The higher I turned up the 100hz Motion Plus, the easier it was to spot the judder. When playing the filmjudder.ts file with 100hz Motion Plus on HIGH, the bar moved beautifully like it was being displayed at 100 frames per second, but then all of a sudden it would shake violently, then carry on perfectly smooth again. Really, really easy to spot. When doing the same at 24hz, it was perfectly constant.
     
  16. Toadus

    Toadus
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    To finish off with...

    interlacejudder seemed to be OK at 1080i/60

    progressivejudder seemed to be OK at 1080p/60

    But pulldownjudder was an odd ball. The edges of the bar looked like haircomes, and appeared to move at a much lower frame rate. I couldn't actually pick up on any judder taking place. I even put 100hz Motion Plus on HIGH and it didn't alter the moving bar at all! How odd, as using this feature before made a huge difference to the apparent frames per second of the moving bar.

    The conclusion here would be that the Samsung appears to be capable of dealing with 24p material with no judder. What's got me totally pondering however, is the fact that many, many owners of this set and a PS3, turn OFF 24p when using 100hz Motion Plus because they notice odd skips and jumps every now and again. My results above contradict this! Maybe there is an issue with the Sony PS3?
     
  17. Toadus

    Toadus
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    I decided to sit down an watch a little bit of Transformers on Blu-ray. I changed the PS3 to output at 24p and set 100hz Motion Plus to LOW. Straight away I noticed the same issue, where every now and again you see small skips, or jerks in the motion. It's not consistent either. For example, there was a short pan scene of a house and I noticed and obvious stutter type effect which only lasted about 1/4 of a second during a 5 second pan. I rewinded the scene and played it again, and it didn't stutter. How wierd!

    If the filmjudder.ts file plays on my PC perfectly at 24hz, with or without 100hz Motion Plus switched on, why does playing Blu-rays in the same manner cause stuttering? I think it must have something to do with the PS3, but I couldn't say for certain.
     
  18. Avi

    Avi
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    Is sounds like the motion plus is resyncing the input/output timing. This can happen when small timining differences accumulate to a point that forces a resync. This is observed as a motion artefact i.e. pause, stutter, speed up etc. Often using pause, chapter skip etc forces a timing reset so the event isn't always repeatable in the same place. Some products use genlock to lock input/output timing to avoid these periodic resyncs.

    For what it's worth I use a PS3 had do have issues with stutter using 1080p/24.

    AVI
     
  19. Toadus

    Toadus
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    How come the filmjudder.ts plays perfectly from my PC in 24hz? With or without 100hz Motion Plus...
     
  20. Avi

    Avi
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    Maybe there isn't enough time/frames to require a reysnc before the clip re starts. Does you PC send 24hz exact or 23.976 etc ?

    AVI
     
  21. EarthRod

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    Hi Toadus

    May I ask - what is the full model number of your Samsung TV please?

    Alan
     
  22. Toadus

    Toadus
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    I have no idea. Can I find out?
     
  23. Toadus

    Toadus
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    I don't know without looking Alan. It's the first panel version IIRC...
     
  24. Nex77

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    Reading the service manual, I noted this: "Check the Power input to the FRC(Frame Rate Conversion) Board." So, seems that one tv board is dedicated to the Frame Rate Conversion, I guess (and hope) that our tv could apply exact multiples of incoming signals (24hzx5 or 60hzx2) bring them to 120hz. It's just a supposition. I can't see judder at 24p and 60p with my ps3, however, with 24hz output activated on ps3 and 100hz motion plus OFF, motion look slighty better than 60hz: maybe the console apply "something" to bring native blu-rays 24hz to 60hz.:confused:
     
    Last edited: Feb 11, 2009
  25. noize

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    its not the console.... its definitely the tv. Mine does the same on 24p from a BDP-S350. I love the MotionPlus, and what it does, but the little skip is annoying enough for me to default the BluRay player to 60p. :thumbsdow
     
  26. Nex77

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    What size is your tv?
    I don't know why, but my 46" lcd doesn't have judder at 24hz via ps3 (motionplus OFF).
     
    Last edited by a moderator: Feb 11, 2009
  27. HyperB

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    Just for the record, I get motion judder on a 40" using a PS3 @ 24hz. I have never seen judder on a 32" and a collegue of mine swears he's never seen and sign of it on his 46".

    Steve
     
  28. choddo2006

    choddo2006
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    I would have thought 60Hz x 2 would still judder. Perhaps not like the described "once every so often" caused by MotionPlus but constantly and much more subtly, and in the same way as a normal 60Hz conversion with 3:2 pulldown.

    It's interesting that Toadus' tests don't show it when using progressivejudder.ts @ 1080p/60. I wonder if he is maybe just less sensitive to it. Having looked closely at a Panny PZ70 which certainly does it (even with 24p sources), it can be quite hard to spot but I'd have thought the test pattern would show it quite clearly.
     
  29. Martinf419

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    Hi All,

    Without picking through all the posts above, in a nutshell here's what I propose is happening in the Sammy with motion-smoothing “OFF”:

    1. With 24Hz **progressive** input material (i.e. blu-ray film HDMI), the TV will:
    (a) switch into “120Hz mode”;
    (b) stream as 120Hz by 5x frame-repeating.

    2. With 30Hz **progressive** input material, the TV will:
    (a) switch into “120Hz mode”;
    (b) stream as 120Hz by 4x frame-repeating.

    3. With 60Hz **progressive** input material (i.e. game console or PC via HDMI), the TV will:
    (a) switch into “120Hz mode”;
    (b) stream as 120Hz by 2x frame-repeating.

    4. With 60Hz **interlaced** 3:2 pulldown input material (i.e. film source converted for NTSC TV broadcast or NTSC DVD), the TV will:
    (a) switch into “120Hz mode”;
    (b) ‘reverse-engineer' the 3:2 pulldown process internally back to 24p;
    (c) stream as 120Hz by 5x frame-repeating.

    5. With 60Hz **interlaced** (i.e. live NTSC TV broadcast input material), the TV will:
    (a) switch into “120Hz mode”;
    (b) de-interlace internally to 60Hz progressive;
    (c) stream as 120Hz by 2x frame-repeating.

    6. With 50Hz **interlaced** (i.e. live PAL TV broadcast input material), the TV will:
    (a) switch into “100Hz mode”;
    (b) de-interlace internally to 50Hz progressive;
    (c) stream as 100Hz by 2x frame repeating.


    Now, with motion-smoothing turned “ON”, the above logic still applies, EXCEPT that in each case, the last step involves interpolating the frames, rather than simply repeating them.

    Any comments – and have I missed anything?

    Martin.
     
    Last edited: Feb 12, 2009
  30. Barcoing Mad

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    That would seem a logical solution. Doesn't mean the TV manufacturer goes that route, though.
     

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