Do we just have to accept that judder is a part of home cinema?

Discussion in 'Projectors, Screens & Video Processors' started by Comer, Dec 12, 2001.

  1. Comer

    Comer
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    Projector: Tosh MT3

    PC:
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    Even when I change the refresh rate to 72/75Hz I still get panning judder (acompanied with dreadful tearing at anything other than 60Hz). I have removed and reinstalled the latest drivers. I even took the pc apart and tried a borrowed motherboard with a P4 1.7G processor and removed the sound card,-no improvement.

    I then tried my Samsung 709 DVD player as a source, and to my surprise, there was judder. Not quite as bad as with the PC but still definately there. How on earth did I not notice it before? I wounder what the PJ refreshes at when using a video source through Svideo in? Anybody know?

    Then my brother said that he could see no judder until I pointed it out to him and that it would not be bothering me had I not been spending hours stuck on AV discusion forums on the Internet. And he was right. I have been watching movies on the PJ and Samsung DVD for five months and never noticed judder. Not IT'S DRIVING ME MAD, MAD I TELL YOU, MAD!

    But that's the curse of the forum. It makes us aware of faults that we may never have noticed and that we certainly never needed to know about. But then if it were not for this forum I would not have attempted to build the PC in the first place and would not be enjoying the excellent improvements that a progress scan picture offers. That's the curse of the forum, it arms us with information that promises such possibilities but which ultimately leads us to disappointment and the need, no, the craving for the impossible...perfection. Except of course for you CRT boys, you seem to think that you have the whole thing in the bag!

    Well, back to the origonal question in this post: is judder something that we must live with and if so does anybody know of a brainwashing technique which would perminately remove this newly learned word from my memory...JUDDER.


    Conor
     
  2. Roland @ B4

    Roland @ B4
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    What do you mean think.

    Problem here is you have two technologies causing the judder. the scaller in the projector and the PC itself.

    Keep going I'm sure you will get it smoth there is no reason why an LCD or DLP will do it once you find the pixel for pixel and refresh rate of the projector (which is not always the same as it says in the hand book)

    I think they should add a coment on the films.
    "Warning contains nudity, bad language, violence and moderate panning shots"
     
  3. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    The judder thing is a problem isn't it....or is it?

    I can happily sit and watch R1 dvd's till the cows come home and not get too concerned about judder..until it's obvious. It isn't obvious in most material though.

    The problem with judder removal, be it 72Hz, 48Hz or whatever, is that sometimes it works well until it doesn't. It's because the difference from smooth pan to sudden stutter is so dramatic that it can be even more annoying as you suddenly get knocked back in to realising you are watching a film and not reality.

    Getting rid of judder completely in all material is hard, very hard I think. I don't even know if it's possible with fixed pixel LCD units.

    Believe me, CRTguys haven't got it all......yet.


    Gordon
     
  4. Comer

    Comer
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    But where do I go from here. I have no idea what to try next.

    Thanks

    Conor
     
  5. tryingtimes

    tryingtimes
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    I didn't think it was possible with fixed panel displays but the new sony 11ht has 3:2 pulldown built in! - what must it be outputting?
     
  6. JohnAd

    JohnAd
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    Alex

    3:2 detection is different from 3:2 removal. THe sony is probably just outputting 60Hz which will have 3:2 judder but cleaner pictures.

    John
     
  7. tryingtimes

    tryingtimes
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    pardon my ignorance (this was one thing I thought I understood!)but why would you need to detect it if you weren't going to remove it:confused: and how would that improve the picture?
     
  8. JohnAd

    JohnAd
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    Alex

    When you deinterlace video you are trying to reconstruct infomation that has been chucked away. With film it's not really been chucked away just rearranged in a special way. If you treat film material like video you get all the atrefacts described by Gordon in Insurrection, if you spot it is film you can put the original frames back together and show only whole frames. This still doesn't help with the 3:2 pulldown judder as you're showing 2 frames then 3 in order to convert 24fps to 60.

    John
     
  9. tryingtimes

    tryingtimes
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    So your saying that recognising what the original frames were is the first step towards effective deinterlacing regardless of whether you reconstruct it to 1:1 or back to 3:2?
     
  10. JohnAd

    JohnAd
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    Yes, you can reconstruct all the original information when deinterlacing film once you know it is film, with video you can get about 75-85% of the original back with simple deinterlacers, with clever things like the Interpolator, Teranex and the Alchemist you get more like 90-95% (wildly approximate numbers).

    John
     
  11. tryingtimes

    tryingtimes
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  12. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    That's exactly what he's saying.

    Film based DVD's are taking 24 WHOLE pictures(ie all the info in the frame was recorded at the same moment in time) and turning them in to 60 (Hz) pictures. These 60 pictures are created from 24 originals by first showing only half the info from each picture at a time (ie interlaceing) creating 48 pictures with first being odd lines and second being even etc. Then you still need 12 more to get to 60....so they show 3:2:3:2:3.........etc where the 2 part is the odd then even line fields and the third one in each string of three is often the second field from a frame repeated....

    3:2 recognition allows a processor to recognise this pattern and put the odd and even line fields back together to create one progressive full frame. Of course you still need 60 of them a second it's just that now they are all the info, not half of it as in interlaced. So what they do is show the FULL FRAME reconstructed in 3:2:3:2 sequence. It's the 3:2:3:2 bit that can create judder in pans. Judder removal systems work out the original frames and then show them as 1:1:1 (24hz) or 2:2:2(48Hz) or 3:3:3 (72Hz) get the picture?

    Now, VIDEO based DVD's or tv programming isn't as simple. That's because video camera's actually record interlaced....ie they record one field of even lines then one field of odd lines. So if there is any motion in the image between the capture of one field then the next you have problems sticking them back together as there will be jaggie edges. Faroudja's chipset is good at dealing with this. Remember there's no 3:2 recognition or anything like that as we aren't converting 24 Frames per second to 60Fields we are trying to de-interlace a 60 interlaced fields per second recording! Wow....nightmare!

    Hope this makes a little sense.

    Gordon
     
  13. Jeff

    Jeff
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    Judder isn't just a home cinema anomaly, pans at the cinema aren't that smooth either. 24 individual fps just aren't enough.

    Jeff
     
  14. mart.stokes

    mart.stokes
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    What amazes me is the amount of money, research and effort being expended on things like this subject. This is a bit like a doctor treating the symptoms instead of curing the disease.

    How long is it going to be before we get a decent source to work with so we don't need all this processing?

    Once we have determined the "refresh rate" of the retina and we develop pixel to retinal cell mapping we may be happy. Of course my newly developed PtRCM technique (thought of it as I typed it) does have a few minor drawbacks; 1) You move your eyes around and the picture moves with them, 2) You are forced to concentrate on the bit of the picture that falls on your more sensitive cells, no choice in the matter! So if the cameraman has concentrated on a vase and Jenna is getting her kit off a few feet away then I'm sorry, you are watching the vase!
     
  15. Mr.D

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    I

    'd take a little bit of issue with this Jeff. Whilst its true that certain camera moves at certain speeds in conjunction with certain shutter angles can produce strobing its rarely as problematic as the stutter/judder phenomenon relating to 3:2 pulldown or refresh issues ( or as I suspect is a likely culpret sloppy MPEG2 decoding or encoding).
     
  16. cg999

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    I was blaming the combination of the PJ with the PC for the extent of the judder, but now I'm seeing judder (to the same extent) watching DVDs on the TV. In some ways I really do believe that I was alot better off before I learned so much about Home Cinema from these forums.

    At least now I can stop trying to improve things with the PC and Proector and try ttto lllive wwith tthis jjudddderrr


    Cconnor


    (My work logon name is Comer)
     

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