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Nebula DigiTV jerkiness and shadowing

Discussion in 'Desktop & Laptop Computers Forum' started by hoyin, Feb 5, 2005.

  1. hoyin

    hoyin
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    Everything is working fine now the picture is great.

    However I have noticed that when I am watching something that has a slow panning shot it seems to not pan smoothly?

    It seems to jerk a bit. This is most noticeable when watching the credits on a film roll by.

    In addition whilst watching the Simpsons yesterday there were huge problems. When anything moved it left a shadow, almost as though it couldn't keep up with the moving picture. So if Bart moved his hand you would see the new position of his hand and for a millisecond the previous position!

    Any ideas as to why? The second point about shadowing only seems to appear in cartoons.

    Any ideas?
     
  2. Mr.D

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    What resolution and refresh rate are you using?
    What deinterlacing type are you using?

    If should really be running at 50Hz or 60Hz unless you only ever watch films.
    If you run at 60Hz switch on frame smoothing to introduce regular pulldown (it will never be entirely judder free but it should be relatively unobjectionable).

    Deinterlacing use bob mostly (everything should like fine with this) for a little extra sharpness when watching folm material run with none. Line average may be the source of ghosting.
     
  3. hoyin

    hoyin
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    Using it with a Sharp LCD so running it at a 1:1 pixel matching resolution 1368x768 .. well 2 pixels out.

    60hz refresh.

    Regarding deinterlacing -

    I find if I use Bob the sides of the screen move about a bit and any still graphics i.e. logos etc jump around on the screen the quality is good especially with football but if you look closely the picture jumps about a bit.

    With it turned off if there is any movement the edges a show jagged edges.

    Hence I have it on line average as this is the most watchable. But I shall try it on other settings again.

    Is this the same for you?

    I am unable to set it at 50hz it won't let me! neither am I able to set it at a higher hz i.e. 75hz.

    I have frame smoothing on all the time.
     
  4. MikeTV

    MikeTV
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    When I watch the Nebula on a CRT, it doesn't look jagged (presumably because of rounded, overlapping pixels), but when I view it on my laptop lcd, it looks very blocky indeed. I think it must be because it is inherently jaggy material, due to digitization. You could try running at 800x600 (or something else), to see if your graphics card makes a better job of smoothing pixels, but I doubt it will make much difference (or may make it worse).

    With the simpsons problem, I tend to think it may be LCD pixel latency problem. This is one of the known problems with LCD TV's. On the other hand, it could be caused by digital conversion/encoding problems by the boadcasters too. Unfortunately, I have deleted my recent simpsons recordings, and so I can't determine whether this problem is in the broadcast material or not (if you look at it frame by frame, you can sometimes see the same effect in a badly encoded/deinterlaced material).

    For what it's worth, on a CRT @ 60hz, I use Bob (except for films) with no frame smoothing. For LCD's it's not so clear, because there will be some loss of definition by any averaging/smoothing, but perhaps less jerkiness.
     
  5. Leporello

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    I use a 17" tft with the Nebula card, I have no jaggies and prefer the LCD to a CRT for all round viewing.
     
  6. Mr.D

    Mr.D
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    I run a plasma at 856x480 at 60Hz and an HS20 at 1368x768 at 56Hz.

    Bob will introduce jitter on fine horizontal detail (its how it gets its name)but for the most part it should look fine and reasonably smooth and sharp. Its primarily for interlaced material but films shouldn't suffer too badly either. Best way to view anythign that isn't frame based to be honest

    Films as long as the cadence hasn't been mucked up and some material shot progressively should be left as off . This will deinterlace as a weave with the frame smoothing repeating frames at regular intervals to meet the required display rate.

    The line average effectively does a bob on each field to turn them into frames and then does a 50/50 mix with each frame to display at 25fps. This can cause ghosting and is quite soft looking it can alos look a little juddery but will not have the vertical jitter on horizontal detail that bob has.

    The scaling with digiTV isn't too good ( they could do with letting it hook into ffdshow) but I can't see its looks jaggy to me if anything its a little on the soft side at higher resolutions.
     
  7. hoyin

    hoyin
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    Mr. D,

    Well whilst watching normal TV if I have deinterlace turned off everytime someone moves I get jagged edges.

    However on weave and bob it is fine apart from the problems described previously.

    So is everyone saying that when you have it turned off you are not getting any jaggedness?

    Perhaps there is some other setting I have wrong?
     
  8. Mr.D

    Mr.D
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    When deinterlacing is "off" in digiTV its doing a weave. If its film or frame based material its the idea way to view. If its field based you will see the mismatched fields as "hairy" edges on moving objects.
     

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