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Plasma resolution again

Discussion in 'Plasma TVs' started by RossC, Aug 5, 2003.

  1. RossC

    RossC
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    Here i was thinking I'd made up my mind to go for the NEC (42VP4) when the thorny issue of resolution was raised - thanks NicholasB ;) - and it's thrown my thinking into a quandry.

    Not concerned about computer use or high def TV (seems a long way off in terms of realistic general availabilty and my likely take up) but this downscaling of PAL is the concern.

    Anyone want to throw in their comments about how much real resolution you loose - not in terms of the numbers, but the actual 'on this scene in that film you won't see xyz' type of real world issue?

    Thanks
     
  2. Liam @ Prog AV

    Liam @ Prog AV
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    RossC - my advice is just go and see one. It takes ten seconds to look at an XGA plasma next to an SVGA plasma and see for yourself whether you can notice the downscaling. Basing your decision on what someone elses eye's see is not entirely recomended and might always leave you wondering if you did go for the right one....
     
  3. RossC

    RossC
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    True, I guess an MXE is probably the most sensible comparison, and nothing specific in terms of scene etc, as it has to be 'in general use'.

    Was really interested to know what others had experienced too.
     
  4. tbrar

    tbrar
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    RossC,

    I agree with Liam - go and demonstrate for yourself, its all very individual.

    The thing with me was the whole concept of loosing the intended TV picture, normal good old PAL broadcasts.

    I just couldnt fathom spending a few thousand pound on a display, that would show me less then my than any existing CRT TV that I had laying around the house.

    Tony
     
  5. steve36

    steve36
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    Ross,
    I'm still pondering the same question.
    When I viewed the new panasonic-6 against the pioneer (HD) (showing Sky) , I thought the pioneer was not quite as good colour definition, with a little 'tearing' possibly due to having to upscale the PAL picture !

    The other day I saw the pioneer MXE in a shop and the detail was superb on DVD's.
    So I suspect that if you watch a lot of DVD's the higher def set is best, if you watch a lot of Sky/DTV then you may find that the higher def sets are less forgiving of any pixel dropouts that sky may have.
    This may have been what gave me the impression that the panasonic was better than the pioneer in several ways.

    I think the lesson in this is always make sure you view the screen with whatever source you watch most, and don't let the shop show you monsters inc, most plasmas look good with that.

    Good luck,

    Steve
     
  6. tbrar

    tbrar
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    RossC,

    Just seen your post on another forum, this is obviously a real bug bear for you. :confused:

    I will try and explain, please bear with numbers:-

    The amount the picture is downscaled from a PAL signal (576 lines of resolution) to a display with a 480 lines of resolution is 16.7%.

    This doesn't mean that the display is going to Physically CUT 16.7% off the top, bottom, left or right of the picture off. What it means is 16.7% of the picture information (ie detail) will be lost in the downscaling process. Hence in a real world x,y,z scenario, the picture information you are viewing will be less detailed by 16.7%, this could apply to backgrounds or faces for example.

    What picture information (detail) you loose is down to the downscale process within the particular scaler/plasma.

    Whether or not this will prove an issue to you is subjective, you do need to go and view with a variety of sources IMHO. But the better the source, the more obvious it is.

    I hope this helps.


    Tony
     
  7. AVWotcha

    AVWotcha
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    Hang on though, PAL broadcasts are interlaced so it's not really 576 but is 228. So this would be upscaled to a 480 line display. Obviously for a progressive source the downscale would apply.
     
  8. tbrar

    tbrar
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    Plasma panels are progressive (apart from ALiS), so a 576 Interlaced signal will be displayed as a 576 Progressive (or more), if the panel can display all 576 lines .
     
  9. NicolasB

    NicolasB
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    No.

    1) 576 divided by 2 is 288, not 228.

    2) If a 480-line plasma were to display an interlaced signal then each 288-line field of the image would be downscaled to 240 lines.
     
  10. tbrar

    tbrar
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    Guys,

    The panels will take the two interlaced feilds, de-interlace and combine - making it a progressive frame, scale up or down to its native resolution, then display.

    Tony
     
  11. RossC

    RossC
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    Thanks for the input everyone - yes Tony it is bothering me, probably more than it should!

    When I had the original demo of a Panasonic 5 (not HD), Pioneer MXE and Hitachi, the detail comparison by the shop used the opening credits of star Wars - their point being that you could physicaly see more stars on the screen with the Pioneer and Hitachi than the Panasonic....however while this was true, the Pioneer looked washed out in comparison to the Panasonic, and the Hitachi didn't look as sharp/clean over all (to my eyes anyway). Plus the fan noise of the Hitachi made it a no no. I also wondered if the increased number of stars visible was due to the lighter screen on the Pioneer rather than the resolution? Hence I chose the Panasonic (well actually chose a Toshiba which is the Panasonic clone)...which has been replaced twice due to nosiy power supplies, so back to square one. NEC looked good, but then I came across all these discussions about resolution and it's got me thinking again....and that's where I am now!
     
  12. AVWotcha

    AVWotcha
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    But that would be crap on a interlaced signal as most sources are still recorded interlaced. Displaying an interlaced signal (where each field is 1/50th sec appart) in progressive would look crap. It only works for movies in which each field is part of the same 1/24th sec frame.
     
  13. tbrar

    tbrar
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    AVWotcha,

    The interlaced feilds are turned into a progressive frame prior to display, this is how the panels work. They are progressive displaying devices.

    If Film then the conversion to progressive frame from two interlaced feilds is done using 3:2 / 2:2 pull down (with PAL). If Video, which is what you are refering to I guess, then other methods of blending are used in the conversion to progressive.

    An extract from my Lumagen Vision documentation :-

    Granted this is a video processor of higher quality than within your average plasma panel.

    However the Plasma Panel has its own inbuilt processor which I imagine will follow a simalar procedure prior to:-

    - scaling up or scaling down (in your example of 576 lines on a 480 vertical resolution display) to the panels native resolution
    - and then finally displaying.

    The point is the two interlaced feilds are turned into a progressive frame, then scaled to fit the Plasma's resolution and then displayed.

    (This is what I think happens, however if wrong please advise.)


    Tony
     
  14. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I'm with Tony on this.

    Upscaling of interlaced fields is a cheap method that I doubt is used anymore. It would result in plenty of scaling artifacts I'd think. Those who were at The Event..think of the opening lecture where I played Insurrection, letterboxed in to a G10 Dila. It's that sort of problem we want to avoid.

    Different methods of de-interlacing are used, then downscaling. That is my understanding. With HiDef though they may still do the upscaling of interlaced on the higher resolution sets. Certainly none that I can do inverse telecine on such signals.

    There is more to it of course than how many pixels etc. The Star Wars scene mentioned earlier could, in all probability, be down to the fact the Brightness was set incorrectly on one or more of the devices......

    Incidentally, much of what we see on TV is actually recorded on film, not videotape. Most scripted drama is on film. Tons of adverts are on film. Most American sitcoms or programmes are film. Inverse telecine is a very useful thing to have on a video processor or plasma, even if you just watch solely TV.

    Gordon
     
  15. tbrar

    tbrar
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    Gordon,

    Thanks for the input/clarification.
     
  16. AVWotcha

    AVWotcha
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    Interesting, if a little crackers IMO.

    The problem here mostly being the time offset between fields. Especially for fast moving scenes (where objects within each field can be in quite different places), the video processing involved to unify each field must be quite extreme. There's no wonder it looks rubbish.

    Surely a much more sensible option would be to upscale each field. i.e. interpolate out the other 50% of the lines of each frame ? Would require a heck of a lot less picture processing.
     
  17. tbrar

    tbrar
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    What looks rubbish, the way current technology deinterlaces pictures ????? :suicide:

    Mmmm...thats interesting.

    Perhaps let Faroudja and Silicon Image know youve got a better way of doing things.......

    Oh and while your at it dont forget; Key Digital, Immersive, Lumagen, Focus Enhancements, Rockwell, Extron....... etc, etc, etc :D
     
  18. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    AVWotcha: Different methods of de-interlcaing are used dependant on the source material. If it is from film stock then the original FRAME can be re-constructed. No motion artifacts.

    De-interlcaing Video source material is much more difficult.

    Upscaling low res signals is a mess. Downscaling hi-res signals is much nicer looking.....

    Gordon
     
  19. RossC

    RossC
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    >>> Upscaling low res signals is a mess. Downscaling hi-res signals is much nicer looking..... <<<

    So extrapolating that view would suggest that standard pal downscaled to fit a 480 line screen is nicer looking than the same signal upscaled to a 768 or 1024 line screen...or is that missing the point?
     
  20. NicolasB

    NicolasB
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    That's missing the point.
     
  21. AVWotcha

    AVWotcha
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    Yep, I was refering specifically to the fact that plasma displays using these methods are just not very good at fast moving pictures, leading to artifacts etc.

    Your right, I should patent my idea and flog it.... but wait, maybe that's why they are using this method. Maybe all the good techniques have been pattented and they are too cheap to pay for the rights to use the technology ? ;):D
     
  22. AVWotcha

    AVWotcha
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    Yeah no i understand the difference between a progressive and video source. But I'm with RossC on the upscaling issue.

    Upscaling 288 to 480 is a ratio of 1.6, a very similar ratio of upscaling a 576 progressive image to a 1024 panel (1.7). And that does not look messy IMO. It can't be difficult. just a bit of interpolation to add extra pixels and some processing to handle edges etc. Bit like "pixel plus" I guess.

    Don't suppose there is any deinterlacing technology available I could try on my computer to get a real world example of how good it really is ? Would like to see what a deinterlaced frame looks like in reality.
     
  23. cwick

    cwick
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  24. RossC

    RossC
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    >>> That's missing the point. <<<

    In what way NicolasB?
     
  25. tbrar

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    AVWotcha,

    What panel are you refering to that has a 1024 x 1024 progressive resolution ??????.

    If you mean ALiS, they are interlaced panels and have a 1024 x 1024i resolution. Hence at any refresh rate the maximum number of pixels that can be used is 1024 x 512. This cannot be avoided it is the way they are designed.

    Consequently, a 576p source is DOWNCONVERTED to 512 vertical resolution at every refresh rate.

    Perhaps have a read of the following:-

    http://www.avsforumfaq.com/~plasma/#alisPlasma

    Youll find within the FAQ (as a whole) a good overview of Plasma technology, including deinterlacing, scaling, resolutions etc.
     
  26. StooMonster

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    AVWotcha

    Upscaling each field is more often refered to as Single Field Interpolation (or "Bob"). It's the most primative form of progressive scan imaging.

    Check out this article http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html for detailed explaination of differences between progressive scan methodologies: Single-Field Interpolation (or “Bob”), Field Combining (or “Weave”), Vertical Filtering, Motion-Adaptive Deinterlacing, and Motion-Compensated (Motion Vector Steered) Deinterlacing. The article includes plenty of pictures to illustrate the text.

    Upscaling? Remember that even the lowest resolution plasmas upscale horizontally -- e.g. changing DVD's 720 pixels to 852. Upscaling vertically does not cause problems either, and will more often than not improve the picture. Here's an example picture of a flag that's been upscaled using interpolation...

    [​IMG]
    Image on the left is interpolated (upscaled) version of flag on the right

    ...notice how the lower resolution has been clarified by the process. You can almost see the stars and read the text. If you use Adobe Photoshop, it's the way images are upsized in this software.

    Downscaling removes picture information, e.g. 576 PAL down to 480 row plasma; there is no two ways about it. As pointed out above, this is equally true of ALiS plasma's 512 rows too.

    StooMonster

    [edited to try and get IMG tags to work, and then asked for help]
     

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