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Do Plasmas do progressive scan?

Discussion in 'Plasma TVs' started by DaveH, May 29, 2001.

  1. DaveH

    DaveH
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    Dear all,

    Do plasma Tv's do progressive scan.

    I know that some of them can do High Definition for the future, but what about Progressive scan.

    Thanks.

    Dave.
     
  2. Guest

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    Yes they do, some of the older models had problems with Progressive PAL but this appears to be solved these days but I never hurts to check the specs.

    Regards

    Alan Roser
    Owl Video Systems
     
  3. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Alan,

    I think that there are some higher resolution Sony plasma's which work in "interlace" mode all the time. Not sure of the models or if they are even available over here yet.

    Gordon
     
  4. Guest

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    Due to the method used to address the plasma cells and render the grey scale, interlaced video is not compatible with plasma displays.

    Most pixel scaling systems also require a progressive frame as input.
     
  5. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I had always presumed that Plasma's could only function in “progressive” mode and was surprised when I heard about the Sony doing “interlace” reproduction. Your post has lead me to look in to this further and here's what I found out…..

    I decided to seek out a Sony plasma dealer over here in Toronto. I found Toronto's leading installation company, ”their words not mine” and asked around. They had one of the 1024 x 1024 pixel plasma's and by their own admission “it's a crappy picture unless you add an external scaler”. I asked if it operated by showing an interlaced picture rather than a progressive one and he commented that it did but only at high input resolutions…….Weird! So further investigation was called for. I went back to the original source of this “mis”information.

    It seems that some of these devices use our persistence of vision to fool us in to seeing what they want us to see. Much like single chip DLP's do with the colour wheel and normal interlace tv's do…. There is a “time sharing of pixels” going on with these things. I haven't looked in to what this actually means yet as I think it may be a whole can of worms but I'd guess that if you send a high res signal to one of these things it shows a progressive image but not using all the information in one pass. Perhaps it only refreshes some of the pixels every field it shows, like showing the odd and even lines of field one, then the even lines of field one interleaved with the odd lines of field two (done as a progressive image but only half the pixels have been refreshed) then the odd lines of field two along with the even lines of field two.

    Are there any Plasma specialists out there who can enlighten us or should I continue my investigation.

    Gordon
     
  6. DaveH

    DaveH
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    Thanks for the replies.

    This is beginning to turn into quite an interesting topic.

    If anyone has any further information to Gordon's findings this would be very helpful.
     
  7. Brian Storm

    Brian Storm
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    Plasma displays certainly employ progressive scan, but it gets much more complex than that. Instead of showing a single field or two fields converted to one progressive frame. Plasma employs a system called sub-field drive which can be eight to twelve scans per field depending on the set. Also Panasonic use dual scan progressive technology, which in effect splits the screen in two vertically, and scans both parts simultaeniously. See my write up of Panasonic Plasma displays in a future issue of Television magazine.
     
  8. Guest

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    Plasma displays use the sub-field drive method in order to build up the grey scale or brightness levels, the pixel data used to generate the sub-fields is derived from a progressive frame.

    I think that Gordon, in his post above, may have been refering to the new range of plasma displays available that have increased resolution (usually in only one axis (i.e. vertical)) by increasing the pixel RGB surfaces but driving them with the same number of electrodes in the matrix as a lower resolution panel. They do this by alternating the lighting of the RGB surfaces (one electrode can drive only one pixel at a time). The pixel data could therefore be described as interlaced, two fields of a progressive frame are lit alternately, but they are not scanned in the same way as a CRT interlaced display.
     
  9. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    O: That is exactly what I was talking about. Thanks for clearing things up.

    Gordon
     
  10. DaveH

    DaveH
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    Thanks everyone.

    So what does the Delphi plasma fall under?
     

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