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1080i on a CRT

Discussion in 'Projectors, Screens & Video Processors' started by Boris Blank, Oct 29, 2003.

  1. Boris Blank

    Boris Blank
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    A question elsewhere made me wonder - just what the heck is 1080!??

    I know that most 8" projectors will not resolve 1920x1080p. Now, I know that 1920x1080i is different and can be resolved BUT how?? Is interlaced not the same pixel resolution or something (electronically speaking, I know its a lower bandwidth but.....?). Perhaps they are not showing a "true" 1920x1080 display?

    Totally confused over 1080i.

    Regards,
    Paul
     
  2. BrianCurran

    BrianCurran
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    Paul

    Say you want a HTPC to display 1080i, you use Powerstrip to set the desktop resolution to 1920 x 1080 and set the scan mode to interlaced instead of progressive. (Providing your graphics card supports interlaced overlay)

    Although the image is interlaced your eye will see 1080 pixel lines instead of 540 per field so the perceived resolution is 1080.

    1080i is awesome for images with limited action, But for sports etc.... a progressive scan is preferred eg 1024 x 576p for 7" PJs or 1280 x 720p for 8" PJs
     
  3. Boris Blank

    Boris Blank
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    Ok, I'm with you. So its not a full 1920x1080 resolution, rather its like 960 x 540 repeated sort of (or the image is split into 2 sets of lines) but the human eye is fulled into seeing one complete set of lines.

    Ok that makes sense now (at least if my rather simple interpretation is correct). I just couldn't understand how you could fit a pint pot into a half-pint jug so to speak.

    Thanks Brian, I think I've got it now!
    Paul
     
  4. RichardA

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    1080i has the same apparent resolution as 720P (i.e. about 2/3rds the total lines)

    As mentioned before a 1080P (for Progressive) signal draws the full frame of image in a single pass. 1080i (for interlace) draws the image in two separate passes of 540 lines and takes, usually, twice the time to do it.

    Therefore the 1080i signal uses half the bandwidth of 1080P but due to the slower update on screen looses some perceived resolution to give an image similar in feel to a 720P signal.

    This really is the whole idea of interlace, it gives good resolution and uses lower bandwidth than a progressive signal.

    Of course if you took the 1080i signal to a de-interlacer, and had film originated material then you could resolve the full 1080 lines of image. In broadcast speak we call it 1080PsF (For Progressive scan Segmented Frame) :lesson:

    Hope this helps.
     
  5. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Paul,

    I guess this was posed due to an answer I gave in a previous thread about inability of many CRT's to display 1080i. This inability is due to the short flyback time for drawing each line (i believe) .Many CRT's are not up to the task even although the bandwidth is within their specs. Sony D50 for example cannot as can't some BarcoXXX series units (Roland can advise)

    Gordon
     
  6. Boris Blank

    Boris Blank
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    Thanks very much indeed guys. Yep, the mention of 1080i did get me thinking as to how a "higher resolution" could be displayed on a device with a lower resolution.

    I suspect that this will be very much an issue in the coming months with Euro1080 kicking in!

    Very interesting indeed!
    paul
     
  7. Rob

    Rob
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    1080i can look incredible. Fed directly from a D-VHS player, I've never seen anything like it, particularly the material shot in HD ie the HD- net stuff, (Bikini destinations, trains of the American west etc) and of course, Beauty of Japan

    I've never seen this stuff scaled to a progressive output and would be interested to do so. Its difficult to believe it can get any better.

    Watching the famous opening of Insurrection that we know so well, I was able to switch between the DVD (scaled to 720p) and a copy on D-VHS (1080i). The Hi-def version seemed to be smoother, despite being interlaced, and of course had much more detail. I guess the interlaced artifacts are less noticeable at a higher resolution. Interesting though.

    Rob.
     
  8. Boris Blank

    Boris Blank
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    Rob,
    So you are watching 1080i fed directly into you (9"?) crt without any processing - thats excellent news! I suppose it would be better if it was run through a deinterlacer but by how much and would the difference be worth it? Dunno, food for thought certainly. I'll not get into 1080p as thats beyond us mere mortals (at the moment;) ).

    If you aren't having a problem with 9" then likely 8" won't (screen size variations aside).

    Interesting, thank you.
    Paul
     
  9. Rob

    Rob
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    Paul,

    You can view D-VHS strait into projector, if you have a HD input card. Otherwise you will need to use some kind of transcoder. I think the input card can be fitted to any of the S series (Barco). If you contact www.crtprojectors.co.uk they will be able to advise. I use port 4/5 for HD input, and port 3 for DVD.

    I guess using a deinterlacer/scaler for any source, such as the HD Leeza or PC with the Holo3D 2 would be the ideal scenario, I havent got that far yet, although I'm certainly pleased with the setup I'm using presently.

    Cheers Rob.
     
  10. Jenz

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    With regards to Holo3D 2 you must have the HD Aux board. Roland and I recently fed 1080i DVHS into my Clarus Video Processor and deinterlaced/scaled to 1080p and beyond.

    Neil.
     

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