1080i vs 1080p idiots guide please

Discussion in 'Plasma TVs Forum' started by kevantlin, Dec 29, 2006.

  1. kevantlin

    kevantlin
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    Please could someone tell me in laymans terms (or point me to a website) what is the diff between 1080i and 1080p

    i know it means interlaced and progressive--------but what does that mean?

    :lease:
     
  2. Badger0-0

    Badger0-0
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    Put simply, interlaced shows a frame in two parts. Imagine the picture being in lines from top to bottom of the picture. In the first sweep, the telly shows you lines 1,3,5,7 (odd), then in the next sweep, it shows the even lines. Your eyes can't keep up, so it doesn't see this happening :rolleyes:
    Progressive shows the frame as line 1,2,3,4 etc so is an improvement, especially for motion.
    That's very simple, though, you should find plenty on the net :smashin:
     
  3. choddo2006

    choddo2006
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    Say you have a 50Hz signal (UK standard)

    In the first 50th of a second, a 1080i/50 signal will send all the odd lines (540 lines) and in the second 50th of a second, it will send all the even lines. Typically for video, these were filmed a 50th of a second apart but for film a single frame was effectively split into 2 to create the interlaced version.

    the TV then has to work out what to put "in the gaps" based on content & whether it thinks it's a video or film signal. A CRT can get away with only drawing what it received because the overlap of the phosphors disguises the line structure which is where interlaced signals (therefore only using half the expensive analog bandwidth) originated.

    in a 1080p signal, in the first 50th of a second, all lines are sent.

    You can also get 1080p/24 which is an emerging standard for film material which can also be split ala interlacing into something called 1080p/24psf (progressive segmented frame) which is a kind of 48Hz 1080i with a "guarantee" for the TV that just weaving it back together will give 1080p/24 equivalence.

    And of course, there are 60Hz versions of both too.

    There's no 1080p TV broadcast yet but the x360 and ps3 can do 1080p/60 for games and BluRay and HD-DVD can do 1080p for movies which ideally would be output at 24fps but are usually converted to 60Hz just like NTSC DVDs are or may be sent as 1080i (hoping the TV will figure out how to re-build the full frames properly)

    Sorting out this whole mess is one reason people buy things like video processors.
     
  4. Badger0-0

    Badger0-0
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    Much more eloquently put Choddo :smashin:
    And there was me trying to keep it simple, clever clogs ;)
     
  5. MAW

    MAW
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    The upshot of this is that there is, in theory, trice as much data in a 1080p as a 1080i signal. Except, there are almost no sources of 1080p 50 or 60Hz. Film material on HD disc formats is 1080p/24, ie knats willy data wise from 1080i. However, the difference may be much much more than it sould be, depending on your screen's ability to correctly process and display the signals, various. An alarming number of screens, (and not always the cheapest, the big S are guilty here) fail to reconstruct 1080i frames at all before displaying them. Bummer, not HD any more really. Nice simple explanation from Badger, preferred your old sig, mate. If only real world was nice and simple like that.
     
  6. kevantlin

    kevantlin
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    dont you just love this forum?

    Thanks Guys
     
  7. robin

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    I was of the understanding that a 1080i pic refreshed at a 50 times a second but a 1080p only refreshed at 25 times a second.
     
  8. choddo2006

    choddo2006
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    Yeah I was for a while too, not sure where that one came from to be honest. There's certainly 1080p/50 and 1080p/60
     
  9. Badger0-0

    Badger0-0
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    I think you're correct, in the real world, see MAW's post above.
    As far as I know and I may be wrong here, nothing is true 1080P/50/60 because of the bandwith issue.
    Certainly, having thought about it, it'll never be transmitted via Sky (inherently cable too, in that sense) as the whole idea is to save bandwidth.
    Then again, when they get new codecs/formats, I suppose it will happen, but not for donkey's, IMO.
    Another reason why the future lies in downloaded content, at a guess :rolleyes:
     
  10. choddo2006

    choddo2006
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    PS3, xbox360 are true 1080p/60. Bandwidth not an issue there as content is generated "locally".

    In some ways that's bad as 1080p/24 would be better for HDDVD & BD movies but for games it's a good thing.

    I think all HD-DVD and BD players provide the option of 1080p/60 too, if you need it for your display as not many take 1080p/24.
     
  11. ash

    ash
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    Also not many HD players do real 1080p/24 I think. Something to do with turning the 1080p/24 into 1080i, then making it 1080p.......

    I don't know much about this.
     
  12. choddo2006

    choddo2006
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    Yeah but I think most do an ok job of that since it's a simple weave & needs no cadence detection (Samsung BR being the notable exception although I heard they patched that)
     
  13. General Skanky

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    Sony? Samsung? Sanyo?:)
     
  14. Kalos Geros

    Kalos Geros
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    There is a lot of speculation on this...I'd really like to meet the engineers who are designing our AV kits and ask about what strategies they employ:devil:

    Basically I think that for the reasons of compatibility with older HD displays they are running 1080p/24Hz as 1080i/50Hz with the usual 2:2 cadence i.e. the film is sped up for 50Hz (you lose 1 frame of running time per second = unnoticable)...the 1080i/60Hz also uses the old trick = 3:2 pulldown...I believe that you'd be able to select the 1080p/24Hz mode on the future HD-DVD/BlueRay devices as new plasmas are able to run at 48Hz refresh (I believe 24Hz refresh would introduce flicker since we ARE talking phosphor with plasmas - LCDs may be different animals altogether in this respect)
     
  15. Steve-O 2007

    Steve-O 2007
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    so would the average person realy be able to tell the difference with 1080i and 1080p??
     
  16. choddo2006

    choddo2006
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    Not with the average TV at the average viewing distance. Remember, all LCDs and nearly all projectors and plasmas show a progressive image anyhow, they just have to work harder (harder than some of them can manage) if they're only given 1080i or 576i (SD) for example.
     

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