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DirecTV 1080p?

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by sarfdawg, Jan 23, 2008.

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  1. Jan 25, 2008 #81 of 171
    cygnusloop

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    The enigmatic P Smith is correct.

    Real issue is, how does the processor deal with the fact the the two fields were recorded 1/60th of a second apart. The (LCD, DLP, or Plasma) 1080p TV will refresh the entire frame at 60Hz. At each refresh it has one "fresh" field to use, and one field that is 1/60th of a second old. The next refresh the alternate field is fresh, and one that was new, is now 1/60th of a second old.

    If there is little to no motion in the scene, just displaying the new field and the field that is 1/60th of a second old will look very good.

    Once you add motion, the "smarter" TV's will modify the older field for the current refresh in order to compensate for the motion. Some TV's do a better job of this than others. So who is still not quite getting this?

    Of course if you have an HDTV with a 120Hz refresh rate, things get even more fun. :)
     
  2. Jan 25, 2008 #82 of 171
    P Smith

    P Smith Mr. FixAnything

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    Just imagine video memory buffer with two buses: one for writing - from stream processing, other - (independant) for reading and converting pixels' info into analog (Component, composite, S-Video) or digital signals (HDMI,DVI).
     
  3. Jan 25, 2008 #83 of 171
    gregjones

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    But even at less temporal resolution 1920x1080i is more information than 1280x720p. That is almost always overlooked. 1080i still represents more information per second.
     
  4. Jan 25, 2008 #84 of 171
    greenwave

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    Bottom line it for me: I have a 1080p Sony XBR5 46" LCD. What is going to look better for me, having the HR20 set on 1080i or 720p output? I know it is "in the eye of the beholder", but I just want to know which you honestly think will consistently look the best. I do love my HD sports for what its worth.

    And yes, my LCD has a 120hz refresh rate.
     
  5. Jan 25, 2008 #85 of 171
    cygnusloop

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    The answer is both.

    Set your HR20 to Native=ON, and at least 720p and 1080i selected. The progressive 720 stream will then only need to be scaled to 1080p, which your TV will do very well. (As opposed to the HR20 scaling it, then interlacing it, sending it to your TV to be deinterlaced - less processing is almost always better than more processing).

    The 1080i channels will be sent straight to your TV for deinterlace, which should also look great. The debate about whether or not 720p is better than 1080i for sports has to do with the broadcaster. That decision is, however, already made for you. You will likely do best by giving the native resolution to your TV, and let it do what it has to to get it to 1080p.

    Whether or not you want to include 480i/p is a personal choice, and the subject of many, many, many threads here.
     
  6. Jan 25, 2008 #86 of 171
    Canis Lupus

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    FWIW - I've had the best viewing experience on my Sammy 1080p DLP using 720p. I've found the combination of the DLP and keeping the whole delivery system in progressive has yielded the best results, especially with increased action/motion.

    As always though - eye of the beholder.
     
  7. Jan 25, 2008 #87 of 171
    veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    As another Sony XBR owner, all resolutions selected and native on is the only way to go. :D
     
  8. Jan 25, 2008 #88 of 171
    Canis Lupus

    Canis Lupus You make it, We break it

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    How'd this one make it through? :eek2: :lol:

     
  9. Jan 25, 2008 #89 of 171
    cartrivision

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    Only for a perfectly still image??? Once again you are wrong. As several people have pointed out, 24fps moving images (you know like virtually every theatrical motion picture release that you might see on HBO or Showtime) can be reproduced with 1080i just as well as with 1080p and without any "best fit guessing, or interpolation, but just by using the pure "real" data present in a 1080i signal. In that very common use of 1080i, playback of properly deinterlaced 24fps source material encoded with 1080i will yield the exact same end result that using 1080p would give you.
     
  10. Jan 25, 2008 #90 of 171
    cygnusloop

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    You are absolutely correct, however, the operative phrase is can be reproduced. Unfortunately most displays don't (yet) do this properly.

    From Gary Merson's article...

     
  11. Jan 25, 2008 #91 of 171
    blueline

    blueline New Member

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    But aren't LCD display non-interlaced panels by default? What I don't understand is how is an interlaced signal being displayed on an LCD since there are no horizontal scan lines?
     
  12. Jan 25, 2008 #92 of 171
    P Smith

    P Smith Mr. FixAnything

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    See post#82.
     
  13. Jan 26, 2008 #93 of 171
    cygnusloop

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    I'll expand a bit on P Smith's reply.

    Yes, LCD displays are progressive by nature. Only CRT's can "natively" display interlacing. So, how does it do it?

    Take, for example, a 1080/60i signal coming into a 1080p display that refreshes at 60Hz. The 540 even lines come every 1/30th of a second, and the same for the odd lines, meaning the display receives a "field" every 1/60th of a second. The display is buffering these fields as they come in. So, for every refresh, the display buffer has one field that is brand new, and one that is 1/60th of a second old. The next refresh, the alternate field is new.

    At its simplest, for every refresh, the display will alternatively show the new odd fields with the older even field, then the new even field with older odd field. Some displays will try to modify the older field to compensate for any motion that is happening in the frame. Some do it better than others.

    And, :welcome_s to DBSTalk, blueline.
     
  14. Jan 26, 2008 #94 of 171
    HoTat2

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    OK, I'm still trying to get my mind wrapped around this cygnusloop. So please bear with me. Now this here you wrote seems clear enough, but how exactly does the inverse telecine process work with this "new field + buffered "old field" presentation sequence every 1/60 sec, when and if the receiver properly recognizes a 3-2 field pattern on the input signal indicating 24 fps film source material?

    And I also take it that if the display's refresh rate were higher. Such as the 120Hz of greenwave's Sony XBR5 mentioned earlier, then it is simply a case of repeating the same constructed 1080P frame twice every 1/60 of a second?
     
  15. Jan 27, 2008 #95 of 171
    cygnusloop

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    The short answer is that if the display can only do 1080/60i, it will never be able to reproduce the 1080/24p exactly. If the display has a variable refresh rate that can be a multiple of 24 (72, 96, or the magic number 120 - which is divisible by BOTH 60 and 24) then a good 3:2 pulldown mode can reproduce the 24fps exactly.

    To understand how the inverse telecine process works, you, naturally, need to understand how the telecine process works. Telecine (pron. tele-seen) is the name of the process that converts 24fps film to 30fps (60 fields per second) video. It does this by using a 2:3 cadence. The first film frame is the first two fields, the second film frame is the next three fields, and so on. So, in the case of a telecine converted program, the complete frames are available. A good inverse telecine processor is smart enough to recognize the cadence, and not combine fields that are from different frames. This is what a 3:2 pulldown mode (or film mode) on some HDTV's do.

    Here's how it works. Lets call some four frames of a film, A B C D. The telecine process would convert that to A A B B B C C D D D. When these fields are combined into frames with a straight deinterlace, you get AA BB BC CD DD. A good inverse telecine deinterlace process will not combine fields from different frames. It will give you AA BB CC DD, the original four frames.

    In order to reproduce the original 24fps, the display must have the aforementioned variable refresh. A 60Hz only TV is stuck with combining fields from different frames together in some fashion, as 60 is not divisible by 24. Some 60Hz only displays use the same type of motion adaptation to minimize the "combing" that happens when dissimilar fields are combined. Some do this well enough to pass the HQV deinterlacing tests.

    I would expect that, for the most part, a 120Hz display will simply repeat the same constructed frame when reproducing true 1080/60i video. The great thing about a 120Hz refresh rate is that it is capable of exactly reproducing both 24fps (24*5=120) material as well as 30fps (30*4=120) material.
     
  16. Jan 27, 2008 #96 of 171
    HoTat2

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    OK, thanks cygnusloop;

    So when and if the inverse telecine process has been completed properly. And the HD TV set derives the original 24 Hz frame rate of the cinema source material (and this is a big "if" I realize). Then using the Sony XBR5 120Hz refresh rate example again. It is then simply a matter of repeatedly displaying each 1080P reconstructed film frame five times every 1/24 of a second. Or the same 1080P frame once per 1/120 of a second, 5 times before presenting the next film frame 5 times this way?
     
  17. Jan 27, 2008 #97 of 171
    cygnusloop

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    Frankly, I don't know, but 5 repeated 120Hz frames would be my guess. I suppose some enterprising designer could try to interpolate the changes between the film frames and update through the 5 120Hz refreshes, but that would require some serious voodoo that I wouldn't pretend to understand. My understanding is HDTV's with true 5:5 pulldown are just coming to market.
     
  18. Jan 28, 2008 #98 of 171
    cartrivision

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    So when the 3:2 pulldown process isn't done correctly and some video frames are a combination of two different film frames instead of a repeat of the previous frame, how does that manifest itself visually on the TV screen? I know how it would look if you could freeze the frame, but I mean what is the effect when you are watching it in real time? Does it look obviously worse than if it was done correctly. I'd guess not since I have never noticed any obvious difference between 1080p and 1080i when watching something that was encoded from a 24fps film source, but then I've never done a true side by side comparison.
     
  19. Jan 28, 2008 #99 of 171
    inkahauts

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    It won't look quite as sharp. It may even look grainy. Frankly, you are probably more likely to notice a problem if it does some of a program right and some of it wrong, than if its just being done wrong all the time, because you would never see it done right and would assume that the picture you are see is as sharp as its meant to be.... and most people at this point find HD so much better than watching sd that the differences won't show much to the average consumer....

    Then there are people like me that notice every detail in my screen, and I hate improperly processed material, so I always try and buy the highest quality dvd's and tv's and turn off as many stupid noise reduction junk as I can, because those functions are usually trying to compensate on this type of material and end up doing more harm than good.....
     
  20. DanER40

    DanER40 Legend

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    How do these threads turn in to a 1080i vs 1080p debate so often? Are you guys just bored at work? :D
     
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