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1080p Question

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by RMSko, Apr 23, 2013.

  1. RMSko

    RMSko Legend

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    I have the HR34 and just got a new 1080p TV. I have native off and have the resolution fixed at 1080i, however, I'm wondering if there is a way to have a fixed 1080p resolution or will it only switch to 1080p when the source is 1080p? When I cycle through the resolutions it is skipping over 1080p so I assume it can't be a fixed resolution, but I just want to make sure.
     
  2. Yoda-DBSguy

    Yoda-DBSguy Hall Of Fame

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    It will only switch and display 1080P when the source content is broadcast or presented in that format.

    Currently, only some VOD and PPV area available at those resolutions since no programing source broadcasts at anything higher than 1080i.
     
  3. peds48

    peds48 DIRECTV A-Team DBSTalk Club

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    Yep, it is not a fixed resolution, but it will switch over to 1080p whenever you have 1080p content and assuming your TV supports DirecTV format of 1080p/24fps
     
  4. hasan

    hasan New Member

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    It will auto-switch to 1080p/24 when the source material is at that resolution and frame rate. However, some TVs, while supporting 1080P, do not support 24 fps (frames per second), and if they don't, they are incompatible with the D* equipment. Your D* box should auto-detect if your tv suppports 1080p/24, and show it in its resolutions. There isn't a discrete 1080p indicator light on the front panel, but as I recall, multiple LEDs light up in the 1080p/24 mode.
     
  5. peds48

    peds48 DIRECTV A-Team DBSTalk Club

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    all of the newer DirecTV receivers (H24 and HR24 and H25 and HR33/44) have "discrete" 1080p indicators. all others light up BOTH the 720p and 1080i LEDs to indicate 1080p mode
     
  6. hasan

    hasan New Member

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    Good info, all my stuff is old and uses the "dual light" approach.
     
  7. Smooth Jazzer

    Smooth Jazzer Legend

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    I can' t talk about how 3D affects your situation. However it will only show 1080p on the PPV 1080p movies as far as I know.
     
  8. jimmie57

    jimmie57 Hall Of Fame

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    A TV that is 1080p resolution converts all signals to it to that format before putting it to the screen.
    The 1080i ( interlaced ) is converted to 1080p ( progressive ).
    720p enlarges the pixels to fill the 1080p screen.
    Edit: fixed error.
    720p picture is manipulated and distributed to the larger pixel screen
     
  9. P Smith

    P Smith Mr. FixAnything

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    Not that easy, son.

    Not the pixels but a picture ! And it's very ineresting process if you know the chips ... just one aspect: enlarge moving moving object if a video source is interpolated fields...
     
  10. peds48

    peds48 DIRECTV A-Team DBSTalk Club

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    Yep, Agree with previous post. There is more to it.

    Here is a place to start.

    http://en.wikipedia.org/wiki/Video_scaler
     
  11. texasbrit

    texasbrit DIRECTV A-Team

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    The pixels are always the same size, for a particular piece of hardware. If you have a signal that is lower resolution than the TV, the scaler creates the missing pixels by looking at the "real" pixels surrounding the empty ones. Here's an article describing the process in more detail http://hometheater.about.com/gi/o.htm?zi=1/XJ&zTi=1&sdn=hometheater&cdn=gadgets&tm=61&f=20&su=p284.13.342.ip_&tt=13&bt=5&bts=5&zu=http%3A//www.hometheater.com/content/scaling-size-matters
     
  12. harperhometheater

    harperhometheater Legend

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    And 1080i has the same spatial resolution as 1080p, so if the display and/or scaler deinterlaces properly there should be absolutely no difference in picture resolution between the two.
     
  13. texasbrit

    texasbrit DIRECTV A-Team

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    That's true with DirecTV, because the only 1080p signals are 1080p/24, and 1080i/60 carries the same information. But if you have a true 1080p/60 signal, although the spacial resolution is the same, there are twice as many frames per second carrying different information. None of the broadcast systems (Off-air, cable, satellite etc) carry 1080p/60, but there are certainly some video camaeras that will capture at 1080p/60.
     
  14. P Smith

    P Smith Mr. FixAnything

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    there are new 4K and 8K models
     
  15. TomCat

    TomCat Broadcast Engineer

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    Put another way, the pixels for any hardware are fixed, they do not change size or move. But we have to clarify what pixels we are speaking of. The pixels in the incoming video do change from format to format, and are larger in 720p than in 1080i, for instance. Also, chroma pixels are 4 times larger in HD (4:2:0) than luminance pixels, even in the same format (so for a 1080p TV displaying 1080p video, each physical group of 4 pixels is assigned the exact same value for every pixel in the set of 4).

    The pixels in a display are physical chunks of LCD or plasma light engine arrays of R, G, and B, but the pixels in the video signal are instead virtual location assignments, and so they can change size and move from format to format.

    A 1080p TV simulates the larger pixels of 720p by rescaling. Since the same piece of real estate (the screen raster) is used for both, that means dividing 1920 fixed hardware pixels per scan line by 1280 formatted pixels per line, which is 1.5. That means that each virtual 720 pixel really needs a hardware pixel location that is 1.5 times wider and 1.5 times taller.

    But that is a very simple task, using a very simple algorithm. The way to do that (for the first three pixels of line 1) is to assign the value of 720 pixel 1 to 1080 pixel 1, then assign the average of the value for 720 pixel 1 and 720 pixel 2 to 1080 pixel 2, then assign the value of 720 pixel 2 to 1080 pixel 3. Two 720 pixels stretched across three 1080 pixels. And the pattern repeats all down the line.

    It gets slightly more complicated in line 2, because you have to average in the vertical dimension also. But in reality the math is pretty simple; each new (rescaled to 1080) hardware pixel is assigned a value based on some combination of 1/9th, 2/9ths, or 4/9ths of certain 720 virtual pixels, and the pattern repeats every 3 pixels across, and every 3 pixels down. If you lay one grid over the other, that becomes abundantly clear.

    That's a lot of math, but it is all simple math, and it is repetitive and non-changing, so it can be hard coded directly into the scaler chip which means it can rescale completely accurately and very quickly. Making the conversional math simple is what was behind chosing 1080, 720, 768, and 480 in the first place; they are all even numbers that can be multiplied or divided by the same simple integers to get from one pixel map to another without error.

    But one of the common misunderstandings is that 1080p when it refers to a display is not the same thing as 1080p when it refers to a video signal. They are both progressive and describe the same pixel map, but there are advantages to 1080p the video signal that do not come with 1080p the designation for a display. All flat panel TVs display progressively, regardless whether the input signal is progressive or interlaced, and always have (CRTs are different). But you also have to have a video signal that was originally acquired in the field as progressive (and never interlaced then or later) to see the benefits of that even if it comes to you formatted later as 1080p; a TV that scans progressively still suffers from interlace error if the signal was acquired as interlaced and formatted as 1080p, or is formatted as 1080i.

    And, you have to have a TV set that is compatible with 1080p signals as well. Most TVs that are 1080p TVs are not compatible with 1080p signals, because 1080p refers to two different things. We've had 1080p TVs for about 8 years commercially, but only in the last few years have some of the higher-end 1080p TVs become compatible with 1080p content. Most 1080p TVs and all older 1080p TVs have no idea what to do with a 1080p signal.
     
  16. TomCat

    TomCat Broadcast Engineer

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    That is true for still pictures, for static images. But for 1080i resolution drops dramatically as soon as anything in the picture moves, which is the supposed advantage of 1080p over 1080i. That sounds pretty serious, but in real life resolution also drops dramatically when things begin to move. A speeding car or bobsled in real life is a blur if your eye is not tracking it. And of course if the frame rate is that low (24 fps) any supposed advantage of freedom from interlace error is greatly offset by the flicker rate, which is far inferior in 1080p24 to that of 1080i30 or 720p60.

    This is also why the perceived resolution of 1080i and 720p are virtually the same, with perceived resolution being slightly better for still images when 1080i, and slightly better for moving images when 720p. And this is also why no one can tell the difference between 720p and 1080i from just viewing it, and why one format is not inherently better than the other, which is why the ATSC and DVB chose both.

    Very similar reasons are behind why no one can identify 1080p24 from either 1080i30 or 720p60, and why it's supposed advantage is more hype and myth than reality.
     
  17. texasbrit

    texasbrit DIRECTV A-Team

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    ...and also why 1080p/24 is (simplistically) "the same" when delivered as 1080i. Successive interlaced scans are identical (there's no movement between them) so there's no progressive advantage.

    And your point about losing the advantage of progressive scan unless the signal is progessive all the way from the source is often ignored by people, who think that converting to progressive somehow eliminates the interlacing problem with fast motion (not that, as you say, anyone can see that in practice)
     

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