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Pio 868 aspect ratio

Discussion in 'Blu-ray & DVD Players & Recorders' started by ancientgeek, Dec 24, 2003.

  1. ancientgeek

    ancientgeek
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    When playing widescreen DVD's, the Pioneer appears to always truncate the left and right edges, leaving a slightly less wide screen picture. I only noticed this when I played the same DVD (FOTR extended R2) on my computer and got the full width image. There doesn't seem to be any way of altering this. Are other DVD players the same?

    (Computer is Mac connected to 433MXE by DVI; player is connected by component.)
     
  2. Zacabeb

    Zacabeb
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    I will speculate in two possibilities:

    1.) The active picture. The picture stored on DVD has a resolution of 720x576 (for PAL), regardless of its aspect ratio. But the actual picture should only be 702 pixels wide in theory. Below is an explanation why - don't take offense if you already know this stuff.

    In analog PAL, there are 25 frames per second and 625 lines per frame. That amounts to 15625 scan lines per second, each one being 64µs long. The active part of each scanline that contains picture information is 52µs. DVD Video has a sampling rate of 13.5MHz, and that means there are 864 samples to each scanline. The resolution of the active area is therefore 52/64 of 864, or 702 pixels.

    Since in the digital video world you want resolutions to be divisible by 16, the 702 pixels are rounded up to 704. But on top of that there is a margin of 8 pixels on either side, extending the picture to a width of 720 pixels. The reason is to avoid video that is converted back and forth from analog to digital getting cropped, since it might get displaced a little in the process.

    So, those 8 extra pixels on either side should not really be used as part of the actual picture, but that does not keep studios from using them anyway. Supposedly a lot of people in the industry do not realize that it's only 702x576 that makes up the 4:3 or 16:9 image, and not the entire 720x576.

    So what the Pioneer (and most other DVD players, I guess) might be doing is cropping the margins before video encoding. That is probably the cause if you are getting thin black bars on either side.

    But the second possibility might be more likely:

    2.) Overscan. Regular tube TV's crop part of the image to reduce visibility of geometry fluctuations. In fact they crop a lot, and the unseen part of the picture has been consumed by other stuff. TV productions may have a VITC time code stored in the top of the picture, VHS VCR's will show severe distortion along the bottom where the video heads switch. There may also be a lot of other funny things there, such as glitches in graphic overlays and strange little test signals.

    Therefore, when connecting an analog source of TV resolution to a digital display, it might simulate overscan by scaling the image up a bit and cropping almost as much as a regular TV would. When connecting a digital source or analog source of computer resolution however, the screen will fit the image edge to edge and show everything.

    If this is the case, you should notice that the black bars above and below the picture are thicker when playing back DVD's through the Mac, as it is showing more of the picture vertically as well.
     
  3. Paul D

    Paul D
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    The 868i shouldn't be cropping the picture(but may crop 3 pixels max), your display is proberly to blame.
    ie you shouldn't be noticing much cropping difference from your PC.
    Different displays, and different inputs are set to overscan slightly.
    My Panasonic plasma was overscanning when it arrived, but i just reduced it in the Size/position settings etc.

    What display are you using?
    And how are you connected?
     

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