Vertical Compression??

Discussion in 'Archived Threads 2001-2004' started by Tam Jen Yee, Jul 24, 2001.

  1. Tam Jen Yee

    Tam Jen Yee Extra

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    What do vertical compression really do to a 4:3 TV? What is the difference from watching a DVD in letterbox mode and vertical compression mode? Pls enlighten me. Thanks.
     
  2. Jay Mitchosky

    Jay Mitchosky Producer

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    Vertical compression is a term commonly used to describe readjusting the "drawing area" produced by the CRTs. Instead of passing the electron beam over the full 4:3 screen area the CRTs only draw the central 16:9 portion. The advantage is that a DVD player can be set to 16:9 playback, thereby delivering the full resolution available on anamorphic discs. The monitor no longer wastes valuable scan lines drawing black letterbox bars (or at least not as much, considering that the 16:9 aspect ratio is 1.78 compared to more traditional film formats of 1.85 and 2.35).
    Without vertical compression (also referred to as 16:9 mode or "the squeeze") you would have to set the DVD player to output to a 4:3 monitor. In this mode the player must downconvert the anamorphic image so it fits with the proper geometry and you lose resolution. If you have a player set to 16:9 playback on 4:3 monitor (without compression) the image will appear tall and skinny. Vertical compression unstretches this image to the proper geometry.
    If a DVD is not mastered with an anamorphic transfer (ex. early Fox and Buena Vista releases) vertical compression has no advantage as the lines are "already lost". Do a search for Allan Jayne's posts and go to his site for a detailed description on anamorphic transfers to help explain this.
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    --Jay
    "No one can hear when you're screaming in digital."
    My Home Theatre Pictures...
    "You're no mesiah. You're, you're a movie of the week. You're a ... t-shirt, at best."
     
  3. Maximil

    Maximil Agent

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    So do any 4:3 TV's offer vertical compression as an option?
    My 55HX70 has 1080I mode, but I guess it only kicks in if there is an HDTV signal, which I don't have. I've read posts about doing a manual compression using the service menu to adjust hight and all the fine adjustments to make it look "right", but that seems a bit troublesome.
    Is there a hidden option somewhere or a way to store two different screen sizes?
     
  4. Paul Walther

    Paul Walther Agent

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    Hey, Maximil. I'm the guy that posted the manual vertical compression maneuver for the 55hx70- the article is now here at the Keohi Toshiba Tips Site:
    http://www.keohi.com/keohihdtv/usefu...sh_55hx70.html
    I know the 55HX70 VERY well and, no, it doesn't have any alternate screen memory or way to do the compression without manually doing it yourself. Fortunately, you could try my method using the values (or close to them) that I did and see what you think. If my original service values are close to what you have as your defaults, you ought to be pretty close to just putting in the numbers I discovered, do a user 9-point convergence, and you're there.
    It IS possible to trick the 55hx70 into doing the compression if you use a home theatre PC or external scaler to send it a 540p signal- it will "think" it's getting an HDTV feed and compress automatically. This is, of course, an expensive option, and currently no mass-market DVD players have the ability to output 540p.
    Enjoy your set, it's a good one!
    P.W.
     
  5. John Morris

    John Morris Guest

    The only 4:3 sets that I know that do it are the Sony HS series and the Philips 60pp9601. I'm hoping that some of the new models will also do it.
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    merc
     
  6. Michael St. Clair

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    All the 4:3 RP Toshibas coming out this fall do.
     
  7. Maximil

    Maximil Agent

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    Paul,
    Your post was the one I had seen befor. Looks pretty doable, although my defaults are quite a bit different from yours (mine: HIT=55, WID=22, etc.). I will need to buy the Avia disk.
    By the way, on your TV, do you notice a faint, 1/4" ghost image or lining mostly to the right of edges between different contrast? Like white text on a dark background (movie credits for instance). I'm not sure if this is due to my tweaking the set myself or if it was there to begin with.
    Thanks..
     
  8. Matt_Stevens

    Matt_Stevens Supporting Actor

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    Michael, what month will those TV's be released and will there be a 43" 4:3 with 16x9 mode for DVD and will it allow MANUAL squeezing? I have a lot of SVHS tapes with anamorphic programming.
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  9. Paul Walther

    Paul Walther Agent

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    Paul,
    Your post was the one I had seen befor. Looks pretty doable, although my defaults are quite a bit different from yours (mine: HIT=55, WID=22, etc.). I will need to buy the Avia disk.
    By the way, on your TV, do you notice a faint, 1/4" ghost image or lining mostly to the right of edges between different contrast? Like white text on a dark background (movie credits for instance). I'm not sure if this is due to my tweaking the set myself or if it was there to begin with.
    Thanks..
    Hey, Maximil. I'm not seeing the ghosting you mention. Is your sharpness very high? Is SVM disabled? Both those will ghost a line to the right of an image. I'm assuming you already did a thorough check of service convergence. I was able to get rid of some minor image reflections by covering some shiny interior brackets by the 3 gun lenses with a black cloth material. If you try that, keep the cloth away from obvious heat sources.
    Good luck!
    P.W.
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    DocW
     
  10. Maximil

    Maximil Agent

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    Well, I think I disabled SVM, although I can't really see a difference. I unplugged the small 2-wire (yellow) plug from each of the three boards.
    The convergence looks ok.
    I do notice a green vertical 1/4" wide line along the left edge of the screen/picture, only on media, like video games, that underscan (so you can see the left and right edges of the picture). This only occurs on white or yellow screens (colors that contain green).
    I kinda think that this green line is the ghost I'm seeing. But, like I said, the green looks fine in the convergence grid... strange! [​IMG]
    Any other ideas?
     

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