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Video Display (Aspect Ratios)

  1. Aug 20, 2007 #1

    cepheid

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    Hi there,

    Bear with me, this will take a bit of background explanation. I have a 19" LCD TV. I have a laptop computer (more specifically a brand new Apple MacBook -- I've been a PC user up to now and recently switched).

    I wanted to connect the computer to the TV for the purpose of playing movies. The computer has a VGA port (actually it has something called a mini DVI Port, but Apple provided a mini DVI to VGA adapter with the computer). The TV also has a VGA port. So I connected them with a cable. Success! Getting things to look good is a little more tricky.

    Being a 19" widescreen LCD TV, it's a bit "wider" than the traditional TV -- 16:10 vs. 4:3 (1.6:1 vs 1.33:1). *However*, when I watch TV, the entire area of the screen is not taken up. There are vertical black bars on the left and right (pillarboxing), and the image is the more standard "squarish" image of TV. This is probably because a 4:3 aspect ratio is still the standard for TV. That's fine.

    When I connect the VGA cable to the TV, the image of my desktop *also* does not take up the entire area of the screen. In fact, it takes up exactly the same "squarish" area as that taken up by the TV broadcast. I am assuming that this is because the standard for VGA is, like TV, a 4:3 aspect ratio. This supposition is supported by the fact that when I change my desktop resolution to something with a 4:3 aspect ratio (e.g. 1024 x 768), the image of my desktop "looks good" on the TV. (Side note: the native resolution of the MacBook is also "widescreen" 1280x800 i.e. 16:10).

    Unfortunately, when I play a movie, its original aspect ratio is EVEN WIDER than 16:10 or even 16:9 (1.78:1). It is 1.85:1, and that's apparently the standard for cinema. So, when I play the movie full screen on my laptop, it is letterboxed (it has horizontal black bars on the top and bottom). Of course, the image of my desktop is still pillarboxed. The net result is that the actual movie appears to be "windowboxed" on my TV (it is surrounded by black on all sides and takes up only a very thin sliver of an area in the centre of the TV screen).

    I have found a solution that mitigates this problem: I play the movie in VLC media player, which allows one to change the aspect ratio of the movie, distorting it accordingly. Of course, if I distorted it to 4:3, that would eliminate the letterboxing and the movie would fill the entire desktop image, filling the maximum possible area on the TV. This of course leaves the movie far too distorted. A compromise is to distort the movie to 16:9. The movie is still windowboxed, but it fills up a slightly larger area on the screen. It doesn't appear too distorted either, because 16:9 (1.78:1) is not that much less than 1.85:1. This solution is actually to my satisfaction. The only reason I am writing all of this is to see if I have overlooked something obvious or if you guys have any *better* ideas.

    Thanks! :smile:
     
  2. jcsd
  3. Aug 20, 2007 #2

    mgb_phys

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    There is probably a setting in the video properties to change this, there might also be a zoom button on your TV remote.
    There is a protocol to send serial data down one of the unused pins on a VGA connector to tell the screen what format you are playing but nobody seems to get it right.
     
  4. Aug 20, 2007 #3

    russ_watters

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    My windows pc has a "theater" mode, where it only shows on the external display, thus avoiding the problem of matching resolutions on different pcs. So try having it send the signal to the hdtv only, then try to adjust the resolution.

    I'm pretty sure vga is not 4:3 only.
     
  5. Aug 20, 2007 #4

    mgb_phys

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    VGA doesn't have anything to say about the format it is just analogue RGB with a horizontal and vertical sync.
    It is up to the video card to adjust the relative syncs to set the ratio and is upto the screen to adkust the timebase to set the picture size.
     
  6. Aug 21, 2007 #5

    cepheid

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    There IS a Zoom button on the remote. I feel like an idiot now. How did I not see this before. In fact, I quite like watching TV like this. Sure, it's a bit distorted, but I only notice when I first make the switch. I quickly get used to it. As for telling the screen what format I'm playing, this seemed to just fix itself automatically. Suddenly 1440 x 900 appeared in the list of available resolutions for the external display. Maybe it was hitting the zoom button that prompted this communication to occur. I don't know...

    With the display resolution set to 1440x900 (16:10), you'd think the image of my desktop would now fill the entire TV screen. But for some reason not quite. This is where Russ Watters' suggestion came into play.

    Indeed, I'm not sure about theatre mode, but if I changed the setting so that the displays are NOT mirrored, but rather my desktop is *extended* to the TV, suddenly it works. The TV displays my desktop background, and it fills up the WHOLE TV screen. I can then drag any window I want from one display to the other. In other words, it's the same two choices as in the Windows control panel. Cloning the display = bad. Extending the desktop = good.

    The next problem I was having was that even if I dragged the VLC playback window onto the TV screen, the movie would still go fullscreen on my laptop LCD if I clicked "fullscreen". I solved this problem by going to the video menu in VLC and changing the "video device". Both screens appeared in the list from which you could select the video device. Beautiful! Thanks guys...
     
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