Constant height display (as they do at the movies)

Discussion in 'AV Receivers & Amplifiers' started by trevsorbie, Sep 12, 2007.

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  1. trevsorbie

    trevsorbie
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    I have a projector attached to a DVD32R which I'd like to setup at constant height and change the width rather than the standard way of keeping the width constant and adding bars above and below.

    This would replicate movie theatre behaviour where they use curtains to edge the display left and right.

    Is there a way to do this?

    Thanks

    Trev
     
  2. trevsorbie

    trevsorbie
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    I did ask Udo this question at the Bristol show about six years ago and he said it could be done but I didn't ask HOW!

    Anyone know anything about how this might be done?

    Thanks
     
  3. edward

    edward
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    Wasn't it to do with sensing the film format and sending a signal out one of the switches to control curtain motors? Had a lok through the manual (I wonder if Udo still looks young) but couldn't find anything to support this notion. Oh well...
     
  4. sijones

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    Hi Trev,

    The only thing that I know of is using the action switches on the AV192R (and probably the AV32R). These can be controlled depending on the DVD32R detecting a 4:3 or 16:9 recording.

    Regards,

    Steve​

     
  5. Dr Udo Zucker

    Dr Udo Zucker
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    Hi Trev, the DVD32R senses the aspect ratio of a DVD disc which it then passes to the AV32R DP or AV192R (via TAGtronic Bus) to be (potentially) processed by an action switch.

    It can work like this: if a recording is 16:9 the whole 16:9 screen is used. If the recording is 4:3, then one of the action switches (you need to set it accordingly) is closed and two blinds, one at either side of the screen reduce the screen's format to suit 4:3. However, if you have a letterboxed movie or an anamorphic movie with an aspect ratio wider than 16:9 (say 2.35:1) then there will still be black bars above or below the movie.

    [A letterboxed 16:9 movie can be zoomed to full size (something your display device or video processor has to do) but with reduced vertical resolution compared to an anamorphic recording. This will again remove bars at the top or bottom.]

    P.S.: I am amazed how many letterboxed widescreen movies are still sold (instead of being anamorphic), reducing significantly the ability of the DVD format. Yet another reason to go HD-DVD.

    P.P.S.: The AV192R's video scaler VSM2048 can process the video signal to maintain height or width or fit best, what ever the input signal. If the video signal is not coming from a DVD32, then the user need to declare the input format.

    Hope this helps.

    Udo
     
  6. trevsorbie

    trevsorbie
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    Thanks Udo

    As usual, your post is both informative and fairly comprehensive. It was those wider aspect ratios (>16:9) that I wasn’t sure how to handle. I now have further questions I hope you or someone else can help with:

    You mention the aspect ratio is transmitted by TAGtronic bus. I have an AV32R so with no action switches it can’t use this signal. As I recall (my DVD player is currently with a friend, I don't have the manuals to hand and the ones on this forum only download as 1k!) the DVD32R has a couple of action switches. Can they be used to trigger a blind directly from the DVD32R? If not what can these switches be used for? I'm guessing Auto-on of a display device when the dvd player switches on and similar.

    If it's not an option to use the DVD32R switches then an option for me MAY BE to write some software for a PC (if I can sort out CRCs - see my other post http://www.avforums.com/forums/showthread.php?t=620409 ) to receive the aspect ratio by TAGtronic bus and then have a separate trigger for the blinds.

    I'm still not sure how a display device with aspect ratio of 16:9 (my projector for example) would be able to display a 2.35:1 image at the same height as a 16:9 without projecting a much larger area and 'zooming out' the image to the point where the height of the 2.35:1 image is now at the original 16:9 height. Any clarification on any other methods of achieving this?

    In your experience will an anamorphic movie at 2.35:1 ratio scale up to the same height as a 16:9 image or will a scaler be required due to the lower resolution? I run my projector at 150cm height and view from about five metres.

    Thanks for your help so far.

    Trev
     
  7. Dr Udo Zucker

    Dr Udo Zucker
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    Hi Trev, the DVD32R does not have action switches (at least I cannot remember that he ever had). One could use a PC to detect the aspect ratio information transmitted by the DVD32 via TAGtronic Bus in order to let the PC lower/rise the blinds. However, it might be much easier to simly use a manual switch to do this when the aspect ratio switches from 16:9 to 4:3 or vice versa.

    If you have a screen of an ratio width to height of 16:9 then you cannot display a movie which is wider than 16:9 without either black bars at the top/bottom (the usual way) or cutting/removing a part of the movie at either side (undesirable). In other words, one would rather need a screen of an aspect ratio, say 2.5:1 if one wanted to show all (or are there movies wider than 2.5:1?) movies at constant height. A cinema usually has a screen aspect ratio which is wider than 16:9 because many movies are around 2.35:1. For practical reasons, I guess, home cinema installations seem to use screens around 16:9, mine for example is 1.85:1.

    Having said this, if you want to keep the height constant, then you will not only need a wide enough screen but also a powerful display device/video processor. In addition, let's nozt forget, you will also suffer from a perceived decreasing picture quality the wider a movie (because of its increasing need to zoom). This is caused because (unfortunately) even anamorphic recordings only "press" a letterboxed 16:9 image into the recording, whatever the true aspect ratio (please let me know if I made this point clear enough. It isn't entirely easy without showing some sketches).

    A way out, or better said an significant improvement, is to use HD sources as there inherent higher picture quality allows more zooming. Zooming or expanding an anamorphic recording will still degrade the perceived picture quality, but the resulting image is still much better than SD.

    P.S.: When zooming, the perceived picture quality drop can be significant. For example, I consider a letterboxed 16:9 movie, zoomed to fill the height of a 16:9 screen in most instances unbearable, hence my total disregard for studios who sell us widescreen movies without making use of the anamorphic option.

    Hope this could clarify things better.

    Regards Udo
     
  8. mr_yogi

    mr_yogi
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    Not sure if this will be of any help but about a year ago I asked the same question on the DPL projector forum and was told there are projector lenses which can provide constant height images for wide aspect films, but the prices were :eek: :D
     
  9. Dr Udo Zucker

    Dr Udo Zucker
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    Hi, please let me clariy this a little more: the lenses, you mention, are used to expand an anamorphic recording as LCD/DLP cannot do this without reducing the horizontal resolution and potentially generating some artefacts (this is particularly the case when the pixel count is rather small. True HD panels, as available lately, should be able to do a decent job).

    However, as I mentioned, one can not show a movie without black bars (top/bottom) if the aspect ratio of the movie is wider than that of the screen. Therefore without investing in a specially manufactured very wide screen, say 2.5:1, one has to compromise. These very wide screens can be ordered (and might exist) but are most likely rare, simply because of the dominance of 16:9 and the usual dimensions of our living rooms.

    Regards Udo
     

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