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Please explain aspect ratios to me!

Discussion in 'Microsoft Windows' started by Slinkoff, Aug 11, 2005.

  1. Slinkoff

    Slinkoff
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    Am very confused with this one. My TV has auto, 16:9, 14:9, 4:3, Zoom 1,2 & 3. MCE has its own zoom 1,2 & 3.

    How on earth are you supposed to get it right?

    It seems that in MCE, DVDs are in a very tiny letterbox and zooming seems to cut bits off or stretch people out.

    Should there be some kind of autoswitching going on? Does anamorphic mean that the widescreen is supposed to fill the screen on a 16:9 widescreen TV?

    An idiot's guide would be much appreciated!

    Thanks
    Slink
     
  2. AV Junky

    AV Junky
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    Are you watching on a 16:9 conventional TV, or an LCD? To watch DVDs properly on a 16:9 screen, the desktop on MCE needs to be set for a widescreen resolution (depending on the screen attached). The TV should then be in 16:9 mode.

    Don't forget of course that many films these days are not shown in 16:9 format, but instead use wider formats such as Cinemascope. This means that should black bars are necessary top and bottom when the film is framed for DVD. Attempts to zoom these bars out will lead to the sides ofram being clipped off.
     
  3. LV426

    LV426
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    Idiot's guide:

    Aspect Ratio means the ratio of width to height. For example, if it's 16x9, then, if the image is 16 (cm, inches, feet, anything) wide than it should be 9 (same units) high.

    You have to be aware that, in the context of DVDs, there are TWO aspect ratios to concern yourself with.

    The first is the intended aspect ratio of the video signal. Video signals don't have an aspect ratio per se; they are just a sequence of lines. However, they do have an intended shape; in other words the shape of display (TV screen or window on a PC, etc) that it should just exactly fill (in both directions *2). Video signals only come in two intended shapes: 16x9(*1) and 4x3. But before you leap to conclusions at this point, read the next bit.

    The second is the aspect ratio of the original material. TV shows are typically produced in one or other of the two video shapes - 16x9 or 4x3. However, films (which are primarily intended for projection in cinemas) can be made in a wide range of aspect ratios, starting at 4x3, through 16x9 right through to 22x9 (or more). Such (very) wide widescreen films are wider than the fixed shape of a widescreen TV.

    So, to recap: Video signals - always one or other of two fixed shapes - 16x9 or 4x3.
    Source material - can be pretty much any shape.

    How do they fit a wider-than-widescreen source (film) into a fixed 16x9 shaped video signal? They could
    1) Make it narrower than it should be and hence fill, exactly, both width and height of the screen. This would cause people and other objects to become the wrong shape.
    2) Crop bits of the left and/or right edges to make it narrower. This would mean you not seeing the whole film.
    3) Keep all of the film intact, at it's correct shape, and fill up the excess height of the screen with plain black areas.

    (3) is what they do for wider-than-widescreen films. In such cases, whilst the film might be (say) 22x9, the video signal coming off the (widescreen *1) disc is exactly 16x9 - but contains both film and the necessary black padding.

    The long and the short of all of this is:

    1: A widescreen film may be presented with black bars. However the widescreen video signal should always exactly (*2) fill a 16x9 screen or window.

    2: If people are people shaped, if circles are round, and so on, AND you are seeing all there is to see (*2) and you don't have black bars on more than two sides of your image, then you are displaying things correctly. If circles are oval and/or parts of the image are truncated (*2) then you are not. Simple as that!




    (*1) also known as widescreen, and "anamorphic".

    (*2) subject to a little overscan, which truncates all four sides of a video image. This is correct, within standard, and another subject entirely
     
  4. Slinkoff

    Slinkoff
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    Great, thanks for that, I think I understand that all a bit better now...

    I should keep my TV (a CRT) on 16:9 for (most) DVDs. If it's a 2.35:1 or greater ratio then I'm going to get black bars and that's the correct and full picture. If it's 1.85:1 I'm going to get a full screen picture.

    I should avoid any of the zoom options both on my TV and in MCE because they're only going to either distort the picture or crop it. (MCE has to be in 1 of 3 zooms and it appears zoom 2 gives the correct setting)

    I think I'm right in saying that most Freeview broadcasts are in 16:9 too so I can keep my TV on 16:9 most of the time and only switch to 4:3 if I notice any stretching.

    Am I on right track?
     
  5. LV426

    LV426
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    Yes, you are.

    On other thing, though. Some DVDs have wide- (or even, wider-than-wide-) screen picture contents in a 4x3 video signal - padded with black. Thankfully these are fairly rare nowadays, but a couple of significant examples of this are Titanic and The Abyss. There are many others - mostly older releases - which are still on sale. In such cases, the "zoom" option of a widescreen TV (if that's what it's called) enlarges the whole image at the expense of cropping the top and bottom off, but keeps things the right shape; since the top and bottom contain only black padding, nothing useful is lost. For such discs, then "zoom" is the right choice. You will work this out if you follow my "long and short" point (2) above.
     
  6. Slinkoff

    Slinkoff
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    Sorry to drag this thread up again. I thought I'd grasped it but something has made me a bit uncertain again. Watching Six Feet Under broadcast on E4, it's a widescreen broadcast so I left my TV on 16:9 thinking that was going to give me the accurate picture, and most likely a full screen one rather than a letterbox being that it was TV and not film. I was surprised to see then that 16:9 gave me a squashed letterbox image. If the material was in wider-than-widescreen I would have expected letterbox but in proportion. (I've included images, sorry about the quality, I havent got TV on MCE yet so couldn't do screengrabs, only photos.)

    I switched my TV to autozoom and this appeared to put the image in the correct proportions and it took up the full screen. I took a look at 4:3 and the image appears as a small rectangle in the middle of the screen. Is this a 16:9 picture in a 4:3 video signal described in the last post? That's the only way I can explain thngs unless I still havent grasped something. I thought that this was unusual now and that widescreen broadcasts were true 16:9 broadcasts?
     

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  7. LV426

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    Is this a 16:9 picture in a 4:3 video signal described in the last post?

    Yes, it has to be. But it can come about in one of two ways

    a) it was broadcast like that. Unlikely, but not impossible
    b) if you have one, your $ky/freeview box or card or whatever, is set, in its menu, to generate 4x3/letterbox, rather than 16x9, from 16x9 broadcasts. More likely.
     
  8. Slinkoff

    Slinkoff
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    you are right, my freeview box was set to 4:3 Pan&Scan. Now I have a new issue! The Freeview box (a Thomson DTI2300) has two settings: 16:9 Video & 16:9 Letterbox (as well as 4:3 letterbox & pan&scan). I'm assuming that I want it on 16:9 letterbox because I think 16:9 Video is just going to put every broadcast to 16:9, even if it isn't. Is that right do you think?
     
  9. AV Junky

    AV Junky
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    Just try them and see which one gets the result your after. Simple as that really.
     
  10. Slinkoff

    Slinkoff
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    well obviously i've done that, i just wondered if there was a proper explanation behind it. 16:9 letterbox puts my TV in what appears to be 14:9 for ITV and channel 5 broadcasts, which I believe are still not widescreen, and 16:9 for the other channels so I'm pretty sure that's correct. I think I've got my head round it now:

    16:9 Letterbox - for widescreen TV owners who want 16:9 in widescreen and 4:3 with black bars down the sides (although it appears my TV shows this in 14:9 rather than 4:3)

    16:9 Video - for widescreen TV owners who want every broadcast in 16:9, even if it's not meant to be.

    4:3 Letterbox - for normal TV owners who want widescreen broadcasts to be letterboxed.

    4:3 Pan&Scan - for normal TV owners who want widescreen broadcasts stretched and cropped to fit the screen.

    There. Finally think I've got it all now :) Thanks for the help.
     

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