How come 640x480 videos have vertical black bars on a SDTV?

Discussion in 'Apple TV and Home Theater' started by loft3, Mar 28, 2007.

  1. macrumors regular

    Joined:
    Feb 24, 2006
    #1
    All my iTunes videos with resolutions of 640x480 (regular old TV resolution as far as I know) play thru AppleTV on my standard-def (non-widescreen) TV with black bars on the left and right side of the screen? Video bought from iTunes and video encoded by me both do this.

    It's very frustrating, I thought 640x480 resolution would take up the whole standard def TV area - just like watching normal TV does.
     
  2. macrumors 6502a

    Joined:
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    Finland
    #2
    That's because ATV doesn't support 4:3 TVs like yours. When 4:3 material is displayed on a widescreen TV, black bars are added to the sides as in your case. Since ATV thinks it's hooked up to a widescreen TV, it adds the bars even though it shouldn't. Everything looks a bit squished (narrowed) too when watching the ATV, right?

    One solution is to find out if your TV, although non-widescreen, can simulate a widescreen TV. It would then add black bars to the top and bottom of the screen when using ATV. The problem with that is going to be that you get black bars on the sides and top and bottom when watching 4:3 material unless your TV has a zoom function. You're pretty much ***** out of luck. Apple never meant ATV to work on 4:3 TVs. Even though it displays a picture on your TV, it's most likely squished, not of the correct aspect ratio.

    Joshua.
     
  3. macrumors regular

    Carrot007

    Joined:
    Sep 18, 2006
    Location:
    Yorkshire
    #3
    In theory if you can change the apect ratio of the 4:3 material to 16:9 they would play fine on a 4:3 tv.

    I do not know if there is an easy way to do this though!
     
  4. macrumors 601

    eXan

    Joined:
    Jan 10, 2005
    Location:
    Russia
    #4
    The resolution of the "old" TVs is 720x480 (NTSC) and 720x576 (PAL), so even if you have NTSC, the horizontal side is not long enough, though the vertical fits fine. Thats why the black bars on the sides.
     
  5. macrumors 6502a

    OttawaGuy

    Joined:
    Mar 28, 2006
    #5
    Correct
    [​IMG]
     
  6. macrumors 6502a

    sycho

    Joined:
    Oct 7, 2006
    #6
    No, incorrect, the sidebars are because the AppleTV is meant only for 16:9 TV's.


    NTSC being 720x480 means nothing because there is not a set number of horizontal lines in a NTSC set. The use of 720(x480) in the digital world was just because that worked the best.

    Think about it like this, the vertical lines are discrete, while horizontal lines are interpolated from the analog signal.
     
  7. macrumors 6502a

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    #7
    Quite right. I guess they didn't bother reading my previous response where I think I made myself pretty clear on the matter.

    Joshua.
     
  8. macrumors 601

    ftaok

    Joined:
    Jan 23, 2002
    Location:
    East Coast
    #8
    Not saying who's wrong or who's right (the OP will need to take a photo before the real cause can be diagnosed). If it is indeed because the aTV isn't designed for a 4:3 TV and sending out a "squished" picture, then why would there be black bars on the sides? The OP didn't mention anything about the picture being squished.

    ft
     
  9. macrumors 68000

    bigbossbmb

    Joined:
    Jul 1, 2004
    Location:
    Pasadena/Hollywood
    #9
    Not just that... but Standard NTSC 720x480 has a .9 pixel aspect ratio which means the pixels are slightly taller than they are wide. 720x480 with a .9 pa is the same as 640x480 with square pixels (which is what computers use).
     
  10. macrumors 6502a

    Joined:
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    #10
    I based my "assumption" on other cases where users have reported squished images on 4:3 TVs using the ATV. It's quite obvious at this point that the ATV does not support 4:3 and does not allow a user to configure the ATV for a 4:3 like DVD players do. Therefore, the only logical explanation for the black bars on the sides is exactly what I have said so far.

    Joshua.
     
  11. macrumors 65816

    Avatar74

    Joined:
    Feb 5, 2007
    #11
    You have this backwards. When a 4:3 aspect signal (e.g. 480p) is fed to a 16:9 TV, vertical matte bars are added to make the 4:3 frame fit the 16:9 TV, not the other way around.

    Nope. Original poster was right.

    First, let me point out that while CRT displays do not have a "native resolution" to speak of in digital terms, LCD, Plasma, DLP and LCoS do.

    Second, it's not the display resolution that's relevant here. It's the resolution of the INPUT SIGNAL from the file, and the OUTPUT SIGNAL from AppleTV that drive this issue.

    More specifically, it's the RATIO of the input resolution of the content (H.264, etc.) to the output resolution of the player (AppleTV).

    So you've got this 640x480 file playing through AppleTV. AppleTV has, let's say, been configured for 480p in the setup. 480p means the AppleTV output signal is 720x480. The content being fed through AppleTV being smaller than the output resolution means that AppleTV will send a signal that inherently has some vertical matte bars.

    Regardless of how a 480p display might distort/stretch/squish the signal to fit its actual native display resolution, the vertical matte bars are IN the output signal sent to the TV just as horizontal matte bars on anamorphic DVD's are added by the DVD player in the output signal sent to a 4:3 TV.
     
  12. macrumors 6502a

    sandman42

    Joined:
    Oct 23, 2003
    Location:
    Seattle
    #12
    You're both right. The :apple:TV thinks it's sending its signal to a 16:9 tv, because that's all it was intended to work with. When you view this on a 4:3 tv, you still see the black bars, because the 4:3 tv doesn't crop them out, it compresses the image horizontally to show the whole thing, including the bars.
     
  13. macrumors 6502a

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    #13
    Exactly. Can we all now agree on this? I'm sure the OP got the answer he was looking for.

    Joshua.
     
  14. macrumors 601

    ftaok

    Joined:
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    Location:
    East Coast
    #14
    OK, after reading this and sandman's post, I went back and re-read the original post. This time, I picked up on the fact that he's watching 4:3 material on the aTV, which is sending out a 16:9 output back onto 4:3 TV. Therefore, I would expect the picture to have black bars on the sides AND to be squished.

    I think I'm on the right page now. Thanks.
     
  15. macrumors 603

    Multimedia

    Joined:
    Jul 27, 2001
    Location:
    Santa Cruz CA, Silicon Beach
    #15
    Get Over It, Sell Your 4x3 Set And Buy A Cheap HDTV For $499

    You know the :apple:TV was never intended to be used on a 4x3 set yet you insist it should. Get over it Loft3, get rid of your obsolete 4x3 piece of analog crap and buy an ATSC HDTV For $499 at Costco like a real red blooded American consumer should. :eek: :rolleyes: :D

    Analog TV blows and the sooner you hook up an off air antenna like a Terk TV5 to an ATSC Tuner in a HDTV the better off you're gonna be. Can we Please Stop Hanging on to the past people!! Analog TV is DEAD in 22 months. The sooner you face reality the better.

    That's why :apple:TV don't work with crap analog 4x3 sets (bad grammar for dramatic purposes). If Apple wanted to hang on to the past they would have made it work with the past. But they don't cause they have vision. So follow the leader and lose the crap TVs please.
     
  16. macrumors 604

    gkarris

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    #16
    How am I going to watch my CED's and Beta tapes??? :rolleyes:
     
  17. Moderator

    balamw

    Staff Member

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    Aug 16, 2005
    Location:
    New England
    #17
    Most HDTVs still have legacy composite video inputs. :rolleyes:

    B
     
  18. macrumors 603

    Multimedia

    Joined:
    Jul 27, 2001
    Location:
    Santa Cruz CA, Silicon Beach
    #18
    All HDTVs Include Analog NTSC Tuners In Addition To Digital ATSC Tuners

    Not only that. All have an analog NTSC tuner in them as well as the digital ATSC tuner. Wake Up!! :eek:
     
  19. macrumors 6502a

    sandman42

    Joined:
    Oct 23, 2003
    Location:
    Seattle
    #19
    What's the bad spelling for? (psst, it's "grammar").
     
  20. macrumors 601

    eXan

    Joined:
    Jan 10, 2005
    Location:
    Russia
    #20
    Not all analog TVs are "crap". We still have 9year+ old Sony 32" TV that shows superior color compared to new and very expensive HDTVs. Its also better to view interlaced content on the analog TVs.

    Not to mention that there's no HD television here, so buying a HDTV just to watch HD trailers for apple.com is pointless. (This may be different in other countries though)
     
  21. macrumors 6502a

    Joined:
    Jan 29, 2006
    Location:
    Finland
    #21
    Yeah, good analog TVs still have superior color, contrast and black levels. LCD/Plasma are getting better at that all the time and will eventually catch up to analog. OLED technology is something to watch for. It's quite amazing to see.

    Oh, and to the rest of yous: Keep in mind that Analog TV will still live many years in other countries. Finland, where I'm currently living, is moving to digital-only-tv in August but it's not HDTV, and while digital, most STBs only have analog outputs to analog TVs.

    Joshua.
     
  22. Moderator

    balamw

    Staff Member

    Joined:
    Aug 16, 2005
    Location:
    New England
    #22
    You know there are CRTs that have HD resolution/inputs too. They're actually cheaper than LCD or plasma, but have all the same features of "standard" CRTs.

    B
     
  23. macrumors 6502a

    Joined:
    Jan 29, 2006
    Location:
    Finland
    #23
    I've heard. Quite rare in europe though. I only know of one available in limited quantity in Finland and that's the Philips Cineos 32PW9551/12. It's got HDMI and all. Seems to be sold out in most places though.

    Joshua.
     
  24. macrumors 65816

    Avatar74

    Joined:
    Feb 5, 2007
    #24
    There's a reason the Sony Trinitron has been the display reference standard for NTSC calibrated studio monitors for 40 years. :)

    I have a 36" Sony WEGA Trinitron XBR HDTV and aside from minor geometry issues typical of large CRT's, the color, clarity and contrast are stellar and unmatched by even the $7000 70 inch Sony SXRD XBR 1080p.
     
  25. macrumors 68030

    Joined:
    Dec 17, 2003
    Location:
    Los Angeles, CA
    #25
    I don't have an ATV, but I do have a 32" 4:3 analog Sony HDTV.

    I don't think the image is being squished on the OP's experience (since he only mentions the bars.) This is what it sounds like is happening (same thing happens to me with my XBox hooked up through HDMI/DVI)-

    1. The ATV signal is being output to the TV in 16:9 ratio.

    2. The TV compensates for this by letterboxing the display on the top and bottom, so you see the entire 16:9 picture.

    3. When ATV has 4:3 content, it compensates for this by putting black bars to the left and right of the picture, since it only outputs in 16:9.

    4. The TV gets this 16:9 content, and still adds the letterbox bars. So what you get is a smaller 4:3 picture inside a larger 4:3 screen. This happens to me when I play 4:3 video files in my XBMC.

    The TV is not smart enough to automatically 'zoom' the content to fill the screen- it has no way of knowing that it's actually 4:3 content with bars on the sides. Although some TVs have zoom that might help fill the screen.

    Most DVD players have the option of automatically changing output if you have a 4:3 HDTV like my Sony TV. So 4:3 content is fullscreen, and 16:9 content is letterboxed (but the Sony also has a 16:9 enhanced mode that compresses the scan lines so no extra resolution is wasted on drawing black bars.)
     

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