Need clarification on video basics

Discussion in 'Archived Threads 2001-2004' started by Jay Reddy, Nov 5, 2002.

  1. Jay Reddy

    Jay Reddy Auditioning

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    So I've read a few articles (including this site's primer) about the new video, DVD, and HD technologies, but there are a few things I'm not clear about....

    1. I've read an article explaining 3:2 pull-down, but what does it mean when a TV has this technology? As I understand it, 3:2 pull-down is a system where 24 frames per second features (i.e., movies) are converted to a TV's 60 fields per second method. Since this would be coded onto a DVD, what is the benefit of having a TV with this feature? I'm asking because CNet made a big deal about the new Sony 40XBR800 having this feature.

    2. When viewing anamorphic DVD's on a 4:3 analog TV, does one still get the 33% increase in resolution?

    3. I've noticed a few inconsistencies on several websites about aspect ratios. Some say that viewing 1.85:1 features on a 16:9 (widescreen) TV has no black bars (because a miniscule fraction of the picture is omitted), and others say that there are miniscule black bars (because the feature is only slightly wider than the screen. I realize I'm asking about something I may not even be able to notice, but I'd like to know what's really happening.

    4. Back to the Sony 40XBR800. CNet also mentioned that this 4:3 TV has an "16:9 enhanced widescreen" tool for viewing anamorphic DVDs. What does this mean? How does it work. Hoes is this different from any DVD player outputing an anamorphic feature to any old 4:3 set?

    What a mouthful! Thanks in advance.
     
  2. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    If the DVD player is not progressive scan, then the 3:2 pulldown in the TV is used. The TV also employs 3:2 for non DVD film material like regular cable stuff.

    If you set your DVD player for 16:9 ... any 4:3 TV will give you the additional resolution. It's just that the image is stretched ... aka skinnyvision. Geometric distortion until you use vertical compression to fix geometry.

    1.85:1 aspect ratio leaves 7% black bars on the top/bottom. Since most TV's have overscan set at 10% top bottom combined ... the 7% bars aka 3.5% top and bottom are tranparent to the end user.

    Enhanced mode in tv is a vertical compression mode. It squeezes the TV's scanning rasters into a 16:9 area instead of the 4:3 area of the screen.

    Regards
     
  3. Allan Jayne

    Allan Jayne Cinematographer

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    1. ... 3:2 pull-down, but what does it mean when a TV has this technology ...
    The 3-2 pulldown sensing and optimizing is only put in progressive scan TV's, which display 60 full frames per second as opposed to 60 fields. This technology figures out when the incoming video is from a 24 frame per second film (may be DVD or VHS or regular broadcast, etc.) and therefore has the 3-2 pulldown in it. Picking out matching fields to weave together and make each complete frame gives superior results to simply using the current field and the next field to make each complete frame.
    Non-progressive scan TV's do not weave together video fields so they don't need to look for the 3-2 pulldown pattern.
    Video hints:
    http://members.aol.com/ajaynejr/video.htm
     
  4. Chet Hayes

    Chet Hayes Agent

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    "If you set your DVD player for 16:9 ... any 4:3 TV will give you the additional resolution. "


    I didn't think pulldown was a resolution issue, but rather one of helping eliminate artifacts caused by the different frame rates. Do I have this wrong?
     
  5. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    It's not a resolution issue. 3:2 is simply about properly converting a 24 frame source to 30 frames.

    Regards
     
  6. Jay Reddy

    Jay Reddy Auditioning

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    I thought 3:2 pull down was built into progressive-scan DVD players because films specifically needed such things. I can understand why a HDTV mated to a non-progressive-scan DVD player would need 3:2 pull down to reduce the resulting artifacts. However, there seems to be a universal consensus that progressive-scan players should be mated to a HDTV rather than analog TVs because such players create artifacts on analog TVs.

    Also, I was under the impression that TV was broadcast in 60fps, thus negating the usefulness of 3:2 pulldown for anything but film.

    Thanks.
     
  7. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    Jay, that would be 60 fields per second ... not frames.

    A field is 1/2 a frame.

    Regards
     
  8. Jay Reddy

    Jay Reddy Auditioning

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    I see--thanks for the clarification. But whether we're talking 30f(rames)ps on an analog set or 60fps on a new HD set, why is 3:2 pull-down necessary on a TV coupled to a progressive-scan DVD player or one used exclusively for cable TV.

    I apologize if I'm being a bit anal.
     
  9. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    Maybe because non hd analog sets cannot take a progressive signal so you would kinda get a blank picture if you tried the mate that signal type to the TV.

    Well if my HDTV does not do 3:2 ... and I have a 480P dvd player ... that's really gonna do me a lot of good when I watch movies on HBO and Showtime. I'll still get plenty of deinterlacing artifacts.

    And if I use the TV exclusively for cable, what good does a 480P dvd player do me? What good does a 1080i DVD player do me? What good does a porsche do me? None of that is gonna do 3:2 on my HBO or Showtime or Everybody Loves Raymond.

    Regards
     
  10. Jay Reddy

    Jay Reddy Auditioning

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    It is my understanding that TV broadcasts are in 60fps (frames or fields depending on the TV). How would 3:2 pull down work in this instance? Or am I completely off base?

    Thanks.
     
  11. Michael Reuben

    Michael Reuben Studio Mogul

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  12. Jay Reddy

    Jay Reddy Auditioning

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    Thanks for all the replies. I think I've got it now.
     

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