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Primer: The Principles Of 3D Video And Blu-ray 3D

3D Displays

A 3D display must be able to display two separate video images on the same screen. There are several methods that are used to accomplish this. Each display method must be paired with the corresponding 3D glasses technology designed to assure that each eye only sees the video meant for that eye.

Polarized Displays and Polarized Glasses

Modern TVs and displays emit light from each pixel in some combination of red, green, and blue wavelengths. The light emitted by a TV or display can be filtered, such that all of the light coming from a row of pixels has the same electromagnetic orientation. Though the light travels in a straight line from the display pixel to your eye, it may be filtered so that it has one of two circular polarization states (left-hand or right-hand). 

For example, imagine that a beam of light is traveling along the center of the spiral graphic below. The arrows pointing outward from the axis of the direction of travel represent the changing direction of the orientation of the electric field of the light beam (though we don’t think of light in the same way we think of radio waves, light is another type of electromagnetic wave). If you align the thumb of your left hand along the center axis of the spiral graph below (the direction of travel of the light), you will be able to close your fingers into a fist in the direction that the electric field rotates around this beam of light. Light with this circular polarization is said to be left-handed.

The graphic below shows the direction that the electric field rotates around a beam of circularly-polarized light with right-handed orientation.

Circularly-polarized light with one orientation can pass through a polarizing filter with the same orientation, but will be blocked by a polarizing filter with the opposite orientation. In this way, half of the pixels of a 3D display can be used to display the video for one eye, while the other half display the picture for the other eye.

3D displays can be manufactured with polarization filters, which are aligned with the rows of pixels on the display. This allows half the pixels on the display to be dedicated to displaying the picture for one eye, and the other half of the pixels for the other eye. Note that the effective resolution provided by a polarized display to each eye is half of the full display resolution.

Row interleave polarized 3D display. Odd horizontal rows of pixels are used for one eye, even rows for the other eye. Red and blue are used to indicate left and right eye images.

To play back a stereoscopic 3D video program, such as a Blu-ray 3D on a polarized display, the left and right video frames are converted to interlaced video frames. The display is designed to show odd rows of pixels to one eye, and even rows of pixels to the other eye.

With polarized 3D glasses, each eye will only see the part of the image meant for that eye. In the image above, red and blue indicate the different circular polarization on the lens for each eye. Though two images appear on the display at the same time. With the 3D glasses, each eye only sees the image meant for that eye. The human visual system combines the image into a single 3D image.

Polarized displays are one of the least-expensive ways to display a 3D video, and polarized glasses are inexpensive. However, polarized displays aren’t always able to filter the light perfectly, such that 100% of the light meant for each eye has the correct orientation. Similarly, polarized 3D glasses aren’t always able to block 100% of the light that is meant for the other eye. This problem, where one signal bleeds into another signal traveling along the same transmission path is known generically as cross-talk. For 3D display systems, cross-talk leads to double images (fuzzy, unsharp images). The image quality of a 3D polarized display decreases noticeably if the viewer is not directly in front of (perpendicular to) the display.

  • JohnnyLucky
    Very informative primer. Lots of information that was easy to undertsand.

    Unfortunately I am one of those who recently purchased a new TV. It will be quite some time before I upgrade.
    Reply
  • TheGreatGrapeApe
    Nice article, but I think there's a few issues with regards to the overall balance of the information being put forth.

    I understand the author's preference for shutter glasses (especially since it's a certain product's preferred method of choice) even if I don't share it, the major limitation is having to buy a pair for all your friends coming over, which gets impractical until they are more commonplace.

    Also polarized solutions are not limited in resolution if they are set-up beyond just the example provided in this article (like they do in the theatre with dual projectors ) and may have an improving single source future with 2K and 4K displays on the horizon. It's a question of preference, but it seems like the full story wasn't explored on that subject.

    Now on to a pet peeve: I love the part about "While set-top Blu-ray players will need to be replaced, PC-based Blu-ray player software can be upgraded." as a subtle product benefit plug.

    Unless it's a free upgrade, you are still replacing the software, not upgrading it (it's not a plug-in), and you're likely forking out nearly the same amount of money for the 1/100th of the cost to produce that software update, so it's not like it's a major advantage. Especially when upgrading requires a FULL upgrade to the most expensive model Power DVD (version #) Ultra 3D, and I can't simply add it to my existing PowerDVD bundles thus potentially changing my backwards compatibility (Ultra 9 already removed my HD-DVD support from Ultra 7 that I upgraded on my LG HD-DVD/BR burner

    , until then it's $99 (or $94.95 for loyal saps) vs $150-200, plus with the set-top route now I have a second BR-/DVD player for another room or to give to a friend (the BR software on its own is useless to give to someone else without a drive), and that's not even compared to the free PS3 upgrade.

    Also can someone explain this statement;
    "Blu-ray 3D video decoding solutions can be expected for ATI Radeon 5000-series graphics in the future."

    Didn't Cyberlink already show their BR-3D solution on ATi hardware last year? So what's the issue?

    Also why is it limited to "GeForce 300M-series mobile graphics" when often the core is the same a previous generation 200M series (example GTS 350M / 250M )?

    And this section "Full-quality 120 Hz frame-sequential 3D video (such as Blu-ray 3D) is only supported through a High Speed
    HDMI cable to a HDMI 1.4-compliant TV. " seems to miss the DVI dual-link to monitor option currently being used for 3D on PCs, and also the dual 1.3 input monitors/TVs.

    A nice little article for people unfamiliar with 3D, but there's a subtle under-current of product preference/placement in it, and far too many generalities with little supporting information. :??:
    Reply
  • hixbot
    well done. I would of liked more detail on the hdmi 1.4 spec, specifically framepacking and the mandatory standards (no mandatory standard for 1080p60 framepacking).
    also some info on AVRs and how a 1.3 hdmi AVR might pass on 3d video and still decode bitstream audio, or not - do we need 1.4 hdmi AVRs to decode audio from a 1.4 source? we shouldn't need 1.4 receivers since the audio standards haven't change, but I'm understanding that in fact we do neeed new receivers. :/
    Reply
  • hixbot
    double post. good article.
    Reply
  • ArgleBargle
    Unfortunately for people with heavy vision impairment (astigmatism, etc.) which require corrective lenses, such 3D technology is out of their reach for the time being, or at least next to useless. Until some enterprising company comes out with 3D "goggles", people who wear corrective lenses might as well save their money.
    Reply
  • boletus
    3D is cool, and high definition video is cool. But Sony's moving target of a BD standard is not cool, and Cyberlink's bait and switch tactics are not cool (unless you have bundles of money you can throw at them every 6-12 months). I sent back my BD disk drive (retail, with Cyberlink software) for a refund after finding out that I would have to shell out another $60-100 just so I could watch a two-year old movie. As far as I'm concerned, high definition DVD video is dead until some more open standards and reliable software emerge.
    Reply
  • cangelini
    Great,

    This piece is a prelude to tomorrow's coverage, by Don, of Blu-ray 3D on a notebook and a desktop. Perhaps that one will answer any of the questions you were left with here?

    As for AMD, Tom and I went back and forth on this piece, and we agreed that it was critical to get AMD's feedback on Blu-ray 3D readiness. The fact of the matter is that it isn't ready to discuss the technology. It's behind.

    The mention of dual-link DVI was in the first revision of this piece and removed in a subsequent iteration. I've asked the author for additional clarification there and should have an answer shortly.
    Reply
  • cangelini
    So it turns out there were two sections on this and one was cut accidentally. Should be good to go now, though--dual-link DVI is discussed with PC displays!
    Reply
  • cleeve
    TheGreatGrapeApeAlso can someone explain this statement;"Blu-ray 3D video decoding solutions can be expected for ATI Radeon 5000-series graphics in the future."Didn't Cyberlink already show their BR-3D solution on ATi hardware last year? So what's the issue?
    It turns out the demo (I think it was at CES?) only used CPU decoding over an ATI graphics card; the Radeon did no software decoding.

    The Cyberlink rep tells me that Blu-ray 3D software decoding is extremely CPU-dependant and might even require a quad-core CPU. He said all four threads were being stressed under software decoding, not sure what quad-core CPU they were using though.

    Definitely something I'd like to test out in the future...
    Reply
  • Alvin Smith
    This was a very informative and well written article BUT, I chose to skip to the last two pages ... Because ...

    These implementations, while ever more impressive, are still being threshed out. Because of possible physiological side effects, I think I will NOT be a first adopter, with this (particular) tech (3D).

    Anyone ever watch that movie "THE JERK", with STEVE MARTIN ??

    = Opti-Grab =

    ... I can see all these class-action suits by parents of cross-eyed gamers ... hope not, tho ... I *AM* very much looking forward to the fully refined "end game", for 3D ...

    Additionally, the very best desktop workstations are only just now catching up to standard (uncompressed) HD resolution ingest and edit/render ... since that bandwidth IS shared, between both eyes, this may be a non-issue.

    I will let the kiddies and 1st adopters take-on all those risks and costs.

    Please let me know when it is all "fully baked" and field tested!

    = Alvin = (not to mention "affordable").
    Reply