LG\'s Passive-Polarized-Glasses 3DTV - Where is my Pixel?

[Rodolfo]

In the previous articles I covered the subject of the current battle between active-shutter glasses 3DTV and passive-polarized-glasses 3DTV technologies to gain consumer acceptance. I also illustrated how both TV technologies show 3D images and briefly introduced LG’s new passive 3DTV.

In this article I illustrate how that 3DTV employs a proprietary feature to claim it displays the full resolution of the original 3D images, a claim LG used to challenge active-shutter glasses 3DTV technology known to be capable of full resolution per eye.

As mentioned in other articles, passive technology discards half of the pixels of the original 3D images and LG’s implementation of the technology has a more complex pixel management. This article discusses that complexity.


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[BuddAdams]

WOW! Mind numbing, but brilliant. I will save this to read again. Like a good Dry Martini, this one's to be sipped, not slurped. One review I've already read, Sound & Vision, as I recall, said it looked good, but the horizontal lines were objectionable at close range. Too bad for me as I've got corrected 20-20 vision and sit around 7-8' form a 60" screen which just about matches my resolution with a 1080p image. I've never understood the sense of "Normal" under resolving viewing distances if you could manage a large enough image.

[Rodolfo]

BuddAdams,

According to LG the recommended viewing distance for a 60” panel similar to yours, believe or not, is about 15 feet.

http://www.lg.com/us/tv-audio-video/tel ... /index.jsp

At that distance you may as well saved the cost of a 1080p set and bought a 480p set instead. DVDs will look similar than Blu-rays, and a SD channel may look HD to you. A typically recommended HD viewing distance has been traditionally about 3 times the screen’s height, which is about 90+ inches for your 60” panel, or 7-8 feet. So in my opinion you are doing OK for your set, but LG says your TV should have been a 32” set for that distance, go figure.

Certainly, at LG’s 15 feet recommended distance, a viewer would find almost impossible to detect the black line structure of the FPR, or the half-resolution for each eye of 3D, not to mention the resultant reduced left-to-right viewing angle, so small that would make a viewer unable to be immersed into a movie, but more like seen it thru binoculars.

If you already finished sipping your Martini while digesting this article you may imagine that I had to drink quite a few of them while writing the findings to reduce my disappointment with what LG’s passive feeds to the brain. Get ready for a refill, my next article gives a side-by-side graphical representation of what active, typical passive, an LG’s passive 3DTVs actually display regardless of what a brain perceives.

What a brain may interpret of anything is always on the eye’s beholder and LG Display’s passive 3DTV is driving their passive’s promotion based in image perception by the brain, which they say is good enough and people like it better than full resolution active-shutter, giving the excuse to shortcut the quality of the displayed 3D images, that is, quality as traditionally measured by standard imaging-science rules and techniques, which apparently are not important anymore if the 3D appearance is convincing enough.

In other words, my interpretation of LG’s message (and the very few that defend it) is: a recorded 3D dual-1080p-image-pair does not need to be shown to the eyes as two fully resolved 1080p images for the brain to be fooled enough for the 3D illusion.

I personally feel cheated on my wallet when I think of that, my first reaction is to get a 50% discount for that set for my brain to be content enough, but quite frankly I would not want such set in my home even if it is free.

In my book, if the current technology permits so, and it does, I always pursue that a display device must produce the most accurate and resolved picture, never less than the quality of the source, regardless if it is in 2D or 3D, so images can be delivered to the eyes as uncompromised as possible, rather than cutting angles and hoping the brain will fill the missing information, 50% of it, and 50% of that 50% shown in reverse video line order.

As I said many times, passive and active should coexist in parallel because there are people that have issues and preferences with one or the other, whether that is headaches, crosstalk, flicker, or image quality. So both are needed, and both should respect each other on what they do for the needs of people, rather than trying to displace each other.


Best Regards,

Rodolfo La Maestra

[ragnars]

Ah, the perpetual argument between the pure scientists and the practical engineers. Do I want 'no compromise perfection' or ‘good enough’ ? To mind come the 50’s Black and white television era, when the NTSC Comittee was weighing the standard for the forthcoming color broadcast system. Working under the serious restraints of double compatibility ( B & W sets to render color broadcast signals in B & W, color sets to display B & W transmissions in B & W ), the engineers came up with a workable scheme. The scientists cried foul, because the proposed RGB ‘triangle’ did not cover the whole color gamut. Luckily the comittee said ‘good enough’ and approved the NTSC color system that has served all of us well, with minor imrovements ( such as PAL) until now, the advent of the digital era.

[Rodolfo]

Good enough was sufficient then, there are some differences though, the limitation of 6 MHz on the transmission was the driver, not the TV set, and broadcast was the only video content available.

In this case 3D is already in full resolution in Blu-ray; imposing a “good enough, people would not notice, through away half of it and sell the idea that their brains will perceive full resolution” is not the same as in the case you describe.

I always say that passive is necessary for people that desperately want 3D and have issues with active-shutter, but instead of being promoted exactly like that to share a 3DTV market, LG chose to degrade active-shutter publicly, saying that passive is better because is the same as the theater (when is not), is full resolution (by showing the ignored pixels in reverse), and is perceived better by the brain of a large group of people (although a much larger group has rather been buying the active-shutter technology).

The passive method for 3DTV should have been introduced as an alternative that would give a chance to some people to appreciate 3D at home when they cannot do it with active-shutter, or the cost of multiple 3D glasses is out of reach, not by fighting with misleading information to take over a market, and a “brain perception” excuse when showing to the eyes/brain half of the information of the competitive technology.

Regarding my other post, I intentionally introduced a quantitative error to see if readers are smart enough, or they are still numbed by the content, or semi-sleeping and happy still sipping Martinis. If you catch the error post it on this thread and I will nominate you the reader of the month, which would make you eligible to receive a preliminary version of my next technical article before is even published (copyrights, no distribution, of course) so you will get the elite treatment.

Best Regards,

Rodolfo La Maestra

[njsss]

As I'm trying to decide which 3D tv to buy, I'm really appreciated your thorough review on the LG cinema 3d hdtv. However, after carefully read your article and LG's blog, I have to agree with LG that the assertion of full hd (1080p) is correct in theory if everything works exactly as they said. The guy from LG might not fully understand what was your concern.
I think the key point here is that you have to consider the eye's spacial resolution. So to make it simple, let's assume the eye is just a simple ccd camera with a low resolution of 1080p (1920 w * 1080 h), and we map our "eye chip" pixel by pixel, line by line to the 3DTV (that is our eye's spacial resolution matches the TV's resolution).
According to the LG diagram on the left for the first circle, signals from odd lines of the TV are sent to the left eye, and even lines to the right eye. Since the circular polarized glasses only block certain light, not distortion of where the light come from. We still have the pixel match. The left "eye chip" now has the the odd lines filled (L1, L3, L5 ... L1077, L1079) with the odd line signals, while leaving the even lines (L2, L4, L6, ... L1078, L1080) blank. Similarly, the right "eye chip" has only the even lines filled (R2, R4, R6 ... ). That is why, I believe, in traditional passive 3DTVs, we can clearly see black lines in between the images (those eye chip pixels = 0).
The LG's trick is in the second cycle, reversing the polarization of the EVEN (odd) line to match the LEFT(right) glasses effectively passes TV's the EVEN (odd) lines signals to the LEFT (right) eye. Since the eye-TV line-to-line correspondence remains the same, the left "eye chip" now has the rest even lines filled (L2, L4, L6, ...) with the even line signals from TV as well; same with the right "eye chip". Now both left and right "eye chips" have full (1920x1080) pixels filled with signals.
So if the two cycles happens really quick before the eye dumping the signal to the brain to process, the brain won't even notice which comes in the 1st or 2nd circles. Actually this is the same with the shutter glass, be fast to fool the brain. In theory, the result is exactly what you have shown in your "original 3D images", thus full fill their full HD claim.

[Rodolfo]

Although both eyes see the even or the odd lines you are forgetting in that the video lines are relatively shifted from each other to convey the angles viewed by the two cameras, the two 540s images of the first cycle do not make a clean/uninterrupted 1080 image because every line show shifted pixels relative to each other, like serrated edges.

The left eye sees an image that misses half of the lines (in between), the objects in the image miss part of the detail and continuity, and the right eye sees a shifted image of the same objects but from the other angle, with also half of the lines missing, when you interleave both together many interlaced artifacts are displayed, more obvious in the jagged edges in diagonals and geometrical images, even on the demos LG uses to seel their 3DTVs, such as the diagonals in the carpet, the inclined edge lines of the TV cabinets shown in the clips, etc.

Regarding the second cycle, the lines are displayed in reverse due to the limitation on the polarization of the passive method and the 1080 resolution of the TV, the lines on the second cycle are not completing the information of the first cycle by displaying them in the correct pixel position relative to the first cycle (the photos on the right column on my article can give you an idea of the effect), they are a) in reverse relative to each other and b) they neither complete the half-lines of previous cycle by filling the exact in-between locations where the lines were dropped on the first cycle, because of the fixed polarization.

The black lines you see are the Film Patterned Retarder all passive 3DTVs use to separate the polarization of even/odd lines, not the video processing of the combined effect of the two cycles, which is used by LG Display as a method to claim it shows all the 1080 video lines of each eye of a Blu-ray 3D source (without disclosing they are shown in reverse with each other).

4K passive will change all that. LGs 4K 84” passive 3DTV shown at CES 2012 was very good. I was impressed, no obvious FPR black lines, 1080p on each eye, allows the use of cheap glasses, and good 3D effect (except when the demo was overusing the parallax depth between the screen and the viewer (in your face bad 3D). Unfortunately the new panel is LCD and still have a very limited view angle for people sitting off center (about 20 degrees to start degrading colors, contrast, brightness). I hope they would be able to do 4K passive in smaller panels at eventually reasonable prices, hopefully using a technology to improve the viewing angle of all LCDs that 3M presented at the show.

Best Regards,

Rodolfo La Maestra