Keep 3D active or make switch to Passive 3D TV - Page 2

I should take a stab, I guess, at explaining why I have doubts. I see this from the perspective of a serious, long time video hobbyist. But I'm not a display technology guru.

Frame packed 3D Blu-Ray looks remarkably good on a passive set at reasonable viewing distance. What disturbs me is that cable 3D, that is, SbS or T/B split screen in 1080i, looks rather poorer than I expected. And it's not because I can now definitely see slight horizontal line jaggies at my 1.5x viewing distance. (A limitation of the FPR screen tech). Nor do I think it's purely the result of the usual low, crappy bitrate of cable HD. To *some* extent it is, definitely. I know very well all the ways low bitrate can manifest itself. If half resolution shows ill effects, I think split screen SbS and T/B must be the threshold. Mind you, I'm not saying it looks bad, but if passive 3D can look like SD, that's where. Cable 3D.

I really wish I had a friend nearby with a large active set so I could test this further and be certain. Maybe cable 3D doesn't look so hot on an active set either.

People read Soneira's demonstration that very small text can be read in 3D on a passive set. Almost as well as in 2D. I've done the tests myself. And image fusion MUST exist, otherwise you could never create a 3D effect on a 2 dimensional screen at all, right? QED, case closed, yes?

Let me offer some analogies from my experience, and I hope it makes *some* sense. In Soneira's demonstration, the information is actually all there, it's merely offset. I actually would expect that result. Yes, image fusion, but that doesn't prove to me it's full 1080p.

This is a bit of a stretch, but I'd liken that to blur and/or shake. At, say, 30 fps, a reasonable frame rate, you can tolerate some of each up to a point. If it's not too bad, many people may not even notice. Usually it will look a damn sight better at native frame rate than the individual stills. Here's the point: Your mind will fill in some information from cues in several frames. I offer this as evidence that often you're not seeing what you think you're seeing. So doesn't that just confirm image fusion? Not so fast. Yes and (maybe) no. Yes there's image fusion, but no, that doesn't necessarily mean it's full resolution.

Not to stray too far from the topic, but in video restoration, applying deshake and deblur filters, that's fairly easy. Depending on the source, you might do a little judicious sharpening and gamma correction too, maybe a little denoise, then render the file. With emphasis on "a little". Nevertheless, and although you can make dim, shaky/blurry footage look better, you're deceived. It's not as shot, the color is not faithful, the sharpness is artificial, and there's some interpolation/averaging going on to achieve the result. The restorer must make some guesses as well as to missing information (chroma, hue, saturation, etc). By its nature, the result is inaccurate.

So some of what you're seeing wasn't there in the first place. Extend that a little further. How about those cop shows where they take a crappy, low resolution still from a security camera to catch the bad guy? It's laughable. You can't create new information. If you don't have multiple frames to average, you're down to maybe a little deblur, a little denoise, sharpening and gamma correction. Anything more is likely to create entirely erroneous and deceptive detail. Now, I'm sure the FBI or whoever has better software than what is available to serious video hobbyists, but the general public's ideas on what's possible are entirely unrealistic.

Sorry for the digression.

I get stuck on the fact that each eye only receives half resolution, half the information. Yes, image fusion allows the mind to put together all the offset information to fill in the picture. But filling it in is not the same as getting full information, each eye.

I fear I have not really made my point. [sigh] But I've learned to be skeptical about what I think I'm seeing.

Again, I love my 65" passive 3D set, and urge all those interested in a 3D TV to have a look and compare. Passive has a lot to offer.
Edited by fritzi93 - 11/11/12 at 6:35pm

Really? My LG 65 has a great 3d picture...not a misplaced horizontal line in sight. Must be some other explanation for what you might have seen. Everyone knows that the TV's in the stores may or may not be adequately set up for best picture quality. There are no interlaced lines visible in the 3d image.....none.

I was at a trade show recently, and Go Pro was demonstrating their 3D cameras with an LG passive 3D TV. Normally, I am bothered by the half-res images sent to each eye on a passive set, but was very surprised that with the content they had, I didn't see this.

Then I read the Displaymate article, and they confirmed that high contrast images with near horizontal lines, will produce the "scan line effect". With more natural images, the brain is able to fuse the images. I think the bottom line is, it depends on the content whether you will be bothered with the lower resolution to each eye.

The passive 3D images are brighter, and somewhat less fatiguing. I think part of the reason for this is each eye gets the image at the same time with a passive set vs. active shutters alternating the images to each eye. This creates a lag time to the right eye, that confuses the brain, because it is the same image only displayed later. Panasonic recently introduced a new video projector that interpolates the images between the left and right eyes to account for the lag that the right eye faces during image motion.

Michael

From what I understand the frames on Blu ray are not 2160p. It is essentially two frames of 1080p being scanned at alternating intervals, and since active TVs merely alternate the frames at different times they are not 2160p either. When they are alternated to produce one image the result is only 1080p, the extra lines from each frame are merely lost. It would take a 2160p TV with true 2160p content to truly be a 2160p TV, and they are only advertising them as 1080p TVs. The result is still displaying 2 million pixels just like passive, not 4 million.

I'll go look at the one at Conn's, then, for comparison, assuming they still have it on the floor.

Might be a good idea. In thinking further about the issue, perhaps some people have a heightened sensitivity to the effect that you describe....like the dlp rainbow effect. In fairness, just because I don't see it doesn't mean it doesn't exist.

My only advice would be to ignore the math and anyone who spouts it, and decide based on what your own eyes tell you.

No. What you have is the regular 1080p 2D version (usually the left view), stored in SSIF files using MVC, a variant of AVC. MVC has support for multiple views. Right view references the left view.

Here's the thing: the right view references the left with motion vectors and some error correction. Very similar to "normal" AVC compression, which uses a key frame (I frame) which contains all the information for that frame. Progressive frames (P frames) reference the preceding frames. Bi-directional frames (B frames) can reference frames preceding *and* following. These reference frames require much less data (and space) because they do not contain all the data key frames do. They only specify differences and where pixel information (already given) is moved to. Together you have a group of pictures (GOP) consisting of the key frame and succeeding frames. A new key frame begins the next GOP. This makes for much greater efficiency in compression.

The right view works much the same. If you had two complete views, you'd need double the space, right? But you don't, the complete 3D version is more like 1.3x or so the file size of the 2D version.

BTW, I know what some of you are thinking: How come I can't play my 3D Blu-Ray in 2D mode? No reason why you couldn't apart from the fact that the studios author them in such a way as to block it. We can't have folks selling their 2D discs from the premium set we make them buy if they want the 3D version. Now can we?

Some discs are unlocked, of course. IMAX Space Station, for instance. It's just a matter of mapping an mpls (playlist file) and associated m2ts file(s) for 2D mode to the appropriate left view SSIF files. Those discs can be played on a 2D player, as the player will recognize the mpls and m2ts as valid Blu-Ray files and ignore the other stuff. Oh, we simply can't have folks doing that either.
Edited by fritzi93 - 11/12/12 at 5:18pm

I unfortunately see the DLP rainbows, even on the newer DLP RPTVs. Not as bad as the first generation, though.

I agree as far as decide based on what you see, and I would encourage the OP to go for the passive despite the math. But the math is interesting too and AVS is the right place for it.

Again, there's this:

"Literally" is a dangerous word, and fritzi above is speaking more literally about how it's stored. The above, at least, is the result of that. This is 1080p frame packed 3D. Two 1080p images packed into a single frame ("2160" comes from simply adding the two up). This is what gets sent through HDMI to your TV, whether it's active or passive. A 1080p passive TV takes this frame and displays 540 lines of the top (left) image and 540 lines of the bottom (right) image. Half of the lines are therefore not shown. A 4k passive TV takes this frame and displays all 1080 lines of the top frame, and all 1080 lines of the bottom frame, with a bit of upscaling. A 1080p active TV rapidly alternates showing all 1080 lines of the top frame and all 1080 lines of the bottom frame. All of the lines are shown, though not at the same time.

The fact that they are not shown at the same time is not relevant as far as resolution is concerned. With the active glasses on, each eye sees its own 1080p image. Where it does matter is in terms of flicker and motion tearing. These are notable drawbacks of active technology, but we're not longer talking about resolution.
Edited by Airion - 11/12/12 at 6:33pm

Okay, I accept the distinction between how it's stored and how the signal is sent over HDMI. From my viewpoint, how it gets from standalone to TV is not what the format actually is.

It's all irrelevant though in regard to the discussion of active vs passive. The difference between the display types lies in what they do with the signal.

I don't think it makes much difference if it's 1080 per eye, the end result is still only 1080p or 2 million pixels. Passive is also using 2 million pixels. instead of displaying them in the way active is done they ignore half the lines for each eye before image fusion, so if you're up close you see the black horizontal lines as if they're not being used, but actually they are being used by the other eye.

Because the displayed pixels are the same I don't think the end image is going to be any higher. Maybe it makes it appear that way on paper but still it's only 2 megapixel image, not 4 unless there are physically 4 million pixels present like a 2160 display. Since digital or HD 3D is still early LG's 540 per eye could progress to 1080 per eye, the same as active, which may eliminate the horizontal black lines and clear up some imaging, I don't see it increasing the end image resolution beyond 1080p. Unless it has 4 million pixels to display it to with discrete content (pixel to pixel match).
Edited by tomtastic - 11/13/12 at 9:46am

Ah, I think this is why you're not getting it. The left and right pixels are not the same. Left/right disparity is the very essence of stereoscopic 3D. If the pixels are the same, it's 2D. In practice, it all depends on the scene and it's fair to say that many of the pixels will be the same in both eyes, or perhaps the same pixel simply shifted left or right (flat objects, or objects in the distance). In these cases, image fusion should work just fine and you're not getting a loss of detail. Relatively flat looking 3D images look flat because the left and right images are very similar. But, the more depth/pop-out/3D you have, the more different the left and right images, and the more you're going to be loosing details on a 1080p passive TV.

As one example, look at the left edge of your monitor and close your left eye. Now close your right eye and open your left, and notice how much more you can see behind your monitor. Alternate opening and closing your eyes to compare. Image this is a scene on a Blu-ray. All that extra stuff you see behind your monitor with your left eye, there's nothing in the right eye image to fuse to make up for the resolution loss.

Hopefully this won't do more harm than good, but here's an approximation what you get with 1080p passive, offering 540p per eye in an interleaved configuration, and 1080p per eye overlapping in terms of image fusion. It's impossible to truly represent this in a 2D image, but this might help you get part of the picture:



Hopefully that's not too abstract. In reality the colors wouldn't combine of course, but think of it in terms of the details of two different images combining into a stereoscopic 3D image in your brain.

But yes, 3D cable using either top/bottom or side-by-side is decidedly worse than Blu-Ray frame packed 3D on active sets too. I have active glasses projectors in 720p and 1080p, and I have a 1080p passive set. As much as I want to love, say, the Olympics from cable on my 106" projected 3D screen with active glasses, it does not look so good.

I understand the theory about 3D passive resolution and know it is correct. Spatial resolution is reduced. But seeing is, um, important. The horizontal lines people complain about are mainly only visible when looking at 2D images with the 3D glasses still on. Pull off the glasses, and the objectional lines almost completely disappear. Likewise, when viewing 3D video, those horizontal lines are hardly noticeable. The brain somehow fuses the left and right eye images, so long as they are different, not matching. Hard to explain, impossible to prove, easy to see.

I still prefer the 106" screen, and will not prefer passive over active until I can get passive in that size. But i'm not very sensitive to eye fatigue, and that is the main only advantage for passive. Each to their own.
Edited by TrickMcKaha - 11/13/12 at 7:13pm

I agree completely, TrickMcKaha, ultimately seeing is believing no matter the technology and its individual merits/disadvantages.

It's one thing to say 1080p passive doesn't have a significant resolution disadvantage in most real content or given most real seating distances. It's another to say 1080p passive has no disadvantage on a technical level.
Edited by Airion - 11/13/12 at 7:51pm

I know the pixels on each active frame aren't the same, as they're not the same on 540 frame of passive. My point is that when they merge the 1080 frames they're still merged into a 1080p image. The only way you could see a 2160p image is if there were actually that many horizontal lines. So in a sense they're doing the same thing passive is doing, they're ignoring have the horizontal lines, it's just done differently with the glasses and screen. The only benefit right now with active is that it will look better with one eye closed and up closer to the TV. When you sit at a normal viewing position they will look basically the same.

That is true, but the top image is only true with one eye closed, the other eye sees the same basic image but the black lines that were not displayed in the top image are now shown.

If active is showing two of the bottom (active) images they combine to what? A 1080p image, same as passive. So what happens to the extra lines? You should have more content? It's ignored just like passive, just differently. When 2160p gets here, I could see where this could change.

The top image there is with both eyes open. Maybe this is easier to understand:



They combine in our brains into that 3D image. Again, maybe this is easier to understand:


Absolutely not. The extra lines and all their details are seen and perceived, never ignored. The stereo construct in our brains sort of put the two together into a single image, but that doesn't change the fact that we're seeing two different images, completely, at once. This is how our stereo vision works in the real world and that doesn't change one bit when we're using stereoscopic technology. I think the problem is you're only thinking in terms of 2D image. You need to stretch your understanding to allow the fact that stereoscopic 3D is about seeing two different images at once. You can fuse the two images together call both cases above 1080p, but that's ignoring the fact that one has potentially only half the detail of the other.

Here's perhaps a better set to show how detail gets lost in 540 per eye passive and not 1080 per eye.


Image fusion works great in areas were the left and right image are the same. Where the left and right images are different, detail is lost.



Areas where the left and right are the same, the per eye resolution advantage proves redundant. Where the left and right images are different, no detail is lost.

This week I saw one of the very few Sony KD-84X9000 (4k, 84") television sets on display in Australia.

Visibility of horizontal black lines when viewing a 2D picture with 3D passive glasses*

As expected, I found the black horizontal lines were far less noticeable than with a 1920x1080 FPR (Film-type Patterned Retarder) display. They ceased to be visible for me at about 6 feet from the display. Six feet is a very close viewing distance for an 84 inch display for 1080p source material. I imagine the 3D performance with a Full HD 3D Blu-ray would be impressive. However the set was not connected to a 3D source.

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* Passive 3D TV sets on the market use the odd numbered display lines to display Left eye image content and the even lines to display Right eye image content. For many viewers, including me, this results in a visible fine pattern of black horizontal lines if viewing from very close to the screen and wearing 3D glasses. However a number of people have been reporting that they do not see such horizontal black lines.
Edited by MLXXX - 11/14/12 at 5:21am

Which is what I see even when standing 8' away from the LG 55" TV at Best Buy.

Edited by tomtastic - 11/14/12 at 9:29am

"This can be seen when you remove the 3D glasses, the black lines disappear and all 1080 lines are used."

This is a direct although partial quote from tomtastic. To me it says it all. conversely If 3D glasses are left on the black lines are there. 1080p even so called perceived has no black lines, glasses on or off.

In my opinion the reduced resolution would not be a problem at that distance. If the display is in the 55" range, 8' - 9' would probably be fine. I've never argued that passive is not a good 3D experience. I'm sure it's the way displays will be in the future. The technology improves every year. I only have a problem with 1080p claims started by LG.

I assume you're talking here about LG's method of showing the missed lines. One of the links Robut gave on the first place talks about that.

http://www.hometheater.com/content/closer-look-active-vs-passive-3d-flat-panels

You should read the whole article and check out the accompanying images, but here's the most important part:

I think that's pretty conclusive.

I agree, and this is the crux of it. Detail is lost and lines are introduced with 1080p passive, so you have to move back far enough that you would not have been able to resolve those details in the first place. Most people are probably already sitting there anyway. Most people probably aren't sitting close enough to their not big enough TV to fully resolve 1080p in the first place. So for most, the detail lost with 1080p passive is irrelevant. But it's important to acknowledge the limitation exists, because some people do sit that close, and would benefit from 4k passive.

540p per eye 3D is far above DVD quality by the way. It's 540x1920, which is roughly equal to the number of pixels in a 720p image, and you get a different one in each eye sourced from it's own 1080p image. By any reasonable measure, it's not lacking for detail. DVD is just a single 480x720 image.

At Best Buy, when simultaneously playing the 3D preview for Titanic on both the LG passive and the Panasonic active TVs at the demo display, there are noticeable thin horizontal "lines" in the way the big letters (film title, e.g.) are displayed on the LG which do NOT appear on the Panasonic - and this is true when looking at the TVs WITHOUT wearing the glasses. I deliberately went back to Best Buy to see if it was just when I wore the glasses or if it was visible in the way the LG transmits the 3D image. Maybe I just need to take a photo to try to show people who can't view a similar setup. As I said earlier, it's kind of like (though on a much narrower scale) the scan lines you see when you watch a DVD on a regular non-HD television. Light letters on a dark background will have an aliased/jagged look to them, whereas on the active TV the letters will be totally smooth.