Blu-ray's 3D spec isn't what it could be
By Ben Drawbaugh 
posted January 8th 2010 1:46AM
posted January 8th 2010 1:46AM
While 3D is all the rage at CES this year, we learned today from the BDA that one of the biggest sources of 3D content isn't what it could be. The first thing that could, should, be better is the limited support for frame rates. Movies have been recorded at 24 frames per second for longer than our parents have been alive, and for about the same amount of time we've had to endure frame rate interpolation to make movies play back on our 30Hz TVs -- you know, like 3:2 pull-down. That changed recently with 120hz LCDs and 72Hz plasmas because those numbers share a common denominator with 24 (so the same frame is just shown three or four times). When choosing an 3D HDTV it is important to understand how the TV displays 24 fps 3D content, don't just asume it does it without 3:2 pull down. But honestly the worst part is that some 3D cameras can capture 3D at higher frame rates and even if the director wanted to, the new 3D Blu-ray spec doesn't support it. The other issue we take with the new spec is that contrary to early reports, it is possible to create a 3D Blu-ray Disc that won't play on 2D only players. This next one isn't a big deal, but still disappointing is that even if the creator goes through the trouble to encode the movie in both formats, depending on the HDTV, you may have no choice but to watch it in 3D -- say if you lost your glasses or whatever. Now don't get us wrong we're pretty excited about the new 3D technology, but the way we see it is that anything worth doing, is worth doing right the first time.
Broadcast 3D cameras capture at 30fps, I think that is what the poster was stating. Film cameras of course only capture 24hz.
So, is it stored in 48p or what?
@Zinn
It is stored at 24p per eye, so yeah 48.
You are never going to convince film producers to use anything but 24 frame. I have sat in many groups that explored other frame rates for film and the arguements are just too numerous (to them) to ignore.
1. Cost of production goes up
2. Going beyond 24hz moves the experience into the realm of television/documentary style of presentation, in other words it does not put the viewer into 'story' mode as the experience is too real, It ends up not looking like 'film'. Yes, this is an actual arguement used by the film industry. I sat in a screening of a scene that was shot at 24, 30, 60, and 72 fps. It was scanned at 6K and presented digitally side by side (butterfly) against the other frame rate so the audience could vote on which half looked better. Guess what.. 24 fps won. I was one of about 10% of the people who preferred the high frame rates (it was stunning). The 'Film' guys (and these guys make apple fanboys look like sissies) were absolutely emphatic that the 24fps looked better,
3. Too much industry knowledge is tied up in 'FILM' and the act of 'FILMING'. It is hard for most DOPs, cameramen, etc to move to digital even when the digital is at 24 fps much less to anything else. Some of these guys still think in inches and feet of exposure, not frames.
Why are Blu-ray's logos always so hideous?
Forget 3D glasses. How about 3D contacts. I'd wear them. Then, there is no more bitching. PLus you could do like snake eyes and crap. Kids would get a kick out of that. Spongebob design 3D contacts. Just an Idea.
@zoran123
That might work for polarized lenses (the kind of 3D glasses you see in theatres), but the theatres wouldn't like it because you wouldn't be able to reuse them -- or at least I hope they wouldn't try to reuse 3D contacts. 3D in the home will be achieved using active shutter glasses, not light polarization, so unless the contact had a shutter (which would entail a power source and a way to receive a signal to stay synced with the TV), I don't really see how that would be possible anywhere in the near future.
@John H Actually they are already announcing and selling Polarized displays for home, but for the most part displays using shutter glasses are going to be way more common as they are easier/cheaper to make.
@RandomGuy
That surprises me. I would have thought a polarized 1080p display would be impossible. That would essentially mean the display would have to output two images simultaneously, each polarized differently. I could imagine if you had a TV that was displaying each frame one after the other that a light polarizer might be able to switch fast enough to switch the polarity as well, but if the frames aren't being displayed simultaneously then you might as well just use active shutter technology and dispense with polarization.
The other thing that puzzles me about a polarized display is a question of resolution. Given that a pixel is by definition the smallest image element of a display, that would mean that a given pixel could only be polarized a certain way at a given time (and only be displaying a certain color at a given time). Therefore in order for a polarized display to display 3D, it would either need to have a resolution greater than 1920x1080p (in order to display full 1080p to each eye) or it would need to only output 1080p total resolution, which would obviously mean half as much resolution per eye (achieved either in reduced horizontal or vertical resolution) and would therefore also require discarding half the image data in a 3D image stream.
Do you have any more information about these polarized displays? This is the first I've heard about them and I'd be curious to find out more.
@John H
The reason why RealD works in movie theaters is because they are NOT showing both images at the same time. They are actually doing the same thing as what you would expect from a display in the shutter set up. However each lens in the polarized glasses sees the individual frames.
If both were projected on the screen at once I'm pretty sure the composite result of both projections would be seen by both eyes.
P.S. I may be wrong.
@John H The polarized models are LCDs that I have seen. Since LCD glass is naturally polarized at one angle, I imagine all they are doing is essentially layering two LCD screens at different polarization angles. Dunno if they could both be active at the same time, or if they have to turn one clear for other to work. Here are a couple links for LG models. I am sure all LCD vendors are working on polarization systems since there are so many drawbacks with shutter.
http://www.engadget.com/2009/12/15/lg-expects-to-sell-3-8-million-3d-lcds-by-2011-partners-with-ko/
http://www.engadget.com/2009/06/18/lg-readies-first-47lh50-3d-lcd-tv-just-29-999-999-to-go/
Since there doesn't seem to be a Source link on this article, I'm wondering where the information came from that 3D Blu-ray would be either 30 or 60 Hz per eye. Given that all the 3D TVs we've been reading about have had refresh rates of 480 Hz, that to me signals 240 Hz per eye, which is obviously a multiple of 24. Even if it's only 120 Hz per eye, you STILL have a multiple of 24.
Ben, care to let us know where you're getting this frame rate information? I find it hard to believe that the industry would require everyone to go back to 3:2 pulldown.
@John H
I had a meeting with BDA representatives Andy Parsons and someone from Panasonic, and this is what I was told.
@BenD
Well then that really blows. I would've thought that the most logical (and easiest) thing to do would be to essentially have 2 sets of 24p streams on the disc, given that that's how the film was shot in the first place. Then the BD player could output the video at 1080p48, which the TV could then display at 240 or 480 Hz to take care of flicker. Did anything from the BDA meeting clue you in as to why they're NOT going this way? It seems that using 30 or 60 Hz to each eye would require increased complexity for a lower quality result.
@John H
Sorry should've read your comment more closely (wasn't focused on the technical part).
The movie is stored on the disc at 1080p24, which is the only supported resolution. My gripe is that the TVs are all 1080p30 or 60 and so we have to use 3:2 pull-down. Obviously the main problem is with the displays, but I still think the BDA should've supported more than one frame rate on the disc.
@BenD
I understand that the current BD spec only allows 24 fps when the resolution on the disc is 1080p (and I certainly agree more frame rates should've been supported), but I had assumed that the 3D BD spec would make that exact revision to allow two 24p image streams (or one 48p depending on how you look at it).
But TVs are not all 30 or 60fps at 1080p; my Kuro can accept a 24p signal and display it 72 Hz, as you yourself mentioned in the article, and I believe all TVs that support 24p except perhaps the earliest ones do something similar. It wouldn't make sense for a TV to support a 24p input only to perform 3:2 pulldown in the TV; the BD player might as well have done that itself.
@John H
Right, so the 3D BD spec defines that the encoded video is 1080p 24 frames per eye. And you are probably right, the pull down is done in the player not the TV. Either way it is function of the player, but also the TV which would have to accept 1080p24 per eye. I'll ask more about this when I stop by the TV booths and ask about specific implementations. But honestly it seems like most of the hardware details are not finalized so we may have to wait until the product ships.
@BenD
Ok, 1080p24 per eye makes much more sense. That to me translates to a total display rate of 1080p48. In that case, it seems to me that this will be accomplished without pull-down; 3D-capable Blu-ray players will simply be required to support 1080p48 output when playing 3D content, and 3D-capable TVs will be required to accept a 1080p48 input. Problem solved, no pull-down required. I really hope that's the way it goes, and honestly it just makes the most sense. It's how the film was shot anyway, and it's the least amount of effort for the best result.
@John H
I'm not following you. If the content on the disc is 1080p24 per eye and the display does 1080p60 per eye, how is there no pull-down?
@BenD
What I'm saying is that the display WOULDN'T be doing 1080p60, per eye or total. I assume that 3D TVs would simply be required to accept 1080p48 (24p per eye) and display it at a 240 or 480 Hz refresh rate. That would equate to either 120 or 240 Hz per eye, each of which is a clean multiple of the 24p feed each eye is getting.
@BenD There really is no problem here. The Blu-ray stores 2 X 1920x1080p24. The HDMI 1.4 3D video signal has vertically enlarged frames, basically 1920x2205p24, capable of carrying the 24 left and right frames per second to the TV. This 1080p24 3D video mode is mandatory for HDMI 1.4 3D TVs, as is 720p50 and 720p60.
Now, what the TV or projector is doing with the 2 X 1080p24 streams it receives from HDMI is completely up to the panel's capabilities. It could do 144 Hz, doing a 3:3 pulldown for each eye. Or it could run at 120 Hz, then it would have to do a 3:2 pulldown for each eye.
TVs that accept 1080p60 in 3D are a long way out. There is almost no hardware that supportes the required 300 MHz over HDMI, most max out around 220 MHz.
@John H
I agree the TVs could do that, what I'm telling you is that no one is saying that is what they are doing. Panasonic seems to be willing to give the most details and they told me it would be displayed at 60hz per eye.
Obviously higher refresh LCDs might have better options, I'll ask Sony when I get the chance.
@Scarabaeus
Yes I realize that that 1080p60 per eye is a ways off. My point is that many of the TVs will be doing 3:2 pull down which is obviously not preferred.
@BenD
Understood. I would certainly hope that part of the 3D certification process for TVs includes having a 240 Hz or better refresh rate in order to display the content without 3:2 pulldown. Seeing as there are already 240 Hz 2D TVs out there, I don't see why it couldn't become a requirement. Otherwise you'd enter into this whole "3D-capable with pulldown" nonsense, as if customer confusion weren't already high enough. I say make it a requirement so that all 3D TVs display content properly without pulldown, and I hope the people in charge of the spec have arrived at the same conclusion.
@John H
Ok I went by and asked the TV people (as apposed to the BDA) and luckily I was wrong. Sony's 3D HDTVs will display at 120hz per eye so 5:5, while Panasonic's will be 48hz per eye.
The BD player outputs 24p per eye, it is up to the TV to display it properly, so like before, the HDTV is the important component.
@Scarabaeus Let me get this straight, as there is some confusion everywhere. For uncompressed video, including blanking regions:
1080p/60Hz/24bit = 148.5 MHz pixel clock
1080p/60Hz/36bit = 225 MHz pixel clock (what state of the art HDMI RX can do)
1080p/120/8bit, 2k/60/8bit or 1080p/60Hz/48bit = ca 300MHz pixel clock
1080p/24Hz/24bit = 74.25 MHz pixel clock (typical BluRay output)
For any "it's the same experience" 3D, just duplicate the pixel clock. And yes, you are right that 300MHz is something nobody supports yet, but it is in the planning for most silicon vendors. And the reason is 2k formats, something for what the BluRay is not suited for. At least not in this rev.
Hmm... sounds like par for the course in regards to the BDA. Put out a half-assed 1.0 now and then just fix it later knocking out compatibility with the prior spec.
You just need to buy a 360hz or 720hz LCDs/plasma.
@(Unverified)
Actually 240hz or 480hz sets should handle 1080p/24 per eye without pulldown.
It's only 60hz (30hz per eye) and 120hz (60hz per eye) sets that would require 3:2 pulldown. This is the point of Ben's post.
So I get that 3D Blu-ray discs may not be backwards compatible with older 2D only Blu-ray players, but how in the hell does that mean you will have to watch a movie on a 3D disc in 3D?
It sounds like they are jumping to a conclusions there. Logically it makes sense that an older player may not handle the new standard of data on the disc, but any newer 3D player (and 3D display for that matter) is going to be able to switch to a 2D mode by simply ignoring the frames meant for one eye. It would be simple to do and insane not to do.
@RandomGuy
Not jumping to any conclusions here, I asked that very question in a direct way and was told it would be a function of the player and that in some cases the 3D movie could only be played back in 3D. I supposed it is possible that the BDA representative (not PR person) was mis-informed, but I highly doubt it because of his position in the BDA.
@BenD Well I will take yours and his word for it, it just seems crazy that's all. I know that when shopping for a 3D TV I will make certain that the display has an option to turn off 3D, just in case I can't trust Blu-Ray players to be able to.
I have to echo what several have already suggested -- you are getting confused in the second half of your article. Frame rate vs. refresh rate. You have it correct initially when talking about how a higher REFRESH rate makes a given FRAME rate less flickery, e.g. 24 FPS played back at 120HZ. Yes, newer cameras can record at higher FRAME rates but that is an aesthetic choice (filmic look or soap opera look).
Of course the HDMI spec does not allow for higher 3D rates either. Or true 120Hz content.
@IanKen The HDMI spec (actually the CEA 861 spec) supports 720p and 1080i/p up to 100 and 120 Hz, and 480i/p/576i/p up to 200 / 240 Hz since August 2008. It's true, not very many TVs have implemented this so far.
(Oops, march, not august 2008)
doesn't anyone see that we come close to full HD TV broadcasts and yet we are already being pushed into 3D format?
@(Unverified) TV OEMs have come up with a "marketing" barrier. I was translating a TV OEM webpage on marketing terms, and as far as I can tell you, I came up with these conclusions:
1) They do a lot postprocessing because their LCD panels are moot
2) Mid range TVs had features like rotating displays or nice bezels
3) The higher end TVs do things with your local network, be it widgets or DLNA client
They do not come up with following information that would be relevant for most of the normal people:
a) Quality of the deinterlacer, as most of the TVs do something like line doubling. Most of the broadcast I can receive in my country are 576i or 1080i, and I can tell you sports look horrible on them.
b) Quality of the scaler. Again, most content is broadcasted in 576i. And some TVs just do simple algorithms.
c) How many bits can the panel represent. What is the point of letting something like the PS3 send you a signal at 36bit per channel if the panels usually can do 15bit/18bit? Please remember the BluRays are still 24bit per channel.
d) Does the panel have a glossy or mate finish?
No consumer grade TVs show any indication on these points, that I think, are the most important ones unless you only see BluRays. I understand that these four points are difficult to understand for most TV buyers, so TV OEMs came up with something that the average buyer would understand: 3D TV. Compare that with what Panasonic and Philips have been doing in the latest years: Ambilight and 24:9 TVs.
I'm probably the only one but, from my perspective, consumer based 3D technology in BluRay players and TV's doesn't capture my interest at all. As an avid consumer of higher end ado/vdo components, I'd rather see the electronics industry invest more R&D in something more practical or by perfecting current technology as opposed to trying to mass capitalize on something that is really best suited to large movie theaters.
For some reason I can't seem to get excited about 3DTV. I've read reports from CES. I've seen video demos. And I just can't imagine myself putting on glasses to watch TV. It's not like a movie theater where I'm captive, and pretty much in my seat for the duration of the presentation. At home, I'm up between commercials, jumping onto a computer, doing stuff around the house. And what if friends or family come over? Do I have to have special glasses for all of them too? I dunno, the whole thing seems like more trouble than it's worth for regular every day viewing. If they were able to pull off 3D without the glasses I *might* be more interested. Right now I'm just totally unenthused about the whole thing.
si will i need a new a/v receiver?
@danhawk911 I really hope not; that's one part of my setup that definitely does NOT need replacing! My receiver has an option to pass through HDMI video without scaling, so I hope it will be able to do the same with these new 3D signals. However, it does add a volume bar to the picture, so who knows...