Goodness gracious me. XKCD’s author has come up with a list of approximations for all sorts of constants and numerical values using all kinds of unintuitive formulations. For example, he offers as a close (1 part in 25,000) approximation of Avogadro’s Constant 69π51/2. Check out the easily memorisable formula for deriving the White House Switchboard’s phone number!
How on earth did he work all these out?
Trying to make sense out of what a passive 3D TV is doing, and how we as human beings are seeing its results, is not an easy thing to do. It is complicated by changing standards, misunderstandings, the inability to capture though photographs what’s going on, and the additional layer of complexity due to processing in the brain.
Thanks to commenter Ryan I have had a number of interesting pieces to read, mostly ones which are of the view that LG passive 3D TVs provide full resolution. I remain of the view that this is not correct, after closely examining a new LG passive 3D TV last week. But to make this clearer, I might need to change terminology and stop using the word ‘resolution’, since this is very confusing.
But, before going any further, I must add that I am talking about this subject kind of in isolation from the whole 3D package. In my opinion, the biggest influence on 3D performance is the level of crosstalk or ghosting. The greater the resistance of a technology to this, the better it looks. Ghosting (the breakthrough of left eye information to the right eye and vice versa) confuses the systems in our brains that assemble the 3D composite.
The best 3D I’ve seen so far is active (ie. flashing glasses) available from DLP front projectors. Passive 3D direct view TVs are either equal with, or very closely behind, these. Then a bit further back is direct view plasma (again, active), followed by various active LCD and LCoS systems, both direct view and as front projectors.
One day the whole resolution question on passive 3D TVs will be moot, because eventually double resolution panels will be used so that a full 1080p will be provided to each eye.
But for now, to be entirely clear, if someone said to me that they want a 3D TV with a real emphasis on great 3D performance, I’d recommend a passive one to them, but note that a plasma active system is also very good, while the latest crop of reputable active LCD TVs are quite reasonable.
Some people writing on this subject seem to find the rapid flashing between left and right eye of active systems to be troubling. I don’t at all. But if you do, then clearly that’s another reason to go passive.
Resolution
Now one problem with the discussion so far is the word resolution. One article goes so far as to use it in a highly idiosyncratic way as to include the third dimension of time as part of a definition of resolution.
Me, I like to keep things apart. I use ‘resolution’ in two ways: to list physical specifications, and as a proxy for what might be called picture detail. These aren’t always exactly the same thing.
A Blu-ray disc has a physical resolution of 1,920 by 1,080 pixels. A full HD TV has a physical resolution of 1,920 by 1,080 pixels. With, these days, the default playback settings and a HDMI connection, there is 1:1 pixel pixel mapping between the two.
But there is more to a picture than simply taking one pixel from the disc and putting it in the matching place on the screen. For example, you don’t get a whole lot more effective resolution from the Donnie Darko Blu-ray than you do from the DVD because the source material is relatively low in detail. In that case, a high resolution format is being used to carry low resolution content.
Of course, most Blu-ray content makes considerable use of the 400% increase in the number of pixels compared to (576i) DVD.
So perhaps we ought to talk about data.
And, at least up until recently, and depending on the setting of your TV, data used to get thrown away by passive systems. Depending on how you want to define it, either half the data was thrown away, or up to a half the data was thrown away.
On a rough examination, ‘half’ is the obvious answer. A Blu-ray 3D disc carries two sets of 1080p video content, one set for the left eye, and one set for the right. In 3D mode, a basic passive TV is only capable of showing half of the lines available for each eye. Every second line is blanked out. It has, for each eye, a physical resolution of 540p.
Which lines are blanked out?
I had a strong view, based on my examination of a Toshiba passive 3D TV that the same line was shed from both the left and right eye views. That is, that what you saw was either all the odd lines, or all the even lines, in both eye views.
The general underlying assumption of much of the writing you see around — without it necessarily being explicitly considered — is that it is the other way round. That is
, that the left eye sees, say, all the odd lines and the right eye sees all the even lines.
To try to work out which view is right, I developed a simple test pattern and displayed that on a new LG TV at the company’s new product launch last week. This seemed to indicate that this second approach was the strategy being used: that is, that one eye sees all, and only, the odd lines and the other sees all, and only, the even lines.
I say ‘seemed’ because I was rushed (this was right at the tail end of the formal demonstrations and I had only minutes to spare before having to leave for my flight home). Of course, over the next couple of days I started thinking of variations on the test pattern that would have corroborated my finding.
Furthermore, since then a new possibility has arisen. I’d thought of this, but dismissed it as too unlikely. That is, that both the odd and the even lines were being shown. There would be two ways of doing that: either by merging each odd/even pair into a single new line and showing that, or alternating between the two rapidly.
It turns out that in the last few months LG has introduced a firmware upgrade that does just that. According to a number of websites which apparently quote LG:
Before the Cinema 3D technology worked like this: During a time period of 1/200 seconds the TV showed 2 frames; 540 lines for the left eye and 540 lines for the right eye. The new algorithm shows 4 frames instead of 2 during the 1/200 second time frame. It shows 1080i for the left eye and 1080i for the right eye.
When these are combined the two pictures create a 1080p picture according to LG. LG believes that this update improves picture quality on their Cinema 3D TVs to compete directly with the active 3D TVs such as 3D plasma TVs. You need to turn off TruMotion to utilize the new algorithm. See the illustration below.
And here’s the picture, which again I assume originates from LG:
So we have an explicit statement that previously (or still, unless you switch off the TruMotion frame interpolation system) 3D worked by discarding every second line. Now (if you switch off TruMotion) you get the odd and even lines flashed extremely rapidly in 3D mode up onto the same display line.
I do not know what the setting was for the TV I examined last week. I didn’t know about this firmware upgrade then. It is possible with the test pattern I used that what I saw was in fact both lines flashing rapidly between each other. But for the time being I am going to assume that the passive image we are talking about consists of odd lines only for one eye, and even lines only for the other. One day I will return to LG’s firmware upgrade.
Now Dr Soneira argues that when your eyes see the left and right images, the content is piped into your brain and your visual processing circuits perform something he calls ‘3D Image Fusion’.
No argument from me. Obviously your eyes do take in separate images that are similar, but not identical. But you do not see two separate images, you see one with certain characteristics which give you a sense of depth. The parts of our brains which process vision do so in such a way as to provide useful, actionable sensory information. And that’s what it has settled on to help us deal with information about proximity.
Dr Soneira then posits that as part of the process of 3D Image Fusion, the content from the half-resolution left and right eye images are merged together in such a way that the brain effectively constructs a full resolution amalgam.
This makes a certain degree of sense, and there are cases where you would think it would work rather nicely. But in those cases it simply doesn’t.
Again I took with me to Sydney to the LG launch my trusty Blu-ray 3D disc of Cats and Dogs 2: The Revenge of Kitty Galore. You will recall that the point of interest with this is its main menu:
Although 3D, most of it is presented flat, with no left/right parallax differences. I popped the disc into a Blu-ray player, displayed the menu, and invited one of my editors over as witness. There were the jaggies I’ve previously mentioned, and the loss of detail on the dog’s fur. Because the image is flat, you can slip the glasses on and off to check the difference.
I carefully stood at various ranges, including 3x screen height (it was a 55 inch TV, so the range for that is two metres), plus even further back. The jaggies and loss of detail were easily visible at all ranges. With both eyes open of course.
Dr Soneira allows that 3D Image Fusion fails sometimes (scroll up three paragraphs):
3D Image Fusion may not work well when there is insufficient image context to allow the brain to pair up the parallax from the right and left eye images. With FPR that happens when there is content with very thin nearly horizontal line structures that occur in high contrast situations.
As an aside, he is surprisingly forgiving of this (‘That’s generally acceptable because they are seldom noticeable and every technology has at least some occasional issues and limits.’)
But the failure does caste doubt on his thesis in my view. Here are two possible explanations for his observed phenomena:
I think you can make a reasonable case for 2.
I note that in Dr Soneria’s discussion of fusion failure, he discusses some scenes which exhibit moire. But as it happens, the appearance of moire is precisely what I use as a marker for poor progressive scan conversion of 576i50 DVDs, and 1080i50 Blu-ray discs! It is too uncertain in my opinion, even with a close viewing range and a full HD front projector, to determine whether a deinterlacer is correctly weaving the fields of progressive sourced content together, or incorrectly treating them as video sourced and therefore bobbing together any moving content. The latter means that half the resolution is being displayed at any instant.
I discuss this fully here. But here is an illustrative image from the 576i50 test clip I constantly use for testing TVs and various disc players. Top is the full frame, scaled down to fit. The bottom three are unscaled from the source and are, left, the two fields properly woven together, middle, the field containing the odd lines only, and right, the field containing the even lines.
Moire on near horizontal diagonals is actually a clear marker of half vertical resolution.
Two thousand words is enough for one blog post, even though I haven’t covered everything. So I expect to return to this subject. But I might hold off until I’ve got my hands on a new LG passive 3D TV for a week or two. Then I can run a bunch of tests, real world and test pattern, to either enhance, or perhaps overturn, my present view.
Channel 9 sought a license for a trial broadcast of the 2012 London Olympics in 3D, and ACMA has approved it. The trial begins on 16 July and is open for a month, covering the games which run from 27 July to 12 August 2012.
All you will need is a 3D TV. A HDTV PVR which supports MPEG4 will happily record the content for later playback.
Oh, and you also need to be in Adelaide, Brisbane, the Gold Coast, Melbourne, Perth or Sydney.
WIN TV, which will be broadcasting the Olympics in ‘Regional’ areas, like here in Canberra, Newscastle, Hobart and such, did not seek a license and will not be broadcasting in 3D. The reason is actually simple: it would have needed dozens, perhaps hundreds, of new transmitters to deliver something which will only be in place for a few weeks. Not exactly an economic proposition.
I’ve pasted the ACMA press release over the fold if you want to read the details.
Continue reading
I’ve just been on the telephone to the Australian Communications and Media Authority (ACMA) to ask about whether the 2012 London Olympics, which is being filmed in 3D (using Panasonic equipment, so says Panasonic) will be available on free to air in Australia.
It turns out that ACMA will be issuing a press release within hours, but that I have the scoop. Yes, it is happening and will be on Channel 9.
Word to come later (today, I’m hoping) on any conditions, and whether it will include regional Australia (such as here in Canberra).
Update (twenty minutes later): Wondering how 3D TV works and what you need for it? Well, you need a 3D display
, and a HDTV receiver with MPEG4 support. That’s it.
As to how it works: I’ve uploaded my previous Sound and Image article on that here (also accessible from the ‘Articles’ menu item above): How 3D TV Works
My woefully out of of date Dictionary of Home Entertainment has been translated into Finnish (with my permission). See it at www.designcontest.com/show/dictionary-hifi-fi.
The plot thickens. I have now had the
, ahem, pleasure of reading the US Council of Better Business Bureau’s National Advertising Division’s finding in the case of Samsung Electronics and LG Electronics.
Much of its 22 pages deal with other advertising claims made by Samsung, some of them silly and which the company readily withdrew, and at least one which NAD held to be well-founded, and which Samsung is therefore entitled to continue to make.
But I am only interested in one claim, which a still substantial part of the report deals with: do passive 3D TVs only deliver half the vertical resolution?
NAD correctly noted that this matter was to a large extent a battle of the experts. But, to cut a long story short, NAD appears to have allowed itself to be persuaded by LG’s case that they do indeed deliver the full resolution. Incidentally, one of the experts on Samsung’s side (ie. that passive 3D is half resolution) was the famed Joe Kane. Indeed, Samsung lined up several studies that, as far as I could tell from the summary in NAD’s findings, seemed pretty solid.
At this point, I think that this is an incorrect finding. I am still working out some tech stuff relating to this, and what makes this case somewhat frustrating is that in the whole damned document, there was only one semi-clear statement of how passive 3D TVs work, and it flies in the face of all my previous understandings! I may write more on that later, but I’d want to quote it properly and I can’t find how to cut and paste from a PDF on my iPad (or perhaps the document has copying disabled).
Tomorrow I am going to LG’s 2012 product launch armed with some test material and I’ll try there to get some answers.
(PS. I’m writing this on an iPad in the back of a minibus taxi, on my way to Samsung’s product launch, so I ought to be getting both sides of the story.)
In my post ‘Sorry, but it is half vertical resolution‘ I claimed that my tests support the view that passive 3D TVs, with current technology, provide only half the vertical resolution of active ones. I made reference therein to an excellent and detailed article, ‘3D TV Display Technology Shoot-Out‘, by Dr. Raymond M. Soneira, President, DisplayMate Technologies Corporation in the US, but disagreed with one aspect of it.
Dr Soneira has kindly responded to my email.
Before getting to that, I shall summarise. By my reading Dr Soneira’s article seemed to suggest that passive 3D TVs effectively produced full vertical resolution because the human eye/brain mechanism can knit together the half resolution content delivered to each eye into a full resolution picture. I disagreed because for this to be true, then the left and right eyes would have to receive different scan lines: say all the odd ones for the left eye, all the even ones for the right eye. But my tests suggest that they both receive the same scan lines in 3D mode: odd for both eyes or even for both eyes. My blog post explains my reason for thinking this.
Here’s Dr Soneira’s response:
First of all, I didn’t make any assumptions. I used an extensive series of specialized test patterns to examine the vertical resolution issues in detail.
Second of all, my article has been thoroughly examined by a very large number of top display experts, including the engineering departments of LG and Samsung. No one has found any technical flaws. While Samsung does not like my results, my 3D article was used as the central technical exhibit in an extensive 4 month investigation with extensive expert testimony by many display experts in an arbitration battle on this 3D half resolution issue between LG and Samsung in the USA. The ruling was against Samsung’s claims of half resolution – and my 3D article was the central technical exhibit that convinced the NAD to rule for LG and against Samsung’s half resolution claims, which were thrown out as without technical merit by the NAD. As a result of this arbitration decision Samsung has agreed to end those claims in the USA, although they disagree with the conclusions of the NAD.
The above is the best explanation as to why my 3D article doesn’t have errors – Samsung couldn’t convince an independent arbitration organization, and the NAD ruled that my article conclusions were valid.
Here are links to the Press Release Announcing the decision:
NAD RECOMMENDS SAMSUNG DISCONTINUE CERTAIN SUPERIORITY CLAIMS FOR 3D TELEVISION
NAD Press Release: http://www.narcpartners.org/DocView.aspx?DocumentID=9039&DocType=1
NAD website with Press Releases: http://www.nadreview.org/
First, I must apologise. I did use ‘assumptions’ as a sloppy shorthand in my email to him. In fact, his article is highly detailed and thoroughly researched. Which is why I find it so intriguing that our results differ on this point.
As to the other matters, they do not address my contrary findings. The next time I have a passive 3D TV to hand, I shall create some special test patterns to determine unambiguously whether in 3D mode such TVs deliver the same scan lines to each eye
, or alternate ones.
As for the NAD’s findings, I’ve addressed this in some detail in the previous post and, at least as far as the press release goes, the ruling did not seem to be definitely ‘against Samsung’s claims of half resolution’. It seemed to be against Samsung making those claims of half resolution because it would give the impression that passive 3D tech was inferior, overall, than active 3D tech.
At this point, I should note that I am open here to a complaint of too closely examining the text of the press release. Can I just say that I’m pretty good at bureaucratese and legalese, having worked in relevant areas for a number of years. Words in these things are usually chosen very carefully, so they have to be read very closely if you are to understand them. Nonetheless, my understanding here is preliminary. I have asked NAD for a full copy of their findings which will allow me to get a better understanding.
Dr. Raymond M. Soneira, President, DisplayMate Technologies Corporation in the US, has drawn my attention to a finding by the National Advertising Division (NAD) of the Council of Better Business Bureaus in the United States. This body has recommended to Samsung that it cease certain advertising claims with regard to the claimed superiority of its active 3D technology compared to the passive technology of some of its competitors.
Here is the press release.
NAD performs an industry self-regulation function with regard to advertising claims.
What does this mean? I have sought a copy of the full decision because the press release suggests that the findings are not quite as clear as one may have thought. Meanwhile, I shall soldier on based on what the press release says.
At issue were a number of claims in Samsung advertising in which its active 3D tech was asserted to be superior to passive 3D tech. Amongst those claims, as reported by NAD, were:
- ‘There are many differences between ACTIVE 3D and PASSIVE 3D technology, but the primary variance is the quality of the home 3D experience. PASSIVE 3D technology uses glasses that effectively cut 1080p resolution in half (540p) to each eye. Samsung ACTIVE 3D glasses deliver the Full 1080p HD experience to both eyes.’
- ‘Passive 3D TV’s, with patterned film on the screen, will not be able to deliver the detail.’
- Active Full HD (1080P Full HD) is ‘2 Times Better!’ than Passive (540P No Full HD)
- ‘Active 3D. A clear winner with two times the resolution.’
- ‘Jagged Lines!’ (in reference to 2D picture quality produced by passive 3D televisions)
The last point is obviously silly. Yes, passive 3D TVs do produce jagged lines on 2D content … but only if you watch 2D while wearing 3D glasses. I have not mentioned another couple of claims which Samsung voluntarily withdrew, and one on viewing angles in which NAD came down on Samsung’s side.
The rest are pretty much to do with the half resolution issues, which I discussed in my Blog post ‘Sorry, but it is half vertical resolution‘.
By my reading of the press release, NAD did not unequivocally find against this half resolution claim, but nonetheless recommended that Samsung discontinue making them.
How could this be?
In this way: NAD in adjudicating advertising claims ‘strives to ensure that denigrating claims are truthful, accurate, narrowly drawn and that they do not falsely disparage a competitor’s product.’
In assessing the evidence in this case, NAD found ‘that consumers receive full 3D imaging and may enjoy the 3D television experience with both parties’ technologies.’ I’d interpret that as meaning that both do a good job, which I’d agree with. They have different strengths and weaknesses.
Samsung attempted to argue that its half-res claims ‘did not convey a message about ultimate picture quality’ — in other words, that it was in fact a ‘narrowly drawn’ claim, and thus not ‘falsely disparaging’ the competition. But NAD found that the half-res point did convey that message.
The press release does not say that NAD made a finding on the half res point. Here’s all it has to say on the matter:
Further, while Samsung asserted that its claims are literally true, NAD determined that the claims at issue – even if accepted as technically true – could reasonably be interpreted by consumers as conveying messages of superior overall 3D picture quality.
I don’t read that as reporting a finding that full 1080p resolution is provided by passive 3D panels.
Nonetheless, Samsung has agreed to comply with NAD’s recommendations
, despite it maintaining the view its ‘claims that Active 3D technology is capable of delivering superior resolution compared to Passive 3D are fully supported by technical and scientific evidence.’
That is a claim with which I also agree.
A while back I analysed the lossless audio encoding of a few hundred Blu-ray discs. The aim? To find out how efficient lossless compression of 24 bit audio was compared to 16 bit.
The results were not entirely unexpected. The first 16 bits score high compression ratios. The next eight bits score low ones.
The reason? I posit that most of the least significant eight bits are simply encoding noise. Noise is random
, and so unpredictable. The efficiency of the lossless algorithm depends heavily on predictability. Therefore, much or most of those eight extra bits do not compress well.
Here’s the full article (a version was previously published in Sound and Image magazine).
(I’ve also changed the menu bar above so that this kind of thing will now appear, along with the ‘Sharpness‘ piece, under ‘Articles‘ above.)
Last night I went to see The Hunger Games at my local cinema, Limelight at Tuggeranong. After my disappointing experience a couple of months ago, I was a bit worried that I might not enjoy the movie due to picture quality.
Different screen within the cinema, though. I was at Screen 1
, and the black levels were quite respectable, without any evident light splash onto dark areas of the picture from light sections.
By respectable, I mean nothing like the best of home theatre projector black levels, but certainly not bright enough to be distracting. There seemed to be a bit of image smearing during fast camera pans that looked to me like it was caused by the projector response time, rather than during photography, but that was only a couple of times.
