https://elvum.net/ life, tech, ponies and pie en-us Nucleus CMS v3.65 © Weblog http://backend.userland.com/rss https://elvum.net//nucleus/nucleus2.gif https://elvum.net/ https://elvum.net/index.php?itemid=34 this article for Slate, that "3D" always has and always will hurt your eyes, is a case in point. Mind you, it's always nice to hear some dissenting views about an industry trend with no shortage of enthusiasm associated with it.

I find it interesting that Daniel finds viewing 3D films uncomfortable - an experience that to some extent I share when watching 3D in regular cinemas which use a single projector (rather than one projector each for the left and right-eye views). These projection systems display the two views of each frame sequentially in time, and use a polarising or spectral filter that flips in synchronisation with the projector along with polarising or spectral filter glasses to perform the "separation" that ensures left-eye images are seen only by the left eye (at least in theory) and so on.

Personally, I see a characteristic "shimmer" when viewing such "time-sequential" 3D systems that is most obvious when I move my eyes around the picture. During this kind of "saccadic motion", the human visual system effectively switches off (or otherwise ignores) much of the signal coming from the eyes, in order to prevent you from experiencing a sensation of motion as your eyes move from place to place. If you're watching a time-sequential 3D image, that means each time you move your eyes, they effectively "switch" off and on at times that are completely unsynchronised with the projector, and there may be a perceptible period during which one eye sees no light at all, leading to the perception of flicker in one eye. It's just a personal theory that this is the cause of the "shimmering" I perceive and a contribution to eyestrain, of course, and if any visual psychologists happen to read this, I'd love to chat about it. But the point here is that this is a minor limitation of current projection technology. It's not a fundamental limitation of stereoscopy.

Daniel is wrong to claim that fundamental advances in 3D technology have not been made in the last 50 years though. Film projectors (and cameras) suffer from registration problems: the mechanisms that move the film behind the camera or projector shutter are mechanical, and there is always a certain amount of inaccuracy in the positioning. If the two images in your stereoscopic 3D presentation dance around the screen due to poor registration, that's going to cause major eyestrain. Digital cameras and projectors have no such moving parts, and the single-lens, time-sequential method of projection in particular ensures that the two eye-views are perfectly overlaid without requiring careful calibration. But there are plenty more ways to give people headaches than with poor registration.

For example, as Daniel correctly points out, viewing a stereoscopic image is fundamentally different to viewing a real-world scene, in that the convergence of the eyes and the distance at which they are focussed is decoupled in the former case. This is an extremely well-known issue, and there are a number of ways of dealing with it artistically: keeping things that the audience will want to concentrate on (usually the expensive actors) at a depth close to the screen, for example.

In the long term, I'm not entirely convinced this will still be an issue: anyone who's ever worn glasses has learned to adjust to a different relationship between convergence and the focussing of the eyes - the whole purpose of glasses is to change the way your eyes focus, after all. People with varifocal glasses learn (and usually learn late in life) to cope with lenses in front of their eyes that cover a whole range of focal lengths depending on the part of the lens they look through, which also effectively decouples convergence and focussing.

Stereoscopic film and television is an evolving, immature medium. It's ludicrious to claim that it would be the ideal medium for every genre that we have now (after all, those genres evolved to suit the medium of 2D film and television). But I think it is equally ludicrous to claim that its well-known limitations will lead to inevitable audience discomfort. There are plenty of technological and artistic challenges to be addressed, particularly if broadcasters want to start 3D television services, but I don't think there's a fundamental discomfort issue that precludes the success of the medium.

Oh, and as for the idea that stereoblindness might preclude the success of stereography - did colour blindness preclude the success of colour?]]> General https://elvum.net/index.php?itemid=34 Wed, 15 Apr 2009 16:12:09 +0100 https://elvum.net/index.php?itemid=32 BBC Research had a fantastically successful time a couple of weeks ago at IBC, Europe's huge annual convention and conference for the broadcast community. We went there to shake things up a bit, feeling that proposals for improving the quality of television (including High Definition television itself, frankly) had concentrated too much on improving the spatial resolution (the number of pixels) while completely ignoring the temporal resolution (the number of frames per second). Television is, after all, about moving pictures.

By the end of the week, we'd shown our demonstration of the benefits of higher frame rates to hundreds of people, who almost without exception agreed that the improvements were very clear. Our criterion for success was that we'd get higher frame rates on the agenda for consideration in future TV standards, and I think we certainly achieved that. We're looking into what to do next, including finding a way to display images at frame rates higher than 120fps (the upper limit of all the contemporary displays we're aware of* - we've been using projectors designed for alternating-frame stereoscopic 3D so far), investigating how increasing the frame rate of video improves the efficiency of video codecs, experimenting with changing the temporal shape of camera shutters (simulated by down-conversion from high frame rates to conventional ones), and verifying our assertion that shooting at higher frame rates doesn't increase the visible noise in the video signal. Problem is, we really want to do some more work on 3D television, too...

We've published a White Paper on our initial work, available here. It's quite short, contains no maths, and would interest (I hope) technically-minded people from both inside and outside broadcasting. Similarities between the historical section and this post need not be pointed out. :-)

*we have CRT monitors that can go up to 200fps, but not at any kind of sensible resolution.

EDIT: We made it into the "press"! Woo! :-)]]> BBC https://elvum.net/index.php?itemid=32 Thu, 25 Sep 2008 14:01:41 +0100 https://elvum.net/index.php?itemid=31

1. Download the ip4500 driver software from Canon - I used version 2.80, available here. You'll need both the "cnijfilter-common_2.80-1_i386.deb" and "cnijfilter-ip4500series_2.80-1_i386.deb" files.


2. Install both these packages, starting with "cnijfilter-common_2.80-1_i386.deb". I got no error messages at this stage.


3. Restart the CUPS subsystem - from a command prompt enter "sudo /etc/init.d/cupsys restart"


4. Launch the KDE "System Settings" application and select "Printers".


5. Select "Add Printer/Class" from the "Add" menu.


6. Click "Next" and choose an appropriate backend. My printer was plugged into a Buffalo Linkstation on my local network, so I chose "Remote LPD queue" and then entered the hostname and queue name ("lp") appropriately. If you have a firewall installed on your machine, you'll need to enable outgoing lp traffic before doing this.


7. In the "Printer Model Selection" dialog, select "Other", and then choose "/usr/share/ppd/canonip4500.ppd".


8. This would be a good point to print a test page, as offered by the printer installation wizard. You may also wish to enable the duplex unit or change other printer settings at this stage, using the "Settings" button.


9. Click swiftly through the banner, user access and quota dialogs (unless you're special) and then enter a name for your printer - this is what it will be known as on the local machine.


10. You're done. To set the printer as the default for all applications, right click it in the "Printers" system settigns panel and select the appropriate option.

So far, setting up this printer has been astonishingly painless on both Windows and Linux.
]]> General https://elvum.net/index.php?itemid=31 Wed, 13 Aug 2008 08:46:50 +0100 https://elvum.net/index.php?itemid=30 selling it as a capability of your VOIP service...]]> General https://elvum.net/index.php?itemid=30 Tue, 22 Apr 2008 22:28:28 +0100 https://elvum.net/index.php?itemid=29 We installed infra-red cameras on top of every TV set. "Monitoring Audience Satisfaction" we called it. Eyes when turned towards the screen would blink white hot and the funding for each show increased in proportion to the number of viewers.

A year later and the effects on daytime telly filtered through. The evenings might be a glitterball parade of quiz shows and talent contests but the days - they were something else entirely. Courageous dogs saved little girls from burning buildings, tigers prowled the jungles indifferent and beautiful, somehow a stream of werewolf movies was scheduled during the school run.

It was an intern who finally pulled footage from the IR cams. Expecting to see the pinprick pupils of housewives and retired grandparents, she saw, instead wide friendly pupils - disproportionately large and canine - and rapt, vertical, feline slits.

That year The Island of Doctor Moreau beat all recorded viewing figures.

- Ariadne]]> BBC https://elvum.net/index.php?itemid=29 Sat, 19 Apr 2008 11:55:28 +0100 https://elvum.net/index.php?itemid=28 Every time physicists prepare to switch on a new particle accelerator, it seems that a small number of people, usually unqualified, manage to whip up a scare story about it destroying humanity (or, occasionally, the universe), and inevitably, the forthcoming switch-on of the LHC is no exception. Ludicrous as they are, I think that these scare stories are not improbable enough, and so I would like to see peer-reviewed rebuttals of the following similarly-improbable scenarios:

• The LHC creates new "very strange matter" that turns normal matter into ripe gruyere upon contact. This leads to the cheese-death of the universe.


• The LHC creates new "queer matter" that turns heterosexual people homosexual. Society is destroyed by the creation of a ghastly legion of divorce lawyers, feeding on human misery.


• The LHC opens up a portal to another dimension, from which pour trillions of deadly alien bees, desperate to lay their glistening eggs in human flesh. Supplies of DDT stored at the LHC collision points in readiness for this emergency prove inadequate. Worldwide, fewer than 10,000 people are within range of a bee-shelter when the bee-raid sirens sound.


• The LHC reveals that the universe we inhabit is actually a game of Second Life. Humanity is destroyed in mass outbreaks of griefing.


• The Higgs Boson is discovered to great initial rejoicing, but soon distrust and fear set in and an angry mob of villagers try to destroy it by burning down CERN. The Higgs ultimately turns against and kills its masters and is last seen disappearing into the Arctic wilderness.


• CERN physicists use their doomsday device to extort one milliongazillion dollars from the UN, bringing on a golden age of physics research but destroying the world economy and killing two thirds of humanity due to starvation.

]]> science https://elvum.net/index.php?itemid=28 Fri, 28 Mar 2008 13:53:42 +0000 https://elvum.net/index.php?itemid=27 a fairly non-technical writeup on the BBC News website. There's one particularly interesting quote:

"One of the first shots of the crowd showed a fan waving a large flag back and forth. It seemed to come right into the room and I had to resist the urge to reach out and touch it."

It's interesting, because I was present at the screening, and I swear that virtually all the shots were framed such that the action was (correctly) placed behind the screen in 3D space. Including the "flag-waving" one that the reporter particularly mentioned. Indeed, one of the few criticisms I'd make of the shot framing was that some shots had unavoidable foreground material (eg the pitch, or people sitting just in front of the camera in the stand) that were placed in front of the screen and were hard to converge because of their extreme disparity and proximity to the edge of the frame. I believe that the 3D team were understandably limited to camera positions not required for the simultaneous international 2D broadcast, and so they might have chosen differently given free reign.

A colleague who was present at the screening mentioned that the cameras were set a bit too far apart, resulting in a "Subbuteo" effect, whereby the players appeared to be a couple of inches high. He had a point, although looking at the "making of" videos linked to from that BBC News writeup, it becomes clear why; using broadcast-quality cameras and lenses and simple (aka foolproof) stereo mounting rigs, it simply wouldn't have been possible to get the cameras' optical axes closer together.

Another noteworthy point is instanced in the second of the three "making of" videos: lots of assumptions and working practices that apply to 2D television and film craft need rethinking when you're shooting stereo. The example here was rain - an annoyance when shooting sport in 2D, but entirely liveable with. In stereo 3D, any kind of blemish that is present only on one of the two camera images, such as raindrops on the lenses, is entirely unacceptable. And that's on top of ensuring that zoom, iris, focus, gain and all other camera parameters are kept synchronised on each camera in a pair - something that's far from trivial with current equipment.

Overall, it was a triumph for the Outside Broadcast team from BBC Resources, all the more so since they discovered to whom the BBC was selling their department on the day before the experiment: the sell-off being a process which is inevitably concerning them at present. I believe that their efforts have unambiguously demonstrated the feasibility of stereo 3D coverage of live sporting events, and hope that they (and we) can go on to develop a craft of 3D sporting coverage - perhaps one day even bringing it to the living room.
]]> BBC https://elvum.net/index.php?itemid=27 Mon, 10 Mar 2008 17:39:48 +0000 https://elvum.net/index.php?itemid=26 blog is worth reading in its entirety if you're interested in the field. His latest post is of particular interest to me and my colleagues - because it reminds us, at a time when we're starting our involvement in a 30-month EC-funded collaborative engineering project to try and make 3D television practical, that television is an art form, that good artists will always push the boundaries of any technical limitations imposed by engineering decisions, and there are no guarantees that a system that is modelled on the human visual system (eg two cameras, 9cm apart) will be optimal, no matter how obvious it seems.
]]> BBC https://elvum.net/index.php?itemid=26 Mon, 3 Mar 2008 11:21:54 +0000 https://elvum.net/index.php?itemid=25 article in the New York Times about HD disc formats (login required) makes the surprising comment, "good animation looks three-dimensional in high definition". Now, isn't that interesting? It reminded me of comments that I've heard several amateur stills photographers make; they often describe a particularly high-quality camera lens as giving photographs a "three-dimensional" look.

I think that there is actually a genuine point to be made here, and that apparently-unrelated technological improvements in image reproduction technologies, such as camera (and lens) resolution, or display resolution, or higher frame rates (which tend to reduce motion blur) can make an image more "three-dimensional". There's a simple explanation of this: that the added detail gives the Human Visual System more information to work with as it attempts to recover what depth cues it can from the flat television screen. In my personal opinion you can state this more generally, and say that *any* aspect of the television (or cinema) experience that has been constrained technologically is a barrier to experiencing the material as "reality", and that "three-dimensionality" is just a step on the road to a "reality-indistinguishable" experience.

Why the effect should be more pronounced for animation is not entirely clear, but I have a theory that animated material (particularly computer-generated animation, to which I think the NYT was referring) can easily have more definition than the average "movie" recorded on film since it lacks film grain, and (unless it has been added in deliberately) motion blur. Poor-quality rendering (eg low-detail textures, or a low target resolution, as was common in the early days of CG films) should therefore exhibit the effect to a lesser degree.
]]> BBC https://elvum.net/index.php?itemid=25 Mon, 31 Dec 2007 14:31:32 +0000 https://elvum.net/index.php?itemid=24 new CGI extravaganza is out, in virtually every cinema format known to man: film, digital 3D and IMAX 3D. The digital 3D format is (like virtually everything 3D at the moment apart from the IMAX) Lenny Lipton's RealD system, which uses circularly-polarised glasses and an liquid crystal polarisation-flipping shutter (the "Z-screen") to display alternate frames from a digital projector running at 144fps, to each eye alternately. (This implies that each frame of the original film, which was rendered at the industry-standard 24fps, is displayed three times to the eye it was intended for, at 72fps; this is a projection technique known as "triple-bladed shuttering".)

A group of nine of us went to see the film at the Odeon in Wimbledon; here are some of my observations.

• Clarity: Digital projection is the future. It was so nice not to have to watch a film through a haze of flickering dust and reel-change blobs!


• Headaches: After 2 hours of stereoscopic viewing, only two out of nine of us had headaches. That's actually pretty amazing in 3D cinema terms, I believe.


• Stereo flicker: The ads and trailers before the show were projected from a film print. Projection switched over to digital when the stern message from our country's noble guardians of copyright appeared, followed by the BBFC certificate for the film. On these static images, mostly white on a black background, clear flickering was apparent to me, particularly when I moved my eye around the screen. This flicker was noticeable to me in high-contrast scenes throughout the first half of the film, but by the time it got to the credits, I was barely able to perceive it. Because the image always flickered when I moved my eyes around the image (a process known as "saccading"), the implication is that it was being caused by some interaction between the system of projection and the behaviour of the Human Visual System (HVS) during the saccade. It is well known (eg see that Wikipedia article) that "saccadic masking" occurs during these movements: the HVS "turns off" its response to low spatial frequencies of monochromatic light. When viewing a 3D film projected with the RealD system, after each saccade, one eye has to wait longer than the other before it sees any light on the screen. While the interval is short (~1/144s), the human eye and the HVS are not used to operating in environments where this sort of thing happens, so it is conceivable that the HVS interprets this as flicker until the brain trains it not to notice it. (And never forget that your ability to interpret the flat, flickering, perspective-projected images of 2D film and television is itself entirely unnatural, but since you were probably brought up with at least one CRT in your house from birth, you don't remember the learning process.) There is probably a threshold of perception too, so increasing the frame projection rate might well render the effect less visible. It would be very interesting to hear of any research that's been done on this issue.


• Judder: I found the judder in this film particularly objectionable. It was particularly obvious in scenes where faces were moving - it was common for the face to be unviewable during the movement. A colleague who saw the film with me thinks that artificial motion blur has been added to reduce the prominence of this artefact, but often only for the middle part of the motion, ignoring the ends. It would be interesting to step through the frames on an HD-DVD or Blu-Ray version of the film when available, and see what really went on. It's also not clear whether or not viewing a film in stereo increases the perception of judder compared to a 2D projection - I have a hunch that it does, but no scientific evidence, so the judder in Beowulf could just be a consequence of poor motion blurring during the rendering process and the use of triple-bladed shuttering in the projection of the film.


• Throwing things at the camera, and making sharp pointy things stick out of the screen and into the audience: Please directors, just stop this already. You're supposed to be making a film, not a theme park ride.

Overall, my gut feeling was that most of the technology problems have been solved. If directors can keep the 3D gimmickry down to a level where it doesn't interfere with audiences' immersion in the film (and that's a big "if" - Lenny Lipton says lots of diplomatic things on the subject here, for what it's worth, but this bit of trivia on IMDB hardly fills me with confidence), I think that 3D cinema could become a long-term mainstream proposition.
]]> BBC https://elvum.net/index.php?itemid=24 Sun, 25 Nov 2007 22:30:32 +0000