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 My Passive polarised Dual-projector setup 
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Location: Montpellier, France
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Hello everyone, I finally completed my Dual projector project, here is my report on how it's doing.

Note: I originally wrote this post at AVS forums on the Epson Home-cinema 8100 projector thread, since it was quite a long post I copied it here, so there is some "3D beginner" speech in the text I didn't remove.
Enjoy the article and do not hesitate to ask questions or comments.
I also keep a copy of this thread in the 3D displays section at AVS forums at the following thread : My Passive polarised Dual-projector setup



Recap on the setup : (all price info include tax & shipping)

-> Projectors
: 2x Epson EH-TW3500 (European version of the Epson HomeCinema 8100)
Price 2x 1400 = 2800 € from French online shop

-> Screen : Harkness Spectral 240 (a professional cinema-grade Silver-screen designed for polarised 3D projection, known to be among the best surfaces for polarised 3D) 235x135cm (230x130cm visible), peak gain 2.4, peak polarisation extinction ratio 130:1 (manufacturer specs), aprox 105/106" diagonal
Price 507 £ (~600 €) from Harkness Screens UK

-> Screen frame : Home made aluminium frame with squared-section aluminum tubes. Screen attaches on top of the frame with 3M-Dual Lock tape
Price : ~100 € at local hardware store and two evenings of "hard" work

-> Polarising filters : Silverfabric POLAR-L-50 with projector mounts (heat resistant polarising filters, linear polarisation 45°/135°, designed to be able to dissipate the heat of projectors, transmitted light intensity up to 5000 Ansi Lumen without damage to the filters and with anti-reflective coating to reduce the amount of light reflected back inside the projector)
Peak polarisation extinction ratio 1000:1 (manufacturer specs)
Price : 669 € for the set of two filters and projector mounts

-> 3D Glasses : Linear 45°/135° 3D glasses, identical design to the RealD 3D glasses you get from cinemas except they are with linear filters instead of circular and different brand.
Price : 30€ for a box of 10 pairs of glasses (3€ per glasses) from Stereomax (French online 3D equipment shop)

Initial budget for the system : 4000 € (not including the computer or software)
Total for the system : aprox 4100 €

Video Source : My computer
Intel Core i5 750
4GB Ram
ATi Radeon HD5870
Windows 7 64bit
3 Displays connected and working simultaneously :
1x Zalman 22" interlaced 3D display (my standard monitor) : connected through Display Port and active DP->VGA adapter
2x Epson EH-TW3500 projectors : connected though DVI with DVI to Hdmi passive adapters.

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Before posting the pictures I would like to remind you that this is my first ever projector setup and the frame is also my first DIY project.

This is not a proper complete Home-cinema setup for a very simple reason :
My apartment is too small for the screen. I have had a lot of trouble finding enough space to assemble everything and I have to move furniture to be able to use the system, and then put the screen away once i'm finished with it so that I can resume normal use of the room. (As you will see on the pictures, the screen blocks the opening of main window)
I still did it this way because I know I will move to some other place some time next year.

I would also like to apologise for the the poor quality of the pictures. I do not have a proper camera, I have to use my camcorder photo mode which is quite bad. I've used the longest available exposure times (1/3 second) on a tripod to try and remove as much noise as possible but despite that, the pictures really don't do justice to the quality of the picture actually being displayed.

Here we go, enjoy and do not hesitate to ask if you have any questions
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The frame before mounting the screen

Image
It's simply made of squared-section aluminium tubes attached together simply with screws. It is not rigid as steel but I have used anough attach points to make sure it is strong enough while being still very light, which is what I need. It can also be unmounted for transport when I'll move to some other place next year (the frame won't fit through the staircase)
It is also adjusted to be within +/-1mm of the actual screen size.

The complete screen :
This was my first screen ever and I was surprised how hard it is to tension the screen properly, not enough or too much tension and the screen starts to fold near the attach points. I also had to be careful with the amount of tension I used to make sure I would not damage the fragile silver-screen surface.
Indeed the projection surface is only a painted coating on a synthetic rubbery/latex material. When unrolling the screen for the first time, I immediately noticed it to the very strong smell of paint solvent coming from the material.
The screen has very little elasticity, I do not have any experience with other screens so I do not know if it explains why it is so hard to tension properly or if it's the same with other screens. Here is what the screen looked like on my first try :
Image
It took me a lot of work but I eventually did it properly. It's much much better
This picture shows the screen in it's final position on the ground.
Image
The screen is almost complete : I now need to add the final finishing touch :
I will add a piece of black plastic that folds over the edge of the frame. It will cover about 2.0~2.5cm from the edges and has multiple roles :
first, it will mask the edges of the screen where the attachment points are visible, it will also create a black-frame to make the frame look better as well as increasing the perceived contrast and finally it will also protect the edge of the frame against accidental hits against walls and furniture during manipulation. Since the apartment is so small, it tends to happen a lot. I do not want to damage my frame.

The projectors and the Living room :
I have used the greatest length of my living room in order to get the biggest picture possible (which is how i calculated the screen size I wanted).
The couch is 3m (9 feet) from the screen, just behind the couch is the bar which separates the kitchen area from the living room area. I put the projectors side by side on the bar.
I noticed yesterday evening that the hot air exhaust of the left projector was shooting straight on the right projector filter mount. The filter itself was protected and stayed cool but the mount itself was definitely getting hot. For safety I decided to add a separator to make sure the exhaust airflow would not disturb the filter in any way. I do not want the filter to overheat in any way. I used the first piece of paper i could find : it's the instruction booklet for mounting an IKEA table.
Image
Image

Picture quality
Well it's not that easy : at first when you just turn on the projectors the first time, you get a completely doubled up picture with completely wrong colours.
An alignment reference picture is worth a thousand words :
This is the DDD alignment test picture. You may already have seen it used by other websites to test the amount of crosstalk of 3DTVs. (download it here)
Image
(note : this picture was taken with the 1st try of screen tensioning and the screen folding shows around the frame)

Two things must be done :

-first the projectors need to be lined up perfectly. This is done through the projector lens shift. At first the super-sensitive lens shift is quite hard to use. I was surprised by the fact the touching one axis on the lens shift would unlock the other axis, ruining your calibration due to the springs. It takes a while to get used to it be eventually, lining up the projectors becomes easy and is performed very quickly. But there is one annoying thing. No matter how precise you are, there is always some portion of the picture that is not perfectly lined up, I can line them almost perfectly but it's never perfect. It took me a few hours to find what it was until i finally understood that it's simply the lens that is not a perfect lens. When using the lens shift you move the lens and it creates small imperfection, a perfect lens costs thousands and thousands of Euro, consumer projectors just can't afford them : so the lenses curve the picture just a little. If I were to use only one projector I would have never ever noticed this but since I am trying to line-up two projectors, the differences show up.

-the second thing you notice on the picture is the colour difference.
This is because when i took this shot, the filters were not perfectly in place. But the colour shift is not due to the filters : it's due to the projectors.
Here is why : The Epson projectors are LCD projectors, which means that the light that comes out of it have gone through sets of polarising filters, the liquid crystal layer and an other set of polarisers, so the light is already polarised, so what's the issue about it ? The Epson projectors are not just LCD projectors : they are 3-LCD projectors. Each RGB component is created by a different polariser and the picture is then assembled by a set of mirrors. This results that some of the colour components are polarised vertically, while an other colour component is polarised horizontally.
This means that in order to display a colour neutral picture : the polarisers need to be placed precisely at angles of 45° and 135°. Well that's a good thing, that's what our filters are designed for (this was planned from the beginning).
It also means that placing the polarisers precisely at the proper angle becomes very easy : no need to use the glasses and close one eye just look at the screen until the picture becomes colour neutral and there you go.

This is what the picture looks like once lined up properly and with the filters in place :
(projector is set to use all default factory settings, colour mode "natural")
Picture without glasses (alignment test) :
Image
This is the two pictures (left and right) overlapping each other.
You can see the grid matches for most of the frame, except the bottom right corner. The picture doesn't have enough quality to really show the grid misalignment, it just becomes a bit blurry, that's not the camera focus, it's the projector misalignment.

Picture with the glasses (crosstalk test) :
Image
Image

Two things to notice here :
-> Crosstalk : 3D Crosstalk is the phenomenon of some of the light intended for one eye to be improperly filtered and becoming visible into the wrong eye. Too much crosstalk and the viewer becomes unable to focus on the 3D picture, little crosstalk is usually not a problem. A perfect 3D system should have zero crosstalk but since this is the real world, predictably there is a little bit of it.
The picture shows the typical pattern of passive polarised systems : the maximum amount of crosstalk is shown when displaying pure white on pure black (the L & R letters in the centre of the picture), any other colour combination (the black&white circles on grey background in the corners) will show significantly less crosstalk, the amount varies linearly according to the brightness difference.
The source of crosstalk is the weakest link for the polarisation in the system : this means the silver-screen : filters have extinction ratios of about 1000:1 while the screen is only rated at 130:1, and this Harkness screen is one of the best screens currently available, most other silver-screens only have extinction ratios rating around 80:1.

If you have read a little about 3D you may already know that a polarised setup will never be absolutely crosstalk-free. It's a strong point used by people defending active shutter glass based 3D systems : in theory an active shutter glass system can be crosstalk free, but then you have to compare that with the actual products on the market and they show a completely different story.
I won't make a complete argument on why one is better than the other here since it's very tricky subject and that some people may have different priorities regarding the picture quality.
I'll just say that this result is extremely good. I have a preference for the look of passive polarised systems and that I am very satisfied with this amount of crosstalk.

-> Colour shift : the edges of the frame have a a slight colour shift, one side of the frame looks green-ish while the other is more purple-ish. I am not sure exactly about the source of this issue but I believe this is due to the lens of the projector modifying the polarisation angles of the light emitted by the LCD projector, twisting the natural polarisation of the 3-LCD panels. I cannot fix this, it's an issue caused by the non-perfect Lens and the 3-LCD projector system.
Possible fixes would be use a DLP projector (which emits non-polarised light and is not affected at all by this issue) or to have the 3D polarising filter built-in the LCD projector before the lens.
However I'm not ready to change projectors for this : I personally think the issue is small enough and I really do appreciate the huge flexibility of the Epson projectors which have no competition at this price range.

Picture quality in the real world
You have all been waiting for this picture, I know you have, it's the biggest 3D blockbuster ever, and here is how Avatar looks on my display... or at least how the trailer looks like (3D trailer captured from German satellite 3DTV broadcast).
(L+R picture : no glasses)
Image
(Right eye only with glasses)
Image

OK so first thing to remember : my camera with which i took this picture is absolute crap. On the screen this picture is gorgeous, super-sharp and the 3D depth is simply perfect. I am really lost for words to describe how good the picture looks. It's better and brighter than what I remembered from the cinema.
I have had this trailer on my computer for over three months, I watched it many times on my 22" 3D display, I discussed about it with some other 3D enthusiasts and they agree everything looked dull and flat on the small display, and now on the big screen it's a complete shock : it's how the movie was meant to be watched.
One thing is very clear : 3D movies are calibrated for the big screen and screen size is extremely important. 3D movies use very little camera separation, this means that when an object moves far in the distance or close to the camera, it will result in a separation between the left and right eye view of just a few pixels on the screen. If the screen is small these pixels are barely a few millimetres, flattening the frame, making the 3D effect look like cardboard cut-outs.
However is the screen is big, these few pixels translate in a few centimetres, which represent much much more depth, this time the 3D takes some real space and the characters and objects gain volume.
I found this shot (also from Avatar trailer) to demonstrate the purpose quite brilliantly :
Image
In this shot Grace (Sigourney Weaver) is in focus at screen depth, now look at the lights in the bottom right corder of the frame, these lights are in the background so they are strongly doubled. On a small screen this separation is very small so the object does not appear as far as it should be, the entire scene looks flattened.
Now on the big screen I measured how big the separation is : here is the picture (ruler is in centimetre)
Image
The maximum 3D effect achievable without giving a headache is if far objects are separated by 6.5cm (the distance between the two eyes) : this way the eyes look perfectly parallel to watch an object that should be far far away (at infinity). It works great but is very tiring for the eyes.
2.7cm is about 1/3 of this distance, giving a good looking 3D picture with enough depth while staying very comfortable and easy to the eye.
This is a good balance.
I reckon that one could watch 3D on screens up to 200" diagonal. Anything more than that and you would have to apply a small correction to the picture to prevent it from being too separated. Most 3D video players do have this feature though so it's not much of an issue.

I also played some videogames, Here is the Unigine Heaven DX11 benchmark and a Prince of Persia (2008) screenshot with simultaneous dual projectors OSD operated in sync by one remote.
(L+R pictures : no glasses)
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(Left eye only with glasses)
Image
(L+R pictures : no glasses)
Image


Hot-spot
All high gain screens are known to have a common weakness : hot-spotting. In order to provide a high gain in front of the screen, they have to reflect less light towards the sides, the centre of the picture which reflects light straight ahead tends to be brighter than the edges of the screen which reflect the light at an angle.
The Harkness Spectral 240 screen material is rated at 2.4 peak gain, so it is no exception to this rule and does suffer from hot-spotting. This is mostly visible on content with large uniform coloured areas. The DDD test image and browsing windows makes it obvious, however I was surprised to see how quickly the hot-spot dissolves into the picture the image starts to have some variety in it. CG animation movies make the hot-spot quite difficult to notice, but you can still kind of see it. With a rich and detailed movie like AVATAR, it's completely gone. An expert's eye could probably still see it, but to my eyes it's invisible.
The annoyance factor of the hot spot then boils down to the content you throw at the screen, some games or movies might be more problematic than others but overall I'm quite satisfied.
I consider the hot-spot a non-issue...
... and that's with the close seating position and short throw of the projectors, placing the projectors further behind and with a greater seating distance to the screen, it would reduce the view-angle difference between the centre of and edges of the frame : making the hot-spot even less visible.

2D image quality
This is where we're in trouble...

If you look closely at the previous picture (the 4th Avatar picture with the close up and the ruler), you can notice something with the screen : screen grain.
It does not show up on the other screenshots because my camera is just not good enough to pick it up but the Harkness Spectral 240 coating is only partly aluminium mixed with other paint stuff it has a tendency to reflect light in a uneven way, creating a very strong very visible grain effect, even though the actual surface is very smooth. When under strong illumination you can see the grain is composed of thousands of shining little stars. The grain is therefore very visible at close distance especially if the picture is bright. (the most obvious times to see the grain is when browsing windows).
when using 3D glasses, the picture becomes dimmer and the linear polarisation eats away a good portion of the bright reflections (known phenomenon to photographers working with linear polarising filters) making the picture comfortable enough to forget it or "see through" it, but for 2D there is no escape.
As you walk away from the screen the grain becomes progressively more and more uniform, unfortunately at 3 metres, the distance of my couch, the grain is still visible in a very obvious way in 2D. For 3D it's alright, you can forget it easily but if you're looking specifically for it it's still obvious.
It's only when I walk behind the couch 5metres away and more (in the kitchen area) that the grain dissolves completely into the picture.

So this silver screen is not a universal 2D/3D surface for the home. It's very good for 3D, it may be a good 2D/3D surface in the theatre as the audience is far away enough from the screen to not see the grain, but for 2D in the home it's simply not acceptable.

There is hope though. With the growing home cinema market, we've seen many new screen technologies appearing in the recent years for home high definition 2D presentation. I have high hopes for similar improvements in silverscreens during the next few years, especially with LG pushing for polarised with a dual-projectors-in-single-box coming soon for the high end projector market. I can't afford the projector but it like the technology and hope LG will continue developing such systems to push for more polarised home setups.

On the usage of a dual projector 3D system...
Using a 3D dual projector setup can be very easy or a horrible nightmare depending on how you look at it or what you want to do. But there is one thing that the dual projector setup has that no other 3D system has : the ability to tweak.
Most other 3D displays have a problem : the programs need to output a very special format to be able to display a 3D image (Interlaced 3D displays, iZ3D monitor). Some displays even need the programs to call a very specific API that cannot be used directly by the user (3D vision, Hdmi1.4 3DTVs).

In one way this is good, it puts the pressure on the 3D manufacturer to find developers to provide good applications that work. On the downside if you cannot find the right application for the job that supports your 3D system, you are screwed.

A Dual projector system is different : no hardware manufacturer really support it because it's mostly home-made so support mostly depend on the good will of developers to implement support on their own. But a dual projector setup has something very special that no other 3D display can do : if you can't find an app that works natively... you can try to hack around with the settings, and sometimes if the application you are using has enough customizable options you can make it work.

When applications support the system (the easy way)
Configuration is usually quite simple : just enable your screens normally like if they were independent screens and open the application that supports dual projectors.
The application will automatically send one picture to display #1 and the other to display #2 at precisely the same on screen location so that the left and right eye views match, sometimes even copying the windows cursor image to provide a seamless experience. If the left and right eye views aren't in the right order, the application almost always has a feature somewhere that allows you to swap the left and right eye views.
ImageImageImage
(note : the 3D projectors usually must be connected as display #1 & #2, on this screenshot the ATI control centre changed the order and determined the numbering according to which display i plugged first since the computer booted)

I have only used the system for short periods of time, I do no know yet all the software that is compatible but here are a few apps of interest I have tried so far :
-Stereoscopic player (well known video player among 3D users, plays almost every 3D video format except BluRay3D which is work in progress)
-sView (freeware, displays 3D pictures as well as 3D videos)
-Avatar : the videogame (the PC version offers native dual projector support)
-Unigine (video game engine) has embedded native 3D support, available if game developpers provide users the option to turn the 3D mode on. I used the Unigine benchmark for a picture shown above).
-iZ3D driver and DDD Tridef ignition drivers (the program automatically hack into DirectX video games to change the camera system in the games for a stereo 3D camera system and displays the picture on various sorts of 3D displays, including dual projectors. They work similarely to the Nvidia 3D Vision software except they work independently of the graphics card you use and support different hardware)
-Upcoming blockbuster videogame Crysis 2 has been announced to support dual projectors natively. The 3D support has also been added to their 3D engine Cry Engine 3 which they sell to other developers and which is available to the user if the game developers provide an option to turn the 3D on.

Issues : what could possibly be wrong with a natively implemented system ???
Well there is a bug. Since the arrival of Windows 7, it seems dual projectors users have synchronisation issues between the two displays and my system suffers from this symptom too. It is not much of a problem for displaying pictures but when the pictures start to move, the difference between the left and right eye starts to cause some big visual artefacts that can cause massive headaches in 3D.
Objects moving horizontally are suddenly no longer at their proper depth, objects that are in the background jumping to the foreground and vice-versa, objects moving vertically getting huge vertical separations : this is so bad that most videogames are unplayable and movies hurt the eyes, even Avatar (which has absolute perfect graphics in 3D)

I have read reports saying the latest Nvidia video drivers have finally solved this issue for their system, I am now waiting for ATi to release new driver updates, hoping for a fix. (ATi has announced releasing drivers supporting 3DTVs before the end of the year, I hope the fix for dual projectors will come with it).

So here we are : 3D ready apps do not work properly, are we screwed ? (have I spent all that money for nothing ?)
Of course no ! because dual projectors have this very special ability to be a very flexible and tweakable system : let's work around the issue and make stuff work !

When stuff doesn't work, work around the issue and make it work anyways !
The synchronization problem is the #1 issue for dual projectors, fortunately it's only a software issue with the graphics card drivers. I know that because there is a simple way of making two displays perfectly synchronized with the ATI display drivers : Eyefinity
Image

Eyefinity is ATi's solution for super-widescreen multi-monitor gaming technology. What it does is basically making believe Windows and the games that you are using one huge seamless screen that spans over multiple screens instead of using multiple smaller monitors. The games and applications only see one big screen as a whole unity so there is no screen border or display number to confuse the application. What's more the displays are always kept in perfect sync, solving the display synchronisation issue.
The whole trick is then to make your applications show the left eye picture on the left half of the huge screen and the right eye picture on the right half of the huge screen.
Viewing picture and movies is actually quite easy since they are traditionally stored side by side, all you have to do is to playback in full screen, maybe use the video player scaler to stretch the picture if necessary and off you go.
For example this is how I played the Avatar trailer in the screenshots above : i used my usual MediaPlayerClassic Home-cinema to play the wmv file and scaled to stretch the frame to full screen. The application is not 3D ready, it did not even know it was a 3D file but it just worked.

The same goes for pictures : the DDD alignment test frame shown in the previous post was displayed through a conventional 2D picture viewer : Xnview in a similar way.

Making games work is more difficult : 3D drivers like iZ3D has a mode for displaying the left and right eye views side by side on the same screen, which is what we need, unfortunately this mode is designed for 3DTVs so it compresses the frame horizontally after rendering, which is not what we need : we want full resolution side by side.
It is still possible to play games if the game allows us to use anamorphic rendering : rendering a 16:9 aspect ratio frame, then stretched to 32:9, which the iZ3D driver finally stretches back to 2x 16:9 side by side.
Some games allow it but they are few and these options have to be tweaked in .ini files. For example I successfully played AudioSurf this way (which is known to always render 4:3 and stretches to whatever display ratio you use).

I also tried to render Avatar the video game this way, unfortunately the use of custom aspect ratios seem to interfere with the native 3D side by side mode, so I'm stuck on this game. I spent an entire evening messing around in the .xml config file of the game to try and find a solution without success. The best I could get was a 1920x1080 rendered anamorphic super-wide screen 32:9 aspect ratio picture squashed to 16:9 screen ratio : the picture was indeed 3D but with the wrong ratio.

I have not tried any other game so far but i am convinced that I can run many other games this way

On BluRay 3D compatibility
I know it's a must have for film enthusiasts but I'm mostly a video game fan, not so much a film guy.
At the moment there are no BluRay3D capable software that support dual projector setups, I know it's just a question of time. Given the current amount of 3D BluRays on the market, there is no real rush, I am not starving for content, there is so much I want to try and experiment with first. I just hope we'll get more universal software by the time Avatar BluRay3D hits the shelves officially (not in the Panasonic exclusive tie-in) that means not before mid 2011.

In the mean time it is still possible to decompress the BluRay3D film into full resolution left and right eye views ready for viewing on a dual projector setup with some software i've seen on a Norwegian website (Biohemmet.se), but the operation lasts for an entire night, and eats a lot of HDD space so I'm not really fond of the solution, I have yet to try it but I know it is possible and it works.


Conclusion
This is a review i would like to not conclude just yet : I have not found everything there is to know or done everything there is to do with the Dual projector passive 3D setup. I am still beginning to use it, but for now I am very impressed with it and do not regret spending my money in any way. It's the best 3D setup I have had the opportunity to see, it's definitely better and brighter than what I can get at my local RealD cinema.

I'll probably have to get a secondary screen for 2D viewing, probably something simple and cheap to roll/unroll over the frame. (it will also protect the 3D frame from dust) I am not a 2D film enthusiast, I do not have much of a DVD or BluRay film collection at all, i mainly use the projectors for 3D and 3D without compromise was the purpose of this project from the beginning.

I will probably come back with more details and updates as they happen, and maybe better screenshots if I ever buy a better camera, and why not put the pic in the screenshot war thread.

Any way if you have any question or request, do not hesitate to ask. I'll be glad to try my best to answer.
(maybe I should put a copy of this post in the 3D section, what do you think ?)

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Desktop : Intel Core i5-750, 4GB RAM, ATi HD5870, Windows 7 64bit
Laptop : Intel C2D-P8600, 4GB RAM, nvidia 9700M-GT, Windows Vista 64bit
Displaying Zalman Trimon 22" and 106" Passive polarised dual projector setup.
Watch my Stereo3D gaming video footage viewtopic.php?f=3&t=2020


Last edited by BlackShark on Thu Feb 24, 2011 1:34 pm, edited 5 times in total.



Mon Aug 30, 2010 6:57 am
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One Eyed Hopeful

Joined: Thu Jan 21, 2010 10:28 am
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A fantastic write up. Thanks for taking the time to do that.

I've got a DLP projector which I'm quite fond of and was wondering about getting another one for a dual projector project. I'm just waiting for one to become available thru ebay.

I'm a bit concerned about the synchronisation issues you mentioned but I've got a nvidia graphics card so hopefully that would be a non-issue.


Mon Aug 30, 2010 12:16 pm
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Petrif-Eyed
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I haven't even read everything yet but need some sleep. Be sure i catch up again tomorrow! 8-)
Btw: Have you tried aligning the projectors on top of each other? (of course having cooling in mind.). By having the lenses closer to each other, the chances increases of getting a more similar image from each beamer and would probably give a great aligned 2d-image without glasses as well.
As you probably noticed the horisontal alignment is the one that's most crucial in 3d (not really crucial once 3d is turned on though) so it should be prioritied getting right. On my 100"er i have a vertical misalignment of +-1.5-2mm when the horisontal matches perfectly. And i use digital keystoning... Image

One-frame-lag is a killer of a good experience and i really hope ati gets their things straightened out. Nvidia works better with their latest drivers but after what i've read i've never been close to the "one-frame-lag" you get no matter what displaydrivers i used. Basically the only game that ever gave me trouble was tm-nations which works great today with recent driver+iz3d driver.
It might have to do with the lower resolution i run but i'm not sure. It would be a pity turning down resolution when having full-hd-beamers....

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Mon Aug 30, 2010 3:42 pm
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Very cool. Congratulations on your new setup.

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Mon Aug 30, 2010 7:50 pm
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One Eyed Hopeful

Joined: Sat Jul 31, 2010 8:19 pm
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Dual setup is impressive. Nice job. I think that alignment issues are being solved by two companies. Both are expensive alternatives to dual projection for passive stereo, but they are good alternatives...

http://www.projectorcentral.com/pdf/pro ... c_5443.pdf
or
http://www.depthq.com/specifications.html, with this: http://www.depthq.com/pdf/DepthQ%20Pola ... %20WEB.pdf

The cost is close to double... too bad about that.


Thu Sep 02, 2010 9:24 am
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Certif-Eyable!
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The LG projector is the next step in dual projection : a dual-head single optics : two projectors in one box pre-calibrated and pre-polarised.
The price is right though (LCoS projectors are the best projectors around, but they are very expensive : it's a very high end projector system)

The DepthQ systems are different : they are based on time sequantial display : they are a shutter systems.

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Thu Sep 02, 2010 12:20 pm
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You got quite a impressive setup there... I envy you ;)


BlackShark wrote:
The LG projector is the next step in dual projection : a dual-head single optics : two projectors in one box pre-calibrated and pre-polarised.
The price is right though (LCoS projectors are the best projectors around, but they are very expensive : it's a very high end projector system)



Wtf? that sound like expensive-but-awsome-shit. Would be intresting to see that in live...

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Fri Sep 03, 2010 2:54 am
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Nice setup! Like ours ;)
Except, we have two 720p DLP projectors, cheap filters frop polarization.com,
and a 3,6m wide Harkness screen.
Yes, try your projectors in above-below position. Maybe your heat issue also will be gone :)
Btw. your screen is also made of two piece, that is glued together?


Fri Sep 03, 2010 8:46 am
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LCoS projectors are the best projectors around

-they used to say powerLED DLP just started to close the image quality gap, compared to CRT. LED's sure kick bulb butt. Not to mention Mitsubishi Laservue (rear projection DLP ), LCOS was always second tier with agressive pricing.

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Fri Sep 03, 2010 10:14 am
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LCoS second tier ? With agressive pricing ?
You are confusing with LCD projectors i think.

At the moment LCoS projectors are unrivalled (both in quality and high prices)

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Watch my Stereo3D gaming video footage viewtopic.php?f=3&t=2020


Last edited by BlackShark on Fri Sep 03, 2010 1:31 pm, edited 2 times in total.



Fri Sep 03, 2010 12:48 pm
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Beware of assuming that lcos works in a passive polarized projector rig though. I have no idea which polarization/polarizationangle the light/colors have in those! It should be easy to circumvent once knowing the properties of lcos-beamers. With some luck they might work with 45/135° just like standard 3-lcd's but's it's no guarantee.

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Fri Sep 03, 2010 1:10 pm
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Likay wrote:
Beware of assuming that lcos works in a passive polarized projector rig though. I have no idea which polarization/polarizationangle the light/colors have in those! It should be easy to circumvent once knowing the properties of lcos-beamers. With some luck they might work with 45/135° just like standard 3-lcd's but's it's no guarantee.

They don't work with standard 45/135 polarisers, LCoS projectors have special polarisation properties : Silverfabric sells specialized filters for LCoS projectors.

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Fri Sep 03, 2010 1:30 pm
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you can buy "3 chip" LCOS projectors for pretty cheap ( 2,000+), compared to 1x DLP with colorwheel( 10,000Eur) http://us.marantz.com/Products/2357.asp , and 1x DLP with 3LED ( 20,000Eur) http://www.aboutprojectors.com/SIM2-Mul ... ector.html , not to mention 3DLP, and 120hz VR stuff. 3DLP doesnt even look like the top-dog to me. ;)

Also JVC's LCOS tech (D-ILA) seems better than Sony's. Many service horror stories about SRXD too.

Quote:
# Max. 6x speed, 7 segments SilentWheel™ color wheel
# 3 Selectable Color wheel speeds


well yeah ;) you can be damn sure thats better color mux technology than LCD projection .

A vs A- ?
http://www.displaymate.com/ShootOut_Comparison.htm

, oh and new firmware arrived with my new H5360, 120hz looks as good as brilliantcolor (R G B W Y ) prievously, LOL.

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Last edited by tritosine5G on Sat Sep 04, 2010 2:08 am, edited 2 times in total.



Fri Sep 03, 2010 1:40 pm
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BlackShark wrote:
Likay wrote:
Beware of assuming that lcos works in a passive polarized projector rig though. I have no idea which polarization/polarizationangle the light/colors have in those! It should be easy to circumvent once knowing the properties of lcos-beamers. With some luck they might work with 45/135° just like standard 3-lcd's but's it's no guarantee.

They don't work with standard 45/135 polarisers, LCoS projectors have special polarisation properties : Silverfabric sells specialized filters for LCoS projectors.
Thanks! Good to know. I'll bring a polarizer and see if a salesman will turn on a beamer for a quick test... :ugeek:

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@ BlackShark

Nice work you have done here. Congratulations. Also thanks for sharing your experience. I have gone the same dual setup way as you and have run into the same issues.
First I should say I am on the movie side, not the game.

I bought two FullHD Lcos VPL-HW15 projectors from Sony and a silverscreen from Demospec-France (Harkness license).

First I tried the polarized filters/silverscreen approach and was highly disappointed with the results: Hot spot, screen grain, color shift. I almost decided to give up and sell my projectors. You now see how I was feeling... All I wanted was the same wonderfull picture quality as I had in 2D. It miserably failed.

So I went the infitec way and made some experiments with both glasses from Infitec and Dolby-3D. I didnt want to put some 4 K$ on the technology (filters and color correction box), so I went the cheap way: using dismantled glasses as filters for the projectors and color correction of my own (thanks to using a PC as the source).
http://www.avsforum.com/avs-vb/showthre ... st18859059

Of course, the drawback is that this technology needs color correction. You simply cannot live without. Forget the very basic algorythm I gave in the link above. I am presently using two LUTs I have built starting from a 27 vertex cube with tri-linear interpolation. Once it is done, all it needs is a simple AVIsynth script which can only be used for movies, I am afraid. It would be better if this could be implemented directly in the graphic card driver, so games would benefit from that.

I am pretty proud of the results: No more silverscreen (500euros => waste basket). The 3D picture is bright, vivid colors, with almost no ghosting (definitely less than in the silverscreen approach). If only I had know from the beginning...

My setup:

- 2x VPL-HW15 - 1000 lumen projectors.
- Dolby filters/glasses
- Regular 1.0 gain 2 meter wide white screen
- AMD phenom 1090T - 6 cores - overclocked to 3.7 GHz
- 4 Gb DDR3 RAM
- ATI 3400 graphic card (DVI+HDMI)
- Windows XP SP2
- Zoom Player

To prevent sync issues, I am using ATI's horizontal span. No need for Eyefinity as I use only 2 outputs.

Unfortunately I can't use the overlay renderer any longer (it only works for one output) and must take either one of VMR7, VMR9, Haali or stereoscopicplayer renderer. So far I have never been able to get rid completely of judder/tearing. Reclock is working as a charm in 2D/overlay. No way to set it properly in 3D/VMR9 (though my typical audience has no problem with that. Only do I, it seems...). How did you fix the tearing issue (vsync, reclock...?)

Jack


Last edited by jackbauer on Fri Sep 24, 2010 9:44 am, edited 1 time in total.



Fri Sep 24, 2010 7:06 am
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Hello,
we have a linear polarized setup,
but i'm very interested in your infitec setup!
Where do you get the glasses, and how much was it?
How many hour do you used it? Filters is still OK?
Not burned because of high lumens?

Picture is really better than a linear polarized setup?
I cannot imagine it. :roll:


Fri Sep 24, 2010 7:18 am
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Hi Jack Bauer

I usually don't use Reclock for movies, I don't notice the small judder in the conversion from 24->60fps, I believe this is because I game a lot and most games have unstable framerates so I got used to it. However I can't stand tearing due to improper V-sync or sync lag between the eyes.
I use the Eyefinity mode so that both windows and mediaplayerclassic believe there is only one screen, the outputs work normally as they would in 2D, so V-sync is perfect and MPC behaves as it would normally with 24fps footage. I usually use VMR9 mode, but i think overlay should work just as well.

Since I merge the displays horizontally, the film needs to be shown side by side, if the film is stored over-under (most of my recorded videos are stored over/under), I use an avisynth script to transform the picture to side by side.

I have never seen span mode in the Ati drivers, as far as I know this feature was only used by nvidia on their old drivers (WinXP). The only options i have are extended desktop, clone and Eyefinity group.
The Nvidia Span mode (WinXP only) did just what I do with the Eyefinity feature : it merges the screen as one single surface and also merges the desktop in one unique surface, making windows and all the applications believe there is only one large display being connected to the computer. The GPU driver ensures proper split of the picture between the displays.
The good thing about Eyefinity is that you do not need to use all 3 outputs, you can use the feature with only 2 displays if you want (i think Nvidia Surround is only for using 3 displays).
The extended mode is different, it creates a distinct desktop surface for each screen, declares one as primary and the other as secondary. The two surfaces have different priorities and are not refreshed at the same rate. When maximizing or fullscreening a window in this mode it will only use one of the screens, not both.

For the 24->60fps judder, I noticed the Epson projectors have a 24Hz mode, and I can tell the Ati drivers to output at 24Hz. I tried it once so I know it works and the projectors do identify the input as 24Hz input but I could not notice the difference when watching a movie, it was only a quick test, i watched it for about a minute only. (i was busy finding about a bug that happen when you have one display running 60Hz and the other running 24Hz. applications don't like it at all)

----------------------------------------------------

Polarisation VS Infitec/Dolby

My main complaint is the screen grain, which makes the frame almost unusable for 2D presentation at such distances, if I had a big home cinema it should be alright but since I'm so close to the screen it just doesn't work.
I have not much problems with hotspotting, I only notice it if i'm really looking for it and I prefer the bright picture and lower ambient light reflected on the (white) walls and ceiling thanks to the screen gain. I know it's a compromise but i like the picture I already have, ghosting is low enough so I just can't notice it (there is some if i look specifically for it on very contrasty scenes) and the colour shift is hard to notice on most content. This is my first ever projector setup so I have no 2D experiences to compare it to.

The Infitec way is simply not an option for me since my main use of the screen is gaming, I don't want a shutter system so I don't have many options. It has to be polarised.

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Displaying Zalman Trimon 22" and 106" Passive polarised dual projector setup.
Watch my Stereo3D gaming video footage viewtopic.php?f=3&t=2020


Fri Sep 24, 2010 7:58 am
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@relaxman

I got the glasses from a french parts provider for theatres.

Normally, they only sell to theaters, not individuals. I took the chance to call them and, after a few minute's talking, the girl said her boss would call me back in the afternoon. So did she (I didnt really expect that call...). I gave her a brief overview of my project and she agreed to send me Dolby-3D galsses @ 20 euros each. That made it around 220 euros for 8 pairs, including taxes and shipment.

If you dont speak french, you can try the same negotiation in your own country:
http://www.dolby.com/uploadedFiles/Asse ... istWEB.pdf

For a little money, you can make experiments (on a regular screen!) and decide which of the approaches you like best. To me, the silverscreen is definetely a no-go, at least for Full HD movies, as the grain and the hotspotting are terrible, not even speaking of the greatly reduced angle of vision. I am seated 3 meters away from the screen.

If you like, I can provide you with the LUT tables to be used in the AVIsynth script. Of course, color correction depends upon your hardware, specifically the kind of lamp your projectors use.To a less degree, it may depend also on the rendering device (LCD, LCos, DLP, ...). Right now, my files are tweaked for UHP lamps and SXRD (LCos). If your hardware is different, I can also give you my calibrating program to build your own LUTs. This program does'nt use any capture device but simply relies upon your own eyes (and friends, family's eyes...). It shows the same set of colors on the left side and the right side of the screen (one projector is enough for that calibration). 2 filters are placed side-by-side on the projector lens. You tweak each color with sliders until they both look the same left and right. After 2-3 iterations, you can be confident enough for the correction.

Some people even use that technology without correction. Only very saturated colors show different from one eye to the other (eye rivalry). For me, color correction is mandatory though if you want the same picture quality as in 2D.

Melting is not an issue as the glasses are made of glass, not plastic.


@ BlackShark
Quote:
...but i think overlay should work just as well.

Overlay can only use one output at a time, not both. Although the virtual screen is double, only half of it is a candidate for the overlay. Too bad for me.
All my movies are side-by-side, so I just do the same thing as you. Should I want to play a top-botom movie, I run an AVIsynth script... easy.

Quote:
...I have never seen span mode in the Ati drivers.

Eyefinity only works if you have two cards working together. In my case, I have only one and Infinity doesnt show in the driver. The horizontal span mode do exist in the ATI drivers and is called "Stretch main horizontally onto digital panel". Not to be confused with "Extend main into digital panel" which, as you said, separates the definitions, the refresh rates, and you get the one-frame lag which is ruining the 3D effect. Thats one of the reasons why I do not use Peter Wimmer's stereoscopic player.

Quote:
...I can tell the Ati drivers to output at 24Hz.

Thats exactly what I am lacking. I use 24Hz for 2D. Probably depends on the card model (I have a very cheap ATI 3400). When in span mode, the refresh rates are only 2x720p 60 Hz or 2x1080p @ 50Hz/60Hz. I can live with 50Hz, as reclock changes the movie rate to match, 50 beeing multiple of 25fps. But I definitely dont want 60Hz for movies.

Quote:
...The Infitec way is simply not an option for me since my main use of the screen is gaming.

Too bad the Infitec way does not work on games. I have heard somewhere that some graphic cards do have LUT support. Some also rely on ICC profiles. I remember having seen something like "dual-profile" graphic cards, which suggests that the outputs gamuts can be tweaked separately. Browsing the web has reported no answer though. Will you be more lucky...

Jack


Last edited by jackbauer on Fri Dec 17, 2010 4:41 am, edited 2 times in total.



Fri Sep 24, 2010 11:50 am
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jackbauer wrote:
Quote:
...I have never seen span mode in the Ati drivers.

Eyefinity only works if you have two cards working together. In my case, I have only one and Infinity doesnt show in the driver. The horizontal span mode do exist in the ATI drivers and is called "Stretch main horizontally onto digital panel". Not to be confused with "Extend main into digital panel" which, as you said, separates the definitions, the refresh rates, and you get the one-frame lag which is ruining the 3D effect. Thats one of the reasons why I do not use Peter Wimmer's stereoscopic player.

I can't find this option, in which menu is it located and which version of windows are you using ? XP, Vista or 7 ?
I noticed that with the latest drivers installed I no longer have the 1 frame lag, but V-sync is broken. I used my favourite ultra-sensitive to sync test application : Audiosurf.
I couldn't notice any misalignment due to motion but because of the bad V-sync the picture hurts the eyes a lot when using extended display, but Eyefinity mode side by side works like a charm.

Eyefinity does not require two cards, just one is enough but you need an ATi HD5xxx series card, I use the expensive HD5870 for gaming but I bet if you don't play games you could try with an entry level card of this series that supports Eyefinity as well and it should solve the sync issue.


jackbauer wrote:
Quote:
...I can tell the Ati drivers to output at 24Hz.

Thats exactly what I am lacking. I use 24Hz for 2D. Probably depends on the card model (I have a very cheap ATI 3400). When in span mode, the refresh rates are only 2x720p 60 Hz or 2x1080p @ 50Hz/60Hz. I can live with 50Hz, as reclock changes the movie rate to match, 50 beeing multiple of 25fps. But I definitely dont want 60Hz for movies.

My bad !
I just tested to set it to 24Hz, it's listed as not supported in Eyefinity mode, I tried to force it but the display driver just stalls with no way of turning back. The damn Windows driver automatically switches to this bogus configuration when it detects the projectors are plugged in and the profile change shortcut keys don't work. I've spent an hour fixing this and returning to a usable configuration.

I can't use 24Hz either when using Eyefinity, the only way 24Hz mode works is in extended display mode.


jackbauer wrote:
@ BlackShark
Quote:
...but i think overlay should work just as well.

Overlay can only use one output at a time, not both. Although the virtual screen is double, only half of it is a candidate for the overlay.

Whoops, I just switched the projectors off before reading this post, i should have tested that.
I won't turn them on again tonight, i'll test this tomorrow. I'm sure overlay will work with Eyefinity, i'll see this tomorrow.

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Watch my Stereo3D gaming video footage viewtopic.php?f=3&t=2020


Fri Sep 24, 2010 1:16 pm
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Very interesting topic about the sync issue.
We have sometimes out of sync (i think) issue.
Our computer is a 2.5GHz intel dualcore, with 1GB dual ddr2 ram, xp sp2
and with Ati 4350 card. (no eyefinity) sw: latest stereoscopic player
I buyed this card, because it was the cheapest silent card with dvi+hdmi connector.
Nvidia 8400 or similar was a little more expensive, and i didn't choose that.
Maybe it was a bad decision?...

I have a 50 minute movie in separate L-R mpeg2 files (1440x1080, 50i)
So, the CPU has a lot to do! BOB deinterlace the two stream,
scale to 1280x720, and play back IN SYNC to the two output.
I use the "Extend main into digital panel" feature.
Maybe this is the reason why we have sometimes out of sync errors?
Rarely! Sometimes I can play my movie 3 times without any error, and sometimes
the problem occured 2-3x in a 50 minute. I stop the movie with space, and
hit again to start, and the problem is gone.
CPU load is between 70 and 90%.
Next step i think i overclock the cpu a little. Or this will not help, because
it's simply the problem of ati driver? If yes, what card can guarantee syncro
for me? Ati 5xxx, and geforce all above 8400 is OK?

Jack:
When "Stretch main horizontally onto digital panel" is also available with your card,
and this guarantees syncro, why don't you use stereoscopic player?
I don't remember, if i have such mode, i think only extend is selectable.

Blackshark:
"The extended mode is different, it creates a distinct desktop surface for each screen, declares one as primary and the other as secondary. The two surfaces have different priorities and are not refreshed at the same rate."

Not all the time.
As is wrote above, i can play my movie without errors for 2-3x times. But sometimes it's still there :(
I search a very stable, 100% problem free solution!

Oh, i forget to mention, that the two videofiles is on separate physical drives, so this also can't be the problem.

Any tips? Faster cpu, another vga card or use one file in sidebyside format?
(to bad mpeg2 doesn't support 2560x720 or even 1280x1440 resolution)

thanks!


Fri Sep 24, 2010 3:04 pm
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Having a CPU usage close to the limit is not recommended, overclocking little the CPU will definitely help but might not solve the sync issue completely.
I have not tested any other GPU, the HD5870 is the only one I have : it's an expensive, power-hungry, hot and noisy gamer GPU so it's definitely not the one you'd want to buy for your theatre system.
When using Eyefinity, the picture looks in perfect sync to me so I think if you use it will make 100% sure there is no sync problem on display.

Try overclocking the CPU a little, if it doesn't fix the issue, then the GPU upgrade might be necessary.
Look for an entry level HD5xxx card that clearly claims Eyefinity support and it should be good enough.

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Watch my Stereo3D gaming video footage viewtopic.php?f=3&t=2020


Fri Sep 24, 2010 3:30 pm
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I use dual passive projection with an 8800 nvidiacard and don't experience the one frame lag anymore (due to latest nvidiadrivers it seems). At least it's reduced to a nonrecognizable level. The one frame lag have until now only been a problem in very fastpaced games like trackmania but this was solved using the native side-by-side and the horisontal spanmode in winxp. Fps and adventuregames were absolutely fine as well as most movies for as long as the load on the computer was moderate. However: When iz3d releases their "eyefinity" option in their driver i'm going for an ati as well since it guarantees the best possible sync.
I'm also curious on the infitec technology, how it looks and performs. Brightness is easy to get spoled with when using a dual projector rig and personally i really don't feel for compromizes about this.

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Fri Sep 24, 2010 4:15 pm
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OK, entry level Ati here is the passive 5450, for about 35EUR. This seems good.
What about 64 bit vs 128 bit, and DDR2 vs DD3 ram in the case of stereo playback?
Or this is only important while gaming, and moving big datas, like textures, etc?
For stereo3d 64bit and ddr2 will be enough? even for 2x full hd?
(maybe in the future we upgrade our infocus projectors)

"overclocking little the CPU will definitely help but might not solve the sync issue completely."
Then quad core is the way to go? Stereo player will support it? Or it depends only from the codec? (ffdshow, gabest mpeg2, etc)

regards!


Sat Sep 25, 2010 12:38 am
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@all
Probably I will change my GPU to be on the "right side" of the sync issue. ATIs 5450 seem to be a good choice.
There is something very interesting with NVIDIA cards: The capability to tweak every sync parameter (Advanced sync in control panel - Warning!). I remember having tweaked 60Hz down to 50Hz for some resolution that was capable of 60Hz only. In fact you can set any refresh rate you want.... I have never found such a feature with ATI drivers. Any comment anybody?

@relaxman
I have the 1090T 6-core Phenom overclocked to 3.7GHz. So far, it is the most powerfull CPU from AMD.
Because of flexibility (ffdshow, AVIsynth...), I only use software decoding (coreAVC 2.0).
What I can do with it:
- Play 1080p movies (overlay, reclock).
- Play 720p movies @double the frame rate (48fps, screen @50Hz, overlay, reclock):
http://www.avsforum.com/avs-vb/showthread.php?t=1025800
- Play stereo side-by-side 2x720p movies with color correction (AVIsynth LUTs, VMR9)
- Play stereo half-side-by-side 1x1080p movies with color correction (AVIsynth LUTs, VMR9)

I didn't push my CPU farther (yet to be done), but I guess thats the best I can do with this hardware.

Trick: Although ffdshow/AVIsynth are supposed to run multithreaded, core#6 is often more loaded than the other 5.
So I always run Zoom Player with affinity to the first 5 cores (imagecfg.exe).That leaves more ressources on core #6 for ffdshow/AVIsynth.
I dont know if this is usefull with Intel processors, but with AMD its a big difference in stability!

@likay
About screen brigthness: Thats the point I am upset in my setup. I still dont understand why the infitec (Dolby-3D) technology is known as killing the brightness. See for example http://www.barco.asia/projection_system ... erview.pdf
Barco announces a ridiculous 7% transmission when using Infitec, as opposed to 38% when using polarizers (dual setups).

38-40% are the numbers we are accustomed to when using polarizers. I have tried both the polarizing way and the Infitec way. I must say that the brightness is exactly the same in both cases (color correction included).
What may benefit to the polarizing approach is the silverscreen gain that you have not when using Infitec. But I happened to see that this advantage is only if you are seated right in front of the screen (2.4 gain - 240% of the light). Even in that case, the screen sides may reflect less than 100% of the light (unless you use a curved screen - that I tried too).

Even if you use a narrow angle of placement for the audience, the side seats may perceive less than a 1.0 gain! You do not have this problem with Infitec. Everybody gets the same brightness, all accross the screen width, wide angle of seat placement.

Pictures are better than speaking... When I took a photo of my screen hotspot, he only words that came to my mind were: "Oh, my God.... I wasn't aware of that disaster..." (*):
Image
Image

"right side view" is for a seat exactly in front of the screen's right edge, which is a reasonable angle of viewing for the audience.


Dont pay attention to the wrinkle, they have been removed:
Image


@blackshark
Have you tested the overlay on both screens? If it works (unlikely), that would be the perfect solution to my last issue...

(*) EDIT: Numbers are reported from photoshop assuming a 2.4 gain in the hotspot.

Jack


Last edited by jackbauer on Fri May 13, 2011 2:12 am, edited 6 times in total.



Sat Sep 25, 2010 3:12 am
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Whoops I just noticed the entry level ATi cards only have one DVI, one VGA and one DP. This might be a problem.
Image

Using different output types may cause delays in processing (either the conversion in the gpu or in the projectors) and break the sync between the displays.
I have not tested this at home, i use the two identical DVI-out on my gpu for the projectors, the DP port is for the monitor only.

The cheapest ATi HD5xxx series card with dual DVI is the 5750, that's not the same price and it's not passive.
Image

Again this is not tested so the 5450 may just work but I have a small doubt.

jackbauer wrote:
@all
Probably I will change my GPU to be on the "right side" of the sync issue. ATIs 5450 seem to be a good choice.
There is something very interesting with NVIDIA cards: The capability to tweak every sync parameter (Advanced sync in control panel - Warning!). I remember having tweaked 60Hz down to 50Hz for some resolution that was capable of 60Hz only. In fact you can set any refresh rate you want.... I have never found such a feature with ATI drivers. Any comment anybody?


Indeed i remember with my previous 8800GTX this feature was in the Nvidia control panel. there is no such a thing with ATI.
However i remember that whenever I tried to tweak anything in this menu, the nvidia control panel required me to perform a test before applying the change and the test systematically failed, so this menu was pretty much useless to me.

Quote:
<pictures of curved screens>

:oops: I knew about curved screens but I can't afford one at the moment (not enough room).
I'll get one once I move to a bigger apartment.

How hard is it to tension a curved screen ? do you need to do anything special ?

------------------------------------
There is indeed something wrong with this Barco document.
This one from Harkness lists Dolby 3D at 12% light efficiency, which is just a few percent below single projector polarised systems.
http://www.harkness-screens.com/pdfs/pu ... ection.pdf

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Sat Sep 25, 2010 3:24 am
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Quote:
...entry level ATi cards only have one DVI, one VGA and one DP.


The 5450 has one DVI, one VGA and one HDMI (not DP). So that could do with adapters. The sync problem when having two kinds of outputs has to be proven.

With my 3400, the HDMI and the DVI ports do not give the same black/white levels so dont forget to tweak them in the driver menu.
When I use horizontal span, there is no sync issue, only tearing, which remains my only problem at this time.

But, if I move to a new card, I will most likely take one with 2xDVIs to be "on the safe side". 120 euros range is still reasonable.

EDIT: I am going to make somme searching on the Matrox side. They claimed in the past to have dual-overlays (parhelia technology).

@blackshark: Please can you check what refresh rates are available on your card for (using Eyefinity):
- 2560x720
- 3840x1080

I am looking for 50Hz in both cases (hopefully with overlay). Thanks

Jack


Sat Sep 25, 2010 3:54 am
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jackbauer wrote:
Pictures are better than speaking... When I took a photo of my screen hotspot, he only words that came to my mind were: "Oh, my God.... I wasn't aware of that disaster...":
Same here! I noticed the hotspotting first when taking a photo of it. Now i see it all the time. :roll:
I use my rig with those stereopol filters which lets through almost all (75%) the light from the projectors. The big screen is actually a tad brighter than my 19" samsung syncmaster comopared with lumens/sqm.
I'm going to try getting hold of infitec filters once again since i'm really curious of the tech. I think those filters works with different results depending on how narrow wavelengths different projectors have for their basecolors. Very narrow wavelength of the colors of course means worse result with infitec. The ideal situation is to modify the basecolors in the beamers into infitec specs (infitec sells their own projectors where thay have done so i think).
I get back myself if i'm successful getting filters.

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Sat Sep 25, 2010 9:11 am
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Take Dolby glasses, not Infitec. Wavelenths are not the same.

Infitec is much much worse as far as color correction is concerned (at least the Infitec glasses I have - flat lenses). Plus the lenses are narrow and cut le beam edges, even if you put the filters touching the projector lens.

See my setup: http://www.avsforum.com/avs-vb/showthre ... st18859059

For the cost of two pairs, it is really worth a try. Still the technology cannot compete with stereopol if you have LCD proj. Expect 40% transmission with Dolby's.

In my case (LCos), I use the eco lamp mode for 2D. For 3D, I use full power. I also included S-curve contrast and a little gamma in the LUT tables. My guess is that I am getting around 70-75% lumens compared to 2D.

Jack


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Thank you for the tip about dolby! And as said: I'm really curious on the tech and it's easy to try once getting a hold of the filters since i have everything else. Are you able to do a somewhat proper colorcorrection by just using the displaydriver (avisynth-scripts isn't really my stuff :oops: and it would be nice playing games with it). Somewhat close would be enough i think (my pj's are quite old by now and one of them is starting to have a slight "yellowish" warmer image which i believe indicates that one of the lamps is aging...). Would be impossible for me to tune the colors equally and i haven't even bothered yet as is now.

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Sat Sep 25, 2010 11:41 am
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jackbauer wrote:
@blackshark: Please can you check what refresh rates are available on your card for (using Eyefinity):
- 2560x720
- 3840x1080

I am looking for 50Hz in both cases (hopefully with overlay). Thanks


I have :
1600x600 50Hz 60Hz
3200x900 50Hz 60Hz
3840x1080 25Hz 30Hz 50Hz 60Hz

i do not have 2560x720 in the list, i think i should be able to force it but have not tried yet.

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Sat Sep 25, 2010 12:36 pm
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@likay
I cannot do color correction through my card driver because I am using ATI and the color parameters tweak both outputs equally. There is also a very basic setting for each output (hue/saturation/brightness/contrast) but it doesn't allow you to set the primaries separately.
The settings in my projector menus are of no use. What I would need is way off range.

I think Nvidia can do that. To simplify, one output should be set at RED=50% and the other at GREEN=50%. But this would be a very very rough correction.

For your yellowish lamp, have you tried to change the color temperature in the proj menu? This could balance your projectors better.

Quote:
...avisynth-scripts isn't really my stuff

You do not have to be an expert in AVIsynth. Once you have the LUT tables, only a couple of lines in ffdshow is required. Period. The most difficult part is to create the LUT tables that suit your projectors (2x48Mb files). If you lamps are UHP, my tables would do I guess. I would be glad to make them available to everybody.
But this is only for movies...

Jack


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I'm not an Avisynth script master either, whenever i do anything in avisynth i have to constantly reference to the Avisynth help/wiki to find the commands I need.
It's just that Avisynth is so powerful and flexible that it will save you from a lot of time and trouble. It's such a magic video input "Swiss-army-knife".

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Sat Sep 25, 2010 5:16 pm
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Just a word about Dolby-3D calibration...

I use the two filters in front of one single projector, side-by-side, 5mm gap in beetween:
Image

Then I use a calibrating pattern, Right-eye on the left, Left-eye on the right (I am accustomed tu use cross-vision for my tests in general).
Because of the gap beetween the filters, the center patterns are not filtered and are used for color reference (115=45% brightness, simulating filter attenuation).
Image

(The above is after calibration and shows the modified colors that will look the same when filtered. That gives you an idea of how badly you need color correction...)

Then I tweak each color for both eyes to match as closely as possible the center pattern, using, for each:
newcolor = k1*R + k2*G + k3*B

When completed, closing the program creates a profile file which in turn is used to build the LUT tables required by AVIsynth.

So 16 millions colors are interpolated from 8 basic colors (the seven lines of patterns plus black). These 8 colors are the corners of a 3Dlut cube in 3D space geometry:
primaries, secondaries, black and white.
Image

This is the basics. Now I am using 27 basic colors with the same method. Mid-range vertexes have been added to the cube.

So, if you use the card driver, you have only access to two points: black and white (tweaking the curves may help though). If you look at the calibration patterns, you can see that white (last line) defines the primaries. That may be a good start. But you also see that the primaries themselves, when calibrated, use other values.

Jack


Last edited by jackbauer on Sun Sep 26, 2010 12:10 pm, edited 3 times in total.



Sun Sep 26, 2010 3:43 am
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Using crossvision to calibrate is brilliant! Some testing to get the values right but only needed to do once.
I hope for driver calibration though since gaming is most important for me. Funny thing: I'm really looking into an ati-card next time (eyefinity and fixed iz3d-driver) but it would be nice to still my curiosity about narrowband filtering. And maybe, just maybe adjusting colors will be possible in the future using ati.
Thanks!

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Sun Sep 26, 2010 3:53 am
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I'm just wondering where you got the DDD alignment test pictures. Does it come with the tri def drivers or could someone maybe send me a link to them.

Thanks :shutter


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The DDD image is part of the Tridef package but I don't use it.
I found the picture on the web and just use it in a picture viewer.

I couldn't find exactly where I found it so I uploaded a copy for you here :
http://www.mediafire.com/i/?g6202hla505p65r
It's a side by side squashed picture for 3DTVs, so in order to use it with dual projectors, just stretch it horizontally.

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Wed Oct 27, 2010 11:31 am
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thanks, i appreciate it.


Wed Oct 27, 2010 11:37 am
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BlackShark : did you try the DDD ghosting test with other 3D displays or CRT monitors ? If that's the case, how do you find the ghosting compared to your dual-projection setup ?

jackbauer : I don't really understand how the Infitec technology really works, but do you think they could be used like classic anaglyph glasses using color correction on standard displays ?


Wed Oct 27, 2010 9:59 pm
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I only tried it on the other display I have : the Zalman Trimon 22" monitor.

There is definitely more ghosting on the Zalman screen, by a significant amount.

Some 3DTV reviews include a screenshot of the TVs displaying the DDD alignment test picture. For example the 3DTV reviews at http://www.digitalversus.com/ do have them.

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Thu Oct 28, 2010 5:57 am
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BlackShark wrote:
I only tried it on the other display I have : the Zalman Trimon 22" monitor.
There is definitely more ghosting on the Zalman screen, by a significant amount.
I'm not really surprised but it's nice to know. Did you publish the DDD test images for the Zalman somewhere on the Web yet ?
BlackShark wrote:
Some 3DTV reviews include a screenshot of the TVs displaying the DDD alignment test picture. For example the 3DTV reviews at http://www.digitalversus.com/ do have them.
Mais c'est le site Les Numériques ! ;)

I already knew about this one, in fact I've collected DDD ghosting tests for more than a dozen 3D displays for now. I'm trying to extend my collection in order to evaluate the different technologies with respect to ghosting.

For now it gives me DLP > Plasma, Dual LCD > CRT > LCD, but I've yet to implement an application to objectively measure the differences in ghosting.

By the way, what settings did you use to shoot the screen with your camera, I've tried some manual settings but I wasn't able to obtain good pictures yet (ISO 800, 1/125 and F2.6 last I tried).


Thu Oct 28, 2010 6:35 am
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