sync-doubling shutterglass mode w/ iZ3D's Over/Under output

[iondrive]

How to try sync-doubling mode with iZ3D's Over/Under output:

What is it and how does it work?
What sync-doubling does is insert an extra vertical sync pulse halfway through each frame of the video signal so that each input frame gets split into two frames. Your CRT stretches each top/bottom half of the original video signal onto the full screen size so that 800x600 @60Hz becomes 800x300 @120Hz. This coincides with the 3d display data output from iZ3D's driver with left-eye view on the top half and the right-eye view on the bottom half. With 800x300 @120Hz stretched fullscreen, the image appears something like interlaced mode since you can see some black between the horizontal display lines. I'll talk more about this later. We will use a 800x600 @60Hz video signal even though other modes can work too if your CRT can handle it.


What you need in order to try this:

1) a VGA input CRT capable of 800x600 at 120Hz,
2) a compatible dongle that can do sync-doubling
3) shutterglasses (wired, or wireless with IR emitter)
4) possibly a DVI-VGA converter. I use these with no problems.
5) you need to have installed the v1.10 iZ3D driver with side-by-side output included and not be out of time on the trial period.

Testing your CRT:
Before we go any further, first a warning, from what I've heard, trying to drive your monitor at a too-high freq can damage it. Personally, I believe that warning is out of date and every monitor I've owned shows an "out of freq" message or just goes black w/o damage because every modern CRT should have over-freq protection circuitry built-in. If you're worried about it, check the docs for your monitor or research it online. Try at own risk.

From your desktop, test your CRT in 800x600 at 120Hz and see if that works, then set your desktop to 800x600 at 60Hz and your game to 800x600 and then exit your game to the desktop. Actually, let's just use the iZ3D logo test for starters. Make sure you select "Fullscreen Window Mode" under Profiles/Game in the iZ3D driver control window.


Dongles (aka Controllers):
Compatible dongles include E-dimensional, X3D (3d-world), H3D, X-Force, and maybe some others that I don't know about offhand.

If you have an X-Force dongle, then you're in luck. Just use the button to enter sync-doubling mode (it's the one that makes your CRT switch modes) and the switch to turn on the glasses.

If you have one of the other dongles, then learn how to use ED-Activator and set up the hotkeys and memorize them so you can switch to normal mode with no problem. Get familiar with your setup control and try it on the desktop. When you're ready, put it back into normal mode.


Do the iZ3D logo test:
Set iZ3D's driver to Side-by-Side over/under mode and activate your dongle's over/under sync-doubling mode. Now your monitor should be running at 120Hz and you should have your shutterglasses on. Close one eye and you should see half of your desktop (top or bottom) stretched across the entire display. Close the other eye and see the other half. It's odd but just use one eye to navigate your pointer to the iZ3D logo dynamic 3d test and click it. X-Force dongle users can activate their mode after they click on the logo test since it's a hardware user-control device. Now things are a little better but still not good. The problem is that the right-eye view is too high compared to the left-eye view. We need to tweak a config file in order to fix this by using iZ3D's gap control feature. Escape out of the test and switch your dongle to normal mode.

Summarizing: the iZ3D driver makes the over/under image on the top/bottom of the screen and the E-D Activator triggers the dongle to split that into two frames via sync-doubling and also shutter the glasses.


How to adjust the gap between top/bottom images:
(also works in left/right mode if somebody needs that)

What we need and have is a way to put a black band (the gap) between the top and bottom images. This has the effect of moving the right-eye view down and the left-eye view up. The total vertical res is still 600 so that means that each image is going to be less than 300 lines tall, ie: there is some more vertical squeezing of the images but it's necessary.

For windows-XP, use Wordpad to edit C:\Documents and Settings\All Users\Application Data\iZ3D Driver\Config.xml and use the search function to find "gap value". Change that value, save and try it. It's a trial and error process. I find that 26 is perfect for me when usinig 800x600 res. Just remember, increasing the gap lowers the right eye view. When you've got the perfect value, go ahead and try your game. The ED-Activator only works on the desktop so if you try it in-game, you're going to exit your game to the desktop and you probably don't want that. Just use ED-Activator on the desktop and start your game using one-eye. Yes that sux. Once again, X-Force users don't need to do that since they have hardware controls.

On second thought, if your game has no problem alt-tabbing out and in, then start the game, alt-tab out, use ED-Activator, and alt-tab back in. That ought to be better than the one-eye method. You can keep your glasses off until you're in-game in sync-doubling mode. It's only some games that crash on alt-tabbing back in.


Enjoy it if you can.


--- iondrive ---

[iondrive]

more info:

How to set gaps based on resolution:

my config.xml also has this line in it:
<Gap Height="768" Value="20" Width="1024"/>
and the Value of 20 is used when I'm in 1024x768 mode, otherwise the default value is used. So it looks like you can follow the same format in order to add more lines to specify different gaps for each resolution you'll be using. That's good. Otherwise I believe it's safe to delete this line and then the default Value gets used.


Ghosting:
Ghosting is just what you would expect with a CRT using shutterglasses at 120Hz. Not too bad on my monitor but easy to see on the top of the screen. I think 120 Hz has more ghosting than 60Hz. I think the phosphors are slow on this monitor and that's what's causing it. Maybe I'll try a different monitor someday.


Comparing this to interlaced line-blanking mode:
This mode has a nice 120Hz flicker-free rate and never loses sync since it's easy for software to always keep the left-eye view "on top" and so the dongle keeps the sync since it generates the shutterglass signal at the same time it splits the video. Interlaced line-blanking mode can operate at 120Hz too and also never loses sync so, so far they're equivalent except that interlaced mode is more convenient since you never have to use one eye to click on things. The one worse thing about line-blanking is that it makes the display darker since half the lines are always blanked out. However, if you're showing 800x300 per frame, then that's basically the same as line-blanking since only half the lines are visible.


Breakthrough: (sort of)
What we need is a way to start out with a desktop of 800x1200. Then when we do the sync-doubling, each frame will be 800x600. I tried this on my 8800GTS using nvidia driver 196.21 and managed to make a custom desktop res of 800x1200 @60Hz. Then using TriDef's "force fullscreen" upscaling function, their over/under mode worked good except that they don't have gap control so the right eye view was too high. Too bad. To be fair, I have to suggest gap control to TriDef and upscaling to iZ3D. Neither have both. Later, I tried 1600x1200 @60 Hz and that worked too so you don't really need the custom res of 800x1200. It would really be best if I could do 800x1226 since my gap is 26, then each half image could be the original res of 800x600 and this mode would be brighter than interlaced mode since it uses no line-blanking. This could be the answer some of you shutterglass users are looking for. 120Hz, fullscreen images that never lose sync. I tried it with one game at 4 fps and never lost sync.


Does anyone know if gap control is helpful with some Left/Right viewing systems?

--- iondrive ---

[cybereality]

Yeah, I experimented with sync-double a bit with my Another Eye 2000 glasses. When it worked it actually looked pretty good and flicker free. I was able to get up to 170Hz which looked butter smooth for shutter glasses. However, at the time, no drivers supported over/under mode so I gave it up (I was only testing with video content). For all practical matters interlaced is just as good, so I am not surprised no one uses this anymore.

[iondrive]

Hi Cyber,

I know that was alot of reading in the first two posts and I wouldn't really expect you to read all of it since you already knew about this method, but just in case you skipped it, go back and read the paragraph labeled "Breakthrough". I just thought it was interesting that I could make a custom res of 800x1200. Given that, I could see someone choosing this mode over interlaced mode. It should be easier to read tiny text and the increased brightness can be important in some games. In Starwars Battlefront, there are often gray/brown robots against a gray/brown background and it's fine if the brightness/contrast is enough but the shutterglasses and lineblanking can take it's toll. Still, I thought of another reason interlaced is better and that is for watching 3d videos on you-tube. Sync-doubling would have a harder time with that.

--- iondrive ---

[tomgiboney]

Thank you so much for this... so what exactly is going on with this? Is this just an odd way of doing interleaving? Because it does look a bit like it, however the quality is sooo much better and there's absolutely no sync loss using this method just as you stated! So is this just an elaborate page-flip method? I'm testing out on higher resolutions as we speak! Thanks again for such an insightful post!

btw, my gear consists of:
X3D dongle with X3D/edim shutters, 19" phillips CRT (with something called lightframe3 which when turned on, it really makes up for the lowered brightness!), Windows 7, iZ3D beta drivers 1.11b or something I think. Also, the game I'm testing on is FEAR 2! Amazing!

UPDATE:
Ok, now I see. Half the horizontal lines of resolution are missing, as is evident in the text on the pda (FEAR 2). So, basically, I need to try and create a custom resolution of 1024x1536 and hopefully FEAR 2 will let me choose it (probably can edit a config somewhere if not). Then I'll see what happens. *fingers crossed*

[iondrive]

yes, it can look like interleaving/interlacing in lower resolutions or with small text and you're welcome. I knew some people would find this handy someday. Anyway, to understand things, separate the 3d process into 2 parts: hardware and software. The iZ3D driver here squishes 2 views vertically into two half-frames with one above the other. Run the driver without the Activator to see this. The Activator triggers the dongle to stretch each half to normal height and double the video refresh rate. Reread the top post and see if that helps. It's a little hardware trick the dongle plays on the computer. The computer outputs 60Hz and the dongle takes that and outputs 120Hz by sticking a vertical sync pulse in the middle of each frame. It's like a reset that tells the CRT to start at the top again. Really it's the CRT that has to resize the image to fit the screen since it assumes it gets a full frame with every v-sync pulse. If the CRT didn't stretch the image tall again, then you would see the image start at the top of the screen, get halfway down, then reset at the top agian. Once again, the CRT assumes that it's getting a full frame even though it's only getting a half frame. It's just built that way to stretch an image between v-sync pulses to fit the screen. So it can look interlaced when you're in 800x600 res and sync-doubling since then there's only 300 horizontal lines on the screen trying to fill the entire height. When you understand this well, it should be obvious why it never loses sync. It's essentially using the top and bottom halves of the "screen" as extra buffers to store image data for each view. Actually, I should also mention that the dongle is making the shutterglasses shutter in lockstep with those v-sync pulses. It knows nothing about the image on the screen and doesn't need to aside from initial sync with left-on-top. All the iZ3D driver has to do is put the correct images on top and bottom so that's why sync is not an issue here since the software has no problem putting the left-eye-view always on top even if the game is only generating 4 frames per second. The images are effectively buffered and the rest of the syncing is done in hardware.

I hope that clears things up.

Regarding 1024x1536 as a doubling of 1024x768, I think that should only help with TriDef's driver since they do things a little differently by using a kind of up-scaling. I've posted to iZ3D that they should do the same and it looks like they eventually will but I don't really know how soon that will be. If you can get your hands on an actual E-Dimensional dongle, you might like Blue-Line-Code shutterglass mod except that it depends on your game and setup. I have an X3D dongle too and it doesn't seem to recognize the BLC code. Hmmm, I'm not sure if I tested White-Line-Code with it. Try it and see if it works if you're curious.

--- iondrive ---

[cybereality]

I don't believe sync-doubling does any stretching of the image. What it does is insert a blank line after every scan line. That is why it will look similar to interlaced but at double the refresh rate.

[iondrive]

right, the dongle doesn't stretch the image, the CRT does that because it thinks it's getting a full image per v-sync pulse. It's just that the dongle causes the stretching indirectly since the extra v-sync causes the CRT to stretch the image. I didn't really re-write the above post like maybe I should have.

[cybereality]

No, that is what I am saying. I am almost entirely sure no stretching ever happens (either in the dongle or on the display). The vertical-sync pulse, all it does is have the next scan-line retrace from the top of the screen. If this were doing without adding blank lines then what you would see would only cover the top half of the screen and be a squished aspect ratio. The way it "stretches" the image, thereby restoring the aspect ratio, is by adding black lines in an interleaved fashion. So, for example, a sync-doubled display at say 800x600@60Hz would look identical to an interlaced (line-blanking) display at 800x600@120Hz. Do you see what I am saying?

[iondrive]

Yes, we are talking about the same thing. It's just that when I say the monitor stretches the image to normal height, I don't really mean that it does any image or signal processing on it. It's not the stretch you would do in Photoshop or the GIMP. I mean it takes the half-height image signal and makes it span the entire screen's height because it assumes it's getting a full frame. It does this like you say except I wouldn't say that it adds black lines between each scan line. I would just say that it increases the spacing between the scan lines. The difference is that there is always some space between the scan lines even when they overlap. OK, that doesn't make sense. The electron beam is only so wide and the phosphor density on the screen is only so much so I guess what I mean to say is that there's not really any kind of "black line insertion" function. There's only the electron beam scanning function and the black lines appear because of the undersampling done when, let's say 300, thin horizontal lines are equally spaced across the entire height of the screen.

Sorry to tell you things you already know.

--- iondrive ---

PS: so as a consequence, once you setup your system to display twice as many scan lines as your display can handle based on it's phosphor density, sync-doubling should be equivalent to page-flipping or at least pretty close assuming your 3d driver can do up-scaling. This almost holds true for line-blanking interlaced mode except for the extra image-darkening introduced by the line-blanking.

[cybereality]

Ok, so I guess we are saying the same thing then.

[iondrive]

I'm sure it will help someone else understand things better someday provided they're interested enough to do all that reading.

[tomgiboney]

I found I was able to use 1280x1024 resolution at 60hz with this method. For some reason, setting 1280x1024 on the desktop with a refresh of 120hz only yielded a black screen. But, I decided to try the iz3D test anyway (at 60hz of course) and to my surprise, it worked great! I had to adjust the gap to 41 and now it's just about perfect. I loaded Fear 2, Dead Space, and Modern Warfare 2... aside from my GPU (HD 4870) crashing every once in a while (but coming back after about 10 seconds or so... driver issue?), it ran sublime! Never missed a sync... and Dead Space in S3D was AMAZING!!! That game was meant to be in 3D! The best part about being able to use this higher resolution is I can no longer make out the missing horizontal lines of resolution! It looks like page-flip!

Simply amazing! Thanks again!

[iondrive]

You're very welcome,

I'm really glad to hear about someone benefiting from this thread. As I posted earlier, if you can get the res high enough so that all the physical phosphors on your CRT are hit by the electron beam, it can be as good as normal lossless shutterglass mode. Correction, that's really only if the driver does upscaling to help out. I say almost the same as shutterglass mode because a few horizontal lines are lost in the extra vertical retrace. In other words, if you wanted 800x600, then you could try a custom res of 800x1220. The extra 20 is for the extra retrace time. I tried this with TriDef but it didn't like it. 800x1200 is good enough but I'm not really telling you what to do, just use whatever works and makes you happy. I think going this far is not worth the trouble. Just use the standard res's.

Regarding why 1280x1024 at 120Hz undoubled doesn't work while 1280x1024 at 60Hz doubled works, I guess it's because the monitor really gets 1280x512 at 120Hz. The monitor can take a certain range of combinations of vertical and horizontal sweep rates and so the 1280x1024@120Hz test is not really perfect for testing if your monitor can take 1280x512 at 120Hz even though I told you to test things that way. It's just that I didn't have any better idea about how to test things like that. Now I guess I could tell people to make a custom res of 1280x512 at 120Hz but that's more trouble than just trying the method for real. Anyway, glad to hear about your success/happiness. I'm still really impressed that this never loses sync even if you're at 4fps even though I know I really shouldn't be that impressed since that's also true for interlaced line-blanking mode.

C-ya,

--- iondrive ---

[mickeyjaw]

Just a heads up to let you know that i have killed e-dim dongles in the past by pushing them too hard in sync-doubling. I think 110khz hsync is about the max safe. Mine died after i tried to sync double 1600x2400@50hz-->1600x1200@100hz IIRC. Now it only works in ddc mode. Didn't really bother me too much at the time as i had a spare though.

[tomgiboney]

Just a heads up to let you know that i have killed e-dim dongles in the past by pushing them too hard in sync-doubling. I think 110khz hsync is about the max safe. Mine died after i tried to sync double 1600x2400@50hz-->1600x1200@100hz IIRC. Now it only works in ddc mode. Didn't really bother me too much at the time as i had a spare though.

Great FYI there... although I do have 4 pairs (bought 4 X3D retail boxes for $5 a piece at a flea market!), I wouldn't want to destroy any. Of course I'll never go that big of a res anyway.