Stereo Movie Player?

[JeremyJessup]

I have experience doing exactly what you're trying to do. I actually helped design a system to do it with and you don't need special software (although if you know a programmer who can build something like you're talking about it would simplify the process).

The way we got our system to work was to get two high end video cards on a SLi motherboard so that we could send high resolution images to both monitors on the dual monitor system (we obviously hooked up the projectors to the video out rather than monitors). Next, we combined the images from the left and right into a single double wide image set and created an AVI file with it. We were able to use Windows Media Player for playback, just setting the player to full screen and using 'screen spanning' for the display output.

This makes the computer view both video cards as one monitor and avoids the problem of your video being out of sync due to a dropped frame on one of the channels. We tried it with Quicktime as well, but it choked on the playback file a bit due to the extreemly high resolution (2048 x 1536 per side).

Handy note.. with a projection, you need brighter than average projectors because each image is half filtered, but the resolution doesn't need to be as high as you might guess because the focus on the projector after the filter is applied is never 100% sharp, but it will look fine with half the resolution we used.

Hope that helps

[pulse]

Sounds to me like a quick and elegant solution, thanks Jess!

I am just not clear about what exactly you mean by 'screen spanning' - is it sufficient to have a horizontal spanning dual desktop set up or as I would guess you would need to 'tell' Media Player somehow to use both screens for fullscreen?

I figured it would span to fullscreen on both screens, but the video overlay on the 2nd screen is blank - maybe I would need SLI to be able to show the movie on both screens simultaneously (by having movie acceleration on both screens)?

[JeremyJessup]

You have it just about right... I think it's called something else if you have an ATI card, but nVidia calls it screen spanning. Instead of needing two machines or having a cloned desktop or a 'second monitor,' Windows uses both monitor outputs as one monitor (and you can see it as a wide rectangle in the display properties once it's set up).

If one screen is blank, you have probably used the Windows function 'expand desktop to this monitor' option. It has to be set up in the display driver, so as to fool Windows into seeing them as one device, rather than using Windows to split it.

What video card/cards are you using? Maybe I can help you find a technical document on how to set it up.

[pulse]

My colleagues are concerned if we really need to buy an SLI graphics card setup for that - is an SLI setup obligatory for displaying movies fullscreen spanning over two monitors on a horizontally spanning dual screen setup or is there another way?

With one graphics card with two video outputs, although the second screen is drawn (windows borders, wallpaper and so on), it does not show the movie on the second screen - instead of the video overlay it shows some completely black or green area.

[JeremyJessup]

Sorry for being unclear on that... we were using very high resolution with a higher than typical frame rate (60 to 100 FPS). The video card and systemboard configuration you will need will all depend on the resolution and framerate you need for your final product. If you will be doing no more than 1024 X 786 per side and running at about 30 FPS, you should be fine to use a single card with two outputs.

We attempted the same thing on a single card first, but the client wanted double or better the resolution and a higher frame rate (which was unnecessary, but once you've explained it and they still want to do it, you do what the client pays you for) using an nVidia gForce 6700 (as I recall) with 512 RAM on it. For pur purposes that didn't quite cut it, but two slightly slower cards with less RAM running parallel worked.

What is your project and how high does the resolution need to be? That will help determine what you need in terms of your system configuration to play it back appropriatly.

The alternative is getting a device that will toggle images out between projectors (single frame sized image at double FPS, the device splitting the images to the projectors alternatly).

This sort of system is costly as well and if you drop a frame, your depth is flipped.

[pulse]

The resolution is two times 1024x768 = 2048x768.

We tried the setup with a single graphics card on three computers:

On two of them (one with a Quadro FX4400, one with a Geforce 6600) the second screen would show the desktop and the window, but not the video overlay (it would show black or green). But in another lab here they use a Geforce FX 5700 and horizontally spanned video playback works just fine - although the settings seem to be equivalent (even the Windows Media Player hardware acceleration is set to full there, the horizontal span etc. is the same). We wonder why it wont work on our machines.

Could you please describe the media player and video driver settings for the stereo playback in more detail (especially the hardware acceleration setting in media player and the video driver version and screen resolution)?

[DBoone]

There's really no reason to separate the avi's to different monitors. Render each view as a separate avi at 320x480 (yes vertical) and import these into After Effects. Then you compose the shot with each view side by side in a 640x480 frame (each side 320x480). If you swap the left and right sides, you can cross your eyes and watch the clip without the need for any fancy technology.

Try it out first...

http://www.studio3d.com/pages/compstereo.html

[JeremyJessup]

Sorry for the delay in getting back to you... it's been busy lately (close to 100 hours a week up to just recently).

As for the specifics on the drivers and the setup, it's been about a year since I worked on the system that we had set up and I'm a few hundred miles away from it at the moment. Shoot an email to john@virtuegraphics.com and tell him that you were getting some info on how to set up a stereographic 3D system. Just let him know you were talking to Jeremy (that's me :) ) on the forums here and that I referred you to him. He has the system we set up and would have info on the exact hardware and settings he is using.

If you're using 3D Studio, there's a free plugin that you can download that creates a stereo camera setup and allows you to render in video post with left/right dual images. The plugin is called XIDMARY (Cross Eyed Mary).

To respond to DBoone, while it is true that you can render your images seperately and then simply put them side by side for cross-eyed viewing, it doesn't give your clients the same bang for their buch that way and some folks can't cross their eyes to see the effect. The reason for doing it out to different monitors is so that you can use two projectors rather than monitors, overlaying both in to the same physical space on the screen and filtering each using the polerized filters on the lenses and polarized glasses for the viewers.

[pulse]

We already were successful in making it work!

Somehow as we connected the workstation to the projectors we must have changed something in the configuration that made the problem of the missing overlay on the second screen disappear.

We did not change much - it may be a different screen resolution or the fact that now instead of feeding both inputs to a dual input monitor with one analog and one digital (DVI) cable, we now connected the system to the projectors with two analog cables.

We should double check before the show to be sure...

Thanks a lot for your input Jess, the horizontal span is just perfect - now we basically can use any video player.

[JeremyJessup]

Glad I could help and that you got it all worked out. Out of curiosity, what is the project for? Do you have any stills you can share from the finished project?

As a pointer, I created a stereographic still which I set up as the desktop image (to match the resolution, without stretching the image, of the spanned screens), so when the system was turned on I could look at the company logo in 3D right away and verify that the screens were set up right and that the projectors were properly aligned.

[pulse]

I will ask my collaborators for some stills and send them after the show. We have quite a lot left to do and the show is already in two weeks... Wish us luck :-)

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