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I just bought a BenQ MX760 DLP projector, and will probably buy a second one to do an over/under dual projector setup. I have not invested in the lens yet but found Tru3d.com has almost everything I will need as far as the glasses and the lenses. Long story short this is the question I can't find an answer to;

If the 3D blu ray/ source output is a single hdmi 1.4 how do I run the signal to 2 projectors? Can I split it then use the projector to eliminate one of the images?
 

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To run 2 projectors you either need a 3D Demultiplexor (seperates a 3D stream into seperate left and right images) or a specially configured PC that has a special graphics card with dual HDMI outputs and software that will do the seperation.
 

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Also Optoma is scheduled to begin shipping a 3D processor box next month and by using two of these, plus a HDMI splitter, you can send left images to one projector and right images to the other. MSRP of these boxes is $399 each. This will provide support for the HDMI 1.4 and 1.3 3D signal formats being output by standalone Blu-ray players, PS3, cable TV and Directv boxes.
 

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Quote:
Originally Posted by Ron Jones /forum/post/19628521


Also Optoma is scheduled to begin shipping a 3D processor box next month and by using two of these, plus a HDMI splitter, you can send left images to one projector and right images to the other. MSRP of these boxes is $399 each. This will provide support for the HDMI 1.4 and 1.3 3D signal formats being output by standalone Blu-ray players, PS3, cable TV and Directv boxes.

Sorry,

but that is not going to work.

There is no handshake connection between two 3D-XLs.

23.97 Hz movies from 3D Blu-ray player require pull-down

process which will make outputs out of sync.


Mathew Orman
 

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Quote:
Originally Posted by icester
Sorry,

but that is not going to work.

There is no handshake connection between two 3D-XLs.

23.97 Hz movies from 3D Blu-ray player require pull-down

process which will make outputs out of sync.


Mathew Orman
icester, you say this like you have seen it in action and you are positive this wont work, is there something you know that everyone else doesn't? the 3DXL has settings for dual 1080p 3D so what is the handshake issue you are referring to? Seems to me that as long as the boxes are receiving the same signals then they should output the left and right image at the same time.... I just don't see how a company like Optoma could release the 3DXL saying it works with a dual projection setup and it not sync.
 

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Quote:
Originally Posted by jmcguire525 /forum/post/19683628


icester, you say this like you have seen it in action and you are positive this wont work, is there something you know that everyone else doesn't? the 3DXL has settings for dual 1080p 3D so what is the handshake issue you are referring to? Seems to me that as long as the boxes are receiving the same signals then they should output the left and right image at the same time.... I just don't see how a company like Optoma could release the 3DXL saying it works with a dual projection setup and it not sync.


I think he's talking about the process of converting 24hz to 60hz. Basically, two frames are displayed twice and the 3rd is displayed once. The issue is that the decision of which frame to convert is made by the processing device, and so it's likely that the selected frame from one box will be different from the selected frame on the other. This could theoretically make the 'judder' we're used to even worse. Theoretically one electronic device should process and sync up to a signal at the same speed as another, but it's not likely to be that consistent in the real world; An hdcp handshake and video acquisition usually takes 2-3 seconds to lock (at least it does for my pro350w). That means if the processor varies by one half of one percent, it's off by a frame or two.


However, that's distinctly different from "not going to work".



As was shown in the discussions about dlp link, icester likes to point out something that doesn't work the way he would prefer and call it "not working".



You know, what I'd LOVE to see? firmware update to add 96hz or 144hz outputs for supported devices when receiving a 24hz signal. I know as a fact the hd66 and pro350w both work in 96hz. Maybe 144 is impossible, dunno. But 96 would work.




*EDIT*

Actually, wait a second. This is EASY to fix, and I bet it already DOES.



When in 3d mode, due to the function of the box, it converts the signal to 120hz, right?


But when displaying L or R frame, there's NO NEED to convert framerate at ALL. For dual projection, the 24hz framerate is not a problem since you're not relying on shutters!


If Optoma simply outputs at the source framerate when displaying L or R - which I bet they do, since the only reason Optoma converts the framerate is to integrate the two streams, which there's no need for when you're only displaying one of them, why would they not simply output the source framerate?


And if they do, boom, no problem.



Though I'd still like to see them support 96 or 144hz so those of us with single-projector shutter systems can operate judder-free
 

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Quote:
Originally Posted by icester /forum/post/19628558


Sorry,

but that is not going to work.

There is no handshake connection between two 3D-XLs.

23.97 Hz movies from 3D Blu-ray player require pull-down

process which will make outputs out of sync.


Mathew Orman

Since the images run on the screen at the same time. Absolute sync is not needed. A few frames off will not be detectable at all. Probably even up to several frames off in all honesty.
 

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Quote:
Originally Posted by JOHNnDENVER /forum/post/19684798


Since the images run on the screen at the same time. Absolute sync is not needed. A few frames off will not be detectable at all. Probably even up to several frames off in all honesty.

I disagree strongly. Improperly synced dual projectors look horrible as soon as something is in motion. I tested this extensively on my dual projector system when I do not lock the two computer outputs together.

The sync does not need to be absolutely perfect by the millisecond, but the closer to perfect sync the better the image will look.


I already find sync artefacts when watching 120Hz frame-sequential displays (sync offset = 8.33ms)

One entire frame of offset on dual projectors at 60Hz (16.67ms) is quite painful, I just can't imagine how horrible an entire frame of offset will look at 24Hz (41.67ms), I did not even dared to try.
 

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Agreed, I can notice a frame offset as well, though in 120hz I don't find it disconcerting at all - but any more severe would be troublesome.


But as noted above, there's no need to alter the framerate for split-signal, so there's no reason to believe there would be any sync issues.
 

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How could there be any sync problems? We're feeding a split signals into 2 adapters and then into two projectors. Assuming that the adapters are 3DXL's and the projectors are the same manufacturer and model and the electronics would all be equivalent. All of that goes through at near the speed of light. What's the problem?


The only problem that would be obvious if there were slight differences in one of the components in the pj or adapter - say different firmware levels or different time of manufacturer with slightly different electronic circuitry - then testing would be necessary.
 

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It depends on what you mean by sync problems. If you're talking about the two simply being in "sequential alignment", you're right. While the transmission is not exactly speed of light (given that the image must be cropped that means it must be processed, and processing takes time), the processing time should be extremely short (
 

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Quote:
Originally Posted by Jkana /forum/post/19600958


I just bought a BenQ MX760 DLP projector, and will probably buy a second one to do an over/under dual projector setup. I have not invested in the lens yet but found Tru3d.com has almost everything I will need as far as the glasses and the lenses. Long story short this is the question I can't find an answer to;

If the 3D blu ray/ source output is a single hdmi 1.4 how do I run the signal to 2 projectors? Can I split it then use the projector to eliminate one of the images?

Very interesting set-up. Could you please describe the advantages of this set-up; thank you.
 

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John,

Even one frame out of sync would cause a problem every time there is a scene change.


defiancedp,

Converting 24fps to 60 fps when using 3:2 pull down means that 1/2 of the frames are displayed 3 time and the other 1/2 are displayed twice by alternating frames. This works since 3X24+2X24=60.

Also only have Plasma digital displays have theability refresh the screen at different refresh rates such as 72fps or 96fps. LCD and DLP displays always refresh the screen display at the same rate from the systems output buffer.

Since 3D PJ such as the HD66 have a native resolution of [email protected] I do not understand what the following quote from the link following it means

"

3D Compatibility

120Hz Frame Sequential 3D for

Resolutions Up to 720p, 60Hz Field

Sequential 3D for Resolutions Up to 480i

"

http://marketing.optomausa.com/PDFs/..._Datasheet.pdf



http://marketing.optomausa.com/PDFs/..._Datasheet.pdf
 

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Quote:
Originally Posted by walford /forum/post/19686111


John,

Even one frame out of sync would cause a problem every time there is a scene change.


defiancedp,

Converting 24fps to 60 fps when using 3:2 pull down means that 1/2 of the frames are displayed 3 time and the other 1/2 are displayed twice by alternating frames. This works since 3X24+2X24=60.

Also only have Plasma digital displays have theability refresh the screen at different refresh rates such as 72fps or 96fps. LCD and DLP displays always refresh the screen display at the same rate from the systems output buffer.

Since 3D PJ such as the HD66 have a native resolution of [email protected] I do not understand what the following quote from the link following it means

"

3D Compatibility

120Hz Frame Sequential 3D for

Resolutions Up to 720p, 60Hz Field

Sequential 3D for Resolutions Up to 480i

"

http://marketing.optomausa.com/PDFs/..._Datasheet.pdf



http://marketing.optomausa.com/PDFs/..._Datasheet.pdf

Simply means that it is compatible with the legacy field sequential stereo such as one found on many 3D DVDs.


Mathew Orman

http://www.*******************-usa.com/
 

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Quote:
Originally Posted by walford /forum/post/19686111


Converting 24fps to 60 fps when using 3:2 pull down means that 1/2 of the frames are displayed 3 time and the other 1/2 are displayed twice by alternating frames.

I know, that's what I said. My point was that it's not a problem if the 3dxl outputs the framerate that's input, and there's no reason it wouldn't do exactly that.



As for your discussion about refresh rates, your point is correct but not as you stated it. While a DLP does refresh at a set rate, that does not preclude its ability to accept different input refresh rates since its screen refresh is at a much higher rate than the frame refresh rate - usually several times per frame, for a common example 480hz. The screen can display any divisible number properly. So in that example 96 would work fine. 144 would involve some frame juddering, but at a ***MUCH*** faster and less impactful rate than standard 24/60 juddering. On the other hand, if it were 360, 144 would work fine but 96 would have the much improved juddering.


For reference, I know that the Optomas can do this with 96 and 72 hz, having used both of those modes. I'm not sure what the physical DLP refresh is in them, but in both cases I can no longer detect judder from 24hz media.


(*edit to clarify*: color wheels in DLPs commonly spin at 120hz, but include multiple sequences of each primary, allowing for screen refreshes at multiple times per rotation, reaching the higher rates mentioned above)
 

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Quote:
Originally Posted by defiancecp /forum/post/19687965


I know, that's what I said. My point was that it's not a problem if the 3dxl outputs the framerate that's input, and there's no reason it wouldn't do exactly that.



As for your discussion about refresh rates, your point is correct but not as you stated it. While a DLP does refresh at a set rate, that does not preclude its ability to accept different input refresh rates since its screen refresh is at a much higher rate than the frame refresh rate - usually several times per frame, for a common example 480hz. The screen can display any divisible number properly. So in that example 96 would work fine. 144 would involve some frame juddering, but at a ***MUCH*** faster and less impactful rate than standard 24/60 juddering. On the other hand, if it were 360, 144 would work fine but 96 would have the much improved juddering.


For reference, I know that the Optomas can do this with 96 and 72 hz, having used both of those modes. I'm not sure what the physical DLP refresh is in them, but in both cases I can no longer detect judder from 24hz media.


(*edit to clarify*: color wheels in DLPs commonly spin at 120hz, but include multiple sequences of each primary, allowing for screen refreshes at multiple times per rotation, reaching the higher rates mentioned above)

It is a problem when you have two 3D-XLs.

Since there is no hand-shake between the boxes the pull-down will get out of sync and there is no button on 3D-XL to reset the pull-down sequence.


Mathew Orman

http://www.******************-usa.com/
 

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Quote:
Originally Posted by icester /forum/post/19688406


It is a problem when you have two 3D-XLs.

Since there is no hand-shake between the boxes the pull-down will get out of sync and there is no button on 3D-XL to reset the pull-down sequence.


Mathew Orman

http://www.******************-usa.com/

As noted above, I agree with you if they change 24hz to 60hz - but if they don't, but there IS NO PULLDOWN if there's no change of refresh rates. So if the devices simply pass on the same refresh rate they get in the first place, there's no issue. And as noted, there's no *reason* for them to change 24hz signals to 60hz if they're just cropping the images. Why would optoma have their device do a bunch of extra work when there's no need or reason to do so?
 

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Quote:
Originally Posted by defiancecp /forum/post/19688654


As noted above, I agree with you if they change 24hz to 60hz - but if they don't, but there IS NO PULLDOWN if there's no change of refresh rates. So if the devices simply pass on the same refresh rate they get in the first place, there's no issue. And as noted, there's no *reason* for them to change 24hz signals to 60hz if they're just cropping the images. Why would optoma have their device do a bunch of extra work when there's no need or reason to do so?

There is only one 24Hz full HD 3D frame packed HDMI 1.4

protocol and that there is always pull-done process involved when the target is 120 Hz.


Mathew Orman
 
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