CurtPalme.com Home Theater Forum

Miller101 · Joined: 16 Jun 2010 Posts: 6 Location: Texas

Hello Everyone,

I was wondering if anyone has tried 3D with their CRT projectors ? It looks like the basic idea behind 3D TV/BD is to have 1080 signal with 120Hz instead of the normal 60Hz and have two slightly offset images sent to the TV. Some of the Mid to high end CRT projectors have enough bandwidth to handle the signal, but not sure if the HDMI devices like HDFury or the HDMI boards from Curt will be able to handle this signal ?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

This is being discussed in several locations across the forum.

Right now it's not possible. This is due to the Blu-Ray 3D implementation NOT including an outboard system to control the LCD shutter
glasses. All sets that can be used to view 3D in 3D include a shutter glasses and controller package. The controller is an IR transmitter
which delivers a synchronizing signal to the glasses. The controlling signal is generated from within the 3D-compatible TV set,
and our projectors do not have this system.

But people are certainly looking into it!

CJ

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4409 Location: Phoenix

Hello

CRTs have been used to display computer-rendered 3D for at least fifteen years. Silicon Graphics pioneered in this field. Use of shutter goggles is called active stereoscopic, and the IR pulses to sync the goggles are generated in the computer to drive IR emitter devices placed near the screen. Emitters were as small as a cigarette pack, and several could be placed near the screen for proper coverage. I did maintenance on several Marquee installations rigged for stereo around the Detroit area. Edge-blending was employed where clients wanted to display cars full-size and in stereo. We had installations at EDS, GM, and Lear to name a few. 3D could also be had in the CAVE immersive environment and well as the more compact ImmersaDesk. P43 fast-refresh green tubes were preferred, and vertical rates at 96hz and 120hz were common.

.

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dturco · Posted: Wed Jun 16, 2010 6:29 pm Post subject:

Tim, as I understand it you need 2 P/J's to do 3-D.

Can 3-D be done with just 1 Marquee?

emdawgz1 · Joined: 14 Mar 2006 Posts: 7949

How is it done in a theater???

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Yes, a single projector can handle the alternating frame format used by 3d Blu-Ray. Provided it has the bandwidth required.

But the sync system required to run the shutter glasses is controlled by sync information embedded in the HDMI data stream,
and only comes from 3D-enabled Blu-Ray players while playing in the 3D mode. That information would have to be extracted
and utilized by an external device that does not YET exist.

The 3D format used by 3D Blu-Ray is almost certainly going to become the de facto 3D standard in the consumer market.
But as Tim mentioned, there are several working 3D formats. However, none of them or their associated equipment will give you
a plug-and-play solution for making 3D shutter glasses work with the 3D Blu-Ray standard.

Yes, a viewable 3D image could be generated without tapping into the sync data from the HDMI data stream but there would be no
assurances that it would stay synched to the picture.

If I knew the precise frame rate the picture needs, whether it be 29.97 Hz, 30.00 Hz, 48 Hz, 72 Hz, 96 Hz, or 120 Hz, or any other
specific frequency, then I could use a precision sync generator to generate a trigger pulse that would drive an Atmel FPGA device which would be programmed to drive an IR emitter with the appropriate sync pulses. Once it was phased to the signal, it should be stable,
at least until there is any disturbance in the picture flow. This would be irritating in the short term, aggravating in the long term,
and not a marketable solution to all but the most tolerant of obsessive-compulsive gadget tweakers.

CJ

JustGreg · Joined: 07 Mar 2006 Posts: 3098 Location: Kenosha, WI

ecrabb · Posted: Wed Jun 16, 2010 9:25 pm Post subject:

Guys,

Until we see definitively how the 3D is stored on the Blu-ray disc and exactly how the new players will output it, it's still a bit of an unknown how- or if this is going to work with CRT, or what hardware solutions would be necessary to make it work. The issue at hand goes well beyond the simple lack of an outboard active-stereo glasses sync emitter. For instance, if the BD-player outputs a 1080p/24 signal for each eye (so, basically 1080p/48), an LCD display might just frame double that... However, it would be utterly unusable on a CRT. Most CRT projectors would sync the 1080p/48 just fine, but the flicker for each eye would be 24hz and completely unwatchable. I meant to mention this issue in the other thread where you mentioned it CJ - but I didn't get around to it.

As I see it, currently at least, the potential (and real) problems with 3D Blu-ray at home on our CRTs are two-fold:
A) Lack of detailed specs on how the video is stored and how the currently 3D-capable BD players output that signal.
B) Depending on A, potentially lack of proper processing to achieve CRT-displayable image.
C) Lack of hardware to generate a sync signal for active stereo LCD shutter glasses.

All could be relatively easily overcome with a high-end computer-based BD player with the appropriate hardware, software and drivers... None could be easily overcome using set-top hardware... Not without some serious design capabilities, and not without seeing how these discs are formatted, and how the players output that format.

The hurdles could be significant... We'll have to wait and see until people have players and content in their hands and get more data on how it all works.

SC

ecrabb · Posted: Wed Jun 16, 2010 9:32 pm Post subject:

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4409 Location: Phoenix

betel · Posted: Wed Jun 16, 2010 11:11 pm Post subject:

chillman · Joined: 09 Apr 2007 Posts: 134 Location: Germany, Bavaria

I just checked the nvidia homepage, and found what i was hoping to find: their 3D Vision system will support 3D bluray blayback.
I'm not 100% sure if there are any restrictions other than 120Hz capability, but if not, this would be the perfect solution for stereoscopic
movies on a CRT projector.

Greetings!

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

The detailed technical specs on how the 3D system on 3D Blu-Ray operates are not openly available to the public. Those documents are restricted to those who enter into the technology licensing agreements with the Blu-Ray Disc Association.

But, I have found some significant information which gives some insight into how it operates though it's far from a detailed "how to" guide.

http://hdguru.com/3d-hdtv-and-hdmi-explained/1336/

http://www.blu-raydisc.com/en/Technical/Updates.html

Check the technical updates on the left side column.

We DO (or at least, I do) understand the fundamentals of how the 3D Blu-Ray sytem operates. It's as I described it. Sync pulses are embedded in the HDMI data stream. (Which is encrypted via HDCP.) Those sync signals are grabbed by the compatible display and
used to drive an IR emitter which in turn provides the sync pulses to the shutter glasses which keep the image synchronized.

Proper image synchronization is important. For example, if you were to get the synchronization inverted, so that the left image was
being displayed while the right shutter was open, the 3D effect works but it will appear inverted. Things that should appear close to
you will appear to be far away instead. It's bizarre but it happens.

If you made a stereographic pair of photos and do the "third eye" wall-eyed stare trick at them to reveal the 3D image, and you were to
flip the pair's order to be incorrect, you'll get that same reverse depth effect.

There are no technical obstacles standing in the way of Blu-Ray 3D becoming available for CRT projection. Every part of the challenge
can be managed by capable engineers, and I KNOW that some are working on the solution already, at least to the extent that they're
starting to look at how the system works and making plans to explore more deeply.

My belief is that what we will have available to us before too terribly long is an outboard device that connects into the HDMI signal chain
and does sync pulse extraction, drives an IR emitter and shutter glasses, and also does framerate conversions by appropriate
fractional pulldown techniques so that we can get the best out of 3D that our projectors will allow. It will be a stand-alone device or
at least available in a stand-alone configuration.

I for one have absolutely no desire to go the HTPC route. I far prefer hardware components.

CJ

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

It can be done with nVIDIA 3D glasses, and im pretty sure, not totally, but pretty sure it will also play the bluray movies in 3D with that set.

The problem there is there is only one set of glasses/sender unit in a box i think, and its dear as f*** to buy when i looked into it.

I have nVIDIA 3D on my computer with the use of red/cyan glasses, and i reckon its great for some games, i have tried it with BattleField 2142 because its not real colourful anyway, but the issue there was i couldnt really tell in a rush who was who, so i shot everything that moved, and consequintly got kicked from a few servers.

I dont think that setup will work for movies, unless they are anaglyph type allready.

Mark_A_W · Posted: Thu Jun 17, 2010 10:41 am Post subject:

CJ

Monsters vs Aliens has already been converted to a side by side 3840x1080 at 24p format, and you can play it back with Stereoscopic Player.

A mate has made a circuit to drive shutter glasses from the sync pulse on a RGBHV output. I need to get some, not sure what type yet.

How good it is will come down to how well a CRT can handle 96hz, or higher (maybe interlaced). I'm skeptical about this.

But technically it can be done right now. With a PC and RGBHV Wink

David_Web · Joined: 02 May 2007 Posts: 418 Location: Sweden

Yeah, sync is not the problem. It's not like a CRT can render at a different frame rate than v-sync dictates.

If you can get the over/under into alternating frames, interlaced or otherwise you should be fine.

Maybe a timer to get proper offset and correct for lag. Doesn't matter if you are one or ten frames behind as frame rate should be stable enough.

ecrabb · Posted: Thu Jun 17, 2010 2:45 pm Post subject:

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Obviously some of you are using the HTPC route, which is fine for those who want to go in that direction, but I don't use an HTPC. Nor do I have any slightest desire to do so. The HTPC route is far less common than people buying components and the market for a 3D converter for the component side of the market is potentially very large.

Maybe you can view 3D with your HTPC but that doesn't help those of us who don't have an HTPC and don't want to go there.

I do understand the advantage of flexibility and custom configurability that an HTPC offers, but to me, the drawbacks and cost outweigh
the benefits and lower price point of separates.

CJ

Sparky015 · Posted: Thu Jun 17, 2010 4:06 pm Post subject:

So what ecrabb is trying to say (I think, correct me if I'm wrong), is that 120Hz refresh is really the optimal rate for CRT (72Hz X 2 to avoid the flicker). If that's the case, your going to need more than a box for the sync pulses, your going to need a processor that can handle that has well. You know your Sony standalone player isn't going to support that, because mainstream is not CRT. So if HTPC is not the way some of you want to go, looks like a Radiance is going to be needed, at least for 1080p viewing. Now your talking thousands of dollars to make CRT work for 3D before you even get to the sync box that's yet to be developed. I don't know guys, that's a bit much for what looks like another fad. Maybe the next go-around if CRT is still around then.