relaxpi4
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Dual output for 3D stereo projection?

Tue Sep 10, 2019 1:28 pm

Hi
i am very happy to see that Pi 4 has two hdmi output.
Does it actually mean , we can use two different videos (left and right view for 3D) and play it in perfect sync?
Or one full sidebyside video (3840x1080 or 2560x720) and playback to the extended display? Is it possible?
If somebody could test it for me i can upload such files.

Many thanks

relaxpi4
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Joined: Tue Sep 10, 2019 1:15 pm

Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 5:33 am

Somebody could check it for me? :roll:

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Gavinmc42
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 8:32 am

Sure, do you know what software can do this?

I got Openkinect to compile, but no luck yet with VRui
https://arsandbox.ucdavis.edu/technical ... s/vrui-vr/
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relaxpi4
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 8:37 am

I dont know the software, thats why i ask here :P

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Gavinmc42
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 9:06 am

You might have to do a google.
I found a -stereo option for glxgears
http://linuxcommandlibrary.com/man/glxgears.html

This looks interesting
https://hub.packtpub.com/rendering-ster ... ng-opengl/

https://www.mesa3d.org/intro.html
I did not have much trouble with compiling the demo examples.
https://www.mesa3d.org/repository.html

I noticed these stereo versions in the examples, but that was before I had a Pi4
http://www.gali-3d.com/archive/articles ... torial.php
Glut code works, if you install the newer freeglut lib.

I would say it will work but it just needs someone to prove it :D

Another option is use a VR app for a smart phone, cheap VR glasses and let the Pi4 serve the images over WiFi.
Dual 4K glasses with two HDMI inputs? Probably expensive?
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relaxpi4
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 9:13 am

Thanks for the link.
I dont want to use a VR headset, i have a dual projector rig for 3D.
So what i only want is to playback two 1920x1080 (left-right) OR one SidebySide 3840x1080 OR at least 2560x720 video in frame perfect sync.
One video for one hdmi out, the other on the 2nd hdmi.

Wifi is not good here..

thanks

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Gavinmc42
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 9:33 am

Are you using shutter glasses?

I have programmed the General purpose clock output 0 on the older Pi's GPIO.
If you use the HDMI clock as the source input, it might divide down and sync.
With 4K the best will be 30Hz? That might be noticeable.

You might have to wait for the new BCM2711 peripheral manual to figure out which registers.
Clues might already be in the device tree overlay sources.

Pi4's have been out now for a few months, some might have made it into the Uni media labs.
Might be too early for the papers to be written up?
Everyone will probably be doing it next year?
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relaxpi4
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 9:37 am

No, i use passive glasses with a silverscreen.

PiGraham
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Location: Waterlooville

Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 9:40 am

relaxpi4 wrote:
Tue Sep 10, 2019 1:28 pm
Hi
i am very happy to see that Pi 4 has two hdmi output.
Does it actually mean , we can use two different videos (left and right view for 3D) and play it in perfect sync?
Or one full sidebyside video (3840x1080 or 2560x720) and playback to the extended display? Is it possible?
If somebody could test it for me i can upload such files.

Many thanks
What displays do you hope to output to? How will you view them as stereo?

AFAIK most 3D displays use a single input port for both eye views, which takes care of synchronisation.


To get good stereo effect on a large screen I suspect you need to go for per-eye filters such as those used with 3dTVs because you probably can't get the optics to work like a headset with one screen for each eye.
Eye convergence is an important factor and two big screens, one per eye, would require the eyes to diverge a lot.

I see your later post mentions dual projectors. How do you get 3D from that? Are they projecting to separate screens? Can you match the view to the users inter-pupillary distance and get the eyes to converge at the centre of each screen? Have you tried this with still images?

ETA is this a polarised system? Two projectors onto the one screen, one through H-polariser the other through V-polariser? If you can match projection geometry between them so that everything lines up that could work I suppose.

relaxpi4
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 9:44 am

I make passive 3D projections since 10 years with dual projectors, polar filters, etc. No problem here, just like in cinemas.
But i like to playback from a Pi4 instead of PC if possible :)

PiGraham
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 9:45 am

OK. Cool.

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Gavinmc42
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 10:56 am

Had a look at VLC, it can do 3D
https://wiki.videolan.org/SoC_2011/Ster ... on_support
But not sure if it can do the polarised output type.
i supposed the source can be modified and recompiled.

Video or computer generated data?

https://escience.aip.de/visualisation/t ... 3d-movies/

This looks very interesting
http://bino3d.org/\
I have starting to "make" it on Gentoo64.
Not sure how long it will take to make or crash
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Gavinmc42
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 11:05 am

Well that was painless.
Let us know if Big Buck Bunny runs in 3D
http://bbb3d.renderfarming.net/download.html
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relaxpi4
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 11:11 am

Thanks but VLC seems only good for Nvidia vision and AMD HD3D, while i don't use these.
There is no "polarized output" its called dual screen output in stereoscopic player.

I simply need to put one video to hdmi1, other video to hdmi2 output.
So it's video in my case.

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Gavinmc42
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 11:19 am

Bino uses OpenGL and has dual/multi screen options.
I will need to try it on my dual screens at work ;)
Might have to have a chat with the media labs guys around the place, this looks useful.

I was looking for VR software, this Bino might do it.
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relaxpi4
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Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 11:30 am

cool, pls check :)

epoch1970
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Location: Paris, France

Re: Dual output for 3D stereo projection?

Mon Sep 16, 2019 11:33 am

relaxpi4 wrote:
Mon Sep 16, 2019 9:44 am
I make passive 3D projections since 10 years with dual projectors, polar filters, etc. No problem here, just like in cinemas.
But i like to playback from a Pi4 instead of PC if possible :)
Purely out of curiosity, do you have a link to examples of contemporary rigs?
I've left the "scene" a long time ago, my FED stereo slide projector is gathering dust (heck even finding a picture of it online is difficult!).
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

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Gavinmc42
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Re: Dual output for 3D stereo projection?

Tue Sep 17, 2019 11:40 am

Plan B long term?
https://www.khronos.org/openxr/
This compiled, but I have no idea how to use it yet.

More for AR/VR games than 3D recorded videos?
Now we just need the Pi equivalent of the google cardboard.
A dual HDMI display headset.
Perhaps with an i2c/SPI based motion sensor?
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relaxpi4
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Re: Dual output for 3D stereo projection?

Wed Sep 18, 2019 3:37 pm

epoch: i dont have a picture near me, but my rig looks like these:
https://www.google.com/search?biw=1920& ... CAc&uact=5

epoch1970
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Re: Dual output for 3D stereo projection?

Wed Sep 18, 2019 3:54 pm

Cool. Thanks!
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

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Gavinmc42
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Re: Dual output for 3D stereo projection?

Thu Sep 19, 2019 5:49 am

I had a play with Bino and Stereoscopic Player in Windows.
Lots of options to tinker with, dual and single screen.

Bino should work on the Pi4 if you can compile it.
Someone with two screen working should try it

I so need to make some coloured glasses 8-)
Saw a new "White" laser from SDL, projectors will get brighter and last longer.
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