Directly drive 3d TV in FullHD?

S.L.P. image questions, stereoscopic video livestream and recording, stereoscopic photo capture etc.
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drayde
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Joined: Thu Apr 08, 2021 8:00 am

Directly drive 3d TV in FullHD?

Post by drayde »

Hi all,

has anyone tried to output the dual-camera video to a 3D TV directly?
I know it can be done using raspivid's preview mode eg in SBS mode when the TV supports that. But would that be possible in FullHD (1920x1080) as well?
The Raspi3 framebuffer is limited to 1920x1080, so it cannot hold 2 FullHD images in SBS or TB mode. But in theory, it is capable of generating an HDMI 1.4 compatible 3D frame-packing output in FullHD. At least omxplayer supports doing this, see https://www.raspberrypi.org/forums/view ... p?t=131954
But I guess raspivid cannot do that. Or can it?

BTW: I was looking for the source code for StereoPi's modified raspivid, but could not find it. Can someone point me in the right direction?

Best regards
Andreas

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Realizator
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Re: Directly drive 3d TV in FullHD?

Post by Realizator »

Hi Andreas,
We try to play with 3D TV, but no success. We used all possible settings, but TV does not recognize Pi's HDMI output as a 3D. The only way was to "force" 3D SBS mode in the TV menu - and this approach works fine.
One trick for you: if you turn on "decimate" mode (it is '-dec' command for raspivid, or you can use a checkbox in our admin panel). In this case, each image is scaled by 0.5 horizontally, and you have a couple of compressed FullHD in one 1920x1080 frame. TV does the opposite work - it scales each camera back to its original resolution.
As for the source code - we found this solution on RPF forum. Please look at my question here, and more detailed info I put for 6by9 here.
To say the truth, I'm still can't get it. If Pi does not support 3D screens at all (as declared by a lot of users), why can't they add a stereoscopic preview on regular 2D screens, which 99.999999% of Pi users are having? :-)
Eugene a.k.a. Realizator

drayde
Posts: 2
Joined: Thu Apr 08, 2021 8:00 am

Re: Directly drive 3d TV in FullHD?

Post by drayde »

Hi Eugene,
thanks a lot for the quick answer!
Yes, the -dec option is what we use at the moment as well. Too bad there is no other way. Maybe I'll dive into the source code (thx for the links to the forum, very helpful!) to understand what's going on there. There should be a way to do this, as omxplayer can do it too.
What will the situation be with StereoPi2? I guess you can have higher resolution SBS video, but this still does not help with FullHD 3D TVs, as they want frame packing for having full 1920x1080 frames.
Kind regards,
Andreas

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