miguelhahn
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Double Full-HD Videowall using a Raspberry Pi 4

Wed Jul 31, 2019 1:59 pm

Hello,

I'm very new to Raspberry Pi, I hope this question hasn't been answered a million times, I couldn't find any topic discussing it anyways.


I'm working on an exhibition project. It is going to consist of a video projected using two full HD proyectors that get fed via HDMI.


So the new Raspberry Pi4 has two HDMI ports, which is great. My idea is to have a 3840x1080 Video File that gets split into two 1920x1080 images, one on each Projector. Is this doable via PiWall on a Raspberry Pi4? Will it have enough power to play the file back without problems? Is there maybe other trouble i might run into that I don't see at the moment?

Thank you :)


6by9
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Re: Double Full-HD Videowall using a Raspberry Pi 4

Thu Aug 01, 2019 1:20 pm

H264 is limited to 1920x1080. HEVC can do 4k.
If you decode a 3840x1080 HEVC stream then you can present it to both displays using DRM (or DispmanX if you want to stick to the old APIs) along with a source rectangle for each screen. Not trivial, especially to do it efficiently, but possible.
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miguelhahn
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Joined: Wed Jul 31, 2019 1:50 pm

Re: Double Full-HD Videowall using a Raspberry Pi 4

Sat Aug 03, 2019 4:43 am

Hi 6by9

thank you for your answer. I'm a little bit unsure if I will be able to make it work smoothly…

miguelhahn
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Re: Double Full-HD Videowall using a Raspberry Pi 4

Tue Aug 06, 2019 7:44 am

Would it be easier to use two Raspberry Pi 3, one for each projector and then synch them?

jamesh
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Re: Double Full-HD Videowall using a Raspberry Pi 4

Tue Aug 06, 2019 8:32 am

miguelhahn wrote:
Tue Aug 06, 2019 7:44 am
Would it be easier to use two Raspberry Pi 3, one for each projector and then synch them?
If you are unfamiliar with coding, and 6by9's comment above means nothing, then yes, it would be simpler to have two devices. This has been done a lot - google should find more help.
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aBUGSworstnightmare
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Re: Double Full-HD Videowall using a Raspberry Pi 4

Tue Aug 06, 2019 9:31 am

There is a splitter in VLC but it's not documented that well.

Click on tools->preferences and select all

Under VIDEO you will find an entry SPLITTER; expand it by clicking the arrow. Now configure your wall for 2 colums and 1 row. In active window you will have to type '0,1' to have two active windows.

Click SAVE, exit and re-start VLC. Now your videos should be splitted into two windows. Move them to the screen of your choice and expand them to fullscreen.

NOTE: I've not tested this on an RPI4 yet!

miguelhahn
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Re: Double Full-HD Videowall using a Raspberry Pi 4

Tue Aug 06, 2019 12:55 pm

Cool thank you guys. I'm trying it with the Pi4. I think I can manage it, I just hope the power is enough to stream the video.

I will report!

miguelhahn
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Joined: Wed Jul 31, 2019 1:50 pm

Re: Double Full-HD Videowall using a Raspberry Pi 4

Tue Aug 13, 2019 8:28 pm

Hello Again,

So I tried it with the solution suggested by aBUGSworstnightmare. Thank you again! And it kind of works, when there is not a lot of movement and on bright parts of the video it works really well. But as soon as there is a lot going on it gets pretty choppy. The video is compressed in H.265, is there an alternative to VLC that might playback more consistently? Or maybe a codec that decodes easier? Well, I'm also trying to see if I can go down with the resolution a little bit.

hiro_pitagonist
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Re: Double Full-HD Videowall using a Raspberry Pi 4

Tue Aug 13, 2019 8:36 pm

For the video wall to work properly with video motion, you actually have to keep the frame syncs of both video ports in sync (vertical sync is in phase and exactly the same frequency).

You should talk to the GPU coders (Popcornmix) to see if that is possible on the PI4. It requires hardware support, which is controlled by the gpu on pi.


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Re: Double Full-HD Videowall using a Raspberry Pi 4

Fri Jan 24, 2020 6:58 pm

My software/service info-beamer can do that. You can decode a single 3840x1080 H265 video and place it on both displays. You can run the info-beamer software yourself on Raspbian, but that's a bit of work to get right. The far easier solution is the software as a service solution. If you have a spare SD card, setting this up takes only a minute or so. See the instructions of the 4K/dual HDMI demo at https://info-beamer.com/pkg/13218.
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