teejaykeezy1
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Using RasPi for multiple display outputs

Tue Jun 18, 2019 7:11 pm

I'm was asked if I could figure how to do a project for work but I have almost zero information on how to start so I came to this forum for some help. At the very least, I'm hoping somebody will be able to tell me if it is possible.

My boss wants to put multiple low-res gifs or images on a raspberry pis then have the devices display the images onto several CRT monitors. We need 8 images so ideally 4 images are displayed by one pi but if i need to get 4 and display 2 images each I think that would still be in the realm of practicality for us. I saw on several videos on youtube of cable tv multicasts which I think would be far more bandwidth than what I would be using so I do not think what I'm trying to do is unreasonable, but I don't yet have the skill to make this happen on my own.

For test purposes, I'm using a RasPi I bought a few years ago but never had the chance to try to use it. I'm brand new to this whole thing so I know I have a lot to learn about this I just don't know where to start looking. Any pointers would be greatly appreciated.

PhatFil
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Re: Using RasPi for multiple display outputs

Tue Jun 18, 2019 10:25 pm

no.

teejaykeezy1
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Re: Using RasPi for multiple display outputs

Wed Jun 19, 2019 12:59 am

Would you mind elaborating?

klricks
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Re: Using RasPi for multiple display outputs

Wed Jun 19, 2019 3:11 am

Not clear what you want to do.
If you want to display different images on each display then you will need one RPi per display.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

aBUGSworstnightmare
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Re: Using RasPi for multiple display outputs

Wed Jun 19, 2019 9:10 am

Speaking of videos on youtube have you seen mine (doing something similiar as what I understand from your explanation):

https://www.youtube.com/watch?v=isqD8UGTBB0
https://www.youtube.com/watch?v=trY4hLSOpjw

I've used a app named 'screen' to do this. Quite simple and effective way (even for running four FHD videos on a 728x128pixel screen)

don't have exact reference to the app on hands, so simly start here http://www.gnu.org/software/screen/screen.html or here https://wiki.ubuntuusers.de/Screen/
Last edited by aBUGSworstnightmare on Wed Jun 19, 2019 10:50 am, edited 1 time in total.

PiGraham
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Re: Using RasPi for multiple display outputs

Wed Jun 19, 2019 9:24 am

A useful search phrase is digital signage. There are various projects using RPi.
Typically use one Pi per display and feed them over a network.
Pi 3A+ might be a good choice for the per-display units.

You can duplicate one HDMI to multiple screens so all display the same image.
You can use USB displays. "HDMI splitter"
Last edited by PiGraham on Wed Jun 19, 2019 10:01 am, edited 1 time in total.

jamesh
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Re: Using RasPi for multiple display outputs

Wed Jun 19, 2019 9:31 am

Although a Pi per display sounds like overkill, with the Pi0WH its still only $14 or so per display, which is insignificant compared to the development time or having to buy HDMI splitters. It's probably still insignificant with the Pi3B+ at $35!!
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PiGraham
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Re: Using RasPi for multiple display outputs

Wed Jun 19, 2019 10:04 am

jamesh wrote:
Wed Jun 19, 2019 9:31 am
Although a Pi per display sounds like overkill, with the Pi0WH its still only $14 or so per display, which is insignificant compared to the development time or having to buy HDMI splitters. It's probably still insignificant with the Pi3B+ at $35!!
Since this seems to be for business purposes I should think RPi prices, low as they are, would not be a problem.

Pi0W would be the lowest cost but availability might be a problem if more than a few units are required in total. I was thinking Pi3A+ would be easier to get.

teejaykeezy1
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Re: Using RasPi for multiple display outputs

Wed Jun 19, 2019 12:59 pm

Thanks for all of the replies. After looking at all the adapters I'm going to need to make the images work with CRTs, it looks like I'll have to go with one RPi per screen and run a 3.5mm to RCA or similar depending on the particular screen. My budget for this is way higher than I initially thought it was so that shouldn't be an issue. The new challenge will be learning SSH

teejaykeezy1
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Re: Using RasPi for multiple display outputs

Wed Jun 19, 2019 9:52 pm

I've been playing around a good bit today with SSH remote access thinking that was the secret to this whole thing. What I can't seem to figure out is how to use a remote command to make the monitor connected to the RPI to display an image file. I"m not sure if I'm asking google the wrong questions or if I have the capabilites of this thing all wrong.

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Re: Using RasPi for multiple display outputs

Wed Jun 19, 2019 10:18 pm

Assuming the Pi is connected to the monitor you need to use a program like feh to display the pictures if you are running in command mode.

https://feh.finalrewind.org

but you are going to have to work on how to start this up (search CRON @REBOOT) when the Pi is started as the main 'screen' needs to run this not the shh session.
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klricks
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Re: Using RasPi for multiple display outputs

Wed Jun 19, 2019 11:30 pm

teejaykeezy1 wrote:
Wed Jun 19, 2019 9:52 pm
I've been playing around a good bit today with SSH remote access thinking that was the secret to this whole thing. What I can't seem to figure out is how to use a remote command to make the monitor connected to the RPI to display an image file. I"m not sure if I'm asking google the wrong questions or if I have the capabilites of this thing all wrong.
If you are trying to run a command or program that requires desktop (GUI) from SSH console then do this:
DISPLAY=:0 program_name &

IIWMIW use RealVNC which will mirror the local RPi desktop on the remote computer.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

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HermannSW
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Re: Using RasPi for multiple display outputs

Thu Jun 20, 2019 12:51 am

teejaykeezy1 wrote:
Wed Jun 19, 2019 9:52 pm
What I can't seem to figure out is how to use a remote command to make the monitor connected to the RPI to display an image file.
Besides what others said, I like to use omxiv to view images.
One reason is that its hardware accelerated and much quicker than eg. "eog" X11 image viewer.
The other is, that it works regardless whether you booted into X11 or console.
So ssh into the Pi you want and call "omxiv yourimage" and it will get displayed.
bookmark list: https://stamm-wilbrandt.de/en/Raspberry_camera.html

https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://github.com/Hermann-SW/fork-raspiraw
https://github.com/Hermann-SW/userland
https://twitter.com/HermannSW

jamesh
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Re: Using RasPi for multiple display outputs

Thu Jun 20, 2019 8:52 am

From the command line, assuming no desktop running (and why would you in this case), I use `fbi`, which is in the repos. Has a slideshow mode as well.

sudo apt install fbi
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