Video wall

“What’s innovative about a video wall?” I hear you cry. “We’ve all seen them. Big…walls of video. Been done for years.”

We’ve said many times that the single most innovative thing about the Raspberry Pi is its price. $25 or $35 gets you something that would have cost you four or five times that amount before the Pi arrived on the market. This means that you can save large sums of money in some applications, especially in applications where you need to buy a lot of separate devices. A video wall requires one device per screen, and another to drive them all together. I’ve seen video wall solutions being run with all kinds of devices at the back end; previously one of the cheapest ways to do this was to buy a Playstation for each of your screens – obviously a much more expensive (and power-hungry – you’re spinning a lot of hard drives all day to get the result you want) way to get what you’re after.

Plus, of course, our HD video capability’s really great.

So Alex Goodyear at Culham Centre for Fusion Energy has put together a really elegant video wall, supported by a group of Raspberry Pis. Energy consumption and cost are both reduced enormously, making video walls like this much more accessible to enterprises which don’t have huge funds, like museums, schools, shops, galleries and offices.

You can use different sizes and orientations of screen in the same set-up here; you can use the screens to show one large moving image or many small ones; you can display static content like photos or web pages alongside moving content on the same wall.

Read more about what Alex has come up with at CCFE – we’re looking forward to seeing more of these in the wild!

23 comments

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WOW, fantastic application, now just got to find a cheap supply of LCDs :)

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Wow…. This is impressive. I’m sitting here thinking of how much a video wall normally costs. And if a collection of Pi’s will run things, and if there’s some open-source software to drive it all, you’ve pretty much reduced the cost of doing this to just the monitors; that is, a small fraction of the normal cost. This is seriously cool.

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I use this cheap Acer 108p monitor with my RPi’s (hdmi -> dvi-d cable needed, about £5)
http://www.ebuyer.com/263863-acer-s221hqldbd-21-5-led-full-hd-monitor-et-ws1he-d02

Very good for the price, viewing angle is not perfect but for the price a bargain and they work perfect with the RPi.

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Been trying to figure out how they sync it together. I’m guessing but I think that as long as each device knows the orientation of each device (3×3, 2×4 etc), it can run the same video, just display the appropriate bit of the video depending on position. You would need to sync up each Pi so they started running video at the same time – GPIO maybe, or perhaps Ethernet would be accurate enough. I do wonder whether they might get out of sync over a long enough time period, and how you would resync them during a video playback.

Great stuff, however they do it.

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Sync shouldn’t be too hard – poll timecodes or get each slave to tell the master what frame it’s on etc. VLC (?and mPlayer) even has built in functionality for this. As long as ping isn’t stupid should be fine.

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How is called the second video? About the fusion, I would like to watch that.

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Next they just need to attach the monitors to rails and some stepper motors and get the RPi to move them about at the same time. :)

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I think the ‘Master Pi’ has the video and sends part images out to each of the others, one per display. I’d like to know how that’s done though and how they’re connected.

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I don’t think there would be the bandwidth over the ethernet to send the imagery. Although that would depend on the size of each image of course.

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When they make monitors with the new flexible oled technology where they can wrap the material around the edge of the device, we can do video walls without the annoying black separations caused by monitor frames. That was one of the other videos after this demo quit.

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Basically, you want to splatter your images/video/desktop across multiple displays using X. Here you go for starters (XRandR, TwinView, Xinerama, Disper):

http://awesome.naquadah.org/wiki/Using_Multiple_Screens

Xinerama source (allegedly works on Debian with Xorg servers):
http://xinerama.cvs.sourceforge.net/viewvc/xinerama/

There may be hardware-specific issues (x86 vs. ARM) requiring special drivers or modified X servers that may need to be tweaked/reimplemented. Since CCFE has something running on the Pi (or multiple Pii in this case ;) ), I’m guessing they’re using something like Xinerama and have done the necessary work. It’s not clear how their software may be distributed, though. You’re supposed to contact videowall@ccfe.ac.uk for info.

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Wow… so there’s no reason why you couldn’t build a 9-screen video wall for under £1500 – incredible!
Something else for Rob to play with at RaspberryPi Towers? ;)

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Rob is being kept busy optimising browsers at the moment – he is not allowed near any fun hardware until he’s done. ;)

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Ooops, that was meant to be a reply to Richard Collins’ comment.

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Hi will this software be available as open source or licensed ?

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Maybe the video plays synchronized on all devices, and on each device the section of video to play is defined and scaled to the actual screen?

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Does someone know how the pi’s are synched? i’m looking to syncstart multiple raspberries.
thanks in advance.

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Server with the video
vlc.exe -vvv VIDEO (h.264) –sout udp:225.0.0.1:1234 –ttl 1 –loop

Raspberry as client (sync-master)
vlc.exe udp://@225.0.0.1:1234 –vout-filter wall –wall-cols X –wall-rows Y –wall-active SCREEN_ID –control netsync –netsync-master -f

Raspberry as Client (sync slave)
vlc.exe udp://@225.0.0.1:1234 –vout-filter wall –wall-cols X –wall-rows Y –wall-active SCREEN_ID(left-up corner = 0) –control netsync –netsync-master-ip IP-Sync-Master -f

use vlc 1.11 otherwise you can’t get fullscreen mode (bug vlc2.x)

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Very interested in this, back in 2004 we set up a New Media Art Gallery in the new Perth Concert Hall which was based on Apple hardware. Details of its set up an capeabilities here. http://www.squarebox.co.uk/threshold.html

The problem now is the hardware needs replaced and the Raspbery Pi looks like an ideal bit of hardware.

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I was told about this project and took a while to find the info online. Im really keen to build one – can the Culham guys update us about if they plan to make it publically available???

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its a great concept. i just need some help in implementing it. cropping videos is getting tough. a delay of minute occurs while live streaming the video.

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