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Re: Showcase Appliance for Schools

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On Sun, Nov 23, 2008 at 04:15:39PM +0100, RalfGesellensetter wrote:
>Am Samstag 22 November 2008 schrieb Jonas Smedegaard:
>> I threw together an info system a couple of years ago, for a
>> gymnastics, climbing and sports center
>Dear Jonas,
>thanks for these insights. Sticking to mere images seems clever to me 
>as long as all connected dispalys have the same resolution. Otherwise 
>scaling might be a problem.

I see no problem using multiple displays of varying resolutions. Just 
make the images large enough, and use nice round numbers to avoid worst 
cases of moiré.

See http://info.dgi-huset.dk/img/areamap.png for an example: I chose 

If you have displays of varying _aspect ratio_ then indeed you need to 
serve images for each aspect ratio (probably 4:3 and 16:9).

>As soon as you have more than one display, a pull system seems to be 
>optimal (as you need not tell the server about further displays). On 
>the other hand, it will be the server knowing when there is time for an 
>update. What is your solution here? Do you use any sockets that are 
>running as multiple instances on server side?

I guess you mean "push", not "pull"...

Server runs a cron job every 5 minute updating the images (generating 
first and then replacing the old one, to not risk clients pulling a
half-baked image).

Client(s) run a daemon rsync'ing every 5 minutes.

Client(s) run another daemon looping through and displaying 
images every 10 seconds.

With that timing, it can take up to 10 minutes for an info to show. That 
was fine for my purpose. If you want a stock ticker or a watch then sure 
you need something more advanced (or perhaps just run xdaliclock locally 
on the clients).

What are your needs currently? What could you imagine in the foreseeable 

  - Jonas

- -- 
* Jonas Smedegaard - idealist og Internet-arkitekt
* Tlf.: +45 40843136  Website: http://dr.jones.dk/

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