Kiosk display on a Mac Powerbook

--D. Thiebaut 10:37, 10 April 2013 (EDT)

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This tutorial is a simple series of step to create a kiosk on a PowerBook mac. The Kiosk displays a Quicktime movie in a loop, in full-screen mode. The movie can be updated remotely, and the kiosk automatically reloads the movie (with a 1-minute down-time, approximately).

Setup and Platforms

The idea is to have the Powerbook download a Quicktime movie from a server when a new version of it has been created, and automatically run it in a loop, full screen.

The mac used for displaying the endless loop is an old Powerbook PowerPC G4 running Mac OS X 10.5.8 that was collecting dust. It is connected to an external display.

The original .mov movie that is to be displayed is located a server, at a given URL, and the Powerbook will check regularly (in our case every 10 minutes) to see if that file has been recently updated. If it has been, the Powerbook uses wget (downloaded from here) to download the movie, and the Powerbook is restarted (automatically) so that Quicktime can restart with the new movie.

Account

The account under which everything runs on the Powerbook is "newccount", which has no password, and admin privileges.

Setup

• Create a Quicktime compatible movie of your presentation. Make sure you set the full-screen and loop options (if available) ON when export the file to Quicktime format.
• Install wget on the Powerbook.
• Using Systems Preferences, go to the Users menu and set newaccount to automatic login
• Load the first copy of the movie to play at startup in the Desktop folder, and call it DisplayCase.mov. This is also the name of the original movie file on the server.
• In the Users pane of the Systems Preference app, with newaccount selected, click on Login Items and put the movie DisplayCase.mov in the window. Leave the Hide box unchecked.
• Create a bin directory in the newaccount directory.
• Create the script updateMovie.sh in the newly created bin directory, and initialize it with this code:

#! /bin/bash
# updateMovie.sh
# D. Thiebaut
# script that will download movie from given url if it is more recent
# than local copy.  If download is performed, the laptop is restarted
# so as to force Quicktime to stop and restart.  The movie will automatically
# be played at login because it is in the "logins" list for the current account.
# 

movie="DisplayCase.mov"
url="http://xxx.yyy.zzz/${movie}"  # <== enter the URL of your movie here
wget="/usr/local/bin/wget"

cd ~/Desktop

# get creation time of local copy of movie
currentTimeStamp=`stat -f "%m%t%Sm" $movie`

# attempt to get newer version of movie from server
$wget -q -N $url

# get creation time of same movie file
newTimeStamp=`stat -f "%m%t%Sm" $movie`

# if creation times are different, a new version has been downloaded
# so we need to restart the system.

if [ "$currentTimeStamp" != "$newTimeStamp" ]; then
    # restarting the Finder will restart the user newaccount...
    osascript -e 'tell application "Finder" to restart'
fi

Then it's time to create a cron job that will run this script every 10 minutes. Run the command:

   crontab -e

in the Terminal window. Add the following contents to the crontab list:

*/10 * * * * /Users/newaccount/bin/updateMovie.sh

and exit the default editor.

Note: If you want to the default editor to be emacs, simply set the EDITOR shell variable before issuing the crontab command:

    export EDITOR=/usr/bin/emacs

You can now restart the PowerBook and the kiosk should start working, loading the movie full-screen, in a loop. Whenever you change the original movie on the server, the kiosk should update its copy within 10 minutes and restart, showing the new movie.