Diary and notebook of whatever tech problems are irritating me at the moment.


webcam-server-dialog: A basic front-end to webcam-server

I'm working on a new Ubuntu configuration to deploy for friends and family. One of the capabilities I wanted to add was simple remote webcam viewing. I saw an article about webcam_server. While it's old and only does images it met my requirements. The primary limitation is that it's a command-line application. It can be launched from a XDG desktop file and will default to /dev/video0 but on systems with more than one video device a terminal is needed. I did spend some time testing streaming with VLC but it doesn't show a device list for selection either and it's streaming configuration dialogs are confusing at best. To deploy webcam-server I had to make it more friendly which meant making a video device selection dialog for it. My current programming hammer is Bash shell scripting (Applesoft BASIC was the other option) but it's not enough for GUI design. To add that capability I turned to what I call "dialoger" utilities that can produce GUI dialogs and provide feedback to command-line applications.

When I started this project the only dialoger I knew about was dialog which is text-based and I needed something that would run in X. From researching alternatives to dialog I found xmessage which led to gxmessage and eventually Zenity. Plenty to choose from and all different. Now I had another problem - which one to use with each desktop environment? I normally use Gnome but some of my clients use XFCE or LXDE. There is also the possibility of a KDE user in the future. While Ubuntu includes Zenity by default, which would work with XFCE also, a GTK application isn't the best choice on KDE. I could use kdialog but either I had to make custom versions of the script for each environment, select the dialoger with a script parameter, or try to select it dynamically. In the great tradition of overdesign I chose the latter.

After spending several days solving a 5-line problem with 300+ I ended up with webcam-server-dialog. It supports dialog, whiptail, Xdialog, xmessage, gxmessage, kdialog, and Zentiy. Because it's rather generic it can be expanded to support more without a lot of effort. It looks for processes that indicate a particular desktop environment or window manager, uses a built-in priority list of dialogers for that environment, checks for availability, then uses the best available to provide the GUI. The core of this script is nothing more than "ls /dev/video*" dumped into an array but the focus here was eye-candy. Getting this to work with all of them was difficult as they all have different command-line parameters, behaviors, and bugs, even between those that are supposed to be clones of each other. Some use exit return status for indicating button presses, some stdout, some both depending on the mode. The fun ones were dialog and whiptail which use stdout for drawing the screen and stderr for indicating list choices. There are a lot of comments and commented-out debug lines if you want to use this with your own projects (GPL v3). It could be useful as a front-end to other programs that lack selection lists like xawtv.

To use it, install webcam-server then put the script in /usr/local/bin with root ownership and rwxr-xr-x permissions. I also made an XDG destop menu item for it. Put webcam-server-dialog.desktop in /usr/local/share/applications. For an icon I used the one from camorama and just copied /usr/share/pixmaps/camorama.png to /usr/local/share/pixmaps/webcam-server-dialog.png (make the directory if it doesn't exist). You can add parameters to the Exec line in the desktop file but the run dialogs always reference port 8888 (I'm too tired of working on this to make the text dynamic) and quotes don't pass through well so the caption format had to be hard-coded in the script.

In addition to direct web-page access a Java applet is included. It works well since it can automatically reload the image at a selectable interval. It has one really bizarre limitation - it will only connect from localhost. Apparently the developers decided to limit it that way instead of implementing remote authentication but you probably could use it from within an ssh connection. This security feature has a bug in it's implementation when resolving the hostname so it requires the IP ( I created a custom PHP web page that works around this. Just rename it to index.php and put it in the client directory on your web server (/var/www/client by default) along with applet.jar from the /usr/share/doc/webcam-server directory and link to it from your default home page. You'll need PHP support installed (php5 metapackage).

I also tested it in Mandriva 2010.0 which worked but with one problem - the webcam-server executable is named webcam_server so just replace all instances of one with the other in the script. You'll also need v4l-info which is in the xawtv-common package. If you are using the firewall you have to add "8888/tcp" to the allowed ports for remote access.

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About Me

Omnifarious Implementer = I do just about everything. With my usual occupations this means anything an electrical engineer does not feel like doing including PCB design, electronic troubleshooting and repair, part sourcing, inventory control, enclosure machining, label design, PC support, network administration, plant maintenance, janitorial, etc. Non-occupational includes residential plumbing, heating, electrical, farming, automotive and small engine repair. There is plenty more but you get the idea.