Video monitoring with Perl and a webcam
FISHING FOR IMAGES
Webcams are useful for monitoring. Using CPAN modules and custom-made C code, Perl scripts can automatically adjust the exposure and fish the most interesting images out of a video camera’s data stream.
Most webcams are accompanied by some kind of Windows software, which is of no use at all to Linux users. Luckily, more recent Linux distributions include Video4Linux, which gives you simple controls for many hot-pluggable USB cameras. The Creative NX Ultra camera I use for my experiments normally provides video output and costs about US$ 70. In fact, it is a waste of the camera’s abilities to use this camera as a simple webcam, but then again, it was just lying around in one of the drawers down at the Perlmeister lab, so why not use it? The camera does not need an external power supply, and it was detected immediately by the hot-plugging subsystem when I connected it to my PC. The video data typically goes to /dev/video0. The Linux::Capture::V4l Perl module from CPAN locks into the device entry, grabs the frame data, and lets programmers change exposure parameters such as the camera sensitivity on the fly. Listing 1 shows a simple application that first sets the camera sensitivity to 40000 before grabbing an image from the video stream, and then storing the image on disk as a JPEG photo (Figure 2).
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
US / Canada
UK / Australia
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
System76 Releases COSMIC Alpha 7
With scores of bug fixes and a really cool workspaces feature, COSMIC is looking to soon migrate from alpha to beta.
-
OpenMandriva Lx 6.0 Available for Installation
The latest release of OpenMandriva has arrived with a new kernel, an updated Plasma desktop, and a server edition.
-
TrueNAS 25.04 Arrives with Thousands of Changes
One of the most popular Linux-based NAS solutions has rolled out the latest edition, based on Ubuntu 25.04.
-
Fedora 42 Available with Two New Spins
The latest release from the Fedora Project includes the usual updates, a new kernel, an official KDE Plasma spin, and a new System76 spin.
-
So Long, ArcoLinux
The ArcoLinux distribution is the latest Linux distribution to shut down.
-
What Open Source Pros Look for in a Job Role
Learn what professionals in technical and non-technical roles say is most important when seeking a new position.
-
Asahi Linux Runs into Issues with M4 Support
Due to Apple Silicon changes, the Asahi Linux project is at odds with adding support for the M4 chips.
-
Plasma 6.3.4 Now Available
Although not a major release, Plasma 6.3.4 does fix some bugs and offer a subtle change for the Plasma sidebar.
-
Linux Kernel 6.15 First Release Candidate Now Available
Linux Torvalds has announced that the release candidate for the final release of the Linux 6.15 series is now available.
-
Akamai Will Host kernel.org
The organization dedicated to cloud-based solutions has agreed to host kernel.org to deliver long-term stability for the development team.