unicap-imaging.org blog - Tips and Tricks

Installing unicap on Fedora / RedHat / CentOS

nospam@example.com (Arne Caspari) — Tue, 24 Jun 2008 16:17:12 +0200

On unicap-imaging.org you will find the unicap libaries and the ucview application as source packages from which you can compile and install on almost any Linux distribution. But normally you do not want to compile the library by yourself because if you do, the resulting files will not be under control of the package manager that your distribution usually uses to keep track of the installed software.

unicap-imaging.org therefore also hosts a repository containing the binary packages for the most popular Linux distribution, Ubuntu. Even though there are no packages for other linux distribution hosted on the unicap-imaging.org website itself, packages are often provided for other popular distributions by third party distributors. I will explain how to install and use unicap on some other distributions in a series of blog posts. Today I will start with Fedora 9.

unciap and ucview packages are already available in the default repositories of Fedora thanks to the work of Robert Scheck who builds and maintains the rpm packages. To install unicap on CentOS or Red Hat Enterpris Linux 5 you need to use EPEL ( Extra Packages for Enterprise Linux ). Please follow this link to learn how to set up EPEL: Fedora Wiki

The most basic case is to install only the libraries and UCView. This can be done by the following command, executed as the root user:



yum install unicap ucview

If you want to compile the examples that come with unicap, you need to install some more packages to be able to compile them:



yum install gcc make gtk2-devel libtheora-devel libvorbis-devel unicap unicap-devel

Afterwards you should be able to compile and run the basic device-info example which just prints information about all supported devices. Many other examples require additional dependencies, for instance the OpenCV example needs opencv, obviously. You should be able to locate the required packages with yum search in most cases ( otherwise, post a comment here ). Please let me know if you face any issue in using unicap on Fedora / RedHat systems.

Using the Trigger and Digital IOs of Imaging Source Cameras

nospam@example.com (Arne Caspari) — Mon, 09 Jun 2008 17:03:16 +0200

Among others, The Imaging Source cameras can be externally triggered and have digital in- and outputs to control external devices. In a series of blog postings on their machine vision blog, The Imaging Source gives some details about the hardware and explains how to build an external trigger circuit:

Trigger Hardware and Timing
Pin Header Layout
Hirose Connector Layout

Software support for this functionality is present in unicap.

Using UCView with Desktop Effects

nospam@example.com (Arne Caspari) — Tue, 22 Apr 2008 15:30:00 +0200

For quite a while now, most modern Linux distributions come with a feature called Desktop Effects. When Desktop Effects are enabled, the processor of the graphics card is used to enhance the visual appearance of the desktop, for example by letting windows drop shadows or by giving windows semi-transparent borders.

If you are using UCView and enabled the desktop effects on your computer, you may encounter strange effects. Depending on your graphics hardware and on the colour format used by the camera, you may see different distortions, like a blue area where windows should drop a shadow or the video image overlaying everything that is placed over it. For example in this picture you see the video image getting placed in front of the About window, obscuring a part of it:

The reason for this behaviour is that UCView uses the XVideo extension to accelerate the video output. Unfortunately, this extension is not very well supported by the compositing feature which is used for the desktop effects.

The use of XVideo is also the reason you can not make screenshots of an UCView window showing video on some systems. You will only see a blue image where the video belongs if you are looking at the screenshots afterwards.

There is a way to get around these issues by disabling the use of the XVideo extension. You can do that with the following command ( enter it in a terminal window ):



gconftool-2 --set --type boolean /apps/ucview/disable_xv true

On the next start of UCView, the video window should behave as expected:

There are other interesting uses of the GConf settings which I will discuss in one of the next blog posts.