Tag: ubuntu

Philips webcams and the Linux 3.x kernel

The Philips SPC900 and ToU Cam Pro II webcams are still very popular by amateur astronomers who want to try out some basic planetary astrophotography.
I happen to be such a person.
A few years ago I said farewell to the Windows operating system and started to use Ubuntu Linux.
I am still very pleased about my decision.

Last Friday was the first imaging session in a while.
Planet Jupiter was tracked by my mount, webcam was plugged into my telescope and connected to my laptop.
I started up my favorite capturing tool wxAstroCapture.
An over exposed image was displayed on my screen so I had to tweak around with the gain.

Bang! Kernel panic.

Using the sliders for controlling gain, brightness etcetera caused the operating system to crash.
After rebooting it happened again, thus so far an evening of webcam imaging 🙁

Now what’s the cause of this?

Philips webcams use special drivers (PWC) to make them work under Linux.
Imaging software such as wxAstroCapture and Qastrocam-g2 use the Video For Linux (V4L) API to communicate with these webcam drivers.
Version 1 of the V4L API was included with the older 2.6 Linux kernel but was replaced with V4L version 2 when Linux kernel 3.x was introduced.
The current status of the webcam drivers is that they aren’t 100% compatible with V4L version 2 and causes, in my case, the OS to crash.

The solution is quite simple: switch back to a Linux 2.6.x kernel.
When booting your machine, choose in the GRUB boot menu the Previous Versions option.
Select a 2.6 kernel version to your taste and the machine will boot with this version.

If you try to use your favorite imaging tool, you’ll notice it works like a charm again.

My laptop runs Ubuntu 12.04 at the moment. I guess switching to another kernel version on other Linux distros with this similar problem will be just as easy.

Happy camming! 🙂