View Full Version : Strange electrical interference problem?

Dead Pixel
December 8, 2008, 15:16:28

Last night I went outside for with my new DMK 21AF04.AS. After installing the driver and IC Capture I started IC Capture. It found the camera and the live image became visible on the screen.

To my surprise the image was rather distorted. It resembled a sort of rolling vertical sync problem that is sometimes visible with (old) tv sets: the top side of the image would appear at the bottom, sometimes moving up and down (a bit like in this image (http://faq.tweakers.net/vb/ext2rgb.jpg)).

After reinstalling the drivers, IC capture, checking the cables etc etc. I decided to give up. The distotions remained. I pulled the powercord of my laptop.. and lo and behold, the distortions instantly went away. Reattaching the powersupply to the laptop caused the distortions to return. Somehow, the camera works fine when the laptop is running on battery power, but not on the external power supply.

I wonder what's causing this. Does my laptop have some kind of electrical problem or is it caused by the software?

My setup:

Acer Laptop
AMD Turion TL-50 dual core CPU
2GB ram
Windows Vista
DawiControl PCMCIA firewire card (powered by a 12v battery pack)



Stefan Geissler
December 9, 2008, 14:31:46
Hello Mike,

I have less experiences with AMD Turion than Intel Duo Core. On Intel Duo Core the image distortions are caused by interrupted data transfer from the FireWire board into the memory. The interrupts happen, while the CPU changes its power states. The FireWire Performance Manager disables these power state changes. This only works on Intel Duo Core CPUs.

I guess, the reason on your computer is the same. As soon as you disconnect the camera from the external power supply, the AMD may changes in a state, in that the DMA transfer between FireWire and memory is no longer interrupted, thus you receive fine images.

It is no problem of your computer or of your camera. It can be a problem of power saving implementation in the comptuer or operating system. It is very hard to narrow down these kind of problems and it is harder to find a simple solution.

In earlier times, we simply connected a USB 2.0 memory stick to the computer and the problems went away. May be this is also a solution for you.

Dead Pixel
December 10, 2008, 22:55:18
Thank you, Stefan. I have found the solution. Switching the Vista power management configuration from "High performance" to "Balanced" did the trick :)

Stefan Geissler
December 11, 2008, 09:06:57
Hi Dead Pixel

thank you very much for the trick! I will keep it in mind! (hopefully)