python opencv VideoCapture ffmpeg libraries failure

[mhaeberli]

I have python OpenCV vision code that works on some machines but not on others. In particular, on many WindowsXP machines, I don't get any image from the camera, even when the camera is working.
There are a lot of suggestions that the problem somehow is my ffmpeg dll library configurations.
Advice would be welcome.
Thanks,
Martin

[virtuald]

Possibly true -- though, you're not using OS-specific functionality to connect to the camera, so I can't imagine *what* specifically would be different. Are you using the same binaries on all machines?

Also, make sure you have SP3 installed on XP.

[mhaeberli]

Thanks - I'll check re SP3. Other paths I think I have checked already. It would be nice to get an error dump from python or something that tells me _why_ the VideoCapture failed. On some systems, it fails for the webcam but not for the built-in cam...

[mhaeberli]

Turns out that my Windows PATH (Path) variable was not set to correctly include OpenCV. It should include something like:
C:\opencv\build\x86\vc10\bin;
...
at the beginning.
(This is set in System / Advanced / Environment Variables)
My educated guess is that this can work also if another appropriate \bin directory is chosen.