OpenCV camera stream stopping while in fullscreen mode

Question

Hi!

I want to have two aplications simultaneously run: one that analyzes image from webcam written using OpenCV (the image is acquired through callback function) and an application that goes into fullscreen mode (let's say a 3D game). The problem is that while the fullscreen mode is launched the webcam image stream is stopping - the frames simply don't turn up, the callback function isn't called. This seems to be an issue with OpenCV - to test that a simple application displaying the image form camera has been prepared.

Why the image stream could be blocked by the fullscreen mode? How to bypass this?

Thanks for any hints.

Answer 1

Your question does not tell if you have tried to search for the problem in the OpenCV community first, so I post this as a hint in case: http://tech.groups.yahoo.com/group/OpenCV/

Also check out the list of issues, maybe its a known bug: https://code.ros.org/trac/opencv/report/1

Answer 2

Actually the behaviour of the OpenCV camera stream is strange. It seems to depend on the native OpenCV window (cvNamedWindow()) that shows the output image form webcam. If the window is on the same screen that went fullscreen the streaming will continue. If the camera window would be placed on another screen, the stream would stop.

Another curious thing is with the screen resolution change. If you change the resolution of the screen and the camera window is not visible (is closed or even minimalized) the image stream would get blocked.

These are just my observations on the topic, maybe it'll be helpful for someone.

Answer 3

I'm not an OpenCV expert so this is closer to a suggestion than an answer - but I've experienced similar on my multi-monitor setup using a number of media players on the second monitor and some fullscreen apps ont he first.

In my limited testing, it comes down to what method is used to render the 3d app - DirectX seems to stop media players, OpenGL doesn't.

So it might not be OpenCV which has a problem - it may be what DirectX does to the hardware during a full-screen game.