Emgu returns _capture.QueryFrame() null

Question

I am developing a software which will detect if car stops and so for testing I froze the frame for a while but emgu returns null while the frame is same I think I need some help.

using (Emgu.CV.Image orignalFrame = _capture.QueryFrame().ToImage())

that thing returns null

Answer 1

This is expected behavior, from EmguCV docs ,

If no more frames are available, null will be returned

It just moves forward and get the next frame, and won't return the same frame again.

For testing purposes you can make a video file using frames read from the webcam, then starting from a certain frame, repeat that frame for several hundred times, this give the same effect as if the car was stopped for several seconds. Then save the video file and test your code with this video file, only this time you pass the video file name to the constructor of the VideoCapture.