Can't use dvi2usb with OpenCV on Linux


Hello community,

I try to use the dvi2usb grabber with OpenCv in C++ and Ubuntu.
For some reason I can’t get it:

cv::VideoCapture cap;

if(!"/dev/video4", cv::CAP_V4L2)){
    cout << "NOT POSSIBLE" << endl;
    return -1;

this works just fine for another cheap usb grabber and my webcam but not for the Epiphan.
I can get the Epiphan on OBS which uses V4L2 as well, but not with OpenCv.
I am grateful for all advises to fix this.
BR Michael