void cvCalcOpticalFlowLK(CvArr* prev, CvArr* curr, CvSize win_size, CvArr* velx, CvArr* vely) {
    void *fptr;

    fptr = dlsym(_Chcv_handle, "cvCalcOpticalFlowLK_chdl");
    if(fptr == NULL) {
        fprintf(_stderr, "Error: %s(): dlsym(): %s\n", __func__,  dlerror());
        return;
    }
    dlrunfun(fptr, NULL, cvCalcOpticalFlowLK, prev, curr, win_size, velx, vely);
}
