OpenCV Error: Unspecified error (The node does not represent a u

Forum: Linux
sachin 
hello everyone,

i am running the code for face recognition but in that the camera capture
part gives me error...when i execute the code it gives me ==>

OpenCV Error: Unspecified error (The node does not represent a user object
(unknown type?)) in cvRead, file
/home/sachin/opencv/sachin/opencv-2.4.10/modules/core/src/persistence.cpp,
line 4991
terminate called after throwing an instance of 'cv::Exception'
what():
/home/sachin/opencv/sachin/opencv-2.4.10/modules/core/src/persistence.cpp:4991:
error: (-2) The node does not represent a user object (unknown type?) in
function cvRead

Aborted (core dumped)

anyone know how to resolved it??

jjm 
Use OpenCV to Access USB Camera

The full name of "OpenCV" is Open Source Computer Vision Library and it is
a cross platform vision library.
When the NanoPi 2 runs Debian users can use OpenCV APIs to access a USB
Camera device

Here is a guideline on how to use OpenCV with C++ on the NanoPi 2
1. Preparations 

---Firstly you need to make sure your NanoPi 2 is connected to the
internet. 
   Login to your NanoPi 2 via a serial terminal or SSH. After login type in
your username(root) and password(fa):
---Run the following commands:


#apt-get update
 (The OS images we provide for the NanoPi 2 by default have the vi utility.
However we suggest you install the vim utility)
#apt-get install vim
#apt-get install libcv-dev libopencv-dev2. Make sure your USB camera works
with the NanoPi 2. You can test your camera with NanoPi 2's camera utility.


3. Check your camera device: 

#ls /dev/video + "Tab" key (This lists available USB camera devices. )4.
OpenCV's code sample: 

#cd /home/fa
#vim test.cpp


#include "opencv2/opencv.hpp"
 
using namespace cv;
 
int main(int, char**)
{
    VideoCapture cap(0); // open the default camera
    if(!cap.isOpened())  // check if we succeeded
        return -1;
 
    Mat edges;
    namedWindow("edges",1);
    for(;;)
    {
        Mat frame;
        cap >> frame; // get a new frame from camera
        cvtColor(frame, edges, CV_BGR2GRAY);
        GaussianBlur(edges, edges, Size(7,7), 1.5, 1.5);
        Canny(edges, edges, 0, 30, 3);
        imshow("edges", edges);
        if(waitKey(30) >= 0) break;
    }
    // the camera will be deinitialized automatically in VideoCapture
destructor
    return 0;
}Compile the code sample: 

#g++ test.cpp -o test -lopencv_core -lopencv_highgui -lopencv_imgprocIf it
is compiled successfully a "test" executable will be generated:


5. Connect NanoPi 2 to USB Keyboard & Run the Following Command: 

#./test

sachin 
thanks @jjm