Revision history [back]

read() = grab() + retrieve() (check the doc) and I don't know what you get when 1 read() is following N grab() ...

Sorry but what happens using simple read() like below:

boolean ok1,ok2;

VideoCapture vc1 = new VideoCapture(filename);
// Thread.sleep(500L);    // file is loading, wait a bit
ok1 = vc1.read(m1);
vc1.release();

Thread.sleep(1000L);      // wait 1 one second to be sure the file has been released

VideoCapture vc2 = new VideoCapture(filename);
// Thread.sleep(500L);    // file is loading, wait a bit
ok2 =  vc2.read(m2);
vc2.release();

if(ok1 && ok2) {
    Mat m3 = new Mat();
    Core.absdiff(m1, m2, m3);
    int differences = Core.countNonZero(m3);
    System.out.println("Total differences: "+differences);
}
else System.out.println("Unable to load both frames");

ok1 (and/or ok2) can be false if 1st frame isn't ready as soon as the file has been opened. In this case try some sleep just before read()

read() = grab() + retrieve() (check the doc) and I don't know what you get when 1 read() is following N grab() ...

Sorry but what happens using simple read() like below:

boolean ok1,ok2;

VideoCapture vc1 = new VideoCapture(filename);
// Thread.sleep(500L);    // file is loading, wait a bit
ok1 = vc1.read(m1);
vc1.release();

Thread.sleep(1000L);      // wait 1 one second to be sure the file has been released

VideoCapture vc2 = new VideoCapture(filename);
// Thread.sleep(500L);    // file is loading, wait a bit
ok2 =  vc2.read(m2);
vc2.release();

if(ok1 && ok2) {
    Mat m3 = new Mat();
    Core.absdiff(m1, m2, m3);
    int differences = Core.countNonZero(m3);
    System.out.println("Total differences: "+differences);
}
else System.out.println("Unable to load both frames");

ok1 (and/or ok2) can be false if 1st frame isn't ready as soon as the file has been opened. In this case try some sleep just before read()

Mat m1, m2, m3,m4;
bool ok1, ok2;
string filename = "C:/Users/xyz/Desktop/AVSS_AB_Easy_Divx.avi";
VideoCapture vc1(filename);
VideoCapture vc2(filename);
int N = 100;
for (int i = 0; i < N; i++) {
    ok1 = vc1.read(m1);
    ok2 = vc2.read(m2);
    if (ok1 && ok2) {
        absdiff(m1, m2, m3);
        cvtColor(m3, m4, CV_BGR2GRAY);
        int differences = countNonZero(m4);
        cout << "Total differences: " << differences << endl;
    }
    else cout << "Unable to load both frames" << endl;
}