marker detection on multiple frames

edit

I have 2 video(.avi) files and i have successfully able to grab multiple frames using C++ threading and store it in frame_queue.

vector<concurrent_queue<Mat>*> frame_queue;

But i want to run marker detection on these captured frames.

Here is the code snippet

while (1)
{
    //Retrieve frames from each camera capture thread
    for (int i = 0; i < capture_source.size(); i++)
    {
        Mat vdo_frame;
        //Pop frame from queue and check if the frame is valid
        if (cam.frame_queue[i]->try_pop(vdo_frame)){
            //Show frame on Highgui window
            marker_detection(vdo_frame);
            //imshow(label[i], frame);
        }
    }
}

If i am not wrong cam.frame_queue[0] holds the frames from video1 and frame_queue[1] holds the frames from video2. But how do i run marker detection for both the videos in parallel? Issue is whenever i run the code it works for some seconds but then my Ubuntu freezes and i have to reboot.