Ask Your Question

Revision history [back]

click to hide/show revision 1
initial version

How to get around camera lag

Disclaimer: I am new to OpenCV and fairly new to Computer Science in general

I'm currently using OpenCV 3.2 on both Windows (with Visual Studio 2016) and Linux (via Virtual Machine) and I am having trouble with the camera. More specifically, I am having trouble opening and closing the camera on my computer. I am running fairly simple code (snippet below) that involves opening the camera, displaying frames, pressing esc to take a picture, saving the picture, and then closing the camera. When I close the camera, the terminal says that the camera is closed, but the frame stays open and says "not responding". Eventually it closes itself (after a good minute or two) and moves on with my code. However, when I try to relaunch the camera again, it won't relaunch. Furthermore, it brings up the last frame that it hung on and continues to say "not responding". It hangs for a while, never opens, and then continues with my code. My question is this: Is there some known way to get around this? Is there a special command for relaunching a camera that is different than the command you use to open the camera for the first time? Are there other ways to prevent the camera (and the computer for that matter) from hanging?

Things I have tried:

-Adding a sleep function after loading a new frame to help do less computation per second (to improve the lag)
-Using two different names for the video capture when launching the camera (cap and cap2)
-Using the exact same code twice in a row
-Simplifying the program to be just the task of opening, closing, and reopening

I have tried snooping around on Google, but my searching abilities have failed me. Is there anyone who has had this problem and/or knows how to solve this?

Code snippet:

VideoCapture cap;
if (! {
    return 0;}
for (;;)
    cap >> frame;
    if (frame.empty()) break; // end of video stream
    imshow("Smile! Press esc to take picture", frame);
    if (waitKey(1) == 27)
        imwrite("../image.png", frame);
        testSample = frame;
        testLabel = -1;
        break; // stop capturing by pressing ESC 

// the camera will be closed automatically upon exit


VideoCapture cap2;
if (!
    cout << "Cap isn't open. Terminating..." << endl;
    return -1;
cout << "Smile! Press esc to take picture" << endl;
for (;;)
    cap2 >> frame;
    if (frame.empty()) cout << "frame empty. terminating..." << endl;  break; // end of video stream
    imshow("Smile! :)", frame);