CODEWITHSUNDEEP
c++opencv
GPPK
GPPK

Reputation: 6666

OpenCV and 4K Videos

I am trying to use OpenCV to read and display a 4K video file. The same program, a very simple one shown in appendix A, works fine when displaying 1080 videos but there is noticeable lag when upgrading to the 4K video.

Obviously there is now 16x more pixels in any operation.

Now I am running generally on a PC with not great specifications, inbuilt graphics, 4Gb RAM & i3 CPU and a HDD (not SSD). I have tested this on a PC with 8GB RAM, i5 & SSD and although 3.XGb of RAM is used it seems mainly a CPU intensive program and is maxing all my cores out at 100% even on the better PC.

My questions are: (to make this post specific)

  1. Is this something that would be helped by using the GPU operations?
  2. Is this a problem that would be solved by upgrading to a PC with a better CPU? Practically this application can only be run on an i7 as I don't imagine we are going to be buying a server CPU...
  3. Is it the drawing to the screen operation or simply reading it from the disk that is causing the slow down?

If anyone has any past experience on using 4K with OpenCV that would also be useful information.

Appendix A

int main()
{
    VideoCapture cap(m_selected_video);
    if (!cap.isOpened())  // check if we succeeded
    {
        std:cout << "Video ERROR";
    }

    while (_continue)
    {
        Mat window1;
        cap >> window1; // get a new frame from camera
        imshow("Window1", window1);
        if (waitKey(30) >= 0) break;
    }
}

Upvotes: 4

Views: 6110

Answers (1)

GPPK
GPPK

Reputation: 6666

The answer to this question is an interesting one, but I think boils down to codecs or encoding of videos.

THe first video I was using was this one (although that might not be the exact download I used) which doesn't seem to play very well in VLC or OpenCV but does play fine in windows media player. I think this is because it is encoded in MPEG AAC Audio.

I then downloaded an elysium 4k trailer which is h264 encoded and seems to work fine in both VLC & OpenCV. so Hooray 4K isn't a problem overall in OpenCV!

SO I thought it might be file sizes. I paid for and downloaded a 7Gb 6 minute 4K video. This plays fine in both OpenCV & VLC with no lag even if drawing it to the screen three times. This is a .mov file and I don't currently have access to the codec (ill update this bit when I do).

So TL:DR: It's not file sizes or container types that causes issues but there does seem to be an issue with certain codecs. This is only a small exploration and there might be differing issues.

addendum: Thanks to the help of cornstalks in the comments who pointed out that WMP might have built in GPU support and to do any testing in VLC which was very helpful

Upvotes: 1

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