Slow video write

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Hi,

I have a very simple program where I iterate over a video frame by frame and draw a circle at a (x,y) coordinate and create a new video. For a 6 second video this takes anywhere from 8-12 seconds. Can some one suggest some way to speed up this process?

Else, suggest if there are other libraries which can do this simple task faster than open cv? I want to process a 45 seconds video in under 4 seconds. I have an i7 processor and want to execute this code in windows 10 using c++. My video file is in .avi format.

VideoCapture inputVideo(source); 

VideoWriter outputVideo;

int ex = static_cast<int>(inputVideo.get(CAP_PROP_FOURCC));

outputVideo.open(NAME, ex, inputVideo.get(CAP_PROP_FPS), S, true);

Mat src;

for (;;) //Show the image captured in the window and repeat

    {

        inputVideo >> src;              // read

        if (src.empty()) break;         // check if at end

        if (Ctr_vid > escape_frame - 1)
        {

            circle(src, Point(x_List[Ctr_frame], y_List[Ctr_frame]), 20, Scalar(150, 150, 150), 5, 8);
            Ctr_frame++;
        }
        Ctr_vid++;
        outputVideo << src;
    }