How do I print the mean of the image as well as the timeline

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C++

picture

Python3.6

import cv2
import numpy as np

cameraCapture = cv2.VideoCapture('test_1.avi')

success, frame = cameraCapture.read()
while success:
    if cv2.waitKey(1) == 27:
        break
    cv2.imshow('Test camera', frame)
    
    success, frame = cameraCapture.read()
    milliseconds = cameraCapture.get(cv2.CAP_PROP_POS_MSEC)
    
    seconds = milliseconds//1000
    milliseconds = milliseconds%1000
    minutes = 0
    hours = 0
    if seconds >= 60:
        minutes = seconds//60
        seconds = seconds % 60

    if minutes >= 60:
        hours = minutes//60
        minutes = minutes % 60

    print(int(hours), int(minutes), int(seconds), int(milliseconds),a)

cv2.destroyAllWindows()
cameraCapture.release()

I want to print the time line of this video as well as the mean of this frame，for example like printf (0h 0m 2s 33m 34)

What I have tried:

cv.cvtColor(image, gray, cv.COLOR_RGB2GRAY);
    Mat mat_mean, mat_stddev;
    meanStdDev(gray, mat_mean, mat_stddev);
    double a = mat_mean.at<double>(0, 0);
    double d = mat_stddev.at<double>(0, 0);

I once wanted to bring the C++ program code into the program, but I couldn't implement the call to the mean function. How can I change my program