获取视频播放时间

def compute_video_playtime(f):
    # Create a VideoCapture object and read from input file
    # If the input is the camera, pass 0 instead of the video file name
    cap = cv2.VideoCapture(f)

    # Check if camera opened successfully
    if (cap.isOpened() == False):
        print("Error opening video stream or file")

    # Read until video is completed
    while (cap.isOpened()):
        # Capture frame-by-frame
        ret, frame = cap.read()
        if ret == True:

            # Display the resulting frame
            cv2.imshow('Frame', frame)

            # Press Q on keyboard to  exit
            if cv2.waitKey(25) & 0xFF == ord('q'):
                break

        # Break the loop
        else:
            break

    # When everything done, release the video capture object
    cap.release()

    # Closes all the frames
    cv2.destroyAllWindows()

    print(time.time() - this_time)