当我想开始/暂停视频时,我应该如何正确使用cv2.waitKey?

def marker(event, x, y, flags, param):
    # Method called by mouse click
    global run

    if event == cv2.EVENT_LBUTTONDOWN:
        run = not run


...

window_name = 'Editor Window'
cv2.namedWindow(window_name)
cv2.setMouseCallback(window_name, marker)
fvs = cv2.VideoCapture(args["video"])
(grabbed, frame) = fvs.read()

while grabbed:

    # grab the frame from the threaded video file stream, resize
    # it, and convert it to grayscale (while still retaining 3
    # channels)
    if run:
        # Code to display video fames ...

        cv2.waitKey(1) & 0xFF # Use A
        (grabbed, frame) = fvs.read()
    else:
        cv2.waitKey(1) & 0xFF # Use B

该代码对cv2.waitKey的使用非常敏感:

1. 如果我没有“使用A”,窗口将冻结,而不会显示视频。我本以为它会运行,然后很快关闭。为什么不是这样?

3. 如果“使用B”的延迟为0(即无限期等待),则似乎只能间歇性地看到鼠标单击事件,尽管有时我在单击时也会周期性地按空格键。为什么会这样?如果我在按键之前(或之后?)足够快地点击鼠标,我是否会感到“幸运”?如果没有,为什么会出现间歇性响应?

最终,我并不真正理解cv2.waitKey()的工作原理。我认为它会等待键盘事件的给定时间延迟,然后继续。用鼠标点击的互动甚至让我感到困惑。