python - time.sleep() 不暂停视频中的计时器

Question

背景

我有一段视频，视频中人们在不同的家中走来走去。我实现了 3 个不同的计时器(针对 3 个不同的人)，当人们在房屋的 bboxes 内时开始计时，当他们在房屋的 bboxes 之外时暂停。作为引用，我提供了视频第一帧的视觉效果。

问题

在下面的代码中实现的检查工作正常 - 当一个人的 bbox inside 时返回 True，否则返回 False。当一个人在家庭 bbox 外走来走去时(即当一个人的 bbox 不在家庭 bbox 内时)，我在暂停时间时遇到了困难。正如您在下面的代码中看到的，每次返回 False 时，我都使用 time.sleep(1) 暂停计时器一秒钟，但是，这不会似乎不起作用。它只是让计时器在后台运行。例如，如果人 1 的计时器在返回 False 前 15 秒，则其计时器应暂停。然后，当返回 True 时，其计时器应从 15 秒开始计时并递增。但是，就我现在的情况而言，它一直在后台运行计时器，因此当在 False 之后返回 True 时，计时器突然显示为 24 秒而不是从 time.sleep() 之前停止的地方继续。我该如何解决这个问题？

# boxes_houses = [(#, #, #, #), (#, #, #, #), ...]

while cap.isOpened():

    # [...]

    def isInside(person, home):
        # Top-left corner
        if home['x1'] < person['x1'] and home['y1'] < person['y1']:
            # Bottom-right corner
            if person['x2'] + (person['x2'] - person['x1']) < home['x2'] + (home['x2'] - home['x1']) and person['y2'] + (person['y2'] - person['y1']) < home['y2'] + (home['y2'] - home['y1']):
                return True
        else:
            return False

    cnt_person = 0
    cnt_house = 0

    for box_person, box_house in zip(boxes_persons, boxes_houses):
        x_p1 = int(box_person[0])
        y_p1 = int(box_person[1])
        x_p2 = int(box_person[2])
        y_p2 = int(box_person[3])
        person_coords = {'x1': x_p1, 'y1': y_p1, 'x2': x_p2, 'y2': y_p2}
        cv2.rectangle(frame, (x_p1, y_p1), (x_p1 + x_p2, y_p1 + y_p2), (0, 0, 0), 2, 1)
        cv2.putText(frame, "House: {}".format(cnt_house), (x1, y1 - 10), cv2.FONT_HERSHEY_COMPLEX_SMALL, 1, (0, 0, 0), 1)

        x_h1 = int(box_house[0])
        y_h1 = int(box_house[1])
        x_h2 = int(box_house[2])
        y_h2 = int(box_house[3])
        cv2.rectangle(frame, (x_h1 , y_h1), (x_h1 + x_h2, y_h1+ y_h2), (0, 0, 255), 2, 1)
        cv2.putText(frame, "Person: {}".format(cnt_person ), (int(box_house[0]), int(box_house[1] - 5)), cv2.FONT_HERSHEY_COMPLEX_SMALL, 1, (0, 0, 255), 1)

        isinside_checks = []
        for house in houses:
            isinside_checks.append(isInside(person_coords, house))

        ### CHECK ###
        
        if any(inside_checks): #if persons inside the home bbox
            # print ("Person", cnt_person, ": True\n")

            if cnt_person==0:
                cv2.putText(main_frame, "Person 0 Time: {}".format(end_time-start_time), (450, 500), cv2.FONT_HERSHEY_COMPLEX_SMALL, 1, (0,0,0),1)
            elif cnt_person==1:
                cv2.putText(main_frame, "Person 1 Time: {}".format(end_time-start_time), (450, 500), cv2.FONT_HERSHEY_COMPLEX_SMALL, 1, (0,0,0),1)
            elif cnt_person==2:
                cv2.putText(main_frame, "Person 2 Time: {}".format(end_time-start_time), (450, 500), cv2.FONT_HERSHEY_COMPLEX_SMALL, 1, (0,0,0),1)

        else: #if persons outside the home bbox
            print ("Person", cnt_person, ": False\n") 
            time.sleep(1) # should pause the time

        cnt_person = cnt_person + 1
        cnt_house = cnt_house + 1
                       
    # show frame
    cv2.imshow('MultiTracker', frame)

    if cv2.waitKey(1) & 0xFF == 27:  
        break

Answer 1

您面临的挑战很有趣。看来你明白问题所在了，即使你休眠了程序的执行，定时器也会继续检查时间。我相信这是因为计时器是基于自多年前某个纪元以来的毫秒数。

The time() function returns the number of seconds passed since epoch. For Unix system, January 1, 1970, 00:00:00 at UTC is epoch (the point where time begins).

https://www.programiz.com/python-programming/time

因此，仅仅因为您暂停了执行，并不意味着自过去那一点以来时间没有增加。

我该如何处理这个问题？

我会跟踪暂停的时间量，并从每个人的总时间量中减去该时间量。

在 for 循环之外初始化:

pause_times = [0, 0, 0] # the total time paused for each person
last_pause = [0, 0, 0] # the times of the last pause for each person
paused = False

然后在检查人们是在屋内还是屋外的地方，适本地更新暂停时间或总时间:

if any(inside_checks): #if persons inside the home bbox
    # print ("Person", cnt_person, ": True\n")
    paused = False
    if cnt_person==0:
            cv2.putText(main_frame, "Person 0 Time: {}".format(end_time-start_time-pause_times[0]), (450, 500), cv2.FONT_HERSHEY_COMPLEX_SMALL, 1, (0,0,0),1)
    elif cnt_person==1:
            cv2.putText(main_frame, "Person 1 Time: {}".format(end_time-start_time-pause_times[1]), (450, 500), cv2.FONT_HERSHEY_COMPLEX_SMALL, 1, (0,0,0),1)
    elif cnt_person==2:
            cv2.putText(main_frame, "Person 2 Time: {}".format(end_time-start_time-pause_times[2]), (450, 500), cv2.FONT_HERSHEY_COMPLEX_SMALL, 1, (0,0,0),1)

else: #if persons outside the home bbox
    print ("Person", cnt_person, ": False\n")
    if not paused:  # the timer hasn't been paused for a while
        last_pause[cnt_person] = end_time # updating the pause point
        paused = True
    pause_times[cnt_person] += end_time - last_pause[cnt_person] # track the total amount of time paused for each person
    last_pause[cnt_person] = end_time

免责声明:

我不得不说，我可能并不完全理解您的问题，而且我不是专家，因此我的解决方案可能存在缺陷。我希望它至少能为您提供不同的视角。干杯。