python实现：

import cv2
import sys

(major_ver, minor_ver, subminor_ver) = (cv2.__version__).split('.')
print(major_ver, minor_ver, subminor_ver)

if __name__ == '__main__':
    # 创建跟踪器
    # 'BOOSTING', 'MIL','KCF', 'TLD', 'MEDIANFLOW', 'GOTURN', 'MOSSE'
    tracker_type = 'MIL'
    tracker = cv2.MultiTracker_create()#获得追踪的初始化结果

    # 创建窗口
    cv2.namedWindow("Tracking")#给窗口命名

    # 读入视频
    video = cv2.VideoCapture("./pig/001.mp4")

    # 读入第一帧
    ok, frame = video.read()
    if not ok:
        print('读取视频失败')
        sys.exit()

    # 定义一个bounding box
    #多目标跟踪，这里定义3个box
    box1 = cv2.selectROI("Tracking", frame)#在第一帧图片上进行选框操作
    box2 = cv2.selectROI("Tracking", frame)
    box3 = cv2.selectROI("Tracking", frame)

    # 用第一帧初始化
    ok = tracker.add(cv2.TrackerMIL_create(), frame, box1)
    ok1 = tracker.add(cv2.TrackerMIL_create(), frame, box2)
    ok2 = tracker.add(cv2.TrackerMIL_create(), frame, box3)
    while True:
        ok, frame = video.read()
        if not ok:
            break

        # 计时
        timer = cv2.getTickCount()

        # 更新追踪器tracker
        ok, boxes = tracker.update(frame)
        print(ok, boxes)

        # 计算FPS
        fps = cv2.getTickFrequency() / (cv2.getTickCount() - timer)

        for box in boxes:
            # 画bonding box
            if ok:
                p1 = (int(box[0]), int(box[1]))
                p2 = (int(box[0] + box[2]), int(box[1] + box[3]))
                cv2.rectangle(frame, p1, p2, (255, 0, 0), 2, 1)
            else:
                cv2.putText(frame, "Tracking failed detected", (100, 80), cv2.FONT_HERSHEY_SIMPLEX, 0.75, (0, 0, 255),2)

        # 展示tracker类型
        cv2.putText(frame, tracker_type+"Tracker", (100, 20), cv2.FONT_HERSHEY_SIMPLEX, 0.75, (50, 170, 50), 2)

        # 展示FPS
        cv2.putText(frame, "FPS:"+str(fps), (100, 50), cv2.FONT_HERSHEY_SIMPLEX, 0.75, (50, 170, 50), 2)

        # Result
        cv2.imshow("Tracking", frame)

        # Exit
        k = cv2.waitKey(1) & 0xff
        if k == 27:
            break

跟踪结果：