Multi-object tracking initialization in Opencv using multiTracker object

  opencv3.0, python-3.x, tracking

I am using multiTracker in cv2 to track multiple objects. My code is built based on this link and this one. I want to initialize all the bounding boxes at once at any point during the video. However, I have trouble doing this. Here is the code:

import imutils
import cv2
from random import randint

trackerName = 'csrt'
videoPath = "C:/Users/Art/testVideo.mp4"

    "csrt": cv2.TrackerCSRT_create,
    "kcf": cv2.TrackerKCF_create,
    "boosting": cv2.TrackerBoosting_create,
    "mil": cv2.TrackerMIL_create,
    "tld": cv2.TrackerTLD_create,
    "medianflow": cv2.TrackerMedianFlow_create,
    "mosse": cv2.TrackerMOSSE_create

trackers = cv2.MultiTracker_create()
cap = cv2.VideoCapture(videoPath)

while cap.isOpened():

    ret, frame =

    if frame is None:

    # for fast processing resize the frame 
    frame = imutils.resize(frame, width=600)

    (success, boxes) = trackers.update(frame)
    for box in boxes:
        (x, y, w, h) = [int(v) for v in box]
        cv2.rectangle(frame, (x, y), (x + w, y + h), (0, 255, 0), 2)

    cv2.imshow("Frame", frame)
    key = cv2.waitKey(1) & 0xFF

    # if the 'p' key is selected, we select a bounding box to track
    if key == ord("p"):
        boxes = []
        colors = []
        boxFlag = True
        while boxFlag:
            box = cv2.selectROI('MultiTracker', frame, fromCenter=False, 
            colors.append((randint(64, 255), randint(64, 255), randint(64, 
            print("Press q to quit selecting boxes and start tracking")
            print("Press any other key to select next object")
            if key == ord("q"):  # q is pressed
                boxFlag = False
    # Initialize MultiTracker
    for box in boxes:
        tracker = OPENCV_OBJECT_TRACKERS[trackerName]()
        trackers.add(tracker, frame, box)


However, there are some problems. First, when I click on ‘p’ key to select bounding boxes, the video pauses and another window opens that shows the frame at which video was paused and I can select bounding boxes on the new window only. Also, when I press ‘q’ key, nothing will happen and basically it stays there forever. My question is how I can fix this problem, and be able to initialize tracking after I select all of the bounding boxes.

Source: Python-3x Questions