为什么我在使用线程时cv2.imshow（）停留在第一帧？

Question

我需要使用带有线程的cv2播放视频文件。它适用于第一个文件，但会冻结在第二个文件的第一帧并停在那里。如何解决？

from threading import Thread
import cv2
files = [ 'video_1','video_2']
def player (video):
    cap = cv2.VideoCapture(video+'.mp4')
    while cap.isOpened() :
        time = cap.get(cv2.CAP_PROP_POS_MSEC)
        fps = cap.get(cv2.CAP_PROP_FPS)
        total_frames = cap.get(cv2.CAP_PROP_FRAME_COUNT)
        print(time, fps, total_frames)
        ret, frame = cap.read()
        if ret == True:
           cv2.imshow('frame',frame)
           if cv2.waitKey(33) & 0xFF == ord('q'):
               break
        else:
            break

for i in files :
   t1 = Thread (target = player , args = (i,))
   t1.start()
   t1.join()