Python Multithread For Multicamera - python-3.x

Question

I'm trying to build an app which will has 2 or more cameras to provide frames and going to display the frames after a few opencv processing. In this case I'm using threads. Each camera has 2 threads; one for receiving frames and put them to the queue and other one for take the frames from queue and display them. When I try to do this with only 1 camera it works just fine. But with 2 cameras I can't get the result that I expected. I'm going to provide my code and the result. I would appreciate for your helps.
Here is my main file:
from MyThread import MyThread
cam_list = [0, 2]
threads = []
if __name__ == '__main__':
for i, cam in enumerate(cam_list):
th = MyThread(cam, f"Camera {cam}")
threads.append(th)
for t in threads:
t.run()
... and this is MyThread class file:
import threading
import queue
import cv2
class MyThread:
def __init__(self, camera_index, window_name):
self.q = queue.SimpleQueue()
self.cap = cv2.VideoCapture(camera_index)
self.window_name = window_name
self.t1 = threading.Thread(target=self.receive)
self.t2 = threading.Thread(target=self.display)
def receive(self):
try:
print("Start Receiving...")
while True:
ret, frame = self.cap.read()
self.q.put(frame)
except Exception as err:
print(f"An error occured: {err}")
def display(self):
try:
print("Start Displaying...")
while True:
if self.q.empty() != True:
frame = self.q.get()
cv2.imshow(self.window_name, frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
except Exception as Err:
print(f"An error occured : {Err}")
def run(self):
self.t1.start()
self.t2.start()
This is the result.(I was expected two windows):