How to capture Multi camera with Opencv Multi threading (python) [closed]

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I am trying to achieve to get the streams from multiple ip cameras and display it. I have two ipcamera with urls : rtsp and rtsp1

When i run the following program, Only first window loads and works fine until the second thread kicks in.

Things works fine with multiple streams in the following methods :

• Works without threads. i.e

:

cam0 = cv2.VideoCapture(rtsp)
cam1 = cv2.VideoCapture(rtsp1)
ret, frame0 = cam0.read()
ret, frame1 = cam1.read()
show imshow(frame0) & (frame1)

But this method is primitive and get lags. Moreover not scalable with more cameras.

• If i run only one thread, the video streaming works fine.
• if i run it as two different python program targeting each rtsp stream, i have no issue. Again not practical for more cameras.

But the objective was to run multiple ipcamera from one single program. Any help to highlight the mistake i made would be highly appreciated.

    import cv2
    import os
    import time
    import threading

    os.environ["OPENCV_FFMPEG_CAPTURE_OPTIONS"] = "rtsp_transport;udp"
    rtsp1 = 'rtsp://userid:[email protected]:8080/h264_ulaw.sdp'
    rtsp='rtsp://userid:[email protected]:10554/udp/av0_0'

    def getPicture(url):      

    cam = cv2.VideoCapture(url)
    a=cam.get(cv2.CAP_PROP_BUFFERSIZE)
    cam.set(cv2.CAP_PROP_BUFFERSIZE,3)
    start_frame_number = 20
    cam.set(cv2.CAP_PROP_POS_FRAMES, start_frame_number)

    print("buffer"+str(a))

    while True:        
        ret, frame = cam.read()
        small_frame = cv2.resize(frame, (0, 0), fx=.50, fy=.50)
        small_frame = cv2.cvtColor(small_frame,cv2.COLOR_BGR2GRAY)
        cv2.imshow("camera",small_frame)

        key = cv2.waitKey(20)
        if key == 27:  # exit on ESC
            break

    # When everything done, release the video capture object
    cam.release()


        # Closes all the frames
    cv2.destroyAllWindows() 

   if __name__ == '__main__':

    t1 = threading.Thread(target=getPicture, args=(rtsp,))
    t2 = threading.Thread(target=getPicture, args=(rtsp1,))

    t1.start()
    t2.start()