Here is a small code snippet that you can use to stream from your Swann DVR security system. The DVR resides within the same local network as the python code streaming the video. The code incorporates the username and password in the RTSP call when instantiated. Take a different approach in the code to make it more secure. Additionally, Secure RTSP protocol over 443 is also available.

videocam

#!/usr/bin/env python -c

# Import OpenCV and threading packages
import cv2
import threading

# Define class for the camera thread.
class CamThread(threading.Thread):

    def __init__(self, previewname, camid):
        threading.Thread.__init__(self)
        self.previewname = previewname
        self.camid = camid

    def run(self):
        print("Starting " + self.previewname)
        previewcam(self.previewname, self.camid)

# Function to preview the camera.
def previewcam(previewname, camid):
    cv2.namedWindow(previewname)
    cam = cv2.VideoCapture(camid)
    if cam.isOpened():
        rval, frame = cam.read()
    else:
        rval = False

    while rval:
        cv2.imshow(previewname, frame)
        rval, frame = cam.read()
        key = cv2.waitKey(20)
        if key == 27:  # Press ESC to exit/close each window.
            break
    cv2.destroyWindow(previewname)

# Create different threads for each video stream, then start it.
thread1 = CamThread("Driveway", 'rtsp://username:SuperSecurePassword@192.168.1.2/Streaming/Channels/102')
thread2 = CamThread("Front Door", 'rtsp://username:SuperSecurePassword@192.168.1.2/Streaming/Channels/202')
thread3 = CamThread("Garage", 'rtsp://username:SuperSecurePassword@192.168.1.2/Streaming/Channels/302')
thread1.start()
thread2.start()
thread3.start()

# check out tutorials point link below for multi-threading sample
# https://www.tutorialspoint.com/python/python_multithreading.htm