Problems trying to stream a video with Jetson Nano

Hi,
From the code, it is not clear what your source is(Bayer sensor camera, USB camera, or IP camera). There should have one cv2.VideoCapture() and one cv2.VideoWriter() like this sample:
Displaying to the screen with OpenCV and GStreamer - #9 by DaneLLL

Please share information about the input source so that we can suggest next.

And we have demonstration of Yolo models in DeepStream SDK. You may also take a look and give it a try.