OpenCV + Python streaming of H264 video over network using UDP protocol

Question

I have a python client code that receives the video stream transmitted using VLC or OBS Studio software.

Client code:

import cv2
import time
target_url = 'udp://@0.0.0.0:1235'
stream = cv2.VideoCapture(target_url)
while True:
        r, f = stream.read()
        if r:
            cv2.imshow('IP Camera stream',f)

It is able to read and display the video stream transmitted using VLC from another machine. Now I want to create the video server app instead of using VLC. I tried to use cv2.VideoWriter but it only takes local files and not udpsink. After browsing through the net, I got few stackoverflow answers suggesting pyzmq [Ref 1] which uses TCP, manually creating socket and handling it [Ref 2] which is not going to work because the client should be able to receive from both VLC as well as custom app.

Then I got to know about NetGear [Ref 3], which is a great tool. But it doesn't support UDP as it internally uses pyzmq [Ref 4].

Basically I am looking for something like cv2.VideoWriter('udp://192.168.1.2:5000', fourcc, ..).

Question: Is there a way in which the live camera feed can be converted into H264 with bitrate and fps then transmitted over UDP so that it can be received using cv2.VideoCapture('udp://@0.0.0.0:5000')?

[Ref 1] Python Opencv and Sockets - Streaming video encoded in h264

[Ref 2] https://stackoverflow.com/a/63717263/12455023

[Ref 3] https://stackoverflow.com/a/57204835/12455023

[Ref 4] https://github.com/abhiTronix/vidgear/issues/281

Answer 1

I'd suggest to use gstreamer for this. You may try:

#!/usr/bin/env python

import cv2
print(cv2.__version__)

# Uncommenting this would allow to check if your opencv build has GSTREAMER support 
#print(cv2.getBuildInformation())


cap = cv2.VideoCapture("udpsrc port=5000 ! application/x-rtp,media=video,encoding-name=H264 ! queue ! rtpjitterbuffer latency=500 ! rtph264depay ! h264parse ! avdec_h264 ! videoconvert ! video/x-raw,format=BGR ! queue ! appsink drop=1", cv2.CAP_GSTREAMER)

# For NVIDIA using NVMM memory 
#cap = cv2.VideoCapture("udpsrc port=5000 ! application/x-rtp,media=video,encoding-name=H264 ! queue ! rtpjitterbuffer latency=500 ! rtph264depay ! h264parse ! nvv4l2decoder ! nvvidconv ! video/x-raw,format=BGRx ! videoconvert ! video/x-raw,format=BGR ! queue ! appsink drop=1", cv2.CAP_GSTREAMER)

width = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
#fps = cap.get(cv2.CAP_PROP_FPS) #doesn't work with python in my case so forcing below...you may have to adjust for your case
fps = 30

if not cap.isOpened():
   print('Failed to open camera')
   exit

print('Source opened, framing %dx%d@%d' % (width,height,fps))


writer = cv2.VideoWriter("appsrc ! video/x-raw,format=BGR ! queue ! videoconvert ! x264enc insert-vui=1 ! h264parse ! rtph264pay ! udpsink port=5001", cv2.CAP_GSTREAMER, 0, float(fps), (int(width),int(height))) 

# For NVIDIA using NVMM memory 
#writer = cv2.VideoWriter("appsrc ! video/x-raw,format=BGR ! queue ! videoconvert ! video/x-raw,format=BGRx ! nvvidconv ! nvv4l2h264enc insert-sps-pps=1 insert-vui=1 ! h264parse ! rtph264pay ! udpsink port=5001", cv2.CAP_GSTREAMER, 0, float(fps), (int(width),int(height))) 

if not writer.isOpened():
   print('Failed to open writer')
   cap.release()
   exit


while True:
    ret_val, img = cap.read();
    if not ret_val:
        break

    writer.write(img);
    cv2.waitKey(1)

writer.release()
cap.release()

This should stream to localhost on port 5001, and you should be able to receive on Linux host running X (expect up to 10 seconds to setup) with:

gst-launch-1.0 udpsrc port=5001 ! application/x-rtp,media=video,encoding-name=H264 ! queue ! rtpjitterbuffer latency=500 ! rtph264depay ! h264parse ! avdec_h264 ! videoconvert ! xvimagesink

If you want to stream to a given host, set host property of udpsink while disabling auto-multicast:

writer = cv2.VideoWriter("appsrc ! video/x-raw,format=BGR ! queue ! videoconvert ! x264enc insert-vui=1 ! h264parse ! rtph264pay ! udpsink port=5001 host=<target_IP> auto-multicast=0

If you want to use multicast (better avoid with wifi):

writer = cv2.VideoWriter("appsrc ! video/x-raw,format=BGR ! queue ! videoconvert ! x264enc insert-vui=1 ! h264parse ! rtph264pay ! udpsink port=5001 host=224.1.1.1

# And you may receive on any LAN Linux host host with:
gst-launch-1.0 udpsrc  multicast-group=224.1.1.1 port=5001 ! application/x-rtp, media=video,encoding-name=H264 ! rtph264depay ! h264parse !  avdec_h264 ! videoconvert ! xvimagesink