#Coding4Fun – How to control your #drone with 20 lines of code! (8/N)

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Hi!

Now that I started to understand how UDP works, I also did my research to find which are the best options to access an UDP video feed. Lucky for me, there are plenty of resources about doing this task using my old friend OpenCV.

Most of the OpenCV documentation is written in C++. However at the end, it all goes down to these basic lines of code

# open UDP
videoUDP = 'udp://192.168.10.1:11111'
cap = cv2.VideoCapture(videoUDP)

# read a frame from the feed
ret, frame = cap.read()
img = cv2.resize(frame, (320, 240))

# diplay the frame in openCV video window
cv2.imshow('Video', img)

Note: At the references section below I shared some of my posts with my experiences on how to install OpenCV in Windows 10.

Let’s go back to our sample Python App. Using the previous sample that display the battery level, I changed this code to be alive all the time and displaying the video feed in a 320*240 window.

The following video display how fast this works:

And of course the complete code with this notes:

Line 96-100. Open video feed and wait 2 seconds
Line 104-118. Main App.
- Get and display battery level
- Get UDP video frame
- Resize frame to 320×240
- Display frame
- When Q key is pressed, exit app
Line 121. Close video stream

	# Bruno Capuano
	# enable drone video camera
	# display video camera using OpenCV

	import socket
	import time
	import threading
	import cv2

	def receiveData():
	global response
	while True:
	try:
	response, _ = clientSocket.recvfrom(1024)
	except:
	break

	def readStates():
	global battery
	while True:
	try:
	response_state, _ = stateSocket.recvfrom(256)
	if response_state != 'ok':
	response_state = response_state.decode('ASCII')
	list = response_state.replace(';', ':').split(':')
	battery = int(list[21])
	except:
	break

	def sendCommand(command):
	global response
	timestamp = int(time.time() * 1000)

	clientSocket.sendto(command.encode('utf-8'), address)

	while response is None:
	if (time.time() * 1000) – timestamp > 5 * 1000:
	return False

	return response


	def sendReadCommand(command):
	response = sendCommand(command)
	try:
	response = str(response)
	except:
	pass
	return response

	def sendControlCommand(command):
	response = None
	for i in range(0, 5):
	response = sendCommand(command)
	if response == 'OK' or response == 'ok':
	return True
	return False

	# ———————————————–
	# Main program
	# ———————————————–

	# connection info
	UDP_IP = '192.168.10.1'
	UDP_PORT = 8889
	last_received_command = time.time()
	STATE_UDP_PORT = 8890

	address = (UDP_IP, UDP_PORT)
	response = None
	response_state = None

	clientSocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
	clientSocket.bind(('', UDP_PORT))
	stateSocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
	stateSocket.bind(('', STATE_UDP_PORT))

	# start threads
	recThread = threading.Thread(target=receiveData)
	recThread.daemon = True
	recThread.start()

	stateThread = threading.Thread(target=readStates)
	stateThread.daemon = True
	stateThread.start()

	# connect to drone
	response = sendControlCommand("command")
	print(f'command response: {response}')
	response = sendControlCommand("streamon")
	print(f'streamon response: {response}')

	# drone information
	battery = 0

	# open UDP
	print(f'opening UDP video feed, wait 2 seconds ')
	videoUDP = 'udp://192.168.10.1:11111'
	cap = cv2.VideoCapture(videoUDP)
	time.sleep(2)

	# open
	i = 0
	while True:
	i = i + 1
	sendReadCommand('battery?')
	print(f'battery: {battery} % – i: {i}')

	try:
	ret, frame = cap.read()
	img = cv2.resize(frame, (320, 240))
	cv2.imshow('Video', img)
	except Exception as e:
	print(f'exc: {e}')
	pass

	if cv2.waitKey(1) & 0xFF == ord('q'):
	break


	response = sendControlCommand("streamoff")
	print(f'streamon response: {response}')

view raw DjiTelloCameraStreamViewUsingOpenCV.py hosted with ❤ by GitHub

Happy coding!

Greetings

El Bruno

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