Brokerless ZeroMq to share live image/video data stream from Raspberry PI B+ (Uses OpenCV)

Makes sure you have the following :

  1. OpenCV 3.x compiled and installed on Rasbperry Pi
  2. Raspberry Pi B+ with Raspbian and a USB webcam attached

ZeroMQ

Read through ZeroMQ in 100 words for a brief description

zmq

Installationhttp://zeromq.org/bindings:python

 

Code

Now lets go through the simple code I wrote for publishing and subscribing to live webcam stream from a raspberry PI to a workstation.

 

Make sure you have the dependencies and imports as below

import os, sys, datetime
import json, base64

import cv2
import zmq
import numpy as np
import imutils
from imutils.video import FPS

 

“”” Publish “””

  • In this piece of code we are creating a Zero MQ context preparing to send data to ‘tcp://localhost:5555’
  • The opencv API for camera is used to capture a frame from the device in 640×480 size
  • FPS module is used from opencv to estimate the frame rate for this capture
  • The byte buffer read from the webcam is encoded and sent as a string over the Zero MQ TCP socket connection
  • Continue to send each buffer out on the TCP socket
def pubVideo(config):
    context = zmq.Context()
    footage_socket = context.socket(zmq.PUB)
    # 'tcp://localhost:5555'
    ip = "127.0.0.1"
    port = 5555
    target_address = "tcp://{}:{}".format(ip, port) 
    print("Publish Video to ", target_address)
    footage_socket.connect(target_address)
    impath = 0 # For the first USB camera attached
    camera = cv2.VideoCapture(impath)  # init the camera
    camera.set(cv2.CAP_PROP_FRAME_WIDTH, 640)
    camera.set(cv2.CAP_PROP_FRAME_HEIGHT, 480)
    print("Start Time: ", datetime.datetime.now())
    fps = FPS().start()
    while True:
        try:
            buffer = capture(config, camera)
            if not isinstance(buffer, (list, tuple, np.ndarray)):
                break
            buffer_encoded = base64.b64encode(buffer)
            footage_socket.send_string(buffer_encoded.decode('ascii'))
            # Update the FPS counter
            fps.update()
            cv2.waitKey(1)
        except KeyboardInterrupt:
            # stop the timer and display FPS information
            fps.stop()
            print("[INFO] elasped time: {:.2f}".format(fps.elapsed()))
            print("[INFO] approx. FPS: {:.2f}".format(fps.fps()))
            camera.release()
            cv2.destroyAllWindows()
            print("\n\nBye bye\n")
            break
    print("End Time: ", datetime.datetime.now())

 

“”” Subscribe “””

  • The ZeroMQ subscriber is listening on ‘tcp://*:5555’ 
  • As the string is received its decoded and converted to image using OpenCv
  • We use OpenCV to visualize this frame in a window
  • Every frame sent over the ZeroMQ TCP socket is visualized and appears as a live video stream
def subVideo(config):
    context = zmq.Context()
    footage_socket = context.socket(zmq.SUB)
    port = 5555
    bind_address = "tcp://*:{}".format(port) # 'tcp://*:5555'
    print("Subscribe Video at ", bind_address)
    footage_socket.bind(bind_address)
    footage_socket.setsockopt_string(zmq.SUBSCRIBE, str(''))
    while True:
        try:
            frame = footage_socket.recv_string()
            img = base64.b64decode(frame)
            npimg = np.fromstring(img, dtype=np.uint8)
            source = cv2.imdecode(npimg, 1)
            cv2.imshow("image", source)
            cv2.waitKey(1)
        except KeyboardInterrupt:
            cv2.destroyAllWindows()
            print("\n\nBye bye\n")
            break

Github: https://github.com/vishwakarmarhl/cnaviz/blob/master/imcol/CvZmq.py

 

Run

In the github code above, you can run the test as follows,

PUB: Webcam source machine

python CvZmq.py pub --pubip=127.0.0.1 --pubport=5555

SUB: Target visualization machine

python CvZmq.py sub --subport=5555

 

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