opencv python camera frame grab and display on different threads with safe synchronization

opencv_webcam_multithread.py

#!/usr/bin/env python

from threading import Thread, Lock
import cv2

class WebcamVideoStream :
    def __init__(self, src = 0, width = 320, height = 240) :
        self.stream = cv2.VideoCapture(src)
        self.stream.set(cv2.cv.CV_CAP_PROP_FRAME_WIDTH, width)
        self.stream.set(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT, height)
        (self.grabbed, self.frame) = self.stream.read()
        self.started = False
        self.read_lock = Lock()

    def start(self) :
        if self.started :
            print "already started!!"
            return None
        self.started = True
        self.thread = Thread(target=self.update, args=())
        self.thread.start()
        return self

    def update(self) :
        while self.started :
            (grabbed, frame) = self.stream.read()
            self.read_lock.acquire()
            self.grabbed, self.frame = grabbed, frame
            self.read_lock.release()

    def read(self) :
        self.read_lock.acquire()
        frame = self.frame.copy()
        self.read_lock.release()
        return frame

    def stop(self) :
        self.started = False
        self.thread.join()

    def __exit__(self, exc_type, exc_value, traceback) :
        self.stream.release()

if __name__ == "__main__" :
    vs = WebcamVideoStream().start()
    while True :
        frame = vs.read()
        cv2.imshow('webcam', frame)
        if cv2.waitKey(1) == 27 :
            break

    vs.stop()
    cv2.destroyAllWindows()

Thanks!

Do you suppose the read method along with imshow also could be threaded? So that it is always reading and displaying from stream while the main function is idle? (i.e : you can do other stuff in the main function)

I am getting this error:

AttributeError: module 'cv2.cv2' has no attribute 'cv'

I am getting this error:

AttributeError: module 'cv2.cv2' has no attribute 'cv'

You probably need to change them to cv2.CAP_PROP_FRAME_WIDTH and HEIGHT respectively, that should solve the problem

Thank you! Very cool.
If someone else gets AttributeError: 'NoneType' object has no attribute 'copy', make sure your webcam is connected... :)

The code is working fine. But I want to implement it for restarted source. E.g. if I am running in background. If the camera is going to restart after 2-3 hours the code should accept it without re-run it. Cloud it be possible?

Good job ! I want to ask you a question privately, how can I contact you ?

FYI for those who stumble upon this gist, I have written a python library for this exact purpose.
https://github.com/nup002/Threaded-VideoCapture