Python QT5 - 多进程 OpenCV 网络摄像头和请求.Get

Question

I'm new to multiprocessing and I'm trying to view my webcam in parallel to making a requests.get, in PyQT5. The current result is the video stutters each time the get request is made - it doesn't seem like a big deal but it's important that this request is made every second with smooth video. For more complex Post requests that take up to 5 seconds for a response, the video looks essentially frozen.

So the expected result is that I have buttery smooth video while a get request is being made in parallel every second.

I know this has something to do with the way I'm calling my processes as per this link :

p1 = Process(target=self.start_webcam())
p2 = Process(target=self.start_web_req())

it should be:

p1 = Process(target=self.start_webcam)
p2 = Process(target=self.start_web_req)

but I get this error:

TypeError: cannot pickle 'Ui_MainWindow' object

This is my code below.

Do you have any ideas, advice, answers to making sure the video is smooth whilst making a get request?

Thank you in advanced!

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import QApplication, QWidget, QTableWidget,QTableWidgetItem, QDialog
import pandas as pd
from PyQt5.QtCore import QTimer, QSize

from PyQt5.QtGui import QImage, QPixmap
from PyQt5.uic import loadUi

import PIL
from PIL import Image
import requests
import sys
import cv2
import numpy as np

class Ui_MainWindow(QWidget):        
    def setupUi(self, MainWindow):
        MainWindow.setWindowFlags(QtCore.Qt.WindowStaysOnTopHint)
        MainWindow.setGeometry(0, 30, 800, 480) # x,y,w,h
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")

        # Camera Label
        self.imgLabel = QtWidgets.QLabel(self.centralwidget)
        self.imgLabel.setGeometry(QtCore.QRect(0, 0, 600, 480))
        self.imgLabel.setFrameShape(QtWidgets.QFrame.Box)
        self.imgLabel.setObjectName("imgLabel")

        MainWindow.setCentralWidget(self.centralwidget)

        # Initiate start_webcam
        p1 = Process(target=self.start_webcam())
        p1.start()

        # Initiate start_web_req
        p2 = Process(target=self.start_web_req())
        p2.start()

    def start_webcam(self):
        self.capture=cv2.VideoCapture(0)
        self.capture.set(cv2.CAP_PROP_FRAME_WIDTH,600)
        self.capture.set(cv2.CAP_PROP_FRAME_HEIGHT,480)

        self.timer = QTimer(self)
        self.timer.timeout.connect(self.update_frame)
        self.timer.start(5)

    def update_frame(self):
        ret,frame=self.capture.read()
        self.cv2_im=frame
        self.pil_im = Image.fromarray(self.cv2_im)
        self.processedImage=self.cv2_im
        self.display_image(1)

    def display_image(self, window=1):
        qformat = QImage.Format_Indexed8
        if len(self.processedImage.shape) == 3:  # rows[0],cols[1],channels[2]
            if (self.processedImage.shape[2]) == 4:
                qformat = QImage.Format_RGBA8888
            else:
                qformat = QImage.Format_RGB888
        img = QImage(self.processedImage, self.processedImage.shape[1], self.processedImage.shape[0],
                     self.processedImage.strides[0], qformat)
        # BGR > RGB
        img = img.rgbSwapped()
        if window == 1:
            self.imgLabel.setPixmap(QPixmap.fromImage(img))
            self.imgLabel.setScaledContents(True)
        if window == 2:
            self.processedLabel.setPixmap(QPixmap.fromImage(img))
            self.processedLabel.setScaledContents(True)


    def start_web_req(self):
        self.timer = QTimer(self)
        self.timer.timeout.connect(self.web_req)
        self.timer.start(1000)        

    def web_req(self):
        res = requests.get('https://www.google.com.au')
        print(res)

    def appExec(self):
        app.exec_()
        self.timer.stop()
        self.capture.release()
        cv2.destroyAllWindows()

if __name__ == "__main__":
    app = QApplication.instance()
    if app is None:
        app = QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(ui.appExec())

Answer 1

With help from eyllanesc, I solved it.

The problem was in start_webcam() and start_web_req() - I had QTimers in there to call update_frame() and web_req() respectively. I removed those start functions and put threading.Timer directly inside update_frame() and web_req() which solved my choppy video problem.

Full code below.

from multiprocessing import Process
import threading

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import QApplication, QWidget, QTableWidget,QTableWidgetItem, QDialog
import pandas as pd
from PyQt5.QtCore import QTimer, QSize

from PyQt5.QtGui import QImage, QPixmap
from PyQt5.uic import loadUi

import PIL
from PIL import Image
import requests
import sys
import cv2
import numpy as np

class Ui_MainWindow(QWidget):        
    def setupUi(self, MainWindow):
        MainWindow.setWindowFlags(QtCore.Qt.WindowStaysOnTopHint)
        MainWindow.setGeometry(0, 30, 800, 480) # x,y,w,h
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")

        # Camera Label
        self.imgLabel = QtWidgets.QLabel(self.centralwidget)
        self.imgLabel.setGeometry(QtCore.QRect(0, 0, 600, 480))
        self.imgLabel.setFrameShape(QtWidgets.QFrame.Box)
        self.imgLabel.setObjectName("imgLabel")

        MainWindow.setCentralWidget(self.centralwidget)

        self.capture=cv2.VideoCapture(1)
        self.capture.set(cv2.CAP_PROP_FRAME_WIDTH,600)
        self.capture.set(cv2.CAP_PROP_FRAME_HEIGHT,480)

        # Initiate start_webcam
        p1 = Process(target=self.update_frame())
        p1.start()

        # Initiate start_web_req
        p2 = Process(target=self.web_req())
        p2.start()

    def update_frame(self):
        self.t1 = threading.Timer(0.01, self.update_frame).start()
        ret,frame=self.capture.read()
        self.cv2_im=frame
        self.pil_im = Image.fromarray(self.cv2_im)
        self.processedImage=self.cv2_im
        self.display_image(1)

    def display_image(self, window=1):
        qformat = QImage.Format_Indexed8
        if len(self.processedImage.shape) == 3:  # rows[0],cols[1],channels[2]
            if (self.processedImage.shape[2]) == 4:
                qformat = QImage.Format_RGBA8888
            else:
                qformat = QImage.Format_RGB888
        img = QImage(self.processedImage, self.processedImage.shape[1], self.processedImage.shape[0],
                     self.processedImage.strides[0], qformat)
        # BGR > RGB
        img = img.rgbSwapped()
        if window == 1:
            self.imgLabel.setPixmap(QPixmap.fromImage(img))
            self.imgLabel.setScaledContents(True)
        if window == 2:
            self.processedLabel.setPixmap(QPixmap.fromImage(img))
            self.processedLabel.setScaledContents(True)        

    def web_req(self):
        self.t2 = threading.Timer(1.0, self.web_req).start()
        res = requests.get('https://www.google.com.au')
        print(res)

    def appExec(self):
        app.exec_()
        self.t1 = None
        self.t2 = None
        self.capture.release()
        cv2.destroyAllWindows()

if __name__ == "__main__":
    app = QApplication.instance()
    if app is None:
        app = QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(ui.appExec())