Load an opencv video frame by frame using PyQT
<p>I am trying to load a mat file ( has position coordinates of object whichis tracked) and load a video file. To load a video file I am using opencv. I made a GUI to load both of them. As soon as someone presses start button the video starts playing and Pause stops it. </p>

<p>Here is the gui for that:</p>

<p><a href="https://i.stack.imgur.com/gA1jH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gA1jH.png" alt="enter image description here"></a></p>

<p>Here are the two issues I am encountering:</p>

<ol>
<li>the video gets loaded in a different window. I want it to appear the main window which has Start and Pause button</li>
<li>I want to add 2 buttons ('Next Frame' and 'Previous Frame') which allow me to go through the video frame by frame. Next Frame Button moves to the next frame and Previous Frame moves the video to previous frame.</li>
</ol>

<p>Here is the code :</p>

<pre><code>import sys
import scipy.io as sio
from PyQt4 import QtGui, QtCore
import cv2

class QtCapture(QtGui.QWidget):
    def __init__(self, filename):
        super(QtGui.QWidget, self).__init__()

        self.cap = cv2.VideoCapture(str(filename))

        self.video_frame = QtGui.QLabel()
        lay = QtGui.QVBoxLayout()
        lay.setMargin(0)
        lay.addWidget(self.video_frame)
        self.setLayout(lay)

    def nextFrameSlot(self):
        ret, frame = self.cap.read()
        # My webcam yields frames in BGR format
        frame = cv2.cvtColor(frame, cv2.cv.CV_BGR2RGB)
        img = QtGui.QImage(frame, frame.shape[1], frame.shape[0], QtGui.QImage.Format_RGB888)
        pix = QtGui.QPixmap.fromImage(img)
        self.video_frame.setPixmap(pix)

    def start(self):
        self.timer = QtCore.QTimer()
        self.timer.timeout.connect(self.nextFrameSlot)
        self.timer.start(1000./30)

    def pause(self):
        self.timer.stop()

    def deleteLater(self):
        self.cap.release()
        super(QtGui.QWidget, self).deleteLater()

class ControlWindow(QtGui.QMainWindow):
    def __init__(self):
        super(ControlWindow, self).__init__()
        self.setGeometry(50, 50, 800, 600)
        self.setWindowTitle("PyTrack")

        self.capture = None

    self.matPosFileName = None
    self.videoFileName = None
    self.positionData = None
        self.updatedPositionData  = {'red_x':[], 'red_y':[], 'green_x':[], 'green_y': [], 'distance': []}
    self.updatedMatPosFileName = None

    self.isVideoFileLoaded = False
    self.isPositionFileLoaded = False

        self.quitAction = QtGui.QAction("&amp;Exit", self)
        self.quitAction.setShortcut("Ctrl+Q")
        self.quitAction.setStatusTip('Close The App')
        self.quitAction.triggered.connect(self.closeApplication)

        self.openMatFile = QtGui.QAction("&amp;Open Position File", self)
        self.openMatFile.setShortcut("Ctrl+Shift+T")
        self.openMatFile.setStatusTip('Open .mat File')
        self.openMatFile.triggered.connect(self.loadPosMatFile)

    self.openVideoFile = QtGui.QAction("&amp;Open Video File", self)
        self.openVideoFile.setShortcut("Ctrl+Shift+V")
        self.openVideoFile.setStatusTip('Open .h264 File')
        self.openVideoFile.triggered.connect(self.loadVideoFile)

        self.mainMenu = self.menuBar()

        self.fileMenu = self.mainMenu.addMenu('&amp;File')
    self.fileMenu.addAction(self.openMatFile)
    self.fileMenu.addAction(self.openVideoFile)
        self.fileMenu.addAction(self.quitAction)

    self.imageCaptureWindow = QtGui.QWidget(self)
        self.start_button = QtGui.QPushButton('Start', self.imageCaptureWindow)
        self.start_button.clicked.connect(self.startCapture)
    self.start_button.setGeometry(0,10,40,30)
        self.pause_button = QtGui.QPushButton('Pause', self.imageCaptureWindow)
    self.pause_button.setGeometry(50,10,40,30)

        self.setCentralWidget(self.imageCaptureWindow)

        self.show()

    def startCapture(self):
        if not self.capture and self.isPositionFileLoaded and self.isVideoFileLoaded:
            self.capture = QtCapture(self.videoFileName)
            self.pause_button.clicked.connect(self.capture.pause)
            self.capture.setParent(self)
            self.capture.setWindowFlags(QtCore.Qt.Tool)
        self.capture.start()
        self.capture.show()

    def endCapture(self):
        self.capture.deleteLater()
        self.capture = None

    def loadPosMatFile(self):
    try:
            self.matPosFileName = str(QtGui.QFileDialog.getOpenFileName(self, 'Select .mat position File'))
            self.positionData = sio.loadmat(self.matPosFileName)
        self.isPositionFileLoaded = True
    except:
        print "Please select a .mat file"

    def loadVideoFile(self):
    try:
            self.videoFileName = QtGui.QFileDialog.getOpenFileName(self, 'Select .h264 Video File')
        self.isVideoFileLoaded = True
    except:
        print "Please select a .h264 file"

    def closeApplication(self):
        choice = QtGui.QMessageBox.question(self, 'Message','Do you really want to exit?',QtGui.QMessageBox.Yes | QtGui.QMessageBox.No)
        if choice == QtGui.QMessageBox.Yes:
            print("Closing....")
            sys.exit()
        else:
            pass


if __name__ == '__main__':
    import sys
    app = QtGui.QApplication(sys.argv)
    window = ControlWindow()
    sys.exit(app.exec_())
</code></pre>

<p>How should I go about doing that? Thanks for the help!</p>