def __init__(self, annots1, annots2, parent=None):
        QDialog.__init__(self, parent)
        self.setWindowTitle('Compare Call Pairs')
        self.setWindowIcon(QIcon('img/Avianz.ico'))
        self.setWindowFlags((self.windowFlags() ^ Qt.WindowContextHelpButtonHint) | Qt.WindowMaximizeButtonHint | Qt.WindowCloseButtonHint)

        self.parent = parent
        self.rec1 = annots1[0].recname
        self.rec2 = annots2[0].recname

        self.annots1 = annots1
        self.annots2 = annots2

        # Set colour map
        # cmap = self.config['cmap']  # TODO Read these from config
        self.lut = colourMaps.getLookupTable("Grey")
        self.cmapInverted = False

        self.topLabel = QLabel("Comparing recorders %s (top) and %s (bottom)" %(self.rec1, self.rec2))
        self.labelPair = QLabel()

        # Volume, brightness and contrast sliders. (NOTE hardcoded init)
        self.specControls = SupportClasses_GUI.BrightContrVol(80, 20, False)
        self.specControls.colChanged.connect(self.setColourLevels)
        # self.specControls.volChanged.connect(self.volSliderMoved)
        # TODO add volume and playback at some point

        # spectrograms
        self.wPlot = pg.GraphicsLayoutWidget()
        self.pPlot1 = self.wPlot.addViewBox(enableMouse=False, row=0, col=1)
        self.pPlot2 = self.wPlot.addViewBox(enableMouse=False, row=1, col=1)

        self.plot1 = pg.ImageItem()
        self.plot2 = pg.ImageItem()
        self.pPlot1.addItem(self.plot1)
        self.pPlot2.addItem(self.plot2)

        # Y (freq) axis
        self.sg_axis1 = pg.AxisItem(orientation='left')
        self.sg_axis1.linkToView(self.pPlot1)
        self.sg_axis2 = pg.AxisItem(orientation='left')
        self.sg_axis2.linkToView(self.pPlot2)
        self.wPlot.addItem(self.sg_axis1, row=0, col=0)
        self.wPlot.addItem(self.sg_axis2, row=1, col=0)

        # The buttons to move through the overview
        self.leftBtn = QToolButton()
        self.leftBtn.setArrowType(Qt.LeftArrow)
        self.leftBtn.clicked.connect(self.moveLeft)
        self.leftBtn.setToolTip("View previous pair")
        self.rightBtn = QToolButton()
        self.rightBtn.setArrowType(Qt.RightArrow)
        self.rightBtn.clicked.connect(self.moveRight)
        self.rightBtn.setToolTip("View next pair")
        self.leftBtn.setSizePolicy(QSizePolicy.Minimum, QSizePolicy.MinimumExpanding)
        self.rightBtn.setSizePolicy(QSizePolicy.Minimum, QSizePolicy.MinimumExpanding)

        # accept / close
        closeBtn = QPushButton("Close")
        closeBtn.clicked.connect(self.accept)

        # init GUI with page 1 data
        self.currpage = 1
        self.leftBtn.setEnabled(False)
        if len(self.annots1)==1:
            self.rightBtn.setEnabled(False)
        self.setData()

        # layout
        box = QVBoxLayout()
        box.addWidget(self.topLabel)
        box.addWidget(self.labelPair)
        box.addWidget(self.specControls)
        midHBox = QHBoxLayout()
        midHBox.addWidget(self.leftBtn)
        midHBox.addWidget(self.wPlot, stretch=10)
        midHBox.addWidget(self.rightBtn)
        box.addLayout(midHBox)
        box.addWidget(closeBtn)
        self.setLayout(box)