使用 OpenCV 和 PyQT5 视频播放速度过快

Question

当在QListWidget 中选择时，我的 GUI 能够自动播放视频。但是，视频播放速度不是正常速度，而是非常快。我以 720p Mp4 视频为例，放在某个文件夹中。我尝试使用cv2.CAP_PROP_FPS 和cv2.CAP_PROP_BUFFERSIZE，但它们都不起作用。我在QThread 和convert_cv_qt 函数中使用了pyqtSignal，我在其他指南中看到了这些函数。 如何以正常速度/帧速率播放视频？

import os
import cv2
import numpy as np
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtMultimedia import QMediaPlayer
from PyQt5.QtMultimediaWidgets import QVideoWidget
from PyQt5.QtCore import pyqtSignal, pyqtSlot, Qt, QThread


class VideoThread(QThread):
    change_pixmap_signal = pyqtSignal(np.ndarray)

    def __init__(self, parent=None):
        super(VideoThread, self).__init__(parent)
        self.get_file_dir = self.parent().file_dir #Get the file_dir from UI_MainWindow

    def run(self):
        cap = cv2.VideoCapture(self.get_file_dir)
        
        while True:
            ret, cv_img = cap.read()
            if ret:
                self.change_pixmap_signal.emit(cv_img)
        cap.release()


class Ui_MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(Ui_MainWindow, self).__init__(parent)
        self.setupUI()
    
    def setupUI(self):
        MainWindow.resize(1720, 863)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.verticalLayout_2 = QtWidgets.QVBoxLayout(self.centralwidget)
        self.tabWidget = QtWidgets.QTabWidget(self.centralwidget)
        self.tabWidget.setTabPosition(QtWidgets.QTabWidget.North)
        self.tabWidget.setTabShape(QtWidgets.QTabWidget.Triangular)
        self.tabWidget.setElideMode(QtCore.Qt.ElideNone)
        self.tabWidget.setTabsClosable(False)
        self.tabWidget.setMovable(True)
        self.tab = QtWidgets.QWidget()
        self.videoimage = QtWidgets.QLabel(self.tab)
        self.videoimage.setGeometry(QtCore.QRect(0, 10, 1280, 720))
        self.listWidget = QtWidgets.QListWidget(self.tab)
        self.listWidget.setGeometry(QtCore.QRect(1290, 60, 391, 241))
        self.listWidget.setObjectName("listWidget")
        self.listWidget.itemClicked.connect(self.itemclick)
        self.tabWidget.addTab(self.tab, "")
        self.tabWidget.setTabText(0, "Testing")
        self.verticalLayout_2.addWidget(self.tabWidget)
        MainWindow.setCentralWidget(self.centralwidget)

        self.listvideos()
        self.tabWidget.setCurrentIndex(0)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    @pyqtSlot(np.ndarray)
    def listvideos(self):
        file_extension = ['avi','mp4','mov']
        arr = os.listdir('D:\\Files\\VSCODE\\APPS\\HDTS\\videos')
        for i in arr:
            for fe in file_extension:
                    if i[-3:] == fe:
                        item = QtWidgets.QListWidgetItem(str(i))
                        self.listWidget.addItem(item)

    def itemclick(self):
        try:
          self.thread.terminate()
        except:
          print("Nothing to terminate!")

        item = self.listWidget.currentItem()
        self.file_dir = 'D:\\Files\\VSCODE\\APPS\\HDTS\\videos\\' + item.text()
        print(self.file_dir)        
        self.thread = VideoThread(self)
        self.thread.change_pixmap_signal.connect(self.update_image)
        self.thread.start()
    
    
    def update_image(self, cv_img):
        qt_img = self.convert_cv_qt(cv_img)
        self.videoimage.setPixmap(qt_img)
    
    def convert_cv_qt(self, cv_img):
        rgb_image = cv2.cvtColor(cv_img, cv2.COLOR_BGR2RGB)
        h, w, ch = rgb_image.shape
        bytes_per_line = ch * w
        convert_to_Qt_format = QtGui.QImage(rgb_image.data, w, h, bytes_per_line, QtGui.QImage.Format_RGB888)
        p = convert_to_Qt_format.scaled(1280, 720, Qt.KeepAspectRatio)
        return QtGui.QPixmap.fromImage(p)
    
if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    MainWindow.show()
    sys.exit(app.exec_())

Answer 1

当您将 VideoCapture 与文件一起使用时，如果您调用“cap.read()”，您将获得视频的下一帧，而不管其实际帧速率如何。因此，每次捕获帧时都应该使用“msleep”：

def run(self):
    cap = cv2.VideoCapture(self.get_file_dir)
    
    while True:
        ret, cv_img = cap.read()
        if ret:
            self.change_pixmap_signal.emit(cv_img)
        self.msleep(1000//30) # You can change 30 with 60 if you need 60 fps.
    cap.release()