opencv pyqt视频正常帧率

问题描述 投票：0回答：2

我正在 Python 3.6 中创建一个专用视频播放器，使用 OpenCV3 和 ffmepg 来处理图像，并在 Windows 环境中使用 PyQt5。 我选择这种包组合是因为 ffmpeg 可以处理比 QtMultimedia 更广泛的编解码器。

我遇到了一个障碍。 我的播放器不以正常速度播放 – 它大约以正常速度的 3/4 播放。 我使用 QTimer.timer 以 1/帧率的速度循环显示引擎 (nextFrameSlot)。

关于如何让视频以正常速度播放有什么建议吗？ 这是演示我的问题的一组简短代码。

import sys
from PyQt5.QtWidgets import QWidget, QLabel, QFormLayout, QPushButton, QMainWindow
from PyQt5.QtWidgets import QAction, QMessageBox, QApplication, QFileDialog
from PyQt5.QtGui import QImage, QPixmap
from PyQt5.QtCore import QTimer
import cv2


class VideoCapture(QWidget):
    def __init__(self, filename, parent):
        super(QWidget, self).__init__()
        self.cap = cv2.VideoCapture(str(filename[0]))
        self.length = int(self.cap.get(cv2.CAP_PROP_FRAME_COUNT))
        self.frame_rate = self.cap.get(cv2.CAP_PROP_FPS)
        #self.codec = self.cap.get(cv2.CAP_PROP_FOURCC)
        self.video_frame = QLabel()
        parent.layout.addWidget(self.video_frame)

    def nextFrameSlot(self):
        ret, frame = self.cap.read()
        frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
        img = QImage(frame, frame.shape[1], frame.shape[0], QImage.Format_RGB888)
        pix = QPixmap.fromImage(img)
        self.video_frame.setPixmap(pix)

    def start(self):
        self.timer = QTimer()
        self.timer.timeout.connect(self.nextFrameSlot)
        self.timer.start(1000.0/self.frame_rate)

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

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

class VideoDisplayWidget(QWidget):
    def __init__(self,parent):
        super(VideoDisplayWidget, self).__init__(parent)
        self.layout = QFormLayout(self)
        self.startButton = QPushButton('Start', parent)
        self.startButton.clicked.connect(parent.startCapture)
        self.startButton.setFixedWidth(50)
        self.pauseButton = QPushButton('Pause', parent)
        self.pauseButton.setFixedWidth(50)
        self.layout.addRow(self.startButton, self.pauseButton)
        self.setLayout(self.layout)

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

        self.capture = None

        self.isVideoFileLoaded = False

        self.quitAction = QAction("&Exit", self)
        self.quitAction.setShortcut("Ctrl+Q")
        self.quitAction.triggered.connect(self.closeApplication)

        self.openVideoFile = QAction("&Open Video File", self)
        self.openVideoFile.setShortcut("Ctrl+Shift+V")
        self.openVideoFile.triggered.connect(self.loadVideoFile)

        self.mainMenu = self.menuBar()
        self.fileMenu = self.mainMenu.addMenu('&File')
        self.fileMenu.addAction(self.openVideoFile)
        self.fileMenu.addAction(self.quitAction)

        self.videoDisplayWidget = VideoDisplayWidget(self)
        self.setCentralWidget(self.videoDisplayWidget)

    def startCapture(self):
        if not self.capture and self.isVideoFileLoaded:
            self.capture = VideoCapture(self.videoFileName, self.videoDisplayWidget)
            self.videoDisplayWidget.pauseButton.clicked.connect(self.capture.pause)
        self.capture.start()

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

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

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

if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = ControlWindow()
    window.show()
    sys.exit(app.exec_())
python-3.x pyqt5 opencv3.0
2个回答
3
投票

已解决 - 我需要在函数 

self.timer.setTimerType(Qt.PreciseTimer)
中的语句 
self.timer = QTimer()
之后指定 
start(self)
。默认情况下，QTimer() 使用粗定时器。对于 Windows，粗略时间间隔为 15.6 毫秒。

0
投票

与 

PyQt6
一起使用时略有变化：

import sys
from PyQt6.QtWidgets import QWidget, QLabel, QFormLayout, QPushButton, QMainWindow
from PyQt6.QtWidgets import QMessageBox, QApplication, QFileDialog
from PyQt6.QtGui import QAction
from PyQt6.QtGui import QImage, QPixmap
from PyQt6.QtCore import QTimer, Qt
import cv2


class VideoCapture(QWidget):
    def __init__(self, filename, parent):
        super(QWidget, self).__init__()
        self.cap = cv2.VideoCapture(str(filename[0]))
        self.length = int(self.cap.get(cv2.CAP_PROP_FRAME_COUNT))
        self.frame_rate = self.cap.get(cv2.CAP_PROP_FPS)
        #self.codec = self.cap.get(cv2.CAP_PROP_FOURCC)
        self.video_frame = QLabel()
        parent.layout.addWidget(self.video_frame)

    def nextFrameSlot(self):
        ret, frame = self.cap.read()
        frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
        img = QImage(frame, frame.shape[1], frame.shape[0], QImage.Format.Format_RGB888)
        pix = QPixmap.fromImage(img)
        self.video_frame.setPixmap(pix)

    def start(self):
        self.timer = QTimer()
        self.timer.setTimerType(Qt.TimerType.PreciseTimer)
        self.timer.timeout.connect(self.nextFrameSlot)
        self.timer.start(int(1000.0/self.frame_rate))

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

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

class VideoDisplayWidget(QWidget):
    def __init__(self,parent):
        super(VideoDisplayWidget, self).__init__(parent)
        self.layout = QFormLayout(self)
        self.startButton = QPushButton('Start', parent)
        self.startButton.clicked.connect(parent.startCapture)
        self.startButton.setFixedWidth(50)
        self.pauseButton = QPushButton('Pause', parent)
        self.pauseButton.setFixedWidth(50)
        self.layout.addRow(self.startButton, self.pauseButton)
        self.setLayout(self.layout)

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

        self.capture = None

        self.isVideoFileLoaded = False

        self.quitAction = QAction("&Exit", self)
        self.quitAction.setShortcut("Ctrl+Q")
        self.quitAction.triggered.connect(self.closeApplication)

        self.openVideoFile = QAction("&Open Video File", self)
        self.openVideoFile.setShortcut("Ctrl+Shift+V")
        self.openVideoFile.triggered.connect(self.loadVideoFile)

        self.mainMenu = self.menuBar()
        self.fileMenu = self.mainMenu.addMenu('&File')
        self.fileMenu.addAction(self.openVideoFile)
        self.fileMenu.addAction(self.quitAction)

        self.videoDisplayWidget = VideoDisplayWidget(self)
        self.setCentralWidget(self.videoDisplayWidget)

    def startCapture(self):
        if not self.capture and self.isVideoFileLoaded:
            self.capture = VideoCapture(self.videoFileName, self.videoDisplayWidget)
            self.videoDisplayWidget.pauseButton.clicked.connect(self.capture.pause)
        self.capture.start()

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

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

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

if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = ControlWindow()
    window.show()
    sys.exit(app.exec())
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