opencv pyqt视频正常帧率

Question

我正在 Python 3.6 中创建一个特殊用途的视频播放器，使用 OpenCV3 和 ffmepg 来处理图像，并使用 PyQt5 作为 Windows 环境。我之所以选择这种包组合，是因为 ffmpeg 比 QtMultimedia 处理的编解码器种类更多。

我运行遇到了一个障碍。我的播放器不以正常速度播放 – 它以正常速度的大约 ¾ 播放。我使用 QTimer.timer 以 1/framerate 的速度循环我的显示引擎 (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缩写代码。

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_())

Answer 1

已解决 - 我需要在函数 start(self) 中的语句 self.timer = QTimer() 之后指定 self.timer.setTimerType(Qt.PreciseTimer)。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。

opencv pyqt视频正常帧率

opencv pyqt video normal frame rate

python-3.x

pyqt5

opencv3.0