python - 使用 QmediaPlayer 的 PyQt5 访问框架

Question

我正在创建一个程序来播放视频然后处理它们。我可以使用 QMediaPlayer 播放视频。我如何访问特定帧作为图像或类似的东西。我的最终目标是将视频格式化为大小为 [帧数、width_of_video、height_of_video、 channel ] 的 4 维张量。

这是加载我的视频的代码:

self.clear_layout(self.vlayout)
videoItem = QVideoWidget()

self.mediaPlayer = QMediaPlayer(None, QMediaPlayer.VideoSurface)
self.mediaPlayer.durationChanged.connect(self.update_duration)     
self.mediaPlayer.positionChanged.connect(self.update_slider_position)

self.vlayout.addWidget(videoItem)
self.mediaPlayer.setVideoOutput(videoItem)
local = QUrl.fromLocalFile(self.video_paths)
media = QMediaContent(local)
self.mediaPlayer.setMedia(media)
self.play_video()

Answer 1

这是一个工作示例，我从这个问题中可用的 C++ 版本转换为 Python:How to save a frame using QMediaPlayer?

import sys
import uuid

import PyQt5
from PyQt5 import QtCore, QtWidgets
from PyQt5.QtCore import Qt, QObject, QUrl, QRect, pyqtSignal, QPoint
from PyQt5.QtGui import QPainter, QImage
from PyQt5.QtWidgets import QWidget, QApplication, QMainWindow, QGridLayout, QToolBar, QAction
from PyQt5.QtMultimedia import QMediaPlayer, QMediaContent, QAbstractVideoBuffer, \
    QVideoFrame, QVideoSurfaceFormat, QAbstractVideoSurface
from PyQt5.QtMultimediaWidgets import QVideoWidget


class VideoFrameGrabber(QAbstractVideoSurface):
    frameAvailable = pyqtSignal(QImage)

    def __init__(self, widget: QWidget, parent: QObject):
        super().__init__(parent)

        self.widget = widget

    def supportedPixelFormats(self, handleType):
        return [QVideoFrame.Format_ARGB32, QVideoFrame.Format_ARGB32_Premultiplied,
                QVideoFrame.Format_RGB32, QVideoFrame.Format_RGB24, QVideoFrame.Format_RGB565,
                QVideoFrame.Format_RGB555, QVideoFrame.Format_ARGB8565_Premultiplied,
                QVideoFrame.Format_BGRA32, QVideoFrame.Format_BGRA32_Premultiplied, QVideoFrame.Format_BGR32,
                QVideoFrame.Format_BGR24, QVideoFrame.Format_BGR565, QVideoFrame.Format_BGR555,
                QVideoFrame.Format_BGRA5658_Premultiplied, QVideoFrame.Format_AYUV444,
                QVideoFrame.Format_AYUV444_Premultiplied, QVideoFrame.Format_YUV444,
                QVideoFrame.Format_YUV420P, QVideoFrame.Format_YV12, QVideoFrame.Format_UYVY,
                QVideoFrame.Format_YUYV, QVideoFrame.Format_NV12, QVideoFrame.Format_NV21,
                QVideoFrame.Format_IMC1, QVideoFrame.Format_IMC2, QVideoFrame.Format_IMC3,
                QVideoFrame.Format_IMC4, QVideoFrame.Format_Y8, QVideoFrame.Format_Y16,
                QVideoFrame.Format_Jpeg, QVideoFrame.Format_CameraRaw, QVideoFrame.Format_AdobeDng]

    def isFormatSupported(self, format):
        imageFormat = QVideoFrame.imageFormatFromPixelFormat(format.pixelFormat())
        size = format.frameSize()

        return imageFormat != QImage.Format_Invalid and not size.isEmpty() and \
               format.handleType() == QAbstractVideoBuffer.NoHandle

    def start(self, format: QVideoSurfaceFormat):
        imageFormat = QVideoFrame.imageFormatFromPixelFormat(format.pixelFormat())
        size = format.frameSize()

        if imageFormat != QImage.Format_Invalid and not size.isEmpty():
            self.imageFormat = imageFormat
            self.imageSize = size
            self.sourceRect = format.viewport()

            super().start(format)

            self.widget.updateGeometry()
            self.updateVideoRect()

            return True
        else:
            return False

    def stop(self):
        self.currentFrame = QVideoFrame()
        self.targetRect = QRect()

        super().stop()

        self.widget.update()

    def present(self, frame):
        if frame.isValid():
            cloneFrame = QVideoFrame(frame)
            cloneFrame.map(QAbstractVideoBuffer.ReadOnly)
            image = QImage(cloneFrame.bits(), cloneFrame.width(), cloneFrame.height(),
                           QVideoFrame.imageFormatFromPixelFormat(cloneFrame.pixelFormat()))
            self.frameAvailable.emit(image)  # this is very important
            cloneFrame.unmap()

        if self.surfaceFormat().pixelFormat() != frame.pixelFormat() or \
                self.surfaceFormat().frameSize() != frame.size():
            self.setError(QAbstractVideoSurface.IncorrectFormatError)
            self.stop()

            return False
        else:
            self.currentFrame = frame

            self.widget.repaint(self.targetRect)

            return True

    def updateVideoRect(self):
        size = self.surfaceFormat().sizeHint()
        size.scale(self.widget.size().boundedTo(size), Qt.KeepAspectRatio)

        self.targetRect = QRect(QPoint(0, 0), size)
        self.targetRect.moveCenter(self.widget.rect().center())

    def paint(self, painter):
        if self.currentFrame.map(QAbstractVideoBuffer.ReadOnly):
            oldTransform = self.painter.transform()

        if self.surfaceFormat().scanLineDirection() == QVideoSurfaceFormat.BottomToTop:
            self.painter.scale(1, -1)
            self.painter.translate(0, -self.widget.height())

        image = QImage(self.currentFrame.bits(), self.currentFrame.width(), self.currentFrame.height(),
                       self.currentFrame.bytesPerLine(), self.imageFormat)

        self.painter.drawImage(self.targetRect, image, self.sourceRect)

        self.painter.setTransform(oldTransform)

        self.currentFrame.unmap()


class App(QApplication):
    def __init__(self, sys_argv):
        super().__init__(sys_argv)

        # Show main window
        self.view = QMainWindow()

        self.centralWidget = QWidget(self.view)

        self.gridLayout = QGridLayout(self.centralWidget)
        self.gridLayout.setContentsMargins(0, 0, 0, 0)
        self.gridLayout.setSpacing(0)

        self.video_item = QVideoWidget()

        self.gridLayout.addWidget(self.video_item)

        self.view.setCentralWidget(self.centralWidget)

        self.mediaPlayer = QMediaPlayer(None, QMediaPlayer.VideoSurface)

        self.grabber = VideoFrameGrabber(self.video_item, self)
        self.mediaPlayer.setVideoOutput(self.grabber)

        self.grabber.frameAvailable.connect(self.process_frame)

        self.mediaPlayer.durationChanged.connect(self.update_duration)
        self.mediaPlayer.positionChanged.connect(self.update_slider_position)

        local = QUrl.fromLocalFile('c:/temp/lorem.mp4')
        media = QMediaContent(local)
        self.mediaPlayer.setMedia(media)
        self.mediaPlayer.play()

        self.view.show()

    def process_frame(self, image):
        # Save image here
        image.save('c:/temp/{}.jpg'.format(str(uuid.uuid4())))

    def update_duration(self):
        pass

    def update_slider_position(self):
        pass


if __name__ == '__main__':
    def except_hook(cls, exception, traceback):
        sys.__excepthook__(cls, exception, traceback)


    if hasattr(QtCore.Qt, 'AA_EnableHighDpiScaling'):
        PyQt5.QtWidgets.QApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling, True)

    if hasattr(QtCore.Qt, 'AA_UseHighDpiPixmaps'):
        PyQt5.QtWidgets.QApplication.setAttribute(QtCore.Qt.AA_UseHighDpiPixmaps, True)

    app = App(sys.argv)
    app.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)

    sys.excepthook = except_hook
    sys.exit(app.exec_())