pyqt5中qabstractvideosurface的present()的错误视频帧

Question

我正在使用pyqt5配置应用程序。我使用QMediaPlayer和QVideoWidget播放视频，首先需要做的是在暂停视频时获得当前视频帧。我已经用QmediaPlayer阅读了答案PyQt5访问帧，我已经实现了QAbstractVideoSurface并覆盖了这些方法。最后我可以得到视频帧和QAbstractVideoSurface代码如下所示：

class VideoFrameGrabber(QAbstractVideoSurface):
frame_available = pyqtSignal(QImage)            
def __init__(self, widget: QWidget, parent=None):
super().__init__(parent)
self.widget = widget
self.current_frame = None
self.image_format = QImage.Format_Invalid
self.target_rect = None
self.source_rect = None
self.image_size = None
def supportedPixelFormats(self, type):
print("supportedPixelFormats() called")
print("supportedPixelFormats() finished")
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):
print("isFormatSupported() called")
image_format = QVideoFrame.imageFormatFromPixelFormat(format.pixelFormat())
size = format.frameSize()
print("isFormatSupported() finished")
return image_format != QVideoFrame.Format_Invalid and not size.isEmpty() and 
format.handleType() == QAbstractVideoBuffer.NoHandle
def start(self, format):
print("start() called")
image_format = QVideoFrame.imageFormatFromPixelFormat(format.pixelFormat())
size = format.frameSize()
if image_format != QImage.Format_Invalid and not size.isEmpty():
self.image_format = image_format
self.image_size = size
self.source_rect = format.viewport()
super().start(format)                      
# self.widget.updateGeometry()
# self.update_video_rect()
print("start() finished")
return True
else:
print("start() finished")
return False
def stop(self):
print("stop() called")
self.current_frame = QVideoFrame()
self.target_rect = QRect()
super().stop()                                
print("stop() finished")
def present(self, frame: QVideoFrame):
print("present called")
if frame.isValid():
clone_frame = QVideoFrame(frame)
clone_frame.map(QAbstractVideoBuffer.ReadOnly)
image = QImage(clone_frame.bits(), frame.width(), frame.height(), frame.bytesPerLine(), 
QVideoFrame.imageFormatFromPixelFormat(frame.pixelFormat()))
clone_frame.unmap()
# image.save("frame.jpg")
self.frame_available.emit(image)         
if self.surfaceFormat().pixelFormat() != frame.pixelFormat() or 
self.surfaceFormat().frameSize() != frame.size():
self.setError(QAbstractVideoSurface.IncorrectFormatError)
self.stop()
print("present finished: Return False")
return False
else:
self.current_frame = frame
# self.widget.repaint(self.target_rect)
print("present finished: Return True")
return True
def update_video_rect(self):
print("update_video_rect() called")
size = self.surfaceFormat().sizeHint()
size.scale(self.widget.size().boundedTo(size), Qt.KeepAspectRatio)
self.target_rect = QRect(QPoint(0, 0), size)
self.target_rect.moveCenter(self.widget.rect().center())
print("update_video_rect() finished")
def paint(self, painter):
print("paint() called")
if self.current_frame.map(QAbstractVideoBuffer.ReadOnly):
old_transform = painter.transform()
if self.surfaceFormat().scanLineDirection() == QVideoSurfaceFormat.BottomToTop:
self.painter.scale(1, -1)
self.painter.translate(0, -self.widget.height())
image = QImage(self.current_frame.bits(), self.current_frame.width(), self.current_frame.height(),
self.current_frame.bytesPerLine(), self.image_format)
self.painter.drawImage(self.target_rect, image, self.source_rect)
self.painter.setTransform(old_transform)
self.current_frame.unmap()
print("paint() finished")

因为我使用QVideoWidget播放视频，所以我需要将QMediaPlayer的输出更改为我的QAbstractVideoSurface，以获得这样的视频帧。

# definition here
class PlayerMainWindow(Ui_MainWindow, QMainWindow):
def __init__(self, parent=None):
self.player = QMediaPlayer(self)
self.player.setVideoOutput(self.video_widget)
self.auto_video_grabber = VideoFrameGrabber(self)
# what I need to do next is to detect faces in the frame
self.auto_video_grabber.frame_available.connect(self.auto_detect)
def auto_detect_clicked(self):
# the detector_widget is a widget contains serveral labels to show process information 
# use signal and slot to update those lables 
if self.detector_widget.is_detecting():
return
self.detector_widget.connect_face_available(self.on_face_available)
self.stackedWidget.setCurrentIndex(1)    # the detector widget
self.player.setVideoOutput(self.auto_video_grabber)
self.player.pause()
# Receive frame(QImage) in auto_detect()
def auto_detect(self, frame: QImage):

self.player.setVideoOutput(self.video_widget)
self.player.pause()
if frame is None:
return
frame.save("auto_capture.jpg")

self.detector_widget.start_detector(frame)

但现在的问题是，当我暂停视频时，有时我在auto_detect()中得到的帧不是当前帧(该帧已经播放(，但有时它是正确的。我也试图用present()方法保存帧，但它与我在auto_detect()方法中收到的相同。

Answer 1

天哪，我终于解决了这个问题。上面显示的代码是可以的，我所做的是将视频解码器从LAV更改为K-Lite。