H264GStreamerpipeline流式传输进QVideoWidget，在启动另一个后台线程时会定期冻结的问题

解决方法：在主线程中创建GStreamer管道和QVideoWidget，然后将它们移动到新线程中。这样可以避免在新线程中启动另一个后台线程时冻结问题的出现。

代码示例：

class VideoThread(QThread):
    def __init__(self, parent=None):
        super(VideoThread, self).__init__(parent)
        self.pipeline = None
        self.widget = None

    def run(self):
        Gst.init(None)
        self.pipeline = Gst.Pipeline()
        src = Gst.ElementFactory.make("v4l2src")
        h264parser = Gst.ElementFactory.make("h264parse")
        decoder = Gst.ElementFactory.make("avdec_h264")
        sink = Gst.ElementFactory.make("autovideosink")
        self.pipeline.add(src)
        self.pipeline.add(h264parser)
        self.pipeline.add(decoder)
        self.pipeline.add(sink)
        src.link(h264parser)
        h264parser.link(decoder)
        decoder.link(sink)
        self.pipeline.set_state(Gst.State.PLAYING)
        self.widget = QVideoWidget()
        self.widget.show()

        # move pipeline and widget to new thread
        self.pipeline.set_parent(None)
        self.widget.setParent(None)
        self.pipeline.moveToThread(self)
        self.widget.moveToThread(self)
        self.pipeline.set_state(Gst.State.PLAYING)

if __name__ == "__main__":
    app = QApplication(sys.argv)
    thread = VideoThread()
    thread.start()
    sys.exit(app.exec_())