这个文档中是设置摄像头的:http://www.easyar.cn/doc/EasyAR%20SDK/Unity%20Plugin%20Reference/1.0/CameraDevice.html?highlight=%E5%89%8D%E7%BD%A
这是从后置切换前置的:http://www.easyar.cn/doc/EasyAR%20SDK/Unity%20Plugin%20Reference/2.0/CameraDeviceBaseBehaviour.html#HorizontalFlip