我想加载xscreen驱动程序。所以我打开一个终端并输入以下命令：
$uv4l --driver xscreen --auto-video_nr --display :0 --framerate 10 --server-option '--port=5678'
这是正常的结果：
raspberrypi ~ $ uv4l --driver xscreen --auto-video_nr --display :0 --framerate 10 --server-option '--port=5678'
[core] Trying driver 'xscreen' from built-in drivers...
[core] Driver 'xscreen' not found
[core] Trying driver 'xscreen' from external plug-in's...
[driver] Opening display: :0
[driver] Display open, screen 0: 640x480, depth: 24, bpp: 32, big endian: false
[driver] Specified capturing rectangle: (xorigin 0, yorigin 0, width 640, height 480)
[core] Device detected!
[core] Trying to load the the Streaming Server plug-in...
[server] HTTP Streaming & WebRTC Signalling Server v1.1.18 built on Apr 22 2015
[core] Streaming Server loaded!
[core] Cannot create /dev/video0 because file already exists
[core] Registering device node /dev/video1
[server] Web Streaming Server listening on port 9000
但我收到了这条消息：
pi@raspberrypi:~ $ uv4l --driver xscreen --auto-video_nr --display :0 --framerate 10 --server-option '--port=5678'
<notice> [core] Trying driver 'xscreen' from built-in drivers...
<warning> [core] Driver 'xscreen' not found
<notice> [core] Trying driver 'xscreen' from external plug-in's...
<notice> [driver] Opening display: :0
<notice> [driver] Display open, screen 0: 640x480, depth: 24, bpp: 32, big endian: false
<notice> [driver] Specified capturing rectangle: (xorigin 0, yorigin 0, width 640, height 480)
<notice> [core] Device detected!
<warning> [core] Cannot create /dev/video0 because file already exists
<warning> [core] Cannot create /dev/video1 because file already exists
<notice> [core] Registering device node /dev/video2
我的结果没有这部分：
[server] HTTP Streaming & WebRTC Signalling Server v1.1.18 built on Apr 22 2015
[core] Streaming Server loaded!
我的问题是什么？请帮我！