突然，我的 Ubuntu 停止播放视频。当我打开视频时，播放器建议我安装 gstreamer1.0-libav. 但是，它无法安装。
我尝试手动安装它，这是错误消息：
$ sudo apt-get install gstreamer1.0-libav
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
gstreamer1.0-libav : Depends: …