我第一次尝试在 Ubuntu 21.04 上安装 GStreamer 如下所示：
user@localhost:~$ sudo apt install gstreamer
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: Unable to locate package gstreamer
因为那不起作用，所以我访问了在 Linux 上安装的 GStreamer 网页： https ://gstreamer.freedesktop.org/documentation/installing/on-linux.html?gi-language=c 。按照上述网页上的说明，我第二次尝试安装 GStreamer 如下所示：
user@localhost:~$ sudo apt-get install libgstreamer1.0-0 gstreamer1.0-plugins-base gstreamer1.0-plugins-good gstreamer1.0-plugins-bad gstreamer1.0-plugins-ugly gstreamer1.0-libav gstreamer1.0-doc gstreamer1.0-tools gstreamer1.0-x gstreamer1.0-alsa gstreamer1.0-gl gstreamer1.0-gtk3 gstreamer1.0-qt5 gstreamer1.0-pulseaudio
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package gstreamer1.0-doc is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'gstreamer1.0-doc' has no installation candidate
什么程序可以在 Ubuntu 21.04 上安装 GStreamer？
