我无法在 Ubuntu 16.04 中的 Chromium 中观看视频。我该如何修复？
http://www.quizover.com/oer/course/adaptive-submodularity-a-new-approach-to-by-daniel-videolectures
jalal@klein:~$ dpkg-query -s adobe-flashplugin
dpkg-query: package 'adobe-flashplugin' is not installed and no information is available
Use dpkg --info (= dpkg-deb --info) to examine archive files,
and dpkg --contents (= dpkg-deb --contents) to list their contents.
jalal@klein:~$ sudo apt-get install adobe-flashplugin
[sudo] password for jalal:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package adobe-flashplugin 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 'adobe-flashplugin' has no installation candidate
我安装了这个：sudo apt-get install browser-plugin-freshplayer-pepperflash YouTube 视频播放时没有声音。请提出修复建议。
更新：我添加了这些，更新并安装了 flash，但仍然听不到视频声音：
$ sudo vi /etc/apt/sources.list
48 deb http://archive.canonical.com/ubuntu xenial partner
49 deb-src http://archive.canonical.com/ubuntu xenial partner
$ sudo apt-get update
$ sudo apt-get install adobe-flashplugin