You can uninstall or removes an installed libavutil-extra-51 package itself from Debian 7 (Wheezy) through the terminal,
$ sudo apt-get remove libavutil-extra-51
If you would like to remove libavutil-extra-51 and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove libavutil-extra-51
If you use with purge options to libavutil-extra-51 package all the configuration and dependent packages will be removed.
$ sudo apt-get purge libavutil-extra-51
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove libavutil-extra-51