/usr/share/doc/libav-dbg/changelog.Debian.gz is in libav-dbg 4:0.8.17-0ubuntu0.12.04.2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libav-dbg/../libavcodec53/changelog.Debian.gz
/usr/share/doc/libav-dbg/../libavcodec53/changelog.Debian.gz