/usr/lib/libgmerlin_avdec.so is in libgmerlin-avdec-dev 1.1.0~dfsg-3build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/libgmerlin_avdec.so.1.0.0
/usr/lib/libgmerlin_avdec.so.1.0.0