localhost ~ # emerge media-libs/amd64codecs
Calculating dependencies
!!! All ebuilds that could satisfy "media-libs/amd64codecs" have been masked.
!!! One of the following masked packages is required to complete your request:
- media-libs/amd64codecs-20061203 (masked by: ~amd64 keyword)

For more information, see MASKED PACKAGES section in the emerge man page or
refer to the Gentoo Handbook.