These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.01 s (backtrack: 0/20).


The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by media-sound/soundconverter-4.0.5::gentoo
# required by =media-sound/soundconverter-4.0.5 (argument)
>=x11-libs/gtk+-3.24.52 introspection
# required by media-sound/soundconverter-4.0.5::gentoo
# required by =media-sound/soundconverter-4.0.5 (argument)
>=x11-libs/libnotify-0.8.8 introspection
# required by media-sound/soundconverter-4.0.5::gentoo
# required by =media-sound/soundconverter-4.0.5 (argument)
>=x11-libs/pango-1.58.2 introspection

 * In order to avoid wasting time, backtracking has terminated early
 * due to the above autounmask change(s). The --autounmask-backtrack=y
 * option can be used to force further backtracking, but there is no
 * guarantee that it will produce a solution.

!!! All ebuilds that could satisfy ">=media-libs/faac-1.28-r3[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?,abi_s390_32(-)?,abi_s390_64(-)?]" have been masked.
!!! One of the following masked packages is required to complete your request:
- media-libs/faac-1.31.1-r1::gentoo (masked by: MPEG-4 license(s))
A copy of the 'MPEG-4' license is located at '/Volumes/Disk 1/Repository/portage-git/licenses/MPEG-4'.

- media-libs/faac-1.30::gentoo (masked by: MPEG-4 license(s))

(dependency required by "media-plugins/gst-plugins-faac-1.26.11::gentoo" [ebuild])
(dependency required by "media-sound/soundconverter-4.0.5::gentoo[aac]" [ebuild])
(dependency required by "=media-sound/soundconverter-4.0.5" [argument])
For more information, see the MASKED PACKAGES section in the emerge
man page or refer to the Gentoo Handbook.