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

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

[ebuild  N     ] media-libs/libogg-1.3.6::gentoo  USE="-static-libs" 430 KiB
[ebuild  N     ] media-libs/libvorbis-1.3.7-r2::gentoo  USE="-static-libs -test" 1176 KiB
[ebuild  N     ] media-libs/libtheora-1.2.0-r1:0/2::gentoo  USE="encode -doc -examples -static-libs" 1786 KiB
[ebuild  N     ] media-libs/theoraplay-0_pre20180524-r2::gentoo  15 KiB

Total: 4 packages (4 new), Size of downloads: 3405 KiB