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

Calculating dependencies ... done!
Dependency resolution took 1.14 s (backtrack: 0/20).

[ebuild  N     ] media-libs/giflib-6.1.3:0/7::gentoo  USE="-doc -static-libs" 460 KiB
[ebuild  N     ] dev-lang/yasm-1.3.0-r2::gentoo  USE="nls" 1458 KiB
[ebuild  N     ] media-libs/libde265-1.1.3::gentoo  USE="-debug -dec265 -sdl -tools" CPU_FLAGS_X86="avx2 avx512f sse" 317 KiB
[ebuild  N     ] media-libs/x265-4.3:0/217::gentoo  USE="10bit 12bit cet -numa -test -vmaf" 2005 KiB
[ebuild  N     ] media-libs/libaom-3.14.1:0/3::gentoo  USE="examples (-big-endian) -debug -doc -test" CPU_FLAGS_X86="avx avx2 mmx sse sse2 sse3 sse4_1 sse4_2 ssse3" 6220 KiB
[ebuild  N     ] media-libs/kvazaar-2.3.2:0/6::gentoo  USE="-static-libs -test" 587 KiB
[ebuild  N     ] media-libs/libwebp-1.6.0:0/7::gentoo  USE="gif jpeg opengl png tiff -static-libs -swap-16bit-csp" CPU_FLAGS_X86="avx2 sse2 sse4_1" 4196 KiB
[ebuild  N     ] media-libs/libheif-1.20.2:0/1.20::gentoo  USE="aom de265 jpeg jpeg2k kvazaar threads webp x265 -dav1d -doc -ffmpeg -gdk-pixbuf -gui -openh264 -rav1e -svt-av1 -test -test-full -tools" 1746 KiB

Total: 8 packages (8 new), Size of downloads: 16985 KiB