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

Calculating dependencies ... done!
Dependency resolution took 1.02 s (backtrack: 0/20).

[ebuild  N     ] media-libs/opus-1.6.1::gentoo  USE="-custom-modes -debug -deep-plc -doc -dred -hardened -osce -static-libs -test" CPU_FLAGS_X86="sse" 10228 KiB
[ebuild  N     ] media-video/ffmpeg-chromium-154:154::gentoo  USE="gpl threads -cpudetection -debug -nvenc -vaapi -vdpau -vulkan" CPU_FLAGS_X86="aes avx avx2 fma3 mmx mmxext sse sse2 sse3 sse4_1 sse4_2 ssse3 -3dnow -3dnowext -fma4 -xop" 11374 KiB

Total: 2 packages (2 new), Size of downloads: 21601 KiB