Right now, ffmpeg won't merge in Funtoo Linux on x86-64bit. The default CPU_FLAGS_X86 are "mmx sse sse2". The ffmpeg ebuild expects "mmxext" to be enabled if sse is enabled, resulting in a failed merge.

The workaround is to add "mmxext" to the default CPU_FLAGS_X86 for x86-64bit.

There is not good documentation for what 'mmxext' is, but if it is "MMX 2", or extended MMX instructions, then I would guess that all SSE-enabled processors also have mmxext and the workaround is correct?

I'd like this fixed soon.