'nasm -f elf synthasm.nas -o synthasm.o -l synthasm.lst' fails with a lot of 'error: mismatch in operand sizes'. It doesn't occur with with nasm-0.98.39
However, with yasm, it compils just fine.
same with media-libs/libmp4v2
nasm-2.01 seems fine. Reopen if it's still an issue.