David Liontooth may (or may not) have said:
I thought so! Does anyone have a suggestion as to why these features of the CPU get disabled?
Because transcode doesn't know about x86_64. If you want to build 64bit you cannot use the x86 .asm that comes with transcode, it just isn't going to work. So, effectively you are doing everything with slow C functions. Transcode itself is fine, its the modules that it uses that need to be updated. I got about half way through porting the xvid codec asm over to x86_64, its not as trivial as it seems, fixing the -fPIC differences from x86 to x86_64 takes long enough, and, oh yeah, you can't use nasm either, you'll have to use yasm. (Plus change the function calls to using registers instead of the stack.) And all this is before even looking at optimizing the code for the extra gpr and xmm registers we get. Mike