This is a slightly misleading comparison, because they're comparing naive scalar C code to hand-vectorized assembly, skipping over hand-vectorized C with vendor intrinsics. Assembly of course always wins if enough effort is put into tuning it, but intrinsics can usually get extremely close with much less effort.
For reasons unknown to me the FFmpeg team has a weird vendetta against intrinsics, they require all platform-specific code to be written in assembly even if C with intrinsics would perform exactly the same. It goes without saying that assembly will be faster if you arbitrarily forbid using the fastest C constructs.
For reasons unknown to me the FFmpeg team has a weird vendetta against intrinsics, they require all platform-specific code to be written in assembly even if C with intrinsics would perform exactly the same. It goes without saying that assembly will be faster if you arbitrarily forbid using the fastest C constructs.