Have you heard of AMD? They make both CPUs and GPUs. Any AMD GPU since late 2011 has a hardware encoder included, capable of at least 1080p60 H.264 encoding.
Newer versions of GCN GPUs add B-frames support, better motion estimation. The newest polaris GPUs can encode H.265 at hundreds of FPS.
AMD has an open source SDK to utilize these encoders here: https://github.com/GPUOpen-LibrariesAndSDKs/AMF
I tried to post this before but my post is still not approved. Why won't you support AMD GPUs?