Jetson TX1 --> 4K H.265 encode

I am looking for 4K@60fps video encoding. If 60fps is not possible, 30fps would be acceptable for now. Has anyone tried 4K encoding? what is the delay performance?

  1. 4K@60fps delay in frames: X
  2. 4K@30fps delay in frames: X
  3. 2K@60fps delay in frames: X

What multimedia GPU libraries I need to use for best performance?