I'm having a few problems with the Hardware Decoding...
1) It doesn't seem to work with H265, with H264 it's fine.... if I try H265 it'll just show the color bars and never get an image. (error is "HW Accelerated Decoder Not Found")
2) After several hours of working fine with H264, all the cameras show the no signal screeen and it gives me some "HW Decoding" failure message.
3) This is on my old system with a GTX TITAN on it.... overkill on the GFX card, yes, but i used to play video games.
I guess there are still a few bugs to work out.
.265 hardware decode never worked properly with BI using Intel quicksync. Doubt it would be fixed with Nvidia.