Over 4Mbps bitrates to encoding 720P H264

When I use NVENC to encode 720P video from camera, on xavier, over 4Mbps was consumed, any one know why?

4Mbps is a bit strict for 720p. If there are continuous complex scenes, the bitrate may go higher. Suggest you try 8Mbps. And please check this post:

You may set CBR(control-rate=0) and vbv-size for a try.