When I read the NVR5216 manual and play with bit rate settings I am finding that if I use VBR quality 6 and max out the bit rate to highest allowed the camera will send that bit rate even on an image that is static, seems odd as I would expect VBR to look at trying to maintain quality at lowest bit rate possible not to exceed the max setting. I don't see way to tell camera to try and save bandwidth unless the motion dictates the max bit rate.
From manual:
In VBR mode, the video quality changes
according to the bit stream value. But its max value is
near the specified value.
Oddly I can have a 2MP, 4MP and 8MP camera all with VBR and very static images all driving over 6mb/s seems very odd.