The NT98321BG is a SoC made by Novatek, it is used on DVRs as the main CPU, it talks to the ADC/Video capture chip (NVP6861C by NextChip). It's still pretty unknown for me since I couldn't find the SDK or the datasheet for it. It runs a linux system so it probably has an MMU, It's a Non-XiP system.
There is a firmware dump + unpacking/repacking tools avaiable on my github here