This is the setting for a Duhua 4ch,
How to use HDMI output for NVR
For NVR HDMI output, please make sure:
1. customer connect with VGA output first, and go to NVR setting -> Display
2. change resolution from 1280 x x1024 to 1920 x1080
3. and save it, reboot the NVR
4. Connect HDMI cable from NVR to HDMI Monitor
* BNC output from DVR can't change resolution to HDMI