Vivotek ND8312 User Manual page 36

VIVOTEK - Built with Reliability
5. Why live view is unavailable?
The default live view receives a camera's stream #1. If a camera's stream #1 is configured using
MPEG-4 as the video codec, the following message will prompt.
You can go to the Settings > Camera > Media > Video window to configure the video codec
of stream #1 into H.264. The same will occur if you connect some newer VIVOTEK 9xxx series
H.265 models. You will then need to chanage the CH1 and CH2 video streams to H.264.
36 - User's Manual