Thanks for the photos. Forgetting everything I've typed above, my problem is this. When I recently bought the NVR (8MP) and Camera's (5MP) I was able to view live video and playback through the NVR without problem, and could view live video or video playback via the motion detection / line crossing notifications through the Hik-connect app on my phone. It ran perfectly and consistently with a high resolution. The settings were:
Resolution: 3072 x 2048
Bitrate Type: Variable
Video Quality: Highest
Frame Rate: Full Frame
Video Encoding: H265
Then all of a sudden I was unable to view the single screen camera on the NVR (the TV screen just went black) or any live / playback video on the Hik-connect app ('Network is unstable' message appeared). To get it working as normal I went down through the resolutions where where only 1080P I worked consistently. I've now (ignorantly!) played with some of the settings and it seems to work as follows:
Resolution: 2560 x 1440
Bitrate Type: Variable
Video Quality: Higher
Frame Rate: 20 fps
Video Encoding: H265
These are replicated for Main Stream (Continuous) and Main Stream (Event). Although it's now working, I'm confused why it won't work with the higher settings like it did at first? Obviously I want the best video quality from my system and thought a Hikvision 8MP NVR would cope effortlessly with four Hikvision 5MP cameras. In fact whilst writing this the single screen camera view on my TV turned has turned black again when the sun (at last!) shone bright; is this a bitrate issue? Without fully understanding the relationship between resolution, bitrate and video quality, do you have any advice?! In reality is there much difference between 'highest', 'higher', 'medium' or 'low' video quality? Is it possible the NVR may be damaged/not working correctly?
Thanks again for your help and knowledge!