What I strongly suggest if you think about upgrading is to back up your existing firmware so you have a way back should you wish.
All you need is a copy of mtdblock2 in the as-delivered state. But copy mtdblock0 and 1 also.
The easiest way is if you can add a NAS destination via the GUI. It does not need to be formatted.
Something like this for an NFS mount.
Use 'mount' to find the mount point, then something like:
cd /mnt/tnfs01
umount /dev/mtdblock2
cat /dev/mtdblock2 > mtdblock2_orig
mount /dev/mtdblock2 /home/hik
You could also use
TFTP, something like
TFTP -p -l mtdblock2_orig <IP address of TFTP server>
And the same for mtdblock0 & 1, though these don't need unmounted.
Then you can either at a later date 'cat' the mtdblock2_orig' back where it came from, or you can create new firmware using @
wzhick really useful tool Hiktools to get a digicap.dav that the web GUI and TFTP recovery is happy with.
Also - make a backup copy of the NVR configuration, and the camera settings, via the maintenance menu, with the filename including the associated firmware version. You can't restore configurations across firmware versions.
That way - you can put the whole thing back exactly how it was before the firmware update if you ever need to do so.