NVR keeps changing cbr to vbr recording

Apr 12, 2023
23
3
india
Hello. I have 10 4mp cameras connected to hikvision ds 7616ni k2 nvr. I have applied constant 8192 bitrate for all cameras in both (individual camera setting and nvr also). But still it changes to variable after 1 day automatically. What's the underlying problem.
POE SWITCH: 2× DGS F1010PE
HDD: WD 10TB PURPLE PRO
CAMERA: DS 2CD2143G2 IU