what is the model No. for this cam Cj?
For the IVS to work, the camera needs time to see the object and process it and decide if it matches the criteria. For LPR and tighter zooms for a camera, that can be problematic for some field of views. The car is in the field of view for such a short period of time that it will probably struggle more times than not. Especially at night if all it sees are head/taillights and a plate it will miss most of them.
I am usually a fan of the Dahua AI, but for LPR this is an unique situation that you would be better off with motion detection and a min object size instead of trying the vehicle AI. You will obviously probably get some false triggers, but it beats the alternative of IVS missing a lot of them.
I don't want to discourage you from trying this, just be prepared to get more false positives than you want to deal with. Increasing the pre-record buffer isn't an issue. It just plain doesn't work at all if you're also doing continuous recording.Thanks! I may try regular motion detection tonight because I don't use any alerts, so false positives aren't a huge deal.
For best results, be sure to perform this also.
IVS/Global Setup - Dahua Wiki