Just looked at an Exacq system and it looks like their latest releases support archiving. Scheduling is totaly flexible and you can select the "desired content age" in days. Looks like exactly what you described but I haven't tried it.
Amos, I got feedback from Milestone about options to do this:
To record locally and transfer to HQ and playback the HQ stored recordings, use XProtect Corporate at HQ and one of the other XProtect VMS version locally. They can connect the local VMS to the XProtect Corporate system at HQ via Milestone Interconnect. Retrieval of the recordings can be done via a rule that can be run with whichever schedule/interval you want.
Using the Archiving option, it is not possible to move archives to HQ and have someone there access it. Archives must always be accessed on the site they are recorded.
IPVMU Certified | 01/17/14 09:49pm
For ease of use, the Milestone Expert/Corporate code will allow for scheduled archiving in a cascaded fashion. The ONSSI LS/ES code has the same function. This is discussed in the whitepaper below.
Sean's description of the 'Trickling' is the only other 'simple to schedule' data movement in a VMS that I have used.
The Exacq/Avigilon/Aimetis/others folks will have to chime in if it is possible for video data to be easily moved on a scheduled basis.
Perhaps a VMS that is Linux based and has a simple video database can be scheduled with a 'cron job backup'?
Doing this with Milestone. Archiving is once a day not every three days though. The scheduling setup for Archiving doesn't allow for setting it up to only schedule on certain days but there is the option to Archive on an event which can be just about anything.
My main question is, are there existing cameras already?
I can't say 100% for sure, because I've certainly never had a situation like that to work up; however "in theory" Genetec with Axis cameras recording to a NAS device and then using their Trickling function back to the Genetec Archiver every 3 days should work. When you do an Archived search in Security Desk, you can choose to search both the edge storage and the Archiver storage at the same time by choosing "All Sources". This is really specific and hypothetical; but I'm not to sure of any other manufacturers giving this much flexibility.
Ultimately for this feature set youre probably going to have to look at one of the higher feature large enterprise based softwares... Genetec/Milestone/Exacq/ONSSI etc.