Member Discussion

Overlay Pos Text On Video Feed - Time Synch Issues

Any comments on getting a Hikvision HD-SDI DVR to record a till feed on to the CCTV image without having problems with the time stamp on the till & the DVR moving out of sync with each other




Can you elaborate? What is a till? How far out of sync is it? Is there significant latency?

Do you mean POS overlay?

Hi Guys

Talking about a cash register feed as overlay text onto the CCTV image. I have looked at this before but was under the impression that in most cases it is a problem as the time stamp on the DVR gradually moves away from the time stamp on the POS. So a transaction will show as say 10am on the POS but 10.05 on the CCTV image making it dicey for evidential purposes. As well not sure if the data stream on a HD-SDI system is capable of having the POS transaction details added to it

Hope this helps



Mike, I'm not sure when you last looked at overlays, but time drift is a thing of the past. ;) Both systems, the dvr and the pos video overlay device, should be set for ntp (network time protocol) operation, which will insure the data timestamp matches the video timestamp.

Natively overlaying the sdi stream at the overlay device on the other hand, seems unlikely. Is it a hybrid DVR, with some analog ins as well?

I'd disagree that time drift is a thing of the past (unless that was a joke). It's a problem in a lot of systems. It's relatively simple to manage, as running a time server is easy enough, and syncing the POS terminal and server (if any) as well as cameras (if they're IP) and recorders regularly (I do it every hour because why not?) should keep things showing really close times. See this for more info: Resolving IP Camera / VMS Time Sync Problems

As far as overlay, I'm still seeing lots of DVRs with RS-232 ports on the back of them. So you may be able to overlay POS data that way. I haven't seen any HD-SDI text inserters, but I also really haven't looked much, and they're likely going to be very expensive.

It was a joke of course, but what I was referring to was the fact that possibly when Michael last investigated these systems, NTP wasn't quite in ubiquity, as it is today. Otherwise I assumed he would have used it...

As for running your own local time server, is that still recommended? It seems that as the local server would also drift given enough time, that you would end-up stamping a datetime that, although in sync, might an hour or more off. Probably better to use internet time and not to even have to explain it in a court of law.

As for HD-SDI overlay, agreed expensive, you might be able to pick up a two channel video mixer with a SMPTE input for under a grand, but why?

I personally prefer running my own time server, and having it sync to the NTP pool, then all my other servers and devices sync to it. The reason is simple: internet goes down (and sometimes you aren't connected at all or ports are blocked). So even if the internet is down when the camera(s), server(s), POS terminal(s), etc. try to sync, they still have one and only one server for reference time. So yes, maybe it'll drift a little, but generally from what I've been told it's better for things to all be synched to the same time, even if it's slightly off.

Ok, you win! Time drift has not gone the way of the Dodo, but despite best efforts, endures still (much like Polio and certain members of ABBA).

But you know there's a word for guys like you, guys who insist on running their own hierarchal time network just because its more 'accurate': the word is... fastidious. :)

Fastidious is the preferred characteristic of security professionals when submitting any evidence to a court of law. Lack of this characteristic is the primary driver for defense lawyers getting 'evidence' tossed.

Hi Guys

has been a while since I had a look at it I was aware of the NTP server possability but have previously just advised clients against the whole issue if it was raised and have found that they are quite happy with that. Am meeting with a person tommorow who is intrested in covering three shops and was reffered to me by a contact who sells eftos systems hence the intrest with combining the two. I have also been looking at the HD-SDI option raised this with the local Hikvision suppliers but they seemed a bit unsure of just what the system could and couldn't do. When I previously looked I was selling mainly Bosch analoge systems which the suppliers advised Bosch didn't do the text overlay because of the timeing issues. The Hikvison suppliers have since come back and said they can possibley write the intergration specific to the customer needs but need more info. This sounds like a bit of a mess in the making to me and would rather go with a proven solution

AVE VSI Pro. Serial input-text ouput combined with analog camera (you said it was a DVR). i am usually high tech, but this technique has been used for 10-20 years. Not sure if the receipts are from parallel, serial, or IP printers. Trying to not over engineer this. (I would normally use an IP serial server and NVR software solution to capture ASCII and create serial event profile, but I am still not sure as to the register-printer-system setup).