NTP Servers in the cinema

[Bruce Cloutier]

Not that the JNIOR clock is critical in any way but we have noted that in many cases we don't have access to the Internet to get time from 'pool.ntp.org'. The clock does come into play when we are debugging and are comparing timestamps between logs on the JNIOR and those on external systems.

If you don't allow the JNIOR to get to the outside you might consider making sure that it can use whatever NTP source your media server has to be using. You just need to set a registry key. The command line entry is:

reg IpConfig/NTPServer = xxx.xxx.xxx.xxx

You can put the appropriate IP address there (or domain name). Doesn't require a reboot. By default it synchronizes every 4 hours.

Along those lines the JANOS v2.4 release uses NTP synchronization to tune the hardware RTC and the software clock for better accuracy but it is not critical.

I have also thought about searching for an NTP server on the local subnet assuming that it would be using the NTP port (123).

The uncalibrated clocks can get minutes off. I hate having the JNIOR be that sloppy.

[Steve Guttag]

Presuming there is a TMS on site, we normally set that as the NTP server for the site. That TMS may, indeed, reference the NTP Pool or other (NOC) clock. Yes, it is important to have all clocks be at the same time if log analysis is to be fruitful.

[James Gardiner]

I find it inconceivable that any cinema does not have a device that bridges the time into the projection network. Keeping the clock on the SM (Security managers) of DCI devices is extremely important.
Plus, also screens need to have tight clocks so that sessions start on time.

I cannot see how a cinema operates without it. And as such, I don't understand why a JNIOR device wouldn't have access to the NTP service.
Only if an integrator goes over the top with unneeded security constraints.. likely leading to poor outcomes for the cinema owner.
There is a recent SCO newsletter that goes over an example like this Part 2 of . See: https://www.smallcinemaowners.com.au...al-box-office/

[Dennis Benjamin]

Ironic that this post is on here today.

I typically use the LMS/TMS as the time server but occasionally have issues with doing so. At three of my locations I configured a small computer on the Network just for the purpose of telling all the devices what time it is. The computer is question is configured to obtain the proper time from a NIST server. All the servers then look to that single device for the time.

Here is my question regarding this: We have a Dolby DSS200 server at a location that I need to tell it where to look for the NTP (The IP address). I have no idea how to get into it to set up the NTP info. Any ideas where I would obtain the directions to do so?

[Bruce Cloutier]

Ensuring the proper time on a JNIOR is obviously not going to be a priority but it is critical for the TMS.

The JNIOR wasn't logging all of the time synchronization events as this was a background activity. We will be logging them now and will shortly both be displaying the stratum of the NTP server and the network response time. You could use that to select the IP address of a stratum 1 server that is nearby. Um... assuming that the JNIOR has access to the Internet.

The general 'pool.ntp.org' will present a new server each time (provided your DNS cache of the prior has expired). I have seen servers from that from stratum 1 down to stratum 4. Not all that infrequently it will offer a server that just does not respond. In fact we have just changed the NTP retry time on the JNIOR to insure that the DNS expires so we get a new server on the retry.

I also noticed that network load has an huge impact on the accuracy of the time synchronization. We run offsite backups 3 to 4 in the morning and apparently do that with total disregard for bandwidth. Time syncs during that have upwards of 300ms turnaround time and are clearly not symmetrical. In other words the time syncs have been 200+ ms off. This gets corrected with the next sync where you see the offset shift back.

I think some of your media servers are requiring that you use only Stratum 1 NTP servers that are wired to the NIST reference clock (no network involved).

[Elia Orselli]

Here is my question regarding this: We have a Dolby DSS200 server at a location that I need to tell it where to look for the NTP (The IP address). I have no idea how to get into it to set up the NTP info. Any ideas where I would obtain the directions to do so?

It's part of the config script, in the advanced network settings.

[Leo Enticknap]

Press ctrl+alt+F1, and then enter the username and password to run the config script. Forum rules prevent me from posting it, but I'm sure that Dolby tech support would be happy to give it to you.

DSS servers seem to be very finicky about their NTP sources. I look after an 11-plex consisting of nine DSS220s, an ICMP and an IMS2000. The ICMP and the IMS2000 sync from the TMS without complaining, but the DSS220s simply will not - "no valid synchronization source found" at bootup, and a couple of minutes later, a yellow warning and failed to sync to NTP. I've tried changing the sync between the management and media LANs, and installing a router/gateway on the management LAN and trying to get them to sync to an external server (I've tried 192.12.19.20 and 128.138.140.44), but they just will not sync. Every few months I use the cat745 time adjust script to correct them, but of course, without an NTP sync, they just start to drift again.

[Jason Sharp]

We had NTP problems with Dolby DSS servers several years back. We found a NTP server software that works with DSS servers. Never had a problem since with time synchronization. There is a 30 day trial if you want to test it.
https://nts.softros.com/server/

[Steve Guttag]

DSS servers are more strict than others, is what I've found. That is, it will turn its nose up at too many hops and if there are any misses/dropped packets, the NTP source reboots...it drops NTP until the source is deemed stable again.

All of my DSS servers sync either off of the TMS or off a local windows computer on site. The NTP source for the TMS or local computer will be either the NTP POOL (I found NIST too unreliable and probably because of how many entities are using it as their Stratum 1 clock) or the NOC's NTP. Other than ensuring that the local PC has UDP port 123 open in the firewall, it has been very stable for us.

Note, CAT745s are going drift (as will all mediablocks but nothing like the sundial-esq CAT745 clock) as they do NOT sync on NTP. Only the show clocks do. Mediablocks are supposed to have precision clocks that do not drift (much) such that the +/- 6 minutes/year is sufficient to keep them close enough. The mediablock clock is only critical for KDMs. A server's show clock (often the BIOS clock of the computer that is running the OS) is what syncs to NTP (and responds to UTC time offsets...mediablocks are always UTC-0 to avoid being able to shift one's key open time). The CAT745 which can gain (it is always gain) upwards of an hour a year (depending on off time) does need extra help with that script. If the CAT745 is left on 24/7 it does not drift much. Dolby does have a script for CAT745 users that prevents the DSS200/220 from EVER referencing the CAT745 as a time source for the server's show clock.

[Dennis Benjamin]

Thanks everyone for the replies! I was successfully able to get the time synced with the NTP server.

[Jason Raftery]

On the subject of NTP, has anyone had success getting the CAT1600 in the CP850 to sync to an NTP server on one's local network (TMS, etc.)? The secure clocks in ours do not sync despite all other media blocks, ICPs, JNIORs, network switches, QSYS, etc. on the projection networks syncing fine. Dolby was not helpful in coming up with a resolution. The CAT1600s drift as badly as the CAT745s Steve referenced, which indeed makes lining up logs a pain when something goes sideways. Only the CP750 seems to have a less accurate clock, but those don't support NTP as far as I'm aware.

[Leo Enticknap]

I've synced several CP850s to a TMS or remote access PC without any problems. It's only DSS servers that have given me trouble.

Jason (Sharp) - many thanks for the Softros suggestion. I will run it past the theater manager, but suspect that I might get pushback at $400. Correcting the cat745 with the script every few months is keeping the problem under control, and until things get to the point at which shows aren't starting when they should, I suspect the response will be that money does not need to be spent fixing something that ain't broke.

What is weird is that there are some DSS sites that don't have this problem - for example, there is a single screen arthouse I look after with a DSS200/cat862 that takes its NTP from the remote access PC in a booth, and I have never once seen the yellow exclamation point.