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Author Topic: How common are NTP servers on theater networks? Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 08-20-2013 05:41 PM                     Your media block keeps its own battery-backed clock on UTC and you're only allowed to adjust it +6 minutes or -6 minutes max in a year.  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 08-20-2013 08:17 PM                        I think you are allowed to adjust the clock in the media block up to 6 minutes a year. That is the clock that KDMs compare to. This does remind me of a movie marque that showed a movie starting at 7:34. I asked about the odd start time. The reply was that had run out of zeros. Harold  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 08-21-2013 06:05 AM                     There are multiple clocks in any DCinema server and system. As some have noted...the secure clock...which should be located on the mediablock or IMB is the one the KDMs reference from and has a very limited time adjustment and it/the keys...etc are always in UTC so changing time zones does not help one "cheat the system. The show clock is often off of a less accurate clock that depends on a NTP server to keep accurate. Just like most computers...they are not accurate...they only seem accurate because they call out to microsoft or apple's NTP server when they are on the internet. Note, try rebooting a server that has its clock off...you may find it resets itself on boot up, even without an NTP because some use the secure clock when booting up if the NTP is not available.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 08-24-2013 06:33 PM                     I have installed a couple of GPS locked Net Clocks in locations where internet was unreliable... ie: not always available. IN these systems you just feed the output of the Net clock into the management switch and point the gear at it's I.P. It is automatic from there. Just about any Windows computer can also become an NTP server with a simple easy to do modifications in the regestry and firewall. I was able to purchase some Symetricom NTP clocks used off of Ebay at around 700 bucks each which is not bad as these units generally go for around 3K new. I also use an old Datum 9390 GPS locked rubidium clock at home as well as several other atomic based clocks here as refrence to calibrate test gear. I am never LATE for a service call! Mark  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 08-25-2013 12:43 AM                        A low cost GPS based NTP server is at http://www.broadcasttools.com/view_product.php?pid=208 List price is $409 Harold  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 08-25-2013 01:30 PM                     You can put one together for a lot less than that  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 08-25-2013 03:37 PM                     That's an interesting clock and at a good price. Doesn't offer the direct plug and play of the more expenmsive units but is certainly a great inexpenmsive alternative. Thanks for posting. Mark  |  IP: Logged David Buckley Jedi Master Film Handler Posts: 525 From: Oxford, N. Canterbury, New Zealand Registered: Aug 2004 posted 08-26-2013 02:04 AM                        Not only does that BroadcastTools clock look good, it is very unusual for anything aimed at broadcast folks to be agressively priced, which that clock is. It comes complete with a GPS receiver. Ok, we run Symmetricom clocks at work, but we have a request rate measured in many hundreds per second. For a single compact installation, the BroadcastTools box looks good. However... the big thing about NTP is that you don't have one clock, you have a global network of clocks, which between them maintain good time. A single clock box with GPS will be a lot more accurate than a machine on the end of an NTP network (nanosecond rather than several millisecond accuracy) but if it goes down then there is no backup. Even if one is on the end of a dodgy DSL line, with NTP you should still be good to well under a second, as long as one is running "proper" NTP, and not just SNTP.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 08-26-2013 03:11 AM                     quote: Back in the day, the projecitonist phoned the speaking clock and checked his watch [Roll Eyes] A connection to film, have you ever seen the original speaking clock? It used optical sound recordings. It had a horizontal shaft, about a metre long, on which were mounted several large glass disks, about the size of a LP record. The shaft rotated at 6 rpm and 'At the third stroke it will be' was played from the first disk. Other disks played the hours, minutes and seconds, and the final one, or I think it may have been the first one again, played the three pips. The recordings were not a continuous spiral, but a series of concentric circles. As the pips were played the head on the seconds disk would step in to the next track to play 'Precisely', And ten 'seconds', 'And twenty seconds' etc. At the end of the minute the minute head would step in one track, and the seconds one would come back the the 'Precisely' track, and so on. For many years it was displayed at the Science Museum in London, and the thing used to fascinate me when I was young. When I was last there, a few years ago, I couldn't find it. Most of the interesting things there seem to have been removed from display, and put in store.  |  IP: Logged David Buckley Jedi Master Film Handler Posts: 525 From: Oxford, N. Canterbury, New Zealand Registered: Aug 2004 posted 08-26-2013 04:08 AM                        The Speaking Clock - read all about it!  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 08-26-2013 01:15 PM                     David... And a proper NTP clock locked onto multiple gps satellites also averages out those satellites clocks for even more accuracy. Very similar to how the NBS Time Service works. They don't just look at one atomic clock but at the average of a number of atomic clocks located in different places. Another advantage of the higher priced GPS units is that many of them have an internal rubidium oscillator that is locked and frequency corrected based on the incoming satellite data, I doubt the Broadcast unit shown has that! So in case you are in an area that looses satellite lock you can still maintain nanosecond accuracy for quite a long period...  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 08-26-2013 08:04 PM                     quote: David Buckley However... the big thing about NTP is that you don't have one clock, you have a global network of clocks, which between them maintain good time. A single clock box with GPS will be a lot more accurate than a machine on the end of an NTP network (nanosecond rather than several millisecond accuracy) but if it goes down then there is no backup. And you cannot live without a backup for a day or so? Or are people starting to get worried if their movie starts a few milliseconds off schedule?  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 08-26-2013 09:23 PM                     I don't think anyone is worried about more than a minute or so off-time. You can correct the secure clocks in every server I know much about, up to 6 mins per year (cumulative, I believe - after 10 years you would have 60 mins available if you had never changed it). Using NTP should be better than manual adjustment though: assuming the server's NTP time update utility works the usual way, the internal clock speed will be tweaked - ie the internal clock will be slowed fractionally whenever the time is corrected by being turned back (and the opposite). Eventually the server clock should become adjusted to run very close to "real time" and not drift much any more (some drift is unavoidable because of temperature change at the timing crystal). Having the server clocks get NTP time from the TMS is the usual practice in places with a TMS, then the TMS (which must be connected to a NOC if you're in a VPF program) pulls time from some offsite time server, usually from the NOC.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 08-27-2013 06:19 AM                     The 6 minute drift is NOT cumulative...it is per 12-month period and some use the calendar year (the 6 minute adjustment period begins 1/1 and ends 12/31...at least not all servers allow for a cumulative adjustment. As for drift...NTP does not necessarily mean that the server's clock internal time keeping is adjusted at all. NTP allows for stepping (immediate change) and skewing (slow change) but it is the NTP services that are doing the adjusting, not the clock mechanism itself. Whereas all servers do the license check thing at the start of the show (DCI thing)...being accurate to a fraction of a second exceeds the accuracy required. Anything within a second is sufficient. Note, there are often several clocks at work in a DCinema system. There is the "secure clock" which has the 6 minute limitation...its only required purpose relates to KDMs. Often there is a show clock (determines when shows start if there is a schedule) and that clock can be set to any time you want (and allows for different time zones...the secure clock is always UTC, as are KDMs). I'm pretty critical about getting all clocks in the system on NTP (Enigma, projector, automation...etc.). When trying to troubleshoot an issue...having everyone on the same time allows one to create a much better chain of events.  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 08-27-2013 07:06 AM                        Interesting to read about the British speaking clock. The US version of the "time of day announcement" machine is known as an "audichron" machine and it used a magnetic drum to play back the time announcements. See video here Most major cities have or had one of these installed (along with a similar device for weather announcements). The Boston one seems to have been disconnected without fanfare a few years ago (it was reachable at 617-637-1234). Jane Barbe and John Doyle are the most common voices on these units in the US. (BTW, coming from an IT background, I agree with everything that Steve has posted in this thread with respect to NTP service. In general, mismatched time is bad; therefore, it is a good idea to have a single NTP server on each local network to which all other devices are slaved.)  |  IP: Logged

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