my profile | my password | search | faq & rules | forum home

» Film-Tech Forum ARCHIVE   » Operations   » Digital Cinema Forum   » DOLBY SERVERS, setting TIME (Page 4)

This topic comprises 5 pages: 1  2  3  4  5

Author Topic: DOLBY SERVERS, setting TIME Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 07-13-2014 02:18 PM                     I will confer with Dolby on this one. It is my understanding that the secure clock does NOT sync to NTP or anything else but user input. I've asked for it to be able to be synced to NTP but so far nothing. The DSS all show good NTP sync...are to the second and when one checks the logs everything show up right too. Now my question is to you...do these CAT745s power down nightly? Because if they do, they are going to lose any sort of NTP as a result and run on its own "clock" and it will not "step" via NTP. Looking at the logs, it does imply that the show player clock does try to get time if the NTP is deemed good. But since most CAT745s are off half the time, what good will that do you? It will drift over night, never to regain sync.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-13-2014 03:15 PM                     NTP does step. Anything over 125ms will trigger a step - but it will take time, hours possibly. The NTP will have to trust the server and be 100% sure the clock is off. That's why Dolby use the ntpdate at boot up: that will step the time immediately regardless of the conditions of the NTP server. Those mediablocks are always online, they get rebooted every week or so. I will try and find one where the 745 is turned off every night.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 07-13-2014 08:32 PM                     Dolby deliberately does not allow NTP to step the time...they only allow a "slew." Well yeah, if our CAT745s stayed on all of the time then I guess they would be accurate too. However, Leaving the IMBs on would mean leaving the projectors one which means you are pumping dirt though the filters 24-hours a day. There is nothing (other than overcoming a bad IMB clock design) good about leaving the projector on 24-hours a day. Start shutting your projectors down at night and see what happens to your CAT745 clocks...they'll never sync to NTP again (until you manually get them in the right ballpark).  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 07-13-2014 10:09 PM                     Our two CAT745's stay on all the time. Thus, the necessary reboots to get back in sync....and numerous filter cleaning periods, especially right after construction was over with - it was almost daily during that time.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-14-2014 02:31 AM                     Steve, I can't remember any parameter in the Dolby NTP implementation which is not allowing the step, but I shall check on that. I do not particularly agree on leaving the projectors on 24/7 either. I'm not sure how the NTP is implemented in the 745: if there is a drift file, in theory the system should be able to adjust the speed of the internal clock based on the last NTP sync - and stay relatively synced over time.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 07-14-2014 05:58 AM                     You'd think! What Dolby explained to me about stepping is that it could have issues with the clock suddenly going backwards in time...hence they allow slew but now step. On boot up, when a show obviously isn't going on nor are the logs doing much more than keeping track of the boot up, it does allow step...but only then. Apparently, the CAT745 (or CAT862) isn't allowed to step except via manual input. Again, try an experiment...turn those projectors off at night and see how your CAT745 clock performs.  |  IP: Logged Dennis Benjamin Phenomenal Film Handler Posts: 1445 From: Denton, MD Registered: Feb 2002 posted 07-14-2014 10:23 AM                        All motherboards have a CPU battery. Typically they are "CR2032" type button cells. The type may vary - but they all do the same thing - keep the BIOS time in check. With Cinema server, time is an important thing.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 07-14-2014 02:39 PM                     Yeah but that battery has nothing to do with how accurately the motherboard keeps time. A bad clock is not helped by the battery.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-16-2014 06:39 AM                     Steve, Sure, that's why they use NTP in the first place and not ntpdate (besides during boot time). But the NTP protocol allows steps if the clock drifts more than 125ms and the NTP struggles to slew the clock enough to correct it. But, again, it won't happen straight away and ONLY when the NTP daemon agrees that the NTP source is very stable. If the clock drifts so badly there's likely to be a HW failure and the NTP won't even try to step it.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 07-27-2014 08:19 AM                     A fellow projectionist emails me about his DSS200/CAT745 combo. He is able to correct the secure clock in system->auditorium (within the DCI allowed boundaries)- but after a server power down/reboot, it reverts to the wrong time. Not just any wrong time, but the same offset it had before. The projector with the CAT745 installed is always powered up at boot time. They have no networking, no cables installed, hence no option for NTP. They are on 4.7.1 - Carsten  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 07-30-2014 08:23 AM                     Anyone? What's the sense in making the CAT745 secure clock adjustable and even mention DCI imposed limits, when it reverts to the wrong time after a reboot? - Carsten  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-30-2014 12:27 PM                     I don't know about that. The system clock should sync with the secure clock at boot (if no NTP is found) and not vice versa. I am not aware of the 745 reverting back to the previous time when adjusted. Is he applying the change by pressing APPLY?  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 07-30-2014 04:29 PM                     He says the updated clock is running adjusted as he set it - until the next restart of the projector/CAT745. So I assume he hit's 'Apply'. - Carsten  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-30-2014 05:00 PM                     tell him to press CTRL-ALT-F1 and then CTRL-ALT-DEL Linux as default saves the system clock to the BIOS when the system is shutting down (date --systohc if memory serves), so next time the system starts, it's hopefully not too far away. Since a Dolby does not restart but gets power cycled, maybe a proper shutdown can synchronize the clocks. That said, if no NTP is found the system clock should synchronize to the 745, you can see it within the gibberish the screen throws at you when booting up Is the 745 up and running (projector on) when the system is rebooted?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 07-30-2014 05:19 PM                     Carsten, are you saying that when he sets the CAT745 via the secure time setting that is the time that changes on the next boot? That has not been the case on ANY of ours so something sounds fishy. As described by others...absent an NTP, the bios clock (show clock) will set itself to the CAT745. The CAT745 WILL run fast. It can easily exceed DCI allowed drift in a course of a year...I don't know how it passed DCI compliance with that so called clock. Others claim that if there is NTP present and the CAT745 is left on, it will remain synced to NTP and not drift. None of our customers leave their projectors/CAT745 on 24-hours so I can't verify that one.  |  IP: Logged

All times are Central (GMT -6:00)

This topic comprises 5 pages: 1  2  3  4  5

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.