Receiver Clock Slow By 10sec. - Canadian TV, Computing and Home Theatre Forums

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post #1 of 22 (permalink) Old 2017-12-11, 04:41 PM Thread Starter
 
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Receiver Clock Slow By 10sec.

My 9241 receiver clock is slow by 10 seconds. If I click a program exactly when the guide says it starts, it's already started by 10 seconds. A scheduled recording misses the first 10 seconds.
Not a big deal, just annoying.
I've done a check switch and there is no difference.
Is this a Bell issue or my receiver?
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post #2 of 22 (permalink) Old 2017-12-11, 05:42 PM
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Do you have access to CP24? (I can't remember if it's 1566 or 1503 on BTV). It usually has the time fairly accurate - perhaps a couple of seconds or so slow - try setting a recording and see if the clock there is OK. Is that also "off" by 10 seconds? Some channels have more time error than others - I just checked some of the news channels that show the time and none of them were as accurate as the time signal on my computer. My Rogers PVR is 2 seconds slow but usually catches the start and finish of a programme.

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post #3 of 22 (permalink) Old 2017-12-11, 06:22 PM
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Have you tried rebooting the 9241? It might set the clock. Setting the recording to start 1 minute early should also work, though it might not happen if there is a conflict.
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post #4 of 22 (permalink) Old 2017-12-11, 06:55 PM
 
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I don't think it is the 9241. Some programs just seem to start and end off from time in guide. I often lose the last 2 minutes of show that run past or start early to the scheduled time. I think it is the networks not Bell.
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post #5 of 22 (permalink) Old 2017-12-11, 09:13 PM
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Losing the last 1 or 2 minutes is a common issue, especially with some US networks and some BDUs. That can often be fixed by extending the recording by 2 minutes or by recording from a Canadian network that doesn't run past the hour. Don't know that I've seen many shows start early but I'm not saying it doesn't happen. In my experience, it's more likely that the PVR starts recording a few seconds late, especially if there are back to back recordings. Some shows start right on time, to the second, so any delay by the PVR causes the beginning of the show to be missed.
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post #6 of 22 (permalink) Old 2017-12-12, 03:00 AM
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FIRST, we have to understand that there are several DIFFERENT Time "Standards".....and in many [not all] cases, entering "LEAP SECOND" corrections has been a MANUAL Process that is prone to HUMAN ERROR:
GPS, UTC, and TAI Clocks

The World-Wide accepted "ATOMIC TIME" [aka TAI] is a particular "ATOMIC CLOCK(s)" located in Paris, which continually counts the number of Exceedingly Accurate Frequency Oscillations ever since it was "adopted" as the WORLD TIME STANDARD. It is presumably NEVER "corrected".

OTOH, the PRIMARY way time is distributed around the World is via U.S. GPS [and Russian GLASNASS] Satellite Navigation Systems. "GPS TIME" was calibrated to ATOMIC TIME before launch of the FIRST Satellite and has been free-running ever since WITHOUT CORRECTIONS. Although the GPS TIME Clocks are synchronized to each other, the Frequency Standard in the chosen MASTER isn't as accurate as the ground-based ATOMIC CLOCK, hence the current GPS TIME is now AHEAD (Earlier) of ATOMIC TIME by 19 seconds, as shown in above link.

The time used by MOST people is actually UTC TIME, [Universal Coordinated Time] as kept by the U.S. Navy Observatory in Wash. D.C, and distributed from Ft Collins, CO by WWVB (VLF Freqs to 1-ms accuracy, received by many Wall Clocks), WWV (HF Freqs to about 10+ ms accuracy), Dial-In Phone Announcements and various time.nist.gov Internet Webservers (1-ms accuracy).....the latter is how most PCs get ACCURATE Time.

NOW it gets INTERESTING: Every several years (or NOT), UTC is CORRECTED by infrequently occurring LEAP SECONDS and [mostly] predetermined LEAP YEARS so that it aligns with the actual motion of the Earth (which is slowly spinning slower) so that Apogee and Perigee always align up with the ACTUAL SEASONS.

So UTC TIME is currently Earlier than GPS TIME by 18-seconds...and Earlier than ATOMIC TIME by 37-seconds.

Which doesn't explain the 10-sec difference YOU saw [maybe they decided to split the difference???]. Many (esp. old) GPS Receivers ONLY Output GPS TIME, so Leap Seconds had to be (mostly MANUALLY) entered into the Interfaced Software. And some (later) GPS Receivers can be setup to Output and/or Display GPS or UTC...with Leap Seconds and perhaps also Leap Years being MANUAL entries in most deployed GPS Receivers [I would continue to implement it AUTOMATICALLY in the S/W that Uses GPS TIME].

Since Leap Second is mostly a MANUAL operator action, it is way too easy to forget to do the correction each and every time it is announced....and from my experience repeatedly fighting this issue with my ever changing group of local cable "engineers", it seems to be intermittently entered as they only occur every several years, it's easy to FORGET to DO the requisite procedure.

Also note that the LOCAL Cable "UTC" Guesstimate [which determines DVR Start/Stop Times] is usually DIFFERENT than the "UTC" Guesstimate that the INDIVIDUAL Networks are using to drive their PROGRAM Start/Stop Times...which I THINK also determines LOCAL Ad Insertion Times.

Additional info for the Uber-GeeK:
http://digital.ni.com/public.nsf/all...25733000668351
https://confluence.qps.nl/display/KB...ime+Correction
https://www.nist.gov/pml/time-and-fr...-questions-faq
http://www.oc.nps.edu/oc2902w/gps/timsys.html
http://tf.nist.gov/tf-cgi/servers.cgi

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands

Last edited by holl_ands; 2017-12-12 at 03:32 AM.
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post #7 of 22 (permalink) Old 2017-12-12, 03:39 AM
 
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Wonderful but I have to ask just how much "Free time" you needed to do this?.....lol
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post #8 of 22 (permalink) Old 2017-12-12, 07:44 AM
 
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It is an interesting subject. There is a very long internet RFC on the subject of time servers which were first used so that radio telescopes could use the internet and have their time stamps accurate enough for interferometry.
I have a watch that listens to WWWV, my pc uses a secondary internet time server, my car uses GPS time and I guess my phone and a Rogers set top box use 'Rogers time'.

I hadn't noticed any important discrepancies but then the assorted displays don't show milliseconds or even seconds!


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post #9 of 22 (permalink) Old 2017-12-12, 12:20 PM
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Quote:
My Rogers PVR is 2 seconds slow but usually catches the start and finish of a programme.
I find the Rogers STB time to be fairly close, but the clocks on channels such as CP24 are slow by a few seconds, due to the processing delay of digital video. The same issue occurs when listing to the time signal on 680 News. My cell phone is usually less than a second off, when compared to NTP (Internet) time.

All my computers use NTP to set the time and I have a clock that receives WWVB and it's always close to NTP on my computer.

I haven't lost my mind. It's around here...somewhere...
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post #10 of 22 (permalink) Old 2017-12-12, 12:42 PM
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For most people, NTP time is the correct time. The atomic clock is merely a reference. It counts the number of decayed particles (or seconds if you like) since it was started. It will never be adjusted since that would be almost impossible to do accurately. GPS time will be fundamentally inaccurate due to lack of correction, variable propagation delays and it being a one way protocol. It can be useful in remote areas when the proper correction is made, especially if the satellite position is known. NTP time is more useful because it is a two way protocol that can compensate for propagation delays more easily and because it is adjusted for real world variations between calendar time and observed actual 'Earth time.' Earth time is what ancient people lived by. It's what you get by accurately observing phenomena such as sunset, sunrise and the seasons. Calendar time, or NPT time, is adjusted to closely approximate Earth time. Discrepancies and subsequent corrections are due to inaccuracies in units used to measure time and slight variations in celestial movement.

All that makes little difference to the original issue. I pad timers to compensate but that doesn't always work. When possible, recording from a different channel or at a different time (to allow the proper functioning of program padding) is usually the best workaround.
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post #11 of 22 (permalink) Old 2017-12-12, 02:00 PM
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Does Anybody Really Know What Time It Is?
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I haven't lost my mind. It's around here...somewhere...
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post #12 of 22 (permalink) Old 2017-12-12, 02:24 PM
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I bought the album when it was originally released in 1969, just before the Woodstock Festival. Back then we didn't have NTP or GPS satellites. Atomic clocks were just regular clocks with hands that glowed in the dark. Most people didn't have WWV either since it required a short wave radio. That had to be the most boring station ever. We didn't have digital wrist watches or digital clocks either so most time pieces were a few minutes off, more if we forgot to wind them up. Back then we *really* didn't know what time it was but we also didn't have PVRs or VCRs and most TV shows had the theme song intro first so it didn't matter if we missed the first 10 seconds. Once we got to Woodstock we also didn't *care* what time it was. How times have changed.
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post #13 of 22 (permalink) Old 2017-12-12, 04:53 PM
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Long time ago I spent a LOT of TIME sending to emails to TWC Tech Supervisors....who actually RESPONDED......and then in a few years a NEW Tech Supervisor showed up and I had to re-cycle the old eMails....and of course that ONLY addressed the DVR Start/Stop Times....and NOT the various Network Program Times. As long as Programs consistently come on AFTER DVR Start Time, I'm mostly happy compared to before...although there are quite a few Programs for which I have to remember to ADD a minute to the Record Time so that I don't miss next episode previews.

So I already had the Bookmarks and KNEW exactly what to SAY.....and BTW I've been RETIRED for many years now.....

In order to perform NAVIGATION function, all GPS Sats need to have VERY precise timing (100-ft ~ 97-nsec accuracy spec to 1-sigma uncertainty)...after that it boils down to how many LSB's an equipment designer decides to implement in their GPS Time Standards:
https://www.endruntechnologies.com/timingspec.htm

BTW: At work, I've used WWVB Receiver as well as GPS Receiver Time Standards interfaced to various user systems....and of course, my Wall Clocks are synchronized to WWVB....so BTDT.....

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #14 of 22 (permalink) Old 2017-12-12, 05:09 PM
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We didn't have digital wrist watches or digital clocks either so most time pieces were a few minutes off, more if we forgot to wind them up.
Many years ago, astronomers had to determine the "rate" of their clocks. The rate was how much the clock varied from astronomical time. Rather than trying to adjust the clock to the correct time, they simply factored the rate into their calculations.

Also, back then, to determine local time difference (longitude) from Greenwich, they had to observe the motions of Jupiter's moons and compare them to an almanac published by the Royal Observatory.

I haven't lost my mind. It's around here...somewhere...
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post #15 of 22 (permalink) Old 2017-12-12, 08:22 PM Thread Starter
 
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Wow that is a lot more information than I expected.

To explain more definitively what I am seeing with my receiver:
I checked my wrist watch with the UTC time and the Web clock at NRC, both of which were showing the same time.
A program starting on the hour (whatever that means with all the above information) starts at 6 seconds after the UTC time hour mark. The receiver time, as seen by pressing View on the remote, changes to the displayed exact hour 10 seconds later, or 16 seconds after the UTC hour mark.
Therefore a PVR recording starting on the receiver's hour mark will miss the first 10 seconds of the program.

I guess time is relative. Who'd have thought?
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