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Inacurate Clock on HR20-100

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by socal404, Aug 12, 2008.

  1. socal404

    socal404 Legend

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    Jun 26, 2007
    Hey Texbrit

    I'm going to believe that your observations are unique to your equipment. I did a RBR on my HR20-100 on September 6. After doing it my receiver was again recording on-time. It's now 9 days later, and my receiver clock is about 15 sec. behind. I have a TIVO DVR in my bedroom, and there is never a discrepency in the start time. I believe that Directv needs to do a daily syncing of their receivers.

    Thanks, though, for doing your research.
     
  2. Bilbrey

    Bilbrey New Member

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    FOX, ABC, Showtime, SCI-FI are ones I've confirmed.

    I reset one of my HR21s and recorded some shows today, and the start times are back in line. On other HR21s in the house with the same shows recorded, they start about two minutes late. I'm going to reset them and try more recordings...

    I don't have any properly logged data, but 15 seconds in a week is sounding about right for what I'm observing.

    The local news always used to start right on the money on the same note of the intro music, but then about three to four months ago, the 'drift' started. (I'm guessing, but have not tracked, that it must have been with a software update. But that is only speculation.)

    By the way, I'm not trying to argue with anyone, nor insist "I'm right" or anything like that. My goal would is simply to find a workaround to make sure my recordings are on time. If reseting once a week works well enough, then I can live with that till DirecTV addresses this issue in a later update.
     
  3. Steve

    Steve Well-Known Member

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    I know you shouldn't have to do this, but if you can be in front of a computer and the HR21 at the time the local news starts, you might want to spot-check the "live TV" start of the local news vs, when the HR21 record light goes on vs. "time.gov" to confirm exactly what's going on.

    I find that my HR21's start 5-6 seconds late whether the clock is 3-4 seconds off or 30 seconds off. I do reboot weekly, however, because of the CE downloads.

    /steve
     
  4. DonHac

    DonHac Mentor

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    The weekly reboot is what's keeping you safe and on track. Clock chips tend to drift but the drift in a single week is usually not too bad, and you're never seeing the cumulative effect of many week's drift. Those of us who prefer not to beta test on our TVs enjoy long uptimes (it's now been two months since the last HR-2x national release) and, ironically, get to be the first ones who encounter this kind of bug. I find I have to reboot my HR21-700 about once a month to keep drift under control.

    There's a great discussion of the underlying problem and the (IMHO) correct solution of adjusting the clock speed (rather than its setting) at http://blogs.msdn.com/larryosterman/archive/2004/04/02/106668.aspx. If this is something that Windows has managed to get right for the last 15 years I would think that DirecTV on its Linux base should have no excuse not to do the same.

    DirecTV isn't the only one to flub this issue, though. I have a GPS (a Magellan RoadMate 1200) that does the exact same thing. Even though the thing spends its days receiving time signals from multiple atomic clocks in space, its internal clock drifts, again by ~15s/week. It's dramatically less accurate than the dashboard clock in the car.

    When I contacted Magellan tech support I got the same workaround as posted here: do a full reboot. Apparently that GPS resyncs its clock during a cold boot (after holding down the power button for 10s or longer), but not when coming back from standby (when the power button was held down for under 10s). If you try to simply leave your GPS in the car, having it turn off when the 12V power goes off, it will very rapidly show incorrect times.

    It's an annoying (and I would say embarassing) blemish on both products.

    Don
     
  5. Steve

    Steve Well-Known Member

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    INFO BAR clock drift is really just a cosmetic flaw, IMO. Sorry to repeat myself, but my HR21 start times are a consistent 5-6 seconds behind whether my INFO clock time is 3-4 seconds off (compared to time.gov), as it is right after a reboot, or 20-30 seconds off a week later. /steve
     
  6. harsh

    harsh Beware the Attack Basset

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    I maintain that the problem is not a hardware or interrupt servicing issue. I believe it is related to the size of some sort of database and the delay comes from how long the DVR takes to process the event as the list of events gets large. The series link limitation also points towards the database engine not being up to the task.
    Windows NT did it that way, but that's not the case with more recent perversions of Windows. Now Windows depends on checking with Internet time servers once a week.
     
  7. DonHac

    DonHac Mentor

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    Nov 21, 2007
    I have my doubts about the scalability of the database as well, but I believe this is separate issue. Like others (but apparently not all) I have seen the recording start times drift farther and farther behind the longer the DVR stays up without a reboot, which smells a lot like clock drift. It's always possible that the database is suffering from memory fragmentation (or some other malady that clears with a reboot), but if I were debugging I'd investigate drift first.

    You're conflating two separate issues. One is the reliable time source, which long ago was just the onboard RTC and now can be either an internet time server or a domain controller, depending on whether or not the computer is domain joined (and how the domain is configured). See http://support.ntp.org/bin/view/Support/WindowsTimeService and http://www.ietf.org/rfc/rfc1305.txt. The RTC is still used, but it's synced to the reliable time source, and then the OS can sync to the RTC.

    The second issue, and the one I was discussing, is how the OS clock is brought in sync with that time source. If the clock is way off (I forget the threshold) it's done by jumping the clock. If the clock is only a little off, though, it's done by adjusting the clock rate. Doing that addresses the concerns t_h and others had about what happens if the clock is corrected during a recording. Smoothness is good.

    Don
     
  8. Steve

    Steve Well-Known Member

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    Same with me. My local FOX 5, e.g., sometimes starts shows 15-20 seconds before "time.gov" says they should start. Seinfeld at 7:30PM often shows 7:29 on the FOX on-screen clock displayed in the lower right corner. See below. /steve

    [​IMG]
     
  9. harsh

    harsh Beware the Attack Basset

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    That may explain why nobody speaks of a clock that races ahead.

    Some have mentioned that the recordings seem to stop on time even if they start late. That would indicate a processing tie-up. This is where recording news programs with running clocks comes into play.
     
  10. Steve

    Steve Well-Known Member

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    Assume from a prior post that you're talking about a problematic HR21-700? Curious what reference machine you're comparing it to for measuring start time performance. And are you running the NR or a CE? TIA. /steve
     
  11. texasbrit

    texasbrit Well-Known Member

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    Both Steve and I are as interested as anyone in sorting out this problem, as are several other people who have done testing. If anyone wants to test this on their HR20-100 then by all means do so. But I will tell you that every time we have asked this, no-one has been able to come up with any testing that demonstrates there is an issue like this. Even on my HR20-700 during the early days when the displayed clock used to "wander" by several minutes, it did not have the same effect on program start times.
    To test this you need to record a program that has a displayed clock (assuming thst it is correct of course!) and demonstrate that the recording was several minutes late in starting, or watch an "atomic clock" and record what time the recording started. So far no-one has been able to do that. What typically happens is that when they look at the recording they see the program was actually starting early which is why the DVR appears to start late.
    I am not saying that having an incorrect displayed clock is not a bug, it certainly needs to be fixed, but we're still looking for real evidence of any really late starts.
     
  12. HarryG

    HarryG Mentor

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    If I record the same network program with my HR20-100 and TivoHD, the TivoHD ALWAYS starts recording the program with about a 5-10 second buffer at the beginning of the broadcast. The HR20-100 upon rebooting will start the same network broadcast with about a 5 second buffer. However, after about three days (without a reboot), the HR20-100 will slowly begin clipping the start of the network program that is being properly recorded from cable with my TivoHD.

    This is how the HR20-100 has performed for the 15 months I have had it in service.
     
  13. aa9vi

    aa9vi Godfather

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    My clock is - 1 hr. Maybe it's 0x269 CE firmware. Not sure, but I set it to Eastern time ( +1 hr) and that is a workaround for now.

    But, here's how to help fix the damn clock problem.. D*, put a line of code to reinitialize the clock when new firmware is released. That way, once a month or every 2 months the box is in sync. Either that or program the firmware to go look on the boxes for network connections and connect to time-b.nist.gov and update the clocks once a week. Man, this isn't difficult, D* software folks.
     
  14. DonHac

    DonHac Mentor

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    As I implied earlier, I'm running the NR software, 0x255 if memory serves. And I'm comparing to it the shows that are being broadcast. Specifically, the local nightly news. We have a Series Link that records the local ABC affiliate every night at 5pm. Right after a reboot we'll come into the newscast promptly at 5pm. As the weeks go by we miss more and more of the "welcome to our newscast" intro. It happens on other recordings (on other channels) as well, but this one is the easiest to calibrate.

    Now, it's possible that, as you suggest, it's not our HR21-700's clock that's drifting but rather the broadcaster's, and that somehow their clock gets put right when I reboot my DVR, but that's an awfully complicated hypothesis.

    Mind you, I'm not saying that the clock on your DVR doesn't keep perfectly fine time. That's what the "unreliable" part of "unreliable cheap clock chip" means: some of them don't work as well as others. Lack of the problem on one machine does not imply that the problem does not exist on other machines.

    Don
     
  15. Steve

    Steve Well-Known Member

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    For that matter, why not just re-sync the clock daily during one of the GUIDE update downloads?

    BTW, I think the clock is reset after every reboot, so you are already getting a clock reset with every new national release of firmware, which reboots the machine at that time.

    All that said, based on my own testing, fixing the clock will not solve my HR21-700 recording starts, which have been consistently 5-6 seconds off, no matter what the clock says. I downloaded the latest CE Friday night, but have had difficulty comparing start times because I've run into a new issue on my reference HR20-700 which has decided to spontaneously cancel several of my recordings with the explanation "Recording canceled by the viewer"! Aargh.

    /steve
     
  16. texasbrit

    texasbrit Well-Known Member

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    No, I am not suggesting somehow you manage to reset the TV station's clock. :) :)
    I was just pointing out that one of the things that makes this a very difficult thing to check is that many of the stations are very unreliable with their start times. At least two of my local DFW network affiliates (including my local ABC station) have been starting their local news up to 30-45 seconds early (compared with the "atomic clock"), which is why I'm always suspicious of start times unless you are actually there to watch the program start and then see the recording start also, and can compare both with the "atomic clock" time.
     
  17. DonHac

    DonHac Mentor

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    Again, though, the issue is that my clock reliably matches (or at least is at some constant offset from) the ABC affiliate's immediately after a reboot and that after that my clock drifts slower and slower relative to theirs. Once that has happened either their clock has drifted fast or mine has drifted slow. Since I can bring the two clocks back into sync by forcibly resyncing my clock to DirecTV's satellite (by rebooting), I reject the hypothesis that it's their clock thats drifting.

    All that matters here is the sync between my clock and theirs. You don't need to introduce a third clock into the discussion, that just obscures the issue.

    Don
     
  18. JTAnderson

    JTAnderson Cool Member

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    I too have been having this problem with an HR20-100. I did not notice the problem prior to the 0x254 release.

    So, I thought I would compare times against my watch, which synchronizes with WWVB and has the correct time within 1 second. (Actually, it is probably much closer than that to correct time.) My reaction time is probably the biggest fuzz factor.

    I had rebooted the HR20 last Saturday (one week ago) to correct the problem. Today I checked the displayed time and it was 22 seconds slow.

    I then scheduled a recording from the guide to begin on the hour. The recording started 23 seconds late judging by when the record light came on.

    I then scheduled a manual recording. The manual recording began 22 seconds late.

    I then rebooted the HR20. After the restart the display clock was 3 seconds slow.

    I scheduled a manual recording. It started 3 seconds late.

    I scheduled a recording from the guide. It started 5 seconds late. (I was surprised by this one. Perhaps I dozed off for a couple of seconds.)

    I checked the display time again. It was still 3 seconds late.

    Draw your own conclusions. It seems pretty obvious to me that this is a clock drift problem and that the HR20 only synchronizes time at reboot. (And that it may have synchronized time more often in previous software releases.)

    I also suspect this is not an HR20 specific problem, but is more related to the luck of the draw in how accurate the clock is in any particular HR2x and how often you reboot.
     
  19. Steve

    Steve Well-Known Member

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    I've never watched the record light to see when it goes on, but I guess it's possible the record light lags the actual start of the recording. I say that because my problematic HR21-700 (over a period of months) was always 5-6 seconds late starting recordings, whether its INFO bar clock was 3-4 seconds behind or 21 seconds behind several days later. My reference for this is the same recordings made on my HR20-700, which faithfully starts recordings "on-time", i.e., a second or two before the actual show start, and has been doing so in a rock-solid fashion since February.

    That said, I don't have an HR20-100, and it could be an entirely different beast. I think Texasbrit would disagree, tho, based on his reported testing on that unit.

    /steve
     
  20. jdspencer

    jdspencer Hall Of Fame

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    What you describe here is what I see as well. I check the clock and when it gets ~30s slow, I do a restart to resync the clock. I wish DirecTV would force the units to do resync every other day or so.
     

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