Live TV stutter/discontinuities - usual fixes don't seem to apply

Discussion in 'General Support' started by fugufish, October 29, 2013.

  1. fugufish

    fugufish New Member

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    Hi,

    I'm having problems with stuttering/continuity errors during live TV - hoping someone can help.

    After doing some research on these forums and elsewhere and trying multiple things I think I can rule out rendering/playback issues. The stuttering seems to correspond to discontinuities which show up when I do TV Server Config. > Manual Control > Start Timeshift.

    Disabling Windows Defender and Firewall, power saving options, and all unnecessary background tasks makes no difference. Nor does changing the location of the timeshifting folder (from my HDD to my SSD).

    Most channels have moderate signal strength and high signal quality (reportedly, at least) so it seems the problem could be due to a bad signal. However, two things suggest that this is probably not the case (to my mind at least):

    (1) Live TV does not stutter in WinFast PVR2, the software that came with my TV Tuner (Leadtek DTV 2000 DS Plus) (except when reception is very poor).
    (2) Changing the channel multiple times (usually 4 or 5) fixes the stuttering (and continuity errors) on all channels (with decent reported reception). Not sure if the stuttering eventually returns - it doesn't seem to but I haven't been watching TV for hours. Restarting MP reintroduces the problem.



    Other things I've tried without success:
    - Windows 8.1 upgrade
    - clean install
    - running LatencyMon (lots of hard pagefaults which seem to be caused by Windows Defender)
    - NextPVR (even worse: stuttering and freezing)
    - Microsoft Loopback Adapter (didn't seem to help)

    My computer is new and built for gaming so I take it it shouldn't have any trouble handling timeshifting etc. (unless something is faulty, which is possible - computer has been stable so far, though).

    In sum: I'm stumped. Any suggestions?*

    Thanks in advance for your help.


    *I have attached the logs which were generated while reproducing the problem. Here's what I did:
    - loaded MediaPortal and started watching TV
    - stutter as usual so I changed the channel a few times until it stopped
    - returned to original channel for a short time to see if stutter was gone - it was
    - closed MediaPortal.





     
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  3. mm1352000
    • Team MediaPortal

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    Hello and welcome fugufish :)

    I think your research and investigation has been pretty thorough, and your conclusions seem to be relatively sound.

    Your TV card is built on the Realtek RTL2832U chip. I have one myself, and I can confirm that TV should be watchable at 55 strength 100% quality... but you wouldn't want to have those readings go any lower.

    When you monitored manual control, did the signal quality ever drop below 100%?
    What are you using for an aerial?
    When you tested in the Leadtek software, were you able to force the software to use one specific tuner? (I mean, this is a dual tuner card - there is a possibility that one tuner is affected more than the other or that interactions occur when both tuners are in use).

    mm
     
  4. fugufish

    fugufish New Member

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    Hi mm - thanks for the reply.

    Good to hear from someone with the same card. Signal quality does drop below 100% on some channels (it sometimes rapidly fluctuates between 100% and anywhere as low as 70%). In my testing I've been trying to stick to the channels with the best reception to rule this out. Even when signal quality is stable at 100% I see lots of discontinuities in Manual Control.

    Aerial is a rooftop antenna - I don't know more than that but I can find out if it matters.

    I don't recall there being an option to force the use of one specific tuner but maybe it does this by default. I'll have a look later. I have tried disabling each tuner in Device Manager and testing in MP and I get stutter on both.

    Thanks again for your help!

    fugu
     
  5. fugufish

    fugufish New Member

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    Okay, I tried each tuner in the Leadtek software and both seem to work fine. Time-shifting and recording seem okay as well.
     
  6. mm1352000
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    Okay. I guess the question then becomes: are you sure that the tuning parameters that TV Server is using - in particular, the frequencies - are correct?
     
  7. fugufish

    fugufish New Member

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    No, I'm not. The frequencies do seem to be right (I found a map showing the closest broadcast stations and frequencies) but no idea about the other parameters. I can't seem to find these details anywhere to input them manually.

    Unfortunately I don't see a way to check these within the Leadtek software in order to compare the two.

    I did try doing a scan within the MP TV Server Config. in which I didn't set a region to see if that would force it to find a better set of channels. The problem was still there, though. Interestingly I had to do the same thing within the Leadtek software to get good reception - and it made a huge difference.[DOUBLEPOST=1383186579][/DOUBLEPOST]One thing I do see within the Leadtek software and in the information about broadcast frequencies is a 'callsign'. This is listed before the channel in the Leadtek software - e.g. '45-2 TEN Digital'. All the network TEN channels have the number 45 listed in this way, but I don't see this anywhere in the MP TV Server settings. When I select a channel within the TV Channels menu and click edit I see an ID number next to the green 'T' which seems like maybe it should match this but it does not. Could this be the problem? I notice that I have two of the same in a couple of places and these share the same frequency but have a different ID.
     
  8. fugufish

    fugufish New Member

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    I found some more info on the channels and I can confirm that at least some of those affected have the right tuning parameters (going by the closest broadcast frequencies). Still don't know where the ID number next to the green 'T' in the TV Server Config. comes from...

    I've been considering buying a better antenna cable as mine seems quite dodgy but it's fairly expensive so I'd like to exhaust any other options first. Could someone tell me roughly how Live TV works? Most importantly: is there any point- e.g. when the TV server communicates with the TV tuner card - where things could be getting messed up. I watched several hours of TV last night on two different channels without stutters after performing the channel switching workaround, so I am a bit unsure how this could be possible if this is purely a signal problem.

    Thanks.
     
  9. mm1352000
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    The thing they're calling a callsign is [mostly] an American over-the-air (ATSC) concept.
    45 means physical channel 45 - ie. a frequency
    2 means service or subchannel 2 on that frequency
    All the TEN channel are 45-X because they're all broadcast on the same frequency/multiplex.

    The ID is an arbitrary database identifier. It is unique to MediaPortal and is not expected to match. This is not the problem source.

    This is interesting. I'd normally expect you to only have one per channel. If it isn't too hard, maybe it would be a good idea to delete all channels and rescan.
     
  10. mm1352000
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    As above - ignore the ID number. For all intents and purposes it is irrelevant.

    Fair enough.

    That is a question which deserves a book rather than a one or two sentence answer. :)
    If you have questions, they're going to need to be significantly more specific...

    TV Server doesn't directly communicate with the tuner. It goes through an intermediate layer provided by Microsoft called BDA.
    BDA is not simple, but nor is it extremely complex.
    Basically, if you pass in the right tuning parameters you can usually expect them to be passed to the tuner driver without issue. This is why I asked you if you're sure the channel frequencies are correct. Of course there are a few "gotchas"... but the thrust of what I'm saying is that with this kind of problem, if the continuity errors are not caused by signal quality issues or HDD stress... well, then you're really looking at overheating components and other really unusual issues which are difficult to locate.

    Let's be clear: I'm not sure that this is purely a signal problem. It seems likely from the evidence that you've presented and the probability of it being something else. However, it is not a certain conclusion.

    I note:
    1. Signal quality varies based on time of day and weather. Have you noticed any other pattern to the problem?
    2. MediaPortal doesn't interact with the tuner after tuning unless you're monitoring the signal strength/quality statistics. It seems to me that what you're saying is that when the tuner locks onto signal properly it is fine... but if it doesn't then you have the problem.
     
  11. fugufish

    fugufish New Member

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    Hi mm,

    I decided the buy the new antenna cables and it has fixed the problem as far as I can tell. I see 0 discontinuities now if I monitor a channel. No idea why changing the channel helped before if it was a bad signal but I'm just happy it's fixed.

    Thanks so much for your help!

    fugu

    (For anyone who is interested: I replaced some old RG59 cables with RG6 cables with F-type connectors.)
     
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