Blotchy video issues on only some channels

Discussion in 'TiVo Help Center' started by jfriend, Apr 19, 2017.

  1. jfriend

    jfriend New Member

    26
    1
    Jan 1, 2009

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    For the last couple weeks, we've been having signal issues on some channels. Sometimes we just hear the audio skip a few words. Other times, the video gets totally blotchy/tiled for a short period of time and sometimes the scrambled video lasts for several minutes. I have two Tivos, a Premier XL and a Bolt hooked up to Comcast cable via cable cards and both show the issue, though if I'm recording the same show on both Tivos, I don't always see the same issue at exactly the same point in both recordings, but if one Tivo shows an issue with a show, the other Tivo will also show issues on that same show. So, I think that rules out an issue with a specific Tivo box, a specific cable-card or a specific video cable to either Tivo. There is obviously some in-home shared infrastructure in the splitter and the wiring from the outside cable connect to where the video splitter is in my network closet so a problem in that shared infrastructure could be common to both Tivos.

    The issue only happens on some channels. Other channels exhibit no issue at all. When I look at the Tivo Diagnostic Info, I see many RS Corrected and RS Uncorrected errors on the affected channels and you can often watch both numbers increase rapidly. For example, on one channel that we watch frequently, there were several million RS Uncorrected errors.

    In the Tivo Diagnostics screen, it shows this:

    Signal strength shows 79-88% (varies by channel)
    S/N shows as 31-34db (varies by channel)

    On some channels I can just watch the RS Corrected and RS Uncorrected numbers increase in real-time. On other channels, those numbers don't move much at all.

    Three channels that all have video and audio issues and high RS numbers are 720, 721 and 780 which are all local NBC Sports channels and all running on the same frequency. But, there are some other channels on other frequencies that also have issues.

    I've read all I can find on the RS Corrected and RS Uncorrected numbers and it appears from those numbers that a signal is arriving to the Tivo that has errors, some of which are correctable, some of which are not. The ones which are not correctable are the ones where we hear audio skip or see video blotchiness.

    So, my question is what does it mean that some channels are really bad, but others are just fine? What can we learn from that in troubleshooting this? Does this mean that the issue has to be on Comcast's end of things? Or are there splitter issues or home wiring issues that could affect only certain channels? Just to rule out the splitter, I think I'll go to Fry's tomorrow and get a new splitter. The3-way splitter I have now was provided by Comcast a couple years ago and things have worked fine on Tivo for more than 10 years overall so this problem is brand new. Nothing has changed in the house wiring in the last several years so it's kind of hard to imagine that something suddenly failed there unless an animal did something (cable wiring is in the attic and walls - house is wired for both cable and internet).

    If replacing the splitter doesn't fix things (I'm not expecting it to), then I'm trying to gather as much ammo as I can to convince Comcast that there's a problem with their signal and that they need to do something. If anyone can suggest anything else to try or measure to further narrow down where the problem is, I'd much appreciate help with that. I tried an online chat with Comcast a couple weeks ago and they went down their script of silly things (replace the cable into the Tivo box, etc...), but when I explained that I see the exact same problem in two different Tivos in two different parts of the house, that seemed to short circuit their usual list of silly things they would tell me to do. They checked on my signal remotely (who knows what that actually does) and said everything looked fine to them. We left the online chat with no resolution as I ran out of patience for how time inefficient the online chat is (they leave for minutes at a time to serve other customers) between sentences in the chat so progress is agonizingly slow. Probably have to get on the phone the next time.

    Any help or ideas on other things to measure before engaging Comcast again would be much appreciated. Thanks.

    Edit: I rebooted the Tivo to get all four tuners on the same problematic channel and then looked at the diagnostics. All four tuners showed RS Corrected and RS Uncorrected Errors, but one tuner showed a ton more errors than the others. As an example, it showed:

    RS Uncorrected: 114,103
    RS Corrected: 544,324
    Time: 916 seconds

    That's a ton of errors in 15 minutes. That's more than 100 uncorrected errors per second and more than 500 corrected errors per second.

    So, now I'm also trying to figure out why one tuner shows a lot worse than the others when they are all on the exact same channel? Could that be the CableCard? Or is it an indication of a problem in a Tivo tuner itself? How would you tell which is causing the difference?

    FYI, as a reminder, I'm having a similar video issue on this same channel on my brand new Tivo Bolt in the other room so this issue can't be only a problem with a Tuner/CableCard in my Tivo Premiere XL, but perhaps there is an issue there that is making the problem worse.
     
    Last edited: Apr 19, 2017
  2. JoeKustra

    JoeKustra in the other Alabama TCF Club

    20,122
    3,710
    Dec 7, 2012
    Ashland, PA...
    Just two things. The Bolt counter for RS Corrected doesn't work. You can have one or more bad tuners, but on two different units? That's a stretch.

    Your testing is very good. I would run a cable from your outside box to the Premiere and see if the problem goes away. It could be inside your house. It's unlikely, but possible.
     
  3. jfriend

    jfriend New Member

    26
    1
    Jan 1, 2009
    Good idea. If that still shows the problem, then I can at least get Comcast to focus somewhere else besides my internal wiring.
     
    JoeKustra likes this.
  4. JoeKustra

    JoeKustra in the other Alabama TCF Club

    20,122
    3,710
    Dec 7, 2012
    Ashland, PA...
    On my first Roamio I had two out of four tuners bad. Like you, I could watch the errors count up while there were zero errors on the other two tuners. It was educational.

    If my feed goes bad, which has happened once, I also found large errors on my modem and low SNR on my TV. I still get two clear QAM channels and five analog test patterns.

    Good luck.
     
  5. wannarock2

    wannarock2 New Member

    14
    0
    Oct 1, 2003

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    Same issues on Comcast. Recall they have migrated from MPEG2 to MPEG4. I swapped out my old cable card for one with new firmware and macroblocking/pixalation disappeared.
     

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