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RS Corrected and RS Uncorrected Stat on THD Diagnostic Screen

Discussion in 'TiVo Series3 HDTV DVRs' started by JANNINO, Oct 17, 2007.

  1. JANNINO

    JANNINO New Member

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    Oct 27, 2004
    Does anyone know how to decipher the statistics on this screen?

    I'm having a pixelation issue on one of my THDs and in a post I saw on the Verizon Fios TV forum I was told that if the RS Corrected number is 0, then there is a problem with the Verizon signal coming in. If this number is increasing with with the pixelation, then the Tivo is causing the problem.

    Can anyone provide a little more information on what the meaning of these statistics are??
     
  2. GoHokies!

    GoHokies! O2->CO2 Converter

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    Sep 21, 2005
    KFME
    Do you have a link for what you're talking about? I'd love to read up on it.

    Also, (and this is only a suggestion) you may want to limit the discussions of your problems to one thread to make it easier to follow the discussions, rather than have multiple threads discussing different facets of the same problem.
     
  3. SCSIRAID

    SCSIRAID Active Member

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    Feb 2, 2003
    Vero Beach, FL
    RS stands for Reed-Solomon. They invented a mathmatical coding method which is capable of correcting errors in a bitstream. Their methods are incorporated in many digital data transmission schemes. In digital TV, its called FEC or Forward Error Correction.

    The RS Corrected value tells you how many times the FEC algorithm had to be used to correct an error since the channel was tuned. The RS Uncorrected value tells you how may times the error exceeded the capability for FEC to correct it. If you are seeing RS Uncorrected values of 0 then all is good. Its normal for RS Corrected to increment but the lower the rate the better. The SNR value is also very important. QAM is designed around an SNR of 34db however YMMV. There are many factors driving overall digital transmission error rate.
     
  4. SCSIRAID

    SCSIRAID Active Member

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    Vero Beach, FL
    Re-reading your post... my earlier post didnt fully answer your question.

    If your RS Uncorrected value is holding at 0 and you are seeing video problems such as pixelations, then the problem is either bad data in the stream coming from the original provider (i.e. Discovery HD, TNT etc) or the Tivo is corrupting the stream somehow.

    If you RS Uncorrected value is incrementing more than say 1 or 2 per hour then you most likely have a 'signal' problem.... too much, too little, too noisy, ingress, etc etc.
     
  5. JANNINO

    JANNINO New Member

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    Oct 27, 2004
    SCSIRAID

    I definately am seeing the RS Uncorrect value changing alot, almost by the second which probably means I have a bad signal coming in from Verizon.

    Thanks - now the problem I face is trying to fix that signal and replacing the coax would be difficult at best.
     
  6. JANNINO

    JANNINO New Member

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    Oct 27, 2004
    GoHokies!

    I put two separate posts so as to not ask too many questions on one post. I also am very interested in the RS values which SCSIRAID gave a great explanation for.
     
  7. SCSIRAID

    SCSIRAID Active Member

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    Feb 2, 2003
    Vero Beach, FL
    Couple questions....

    1) Who is your provider? Fios? Cable?
    2) Can you describe how your signal distributed... i.e. exactly what is between the source (ont or cable entring the house) and the Tivo
     
  8. AbMagFab

    AbMagFab What happened, TiVo?

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    Feb 5, 2001
    See multiple other threads on this issue.

    For FIOS, a possible fix (it worked for me and a couple others) is to attenuate your signal down to 31/32 SNR (no more than that). Your signal strength will drop to 60/70, but that's okay.

    I was getting severe pixelation within a few minutes before, and now that I've attenuated my signal down, it's been fixed for a week.

    Now, I only see the RS numbers go up at the beginning of a show, which appears to be when it's changing channels, and only for a brief second or less. So on the diag screen now, I see a couple thousand corrected, and a few hundred uncorrected, but it doesn't go up after the initial channel change.

    Try attentuating your signal down on one of the THD's and see if the problem goes away. I had to attenuate -11db to get to 31/32 SNR. At 33 SNR, I was still seeing the pixelation/macroblocking, so I needed to get down to 31/32.
     
  9. JANNINO

    JANNINO New Member

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    Oct 27, 2004
    SCSIRAID

    I have Verizon Fios TV. The line comes into the house from the ONT to an 8 way splitter (not sure if there is an interim stop in the house). Then there is a home run shot to every TV/router in the house (i.e. 5 TVs, and 1 PC). The coax cable to the TV having the issue is RG6 quad shielded and I installed it 4 years ago (i.e. I don't believe the issue is the cable itself).

    AbMagFab

    Where can you get these "attentuators" from? Radio Shack perhaps? It looks liek they come in different ranges. From what I've read, I should try to attentuate down 5-7 dbs from my 36-38 range to 31 db.
     
  10. mazman

    mazman Member

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    Nov 13, 2002
    Alamo, CA
    Is the RS Uncorrected changing on both tuners? I had an issue with only one of the tuners. After spending much time & effort trying to get a better signal, TiVo RMA'd the box for me and now things are fine.
     
  11. SCSIRAID

    SCSIRAID Active Member

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    Vero Beach, FL
    Those are different 'db's'. The attenuators reduce the signal strength which should in turn reduce the SNR. Not a 1:1 relationship. The Tivo doesnt provide actual signal strength measurements (in dbmv).

    Hey AMF... I recall that Fios has a hot signal but cant remember whether its +10 or +20 dbmv.... do you remember? The 8 way will drop 11db which still is very hot if the ont output is +20. Probably want an extra 10 over that. What did you end up with?
     
  12. SCSIRAID

    SCSIRAID Active Member

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    http://cgi.ebay.com/Brand-New-3db-A...ryZ73384QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
     
  13. litkaj

    litkaj Member

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    Jun 5, 2007
    Exton, PA
    It depends on which ONT you have. I believe the older 610 was +20 or +25 and the newer 612 is supposed to be about +10.
     
  14. SCSIRAID

    SCSIRAID Active Member

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    Vero Beach, FL
    +10 with an 8 way should be right on what is typically good... -1dbm.

    However, +20 or +25 with an 8 way would still be hot hot hot..... too hot... by about 10 db.
     
  15. bkdtv

    bkdtv New Member

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    DC Metro Area
    The 610 and the 612 are the most widely deployed FiOS ONTs, but there are a few other less commonly deployed models, each with varying levels of output. That's one of the reasons this issue affects some customers and not others in the same local area.

    FiOS customers with some ONT installations may require one or two attenuators to get a pixelization-free signal on their Tivo, while others may require none at all.
     
  16. JANNINO

    JANNINO New Member

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    Oct 27, 2004
    AMF

    Can you put on more than one attenuator to get to the level you desire (i.e. can you put a 3db and a 6 db to get 9db in total)?
     
  17. hooper

    hooper Member

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    Sep 22, 2007
    Jannino has a moca setup, which I believe assumes a 612 ONT, no? If so the signal is at +10 before the splitter and around zero after the 8-way.

    Either way, it is worth having VZ out to measure the signal. Ask the tech for some attenuators even if the signal is OK. They are good to have for troubelshooting.
     
  18. JANNINO

    JANNINO New Member

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    Oct 27, 2004
    What would be the ideal signal strength as measured by:

    1) the Verizon tech?
    2) the Tivo diagnostic screen?

    My tivos are running around 36 to 38 dB as measured by the diagonstic screen but it appears that from prior responses I should be no lower than 31 db as measured by the diagnostic screen.
     
  19. SCSIRAID

    SCSIRAID Active Member

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    Feb 2, 2003
    Vero Beach, FL
    The 36-38 is NOT a signal strength.... its a Signal to Noise Ratio. Tivo doesnt provide an actual 'measurement' but more of a 'merit figure' for signal strength.

    'Ideal' signal strength is probably around 0dbmv but from what I have learned about Fios... it defies 'ideals'.

    As to SNR, conventional thinking is that QAM 256 should be in the 34-35 db range. However, that doesnt seem to hold for Fios as evidenced by quite a few folks that have bad results at that level (due to reasons unknown).
     

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