Pixelation debugging - swap cablecards

Discussion in 'TiVo Series3 HDTV DVRs' started by rossman66, Sep 29, 2007.

  1. rossman66

    rossman66 New Member

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    Apr 30, 2005
    I am troubleshooting the dreaded pixelation issue on my S3. I've noticed today, while watching Texas football on ABC HD that one of my cablecards (card in slot 2) is working fine, while the card in slot 1 has constant pixelation. Both on ABC HD (channel 313 in Houston - Comcast).

    So my question is can I swap the cablecards, ie - move the card in slot 1 to slot 2 and vice versa? If I try this, I shouldn't have to call comcast to reinitialize the cards should I? Anyone else tried this with any success?

    My hope is to swap the cards and see if its the actual card that is causing the issue. Then run to the local Comcast store and swap it out for a new one. Any thoughts or suggestions welcome.

    Thanks,
    Mark
     
  2. cableguy763

    cableguy763 New Member

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    Oct 29, 2006
    Austin
    Why don't you try pulling the cards out altogether and see if the pixelization is occurring on in the clear qam?

    To answer your question, if you swap the cards comcast will have to repair them to the correct slot. Not a good idea.
     
  3. SCSIRAID

    SCSIRAID Active Member

    2,333
    1
    Feb 2, 2003
    Vero Beach, FL
    Question for ya... What would you view as an acceptable "QAM Corrected" rate? There is a huge difference between an SA Cablebox and a THD. The THD is even showing uncorrected blocks where the SA Cablebox has never shown any. SNR's are good on both.
     
  4. cableguy763

    cableguy763 New Member

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    Oct 29, 2006
    Austin
    If you know your city's ingress frequencies, tune each box to the same freq. Corrected bytes are not a bad thing, but too many will obviously show a problem. I would say 15-25 are okay for thirty-minutes to an hour. My box in the office has 8 corrected bytes after three hours of watching the same channel.

    S/N should ALWAYS be above 32. This number will go up or down a number, but anything below 30 will create uncorrect blocks/macroblocking. This number is especially helpful when tuned to an ingress channel because this is where S/N will be the lowest.

    As far as the numbers being drastically differnt between the tivo and the SA box, I would guess that the tivo tuner is MUCH more sensitive. Maybe defective. I know you have done extensive testing with your cableco. Do their meters match the SA box?
     
  5. jrm01

    jrm01 New Member

    2,619
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    Oct 17, 2003
    Pittsburgh
    Until Thursday I had virtually no pixalization issues with my S3 for over a year. Now it is horrendous. Four HD channels are unwatchable with macro blocking and freezing. One HD channel will not tune at all.

    Coincidence or not, that is the day that I was upgrade to software release 9.1. It also was the day that I added an external eSATA drive.

    On the bad channels the Signal Strength is 55-60 and the SNR is 28-30. Also, after 15 minutes of tuning the RS Uncorrected is 550,000 and the RS corrected is over 3 million. These numbers are usually very small (many times zero). Not sure what these numbers mean, but I assume it is some kind of error correction.

    This is happening on Live TV, so I don't think it is the e-SATA drive. It really seems to be a signal strength issue, but it seems strange that it happened at the same time as the software upgrade.

    I tried a 10 dB in-line amp, but that resulted in the loss of all HD channels (too strong?). So I threw in a two-way splitter to attenuate the signal, but not much change.

    Any suggestions?
     
  6. SCSIRAID

    SCSIRAID Active Member

    2,333
    1
    Feb 2, 2003
    Vero Beach, FL
    Can I assume that these measurements are taken on a QAM channel and NOT an OTA channel? I would pay more heed to the SNR.... and its too low. Should be 34 minimum. Has zero to do with eSATA....

    RS is Reed Solomon. Digital transmission systems incorporate a scheme called Forward Error Correction which uses Reed Solomon error correction codes.

    RS Corrected indicates that the QAM demodulator detected a block with an error in it and the RS code was able to correct the error. RS Uncorrected means the error was beyond the capability of the RS code to correct. An uncorrected block most likely will result in a pixelation or dropout event.

    Note that this has nothing to do with the cablecards.... they are 'downstream' from the QAM demodulator.
     
  7. SCSIRAID

    SCSIRAID Active Member

    2,333
    1
    Feb 2, 2003
    Vero Beach, FL
    Can you describe how your cable is wired in the house? Such as.... it enters the house and goes thru a 2 way splitter with one leg to cable modem and other to a whole house amp....... etc etc... Essentially what is between the Tivo and where the cable enters the house.

    Any amplification should generally be done where the cable enters the house.
     
  8. jrm01

    jrm01 New Member

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    Oct 17, 2003
    Pittsburgh
    Yes this is with cable and not OTA.

    I have one line entering the house and it is split numerous times to feed cable to five rooms (two lines to each room). When I installed the S3 one year ago I had signal strength issues and Comcast installed a 30 dB amp at the house entry point. That seemed to solve the problem and has been working for one year without problem. I even switched to Comcast phone four months ago and that did not cause any problems (I really thought it would).

    Right now my cable internet and phone are fine. The Tivo S2 in the bedroom is working fine. All other TVs (all SD, analog) are fine. I checked the mainline amp and it is working (I actually unplugged it to see what would happen and lost all signal on TiVo).

    Everything was fine for one year. The only change (both on Thursday) was the eSATA drive and 9.1 Software. Then all the problems started.

    I am in the process of a divorce (eSATA kind), TiVo is rebooting now. I can't believe that was the problem, but just trying to eliminate any other variables.
     
  9. jrm01

    jrm01 New Member

    2,619
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    Oct 17, 2003
    Pittsburgh
    Well the divorce is final. I lost all recording made since Thursday. This being a Community Property State I thought I would get half of them. :)

    However, not surprisingly the pixalation & macroblocking are still there. Just as bad.

    I really don't like to jump to conclusions that a software update could cause something like this, but that is the only noticible change to have happened on Thursday.

    edit: I just crawled down in the basement. The cable split after the amp feed 8 outlets in the house off of one leg. But the other leg just feeds two outlets, my TiVo S3 and the cable modem. It's been that way for one year.
     
  10. SCSIRAID

    SCSIRAID Active Member

    2,333
    1
    Feb 2, 2003
    Vero Beach, FL
    I kinda doubt that a software update would effect the FEC in the tuner/demod.... but I never say never.

    I would more likely suspect something changing at the cableco or your wiring. Did you have a weather change? Neighborhood construction?

    A 30db amp at house entry is a whopper unless you have a ton of splitters!! How many splitters and what type? How many between the amp and your tivo? Is it all rg6 quad shield coax? Compression or crimp F connectors?
     
  11. jrm01

    jrm01 New Member

    2,619
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    Oct 17, 2003
    Pittsburgh
    I agree that it would be an unusual effect for a software update, however...

    OK. I just traced everything from basement to TiVo.

    Mainline comes into the house and into Electroline 15 dB amp (not 30 dB as I prevously stated). Output is split with a two-way splitter, Aeronix (no mhz range listed). The one line coming to the living room is split with Regal splitter (one to modem, one to TV area). The TV Area line is split one more time (Extreme BDS102H splitter), one leg to TiVo, the other direct to TV (where I just checked QAM and ATSC channels and they are all fine). BTW, I experimented by removing this last split, but no help.

    Cable is RG6 (not sure of shielding). It is labled Greyfox CXBUS 6 Series 18 awg.

    I know this is a lot of splits (most were done when house was built), but once the amp was put in last year they all worked fine.
     
  12. SCSIRAID

    SCSIRAID Active Member

    2,333
    1
    Feb 2, 2003
    Vero Beach, FL
    The 'sequential' splits are really not correct. A large count splitter shoudl be placed at the amp with coax then run direct to each device. However, the three sequential 2 ways result in about 12 db of loss which pretty much offsets the amp which may be OK as long as they are 1Ghz splitters. The Electroline amp is good stuff.
     
  13. jrm01

    jrm01 New Member

    2,619
    0
    Oct 17, 2003
    Pittsburgh
    Well now. I forgot to mention one other connection in my cable path. Two months ago I installed a APC UPC and ran the coax thru this. I know some people say not to do this, but I felt safer and it has worked well for two months.

    I had the TiVo turned on to the diagnostic screen while I was tracing this coax. I noticed that when I grabbed the input connector the signal strength went from 57 to 85 on the bad channel! I tightened the connector and straightened out the cable and viola, my software problem was resolved. At least for now. I'll have to monitor.

    My theory is that it was the eSATA upgrade that caused the problem. Probably when I pulled the TiVo out to make the connection I tugged on the coax and did this.

    Think I'll give this 24 hours of operation before I try the e-SATA again.

    Thanks for getting me to crawl around on the floor.
     
  14. cableguy763

    cableguy763 New Member

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    Oct 29, 2006
    Austin
    ingress...good find
     
  15. rossman66

    rossman66 New Member

    17
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    Apr 30, 2005
    I have my cable split from the wall. One goes into my tivo and the other straight into my tv. When I noticed the pixelation on the local hd through tivo, I switched inputs on my tv to view the hd channels through qam. No problems, the signal was clear. I should have noted that before as it helped me confirm that it might be isolated to a single cablecard.

    However, while troubleshooting yesterday, a storm rolled through Houston. Both cablecards started having issues (albeit, CC2 was not nearly as bad as CC1) and viewing the qam channel, it also had noticeable pixelation/audio drops. So maybe Comcast doesnt like rain for some reason. Who knows.

    This is such a frustrating problem to have/troubleshoot. Thanks for the input though.

    -Mark




     

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