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Tivo HD Pixelation Troubleshooting

Discussion in 'TiVo Series3 HDTV DVRs' started by Chimpware, Aug 3, 2007.

  1. Jan 1, 2008 #461 of 1597
    ckgoodwin

    ckgoodwin Remember

    38
    0
    Jul 2, 2001
    San Jose,...
    Thanks for the reply. I will have to check on the cabling scheme. My dad's house is actually about 3000 miles away on the east coast, but I am sure there is at least one splitter, since I know he's feeding at least 4 locations (and one is very long run out to a detached garage).

    We had not checked the RS errors yet - I will ask him to do that next. What error rates are acceptable?

    - Chris
     
  2. Jan 1, 2008 #462 of 1597
    SCSIRAID

    SCSIRAID Active Member

    2,321
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    Feb 2, 2003
    Vero Beach, FL
    RS Uncorrected should be a very low rate.... they come in bursts though. I would expect none over an hour or so.
     
  3. Jan 1, 2008 #463 of 1597
    ckgoodwin

    ckgoodwin Remember

    38
    0
    Jul 2, 2001
    San Jose,...
    Ok, I checked back with my Dad and he's currently seeing zero RS errors - even on channels with signal strength 50 and SNR of 30.

    He also clarified that although he has seen some pixelation/macro-blocking, his most recent issue was a blank screen (with sound) when tuning into the Cotton bowl today. Following the blank screen on that channel - he lost video on all channels and finally had to reboot.

    Any other thoughts?

    Thanks,

    - Chris
     
  4. Jan 1, 2008 #464 of 1597
    SCSIRAID

    SCSIRAID Active Member

    2,321
    0
    Feb 2, 2003
    Vero Beach, FL
    There are several threads on 'black screen'. I believe Pony even confirmed that a fix is being worked (IIRC).

    Signal and SNR is low.... I would get the cableco to check it out. If you split the incoming cable too many times you will perhaps need a distribution amp where the cable comes into the building. Splitters are bad mojo and should be avoided in favor of homerunning to a central distribution point.
     
  5. Jan 2, 2008 #465 of 1597
    richsadams

    richsadams Active Member

    8,893
    2
    Jan 4, 2003
    You're right on the money...the cable signal is far too low. It should be in the 90+ range. Our Comcast signal runs between 95 and 100 on all channels on our Series3 and TiVo HD.

    TiVo is very sensitive to signal strength. If the coax cable is new/good quality (with good connectors) and there are no splitters or attenuators between the cable connection at the wall and your dad's TiVo, Comcast needs to pay a visit. If the coax is questionable try replacing it. If there is anything in between (splitter, amp, etc.) try removing it to see how it affects the signal. If everything looks okay have Comcast roll a truck to check things out and have them bring a couple of new cable cards just in case.

    When the Comcast tech arrives you'll need to be sure that they don't cause problems by making the signal too hot either as it can cause macroblocking (pixelation) as well.

    IIRC the recommend signal strength should be -10 to +10 dBmV (as measured with their diagnostic equipment) with a SNR of 31-32. The tech should be putting a device on the line at the TiVo connection point to measure the signal.

    Let us know how it goes. :up:
     
  6. Jan 2, 2008 #466 of 1597
    bcwaller

    bcwaller New Member

    61
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    Nov 5, 2007
    I just ordered a selection of attenuators and terminators. I may have one or two open ports somewhere, and at 45 cents each I figured I'd buy 5 in case I lose a few. I'll update when they arrive to see if this fixes my intermittent pixelation issue.
     
  7. Jan 3, 2008 #467 of 1597
    esb1981

    esb1981 New Member

    121
    0
    Dec 2, 2007
    Connecticut
    Hello all, thanks for all the great insight in this thread.

    Does anyone know why I might have pixelation on just two channels that are coming in at frequencies of 645mhz and 661mhz? I had a hot signal from Cox, and attenuated it down 7.5 db with a 3-way split and 6 db with an attenuator. This noticeably helped, but did not clear up the problem completely. Cox measured it yesterday at +3db at "channel 2" and -6db at "higher" frequencies. The Cox tech told me I should take out my -6db attenuator and replace with a -3db, but that made it worse.

    The Tivo Diagnostics shows channels with frequencies up around 800 to have signal strength of about 68% and SNR in the low-30's, and I haven't seen any RS Uncorrected errors. The lower frequency channels in the 500's show signal strength of 87% to 93%, SNR in the mid-30's, and no problems. But 645 and 661 are still giving me occasional pixelation and spiking RS Uncorrected errors, though not as often before I started attenuating.

    I'm really baffled. I fear that if I attenuate the signal further then the high-frequency channels will start to have problems since I am already at a pretty low signal strength there. Why would this happen at 645 and 661? Any thoughts are appreciated...
     
  8. Jan 4, 2008 #468 of 1597
    agoldberg

    agoldberg New Member

    10
    0
    Jan 17, 2003
    Queen Creek, Az
    I am having problems with only certain channels. The HD channels are fine, but some of the digital get pixel hiccups.

    Some of the channels that I see problems with are:

    Food Network, Signal strength-54, SNR-28dB, RS Uncorrected-0, RS Corrected-2422
    Nick, Signal strength-77, SNR-32dB, RS Uncorrected-0, RS Corrected-0
    Disney, Signal strength-72, SNR-32dB, RS Uncorrected-0, RS Corrected-34

    I have the Cox cabling going to a distribution panel in my bedroom closet. The feed goes into a SV4G Splitter, labeled 5/1000MHz. The splitter has 1-input and 4-outputs. The main feed goes into a port labeled 7dB, not IN. I switched the feed to the IN port and lost my connection on the cable modem. When I put the feed back on the 7dB, the modem connection came back.

    Are there any suggestion on what I can do to help with the signal strength? Cox wants to charge me if they don't find anything wrong, so I want to try what I can before calling them. Any suggestions would be appreciated...
     
  9. Jan 5, 2008 #469 of 1597
    esb1981

    esb1981 New Member

    121
    0
    Dec 2, 2007
    Connecticut
    You may have the opposite problem as I do - with the 4-way split and no amplifier your signal might be too weak. SNR of 28db is pretty low. When I have pixelation problems my RS Uncorrected errors spike, so I'm not sure why yours are at 0. I wouldn't put much faith in Cox -- they've been out 3 times to my place and can't fix the problem.
     
  10. Jan 6, 2008 #470 of 1597
    esb1981

    esb1981 New Member

    121
    0
    Dec 2, 2007
    Connecticut
    Anyone have any thoughts on my pixellation issues? It's happening on both tuners/cablecards, happening with an attenuated signal and a boosted signal, Cox can't figure it out, and Tivo says it's Cox's fault.
     
  11. Jan 6, 2008 #471 of 1597
    agoldberg

    agoldberg New Member

    10
    0
    Jan 17, 2003
    Queen Creek, Az
    The reason that the uncorrected is 0, is because I had just changed the channel before looking at the diagnostic data.
     
  12. Jan 8, 2008 #472 of 1597
    tivoROCKSme

    tivoROCKSme New Member

    103
    0
    Jun 23, 2003
    Just posting to share the excitement of the arrival of my new TivoHD yesterday. I have it hooked up OTA but cable guy is coming Friday.
    Thanks to RichAdams for the post with IIRC signal strength and SNR specs. I'll be asking the tech to test to hopefully identify issues before he leaves.

    I was only able to watch an hour or so last night, and did notice a few video frame drop outs on the THD, but I'm not getting too concerned about it yet.

    I'm still reading feverishly trying to decide the future of this THD. My first task is to add my 1TB HD, but to hack or not to hack is the real question.

    So, I see that I can move recorded programs to my pc using TivoDesktop. Does that mean I can move them back to the Tivo later? Is it "moving" the files to the pc or just "copying" the files? Obviously I haven't actually used the software yet.

    Finally, why doesn't Tivo offer TWP or their flavor of it? Or do they and I'm just missing it?
    Sorry for the newbie type questions. It's my first SA and I'm like a kid in a candy store.
     
  13. Jan 8, 2008 #473 of 1597
    richsadams

    richsadams Active Member

    8,893
    2
    Jan 4, 2003
    Congrats on your new TiVo! :up:

    If you connected your antenna directly to your TV you'd see a glitch now and then w/HD broadcasts...that's the nature of the beast.

    If your comfortable with removing TiVo's hard drive and connecting it to your computer, you shouldn't have any problem upgrading using WinMFS. You can save the original drive as a backup (or in case you need to pop it back in for warranty service).

    Yes, TiVo Desktop will allow you to transfer (copy) recordings from TiVo to your PC and back again. With TiVo Desktop Plus you can convert them for other uses as well. You can also edit them and burn them to DVD’s using a program like Video ReDo TV Suite (works great by the way :up:).

    Not sure what TWA is. :confused:

    Enjoy! :)
     
  14. Jan 8, 2008 #474 of 1597
    tivoROCKSme

    tivoROCKSme New Member

    103
    0
    Jun 23, 2003
    Thanks Rich,
    Sorry, I meant TWP or TivoWebPlus. Is there any stock item like that available.
    Also, thanks much for letting me know about transfer and even burning!! What about movies? Surely they're not going to let me copy and burn a movie are they?

    I'm definintely comfortable and plan to use the WinMFS method. I'm debating the whole PROM mod thingy. I enjoy hacking and all, but not sure if it's worth it with all the built in tools, especially if you tell me I can burn my movies!
     
  15. Jan 9, 2008 #475 of 1597
    richsadams

    richsadams Active Member

    8,893
    2
    Jan 4, 2003
    Being able to transfer and/or burn any recording depends on your local network or cableco which in turn is at the mercy of the property owners (studios, etc.). Some have no restrictions, others allow one copy to be made and others won’t allow you to transfer the recording at all. For instance, here's a screen shot showing a movie my wife recorded which is copy protected and cannot be transferred.

    [​IMG]

    (Pity what else we have to watch because the studios won't give the writers their few cents. :mad: At least "Corner Gas" is pretty funny. :up:)

    Long answer longer, yes, there are many programs including movies which you can transfer and burn. The bottom line is that the quality won't be as good as the original due to transcoding by TiVo Desktop, etc. Nothing will equal the original HD or of course a DVD, but for keeping some of your favorites, the quality is really quite good.

    Guess I'm not keeping up because I'm not sure what PROM Mod means or what "TiVo Web Plus" might be or do.
     
  16. Jan 9, 2008 #476 of 1597
    lrhorer

    lrhorer Active Member

    6,924
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    Aug 31, 2003
    San...
    What a massive load of horse pookey! CATV amplifiers aren't under any "strain". The number of people watching is totally irrelevant to the quality of the signal. The load on the amplifier output is always dead on 75 ohms.

    A "leak" (properly known as ingress) can sometimes cause problems, and it's even within the realm of possibility temperature changes - which of course tend to track the day / night timeline - could cause a mechanical defect in the cable to grow and shrink in effective aperture, but almost all CATV systems put their digital signals up above 450MHz, and there aren't many other high powered broadcast services in that band to muck up the digital streams. If it did, you would see the effect on a very specific set of channels of no more than perhaps 12 SD channels or else perhaps 2 HD channels and 1 SD channel. In the event, occasional pixelization is unlikely. It's much more likely the channels would be totally trashed. You would also almost surely see interference (probably beats or ghosts) on whatever analog channels are the same frequency as your local broadcast channels. The local off-air channels are generally considered "impaired", and most CATV providers do not put the local broadcast channels on the same channel on cable. Thus, my local broadcast channels are 4 (NBC), 5 (CBS), 9 (PBS), 12 (ABC), UHF 29 (FOX). and UHF 35 (FOX). Of these, only channel 29 (561.25MHz) and 35 (597.25MHz) are in the band used for digital programming. My local CATV provider (TWC) puts CW TV on 4, CBS on 5 (the local CBS affiliate, KENS quite foolishly demanded TWC put them on the same channel as their off-air broadcast. TWC made them sign a contract in writing to the effect they would never change their mind and moved them from 6 to 5 as requested. Four hours later, the KENS station manager was calling TWC totally enraged, demanding they put him back. TWC's local GM just laughed and hung up on the station manager. They remain on channel 5, and are still sorry for it, more than 10 years later), Azteca America on 9, and TBS on 12. There's also an impaired region affecting channel 19, which is Telefutura. A crack in the cable will produce beats on these channels, usually either herringbone or venetian blind.
     
  17. Jan 9, 2008 #477 of 1597
    lrhorer

    lrhorer Active Member

    6,924
    0
    Aug 31, 2003
    San...
    No, he doesn't want to do this. Unless he has multiple outlets (more than 4), or has particularly long house drops (read that: a very big house), the CATV provider is responsible for delivering a high quality signal to the back of his tuner, in this case a TiVo. If the signals are low, it's the CATV provider's problem, not his, and adding a house amplifier is never the solution unless the aforementioned caveats apply. Even in that case, many CATV providers will supply an amplifier free of charge. They did for me, because I have 9 outlets, a large house, and it's a good little way from the eve of my house to the subscriber tap on the pole.
     
  18. Jan 9, 2008 #478 of 1597
    lrhorer

    lrhorer Active Member

    6,924
    0
    Aug 31, 2003
    San...
    PROM mods are at best marginally on topic on this web site and definitely off-topic on the Series 3 forum. TWP is a truly fabulous 3rd party utility which allows tremendous control of the TiVo, but requires the Tivo to be hacked. Both are better topics for a different website than this.
     
  19. Jan 9, 2008 #479 of 1597
    lrhorer

    lrhorer Active Member

    6,924
    0
    Aug 31, 2003
    San...
    This is incorrect. The input must be on the IN port.

    On which port is the Cable Modem? At a guess, I would say the levels to your Cable Modem are too high. Ordinarily most CATV systems run their DOCSIS carriers at such a level that a DC9 or DC12 directional coupler is inserted into the line in order to feed the Modem. A DC9 has a tap loss of 9 dB and a through loss of just under 1dB. A DC12 has a tap loss 12 dB and a through loss of just under 1/3 dB. If the Cable Modem and the input cable are both plugged in to OUT ports on the splitter, then this is almost certainly the case. Port - port isolation on most 4-way splitters is usually better than 20dB.

    Well, first of all, this is just a splitter, right, not a 4-way amplifier? Assuming so, first the plug the cable input into the IN port of the splitter. Then take a regular old TV set and plug it into each of the four outputs in turn. Check several of the lowest channels and several of the highest channels your set will receive. (Note: channels 7 - 21 are not high channels. They are in the mid-band, between channels 6 and 7 in frequency.) The picture quality should look precisely the same on all four outputs. If not, replace the splitter. Next, plug everything back into the splitter, including the CableModem. If everything else works, but it does not, try swapping ports with another device one at a time until you have tried the Cable Modem on all four ports. It's possible the 5 - 45 MHz region could be bad on one or more likely two of the ports. This would cause the Cable Modem to fail, but wouldn't impact pictures. If it still doesn't work, try obtaining an attenuator of about 5 dB and putting it in-line with the CabeModem. You can rig a makeshift attenuator by taking another 4-way splitter and terminating 3 of the output ports.
     
  20. Jan 9, 2008 #480 of 1597
    lrhorer

    lrhorer Active Member

    6,924
    0
    Aug 31, 2003
    San...
    There could be a lot of reasons, but since the problem is very specific to those two streams, it might well indeed be ingress. Check to make sure all of your connections are tight. They should be tightened snugly with a small wrench, not with the fingers. Don't over-tighten, though! Make sure all the cables are tightly crimped. You should be able to supply a very hefty pull to the connector with your fingers without it coming off the end of the cable. Take note of the channel assignments of whatever local VHF Broadcast stations are in your area and look closely at those same channels on your TV without an STB or DVR. Are there beats in the picture? (Note, I don't mean look at ABC, CBS, NBC, etc on your TV. I mean if ABC broadcasts on channel 7 in your area, then look at channel 7 on your TV, irrespective of what station is being broadcast on channel 7 on your CATV system.)
     

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