Very bad pixellation. Post-Viterbi errors huge. Need urgent help.

Forums › TiVo › Very bad pixellation. Post-Viterbi errors huge. Need urgent help.

need2noy

43 posts

Geek

#154489 29-Oct-2014 17:58

Had a look at http://help.spark.co.nz/app/answers/detail/a_id/5113/~/pixelated-or-scrambled-tivo-picture to get some answers to the bad pixellation I have been experiencing. Have really been noticing it over the last couple of months but it has built up really bad now which is making watching tv through my tivos unbearable. I have 5 tivos and they are all doing the same thing but I don't think it's a tivo fault because I would find it really hard to believe that my 5 tivos all decided to pack up at the same time with the same problem. I really think the problem lies with the tv signals pathways coming in from my aerial and all my tivos are having an issue with it for some unknown reason even though my 55in LG LED tv has no problems at all with reception which is connected to the same aerial.

I am based on the North Shore Auckland. I moved to where I am now 3yrs ago and the existing aerial wouldn't give any reception at all so I got an aerial technician to install a new outdoor aerial. At first the aerial was pointing eastward towards (Pinehill?) but the pixellation was very severe. Got the technician back and he turned it around westward towards (Waiatarua?) facing Waitakere. From the get go I did get the odd pixellation but not enough to be really bothersome like what I'm experiencing now.

I also like to point out that I get duplicate channels of every channel and tivo has already checked only one box to each of the duplicate channels. I believe this is caused by the aerial picking up channels from more than one transmitter and they are call 'shadow channels'. I wonder if this is also playing a part in causing pixellations?? I've tried all the channels, even the duplicate ones, checking and unchecking to no avail.

For example the following is a typical readout for a few sample channels from the Media Device Diagnostics:

TV1 - MER = (Fluctuates between 130 to 205), Pre-Viterbi errors = (Heaps), Post-Viterbi erros = (Lots)
TV2 - Same as TV1

TV3 - MER = (Averaging about 280), Pre-viterbi errors = (Lots), Post-Viterbi errors = 0 (Zero)
TV4 - Same as TV3

Of note, TV3 & 4 don't seem to have the same problems with the Post-Viterbi errors as TV1 & 2. Why is that??

The average Signal Quality with all the channels fluctuates between the 70's through to the 90's.

I know that the Post-Viterbi errors should be zero or very close to zero so yesterday I thought I would do some experiments. Because my tv gets excellent reception I thought there must be a problem from the tivo's original RF cables so on one of my tivos I replace it with new RF cable then did a channel scan and to my surprise on all the channels the Post-Viterbi errors were all reading zero. So I replaced all of the RF cables on my other tivos and channel scanned them and of cause the Post-Viterbi errors were also reading zero for them as well. I was elated, I really thought I had fixed the problems.

To my horror the next morning all of the tivos were pixellating again, some worse than others. On lots of channels which were reading zero Post-Viterbi errors were now showing up heaps. The tivos must do auto scans as they did give me messages saying there has been a line-up change. It appears the tivos automatically undone all my good and expensive work I did yesterday. I tried rescanning again but to no avail, the pixillation is even worse.

I re-put my thinking cap on again and I've come up with hopefully possible solutions , but I could be way off track. They are, should I get a new aerial even though my tv has no problems with reception. Though I can't get up onto the roof to get a better look at the aerial, from the ground it looks in very good condition, it's still facing the same way, so it hasn't moved, the cable coming out from it looks to be intact. Or because it's just the tivos that are having the problems should I get TV Signal Booster device to give the tivos a stronger signal. I don't know what's going on, or what to to do. I'm at my wits end. Help!!!

Skolink

1081 posts

Uber Geek

#1164944 30-Oct-2014 12:01

Sounds similar to the problems I have had in the past
http://www.geekzone.co.nz/forums.asp?forumid=83&topicid=113406

No reception problems this year (so far). I still have the 6-way splitter in the roof bypassed, with only a 2-way splitter between the TiVos. TV isn't connected to aerial.

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need2noy

43 posts

Geek

#1164979 30-Oct-2014 12:50

I think I have managed to solve my pixellation problems. The pixellation was related to the tv signals that the tivos were picking up from the aerial and in part the shadows channels weren't helping.

What I did, was that I found it was better to do a channel rescan in the evening as there was less interference than during the day. I manage to get the Post-Viterbi errors back to zero or very close to zero on all my tivos. I realized it makes no difference just by checking the channels I want because the tivos are always automatically scanning the channels all the time and it just upsets everyrthing because of all the duplicate channels etc. So this time I gave all the channels that I received that had no Post-Viterbi errors the green thumbs up.

Today so far, I have had no problems of pixellation whatsoever. The channel list still shows my channels with the thumbs up, even though it still shows the duplicate 'shadow channels' even though I had deleted them last night, obviously tivo did an automatic scan and put them back on, but luckily they are not checked because they all have weaker frequencies.

My only logical reason why I think this has worked is because Tivo regonizes the green thumbs up channels as my favourites and is leaving them well alone, which means these channels are locked in and tivo just ignores them when it does it channel scans.

I reckon what was happening was that the tivos were getting confused with all channels including the duplicate ones and the tivos were checking some channels that had the weaker frequencies as the main channels to be kept. I unchecked those weaker ones and checked only the channels that had the stronger frequencies and greeen thumbs up on them.

It appears the tivos are no longer confused and I am very happy. I will keep my fingers cross and hope that this is a long term fix.

need2noy

43 posts

Geek

#1164985 30-Oct-2014 13:00

Hi Skolink, Just got your reply which must've come through when I was updating my situation. I feel as if I may have solved the problem. If the channels you receive have no problems at all it's best to give them the green thumbs up in the channels list. I also use splitters for all my tivos but I knew that wasn't the problem as I had tested all my tivos out one by one directly to the aerial, bypassing the splitters altogether and I still got pixellations. I knew it had to do with the tv signals coming in from the aerial and the tivos were having really major issues with them. I'm hoping my solution works long term, only time will tell.