Digital Channels Become Corrupt - TV Requires Power Cycle

 

Bronze Member
Username: Magredc5

Southern New Hampshire

Post Number: 15
Registered: Jan-06
I've been battling this problem since I got the TV and hope someone can review some of this data and hopefully point me to possible causes. I'm working with my TV Tech Support (Toshiba) and Cable Company (Comcast using a CableCARD) and both are working with me to help solve this but the question is still where's the issue.

My TV is fine for several weeks then all of a sudden all digital channels with Copy Protection Enabled (Both SD and HD) become corrupt. It's not only tiling but smearing and what looks like scrambling from what I've read on Copy Protection specs. The SD are only mildly corrupt and the HD are severe. This problem will remain until I power cycle the TV then all is fine for another 2-5 weeks until it happens again. I'm attaching a picture of an HD channel with severe corruption.

I've sent screenshots of the TV diags during normal good operation and during corruption to Toshiba's Tech Support but can anyone comment on these:

FAT Modulation Mode: 256QAM
FAT Signal State: Locked
FAT Signal Quality: 99
FAT SNR: 31.00 dB
FAT AGC: 56%
FAT Corrected Errors: 0
FAT Uncorrected Errors: 0

FDC Symbol Rate: 1024000
FDC Modulation Mode: QPSK Mode B
FDC Spectral Inversion: Off
FDC Signal State: Locked
FDC Signal Quality: 70
FDC SNR: 21.15 dB
FDC AGC: 72%

The issue seems to be that the Tuner S/W itself is the problem since there are no errors reported. Since the issue only affects channels with CP (I verify this via the TV's CableCard Menu). The CableCARD is a Motorola with the latest 4.21 F/W, and the TV is at the latest S/W version. My suspicion has been that something is affecting the CP scrambling key in the TV and it becomes out of sync causing the corruption. Toshiba is not aware of other similar issues so it does seem to be localized to something in either my area or TV. The other theory is that the tuner gets hit with some serious corrupted data stream causing it to fall over and not recover, but the diags don't show any errors.

Please let me know if you see any issues with the signal levels or have any ideas that may help.

Thanks,

John
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Silver Member
Username: Cableguy

Deep in the ... U.S.

Post Number: 856
Registered: Mar-05
From your data, it doesn't appear the TV detects any errors, as you have noted, which leads me to believe there is something wrong other then corrupted signal. If there was a problem with the signal you would see corrected and uncorrected errors, and your FAT SNR at 31 is a good level. Has Toshiba offered to replace the TV to see if that corrects the problems? Sadly we don't have Motorola cards where I work, and I haven't heard of anything like this with Toshiba customers. It is quite possible something in the tuner is on the fritz, but the tuner establishes the data shown and it didn't see anything to report. Wish there was something other to suggest.
 

Bronze Member
Username: Magredc5

Southern New Hampshire

Post Number: 17
Registered: Jan-06
Thanks Cableguy.

This has been a strange problem that has taken a while to get to a root of. You may recall that I posted this issue several months ago and until I was able to get some more detailed data it was a question of whether Comcast or Toshiba was the cause. I am now working with Toshiba Tech Support and getting some traction on this issue as a S/W problem in the tuner so I think we'll get to the bottom of it soon. I have heard from other Toshiba customers on the AVS forum that I am not an isolated incident but it's still not widespread.

I believe the issue is the way Comcast has implemented their Copy Protection scheme and must be occasionally changing the key used by CP in the cablecard while the TV uses the old key. Since the keys don't match the result is the "scrambled" picture.

At least now I feel more confident it's not a signal quality issue.

Thanks again.
 

Silver Member
Username: Cableguy

Deep in the ... U.S.

Post Number: 857
Registered: Mar-05
Keep us posted please, I'd like to know the outcome of this.
 

Bronze Member
Username: Magredc5

Southern New Hampshire

Post Number: 20
Registered: Jan-06
Just an update. I've been working with my Toshiba technical support prime and they've been in contact with Comcast to see if they can pinpoint the issue. Toshiba had me take some snapshots of some diag screens before and during the problem so they could see what the TV was doing. They confirmed that it wasn't a signal issue.

I haven't heard anything back for a couple of weeks about their interaction with Comcast but the interesting thing is the problem hasn't occurred for almost a month now (it was happening about every 2 weeks) and I'm wondering if they were able to find something in Comcast's side that gets sent down to the TV.

As soon as I hear the outcome I'll post the details.
 

Bronze Member
Username: Magredc5

Southern New Hampshire

Post Number: 21
Registered: Jan-06
Additional Info:

Toshiba prime said they're working on a similar issue with Comcast in Chicago (I'm in Boston area). They also indicated that a Sony is seeing the same issue in Chicago. Still don't have a root cause, but it does appear that some setting in the cable system is affecting the TV.

Cableguy: My understanding is that for CableCard there is management system used to administer the proper settings, i.e. security, Host/CC Pairing, etc. Is there anything in there related to Copy Protection settings? Would the security settings for CP change, i.e. scrambling keys? Could the STB data stream cause the CableCard to get confused due to some CP setting destined for STB? I'm convinced that some type of network update message is being send down to the CC and causing the Host/CC to get out of sync, and I believe there are separate "types" for CC and STB to distinguish which device should receive messages. Does this sound plausible?

Thanks.
 

Silver Member
Username: Cableguy

Somewhere on... U.S.

Post Number: 874
Registered: Mar-05
Magred~ "Is there anything in there related to Copy Protection settings?" No
"Would the security settings for CP change, i.e. scrambling keys?" No, even if the keys change, the card understands how to decrypt them...that is it's main purpose.
"Could the STB data stream cause the CableCard to get confused due to some CP setting destined for STB?" Absolutely not, I've seen cases where the STB was not scrambling but the card was, and that is related to the different chip sets each manufacturer uses.
"I'm convinced that some type of network update message is being send down to the CC and causing the Host/CC to get out of sync, and I believe there are separate "types" for CC and STB to distinguish which device should receive messages. Does this sound plausible?" Any network update message being sent to the CC would have to be falling within FCC specifications, and it doesn't differentiate between STB or CC, the same type of security measures are used for each as the same, in other words there is no special security for either.

Do you have any of the diagnostic screen shots that you took for Toshiba? If so could you post them here?

Thanks
 

Bronze Member
Username: Magredc5

Southern New Hampshire

Post Number: 22
Registered: Jan-06
Here are some of the screens - they're specific to the TV. Still waiting for Toshiba to get back to me.

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Bronze Member
Username: Magredc5

Southern New Hampshire

Post Number: 23
Registered: Jan-06
Cableguy:

Toshiba is still working this issue and are somewhat stumped. As I mentioned they have one other customer in Chicago with the same issue. They believe Comcast is sending something invalid to the TV.

Maybe you can shed some light on something I'm noticing. During my latest incident last week after I power reset the TV, I noticed that the channel map downloaded to the Cablecard had some changes including some bogus channels in the 2000-3000 range. There were 4 total around 2238, 3000, etc. If I tried to tune to these channels the TV did not recognize them and ignored the input as if they were invalid. This is different behavior from say a premium channel that's in my channel list that I am not authorized to view where if I tune to that channel (i.e. 400 HBO) the TV tunes to it but I only get a black screen.

Would those high order channels be used for some specific purpose? I know their on-demand PPV channels are from 1000 to maybe 1200, so these 2000+ channels appear to be bogus and possibly outside a valid range. This is not the first time that I've noticed the 3000 channel.

2 days later I had the corruption issue again and after that power reset those 2000+ channels were no longer in the new channel list. Maybe when those channels get added/removed it results in the problem due to some out-of-range type issue.

Just a thought. If you have any insight please let me know.

Thanks.
 

New member
Username: Yankee_in_sc

Pawleys Island, SC Georgetwon

Post Number: 9
Registered: May-05
Hi Cableguy; In another thread you had suggested that "Your cable provider should have somebody with a QAM analyzer that can connect in at your house and determine how clean the QAM signal is there.
As for the channel map changing on you, I would ask your provider if they are hiding and un-hiding channels around those dates. It's not uncommon for systems to do that, but as to the regularity of it, it seems kind of odd. My opinion is either they are changing the line-up or there is a problem with the DCM (defined channel map) in your system and can only be answered by their master control."

I have provided this to the local TWC office but they still cannot find the problems. Any help you could provide would be great.

There is intermittent tiling on channels 193 to 197 (all QAM 609). Errors appear on the Diagnostics screen and occasionally unlocks. TWC agrees that all readings are within acceptable levels. Then, TWC swapped out the CableCard a week ago. That has resulted in no improvement.

That card swap has now caused another problem. There is constant severe tiling on the channels listed below that did not exist prior to the card swap. Unlike the above problem though, no errors appear on the Diagnostics screen. Additionally, the severe tiling appears to be effected by audio, the more voices, the more tiling. Temperature and/or time of day also seem to be a factor. The tiling occurs as early as 7:30 AM but, goes away later in the day, 9:30 PM yesterday, 4:15 PM today..

Below are the channels effected by this latest condition.
Chan / QAM
127 / 633
140 / 681
159 663
169 / 609 - also shows errors on the Diagnostics screen (original problem)
368 / 681

I independently made sure there is not any problem with the cable inside the house (there are dedicated cables to the TV (CC) and the STB. A new RG6 cable with digital connectors was connected to block on the house outside and also connected directly to the TV. That test did not result in any positive or negative change to the conditions noted above.

As far as hiding and unhiding channels, the occurrence of that has at least been reduced. TWC has admitted that they are moving QAM frequencies around but, they are saying that the problem will not go away until they are done.

None of these problems occur when using the STB. Please comment. Thanks,
 

Bronze Member
Username: Magredc5

Southern New Hampshire

Post Number: 24
Registered: Jan-06
Update: Toshiba asked me to monitor the diag screens for some specific CableCARD counter, namely PMT Tables, to see if it changes significantly when the problem occurs. I've been tracking these counters almost daily for the past month and they've all been rising linearly with no significant jump.

The problem occurred last night so I followed Toshiba's request to check the diag data and still no significant jumps. They asked me to try something different to reset the issue and it worked.

I went into the Setup/CableCARD menu/Network Setup and they asked me to hit the HUNT link. The screen changed to HUNTING FOR NETWORK DATA" but after a few minutes there was still no change, so I hit the EXIT link. When I did this, the CableCARD lost connectivity to the network as if it reset, then reacquired within a minute. After it did that, the corruption problem was gone - at least it beats crawling behind the TV and pulling the power cord to reset.

Toshiba will review the data I send and see if they see anything interesting. But we are making progress.
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