Hi Larry - thanks for chiming in. Just a couple of points...
Wrong forum: perhaps, but I've always felt it was more important to have all pertinent information in a single place whenever possible. Showing that this impacts more than one person, at various times, will hopefully point out that this is a larger problem. One that requires immediate attention. At this point, we're all better off if anyone having issues with TCM HD Channel 789 delivered via Comcast/Xfinity cable add to this particular thread. Power in numbers sort of thing.
Packet breakdown: Not exactly. The answer you passed on would also mean that other channels that I was meant to be receiving would have the same issues of being out of sync - since they'd all be coming across the same lines. That's not the case for me, or, as far as I can tell, anyone else on this thread. It's actually more likely the case that the HD feed from TCM to Comcast/Xfinity has gotten out of sync. (That's where the packets come into play). This idea is also reinforced via a post mentioned at the beginning of this thread (see: DavidST's post dtd 08 June 2017 - 11:15 AM). My internet speeds slow down when everyone in the neighborhood is home at night/on the weekends using the internet - this is the outdated wiring and technology you refer to, the 'last mile' as it's usually known. However, I don't encounter any problems with my tv channel reception when the internet slow down happens. (And for what it's worth, being a former network engineer in a past life, the first thing I do is troubleshoot anything and everything I have access to, going all the way out to the street, just to ensure the problem isn't on my end. Force of habit.)
But, happy to have you try and further the conversation. The more comments, the more people read it, the better chance of someone actually doing something about it. So THANKS!
That was me. It looks like they lost my post. The correct answer for all combined situations of course would be "any of the above".
In my post I was addressing the throughput differences between various local cable nodes due to congestion at their plants. Also I mentioned the differences in packet loss/recovery between IP streaming and the full TCP/IP stack.
On "packet breakdown", it's not a question of "if", but "where". Also I wouldn't automatically assume that the public Internet and internal cable service networks are that closely intertwined. I wouldn't be surprised if it all came together at the plant just before the "last mile". Also, the channel-to-channel audio offsets can take some time to develop. I have seen it on other low-tier channels. AMC and History channel for instance. So for me it didn't only happen with TCM.
A few years ago I looked into this very carefully. I did my own research, scoured the Internet, read what many people were saying, and even drew some of my own conclusions based on prior work.
Here is a diagram and article for those following. The SDV (switched digital video) cable system sends blocks of channels for the upper channels, and is expected to eventually be migrated to include all channels (if not already). If you have other channels that this never happens on, then those may not actually be using SDV
I had more info handy on this at one time, but it is obscure so I'd have to dig around to see where I put it. So the rest is from memory.
There is a two-way exchange that happens when the customer is changing channels, and the cable box or DVR switches from one block of channels to another. The cable box tells the cable plant to send a different block of channels to its address. Back when I had cable and had this synch issue, one of the sure ways to clear it up was to change channels until there was a longer delay in changing to the next channel (changeover to next SDV block). Then I would go back to the block TCM was on (another delay) and then back to TCM (no delay). Problem resolved, for a while at least.
While I am on this topic, another issue I had was that the signal to my TV would just randomly shut off. I looked into this and treated it as a separate issue. It turned out that the cable plant expects to see a "heartbeat" type of signal from the cable box or DVR, indicating that it is still in use. If for any reason it missed it, then it would decide that the cable box was no longer turned on or in use, and it would free it up for reallocation somewhere else. Hence a blank screen.
After about six months of stewing over these two issues, and after I had exhausted all resources with service calls (including a line change in my yard, new wire and junctions in the house, equipment exchanges), I had nowhere to turn. Also our neighborhood friends had mentioned similar issues in passing. So I went from TW cable to satellite (Directv). Three years later and I have no longer had any such recurring issues as stated. Almost always I am the guy in these threads to say "I'm on satellite. No, it didn't happen to me this time".
It can happen sometimes with the satellite DVR though, as I sometimes record things independently of the DVR (at the same time) and then sometimes find audio offsets later on with the DVR recording that aren't in my own recording (made directly from the live real-time audio/video signals). So it generally just doesn't happen with live satellite for me, but can happen with DVR recordings.
Satellite isn't perfect though. There is the issue of rain or snow fade, which is rare in my case. I need a heavy rainfall or the dish needs to get fully covered in snow - in which case I just reach an extension pole out the window and gently knock it off. There are also tape heaters made for satellite dishes.
I did keep the cable Internet service though. Totally different beast. It worked fine, and I didn't want to commit for two years to an unknown. After seeing it at friends houses, I think though that the DSL service that comes bundled with Directv would probably have been just fine for my purposes.
Obviously there are occasional network-wide issues, but those are few and far between, and often confirmed as such between posters here (if we happen to get enough posters to respond). More often than not though there seem to be one-of-a-kind incidents among the posters, others see it fine, which indicates a more localized problem.
Hope some of that helps.