Comcast - interesting discovery

Matthew

Matthew

Touchdown! Greaser!
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Matthew
Now I know you'll all be trying this -

We have Comcast digital, with OnDemand. We just got a digital TV and are running the cable directly from the wall, instead of through the box (like we were doing with our older analog TV).

I did a channel scan, found all the local HD cannels, and have been playing around with it. I noticed that some of the channels that were found during the scan didn't have anything on them, just a blank signal. Last night I discovered that those blank channels were actually an OnDemand channel of some kind. I was flipping around the digital stations, trying to fiture out what was what and I came across one of those 'unknown' channels. I noticed the program was starting, stopping, rewinding, fast-forwarding, ..., exactly what you can do with the OnDemand service. I think I was watching one of my neighbors shows.

Imagine my surprise when I noticed it was a 'naughty' channel. Fortunately, Grandma and my kids had just left the room.

So, I deleted the channel and no, I didn't watch for another 20 minutes just to make sure,

So, anybody affiliated with Comcast - what happened?

Matt
 
You are, no doubt, now subject to prosecution for pirating an unauthorized digital stream. Write a check to RIAA for, say, $36,000.00, a rough approximation of the damages suffered by RIAA for you seeing boobies without paying the BVAF (Boob Visual Access Fee).
 
SCCutler said:
You are, no doubt, now subject to prosecution for pirating an unauthorized digital stream. Write a check to RIAA for, say, $36,000.00, a rough approximation of the damages suffered by RIAA for you seeing boobies without paying the BVAF (Boob Visual Access Fee).
Click to expand...

heh - I think my fine will have to be mulitplied several times. The rewind, replay took place more than once!
 
Matthew said:
heh - I think my fine will have to be mulitplied several times. The rewind, replay took place more than once!
Click to expand...

Were they re-watching, shall we say, a strategic moment? :D :dunno:
 
Well, in the time it took me to pick up the remote after I dropped it, then say 'D'oh!', then make sure my kids weren't watching, then change the channel, I can't say just how strategic it was. It must have been good, though because they rewound and replayed it.
 
It's been known for a while that the PPV channels are unencrypted (see Slate article). This is known as "clear QAM" reception -- QAM being the modulation scheme that cable companies have used for digital channels for quite some time and being transmitted "in the clear." It's only been recently that QAM receivers have been in HDTV's, so this has never been much of a problem as far as piracy goes.

Comcast will rebroadcast the local HD channels in the clear, but if you're buying an HD package from them for ESPN and such, you'll want to connect through their box, because those channels are encrypted.

-Rich
 
rpadula said:
Comcast will rebroadcast the local HD channels in the clear, but if you're buying an HD package from them for ESPN and such, you'll want to connect through their box, because those channels are encrypted.

-Rich
Click to expand...

That part I knew - I didn't realize until last night that the PPV channels were unencrypted. I guess I'll have to send grandma and the kids to bed early, then channel surf!
 
rpadula said:
Comcast will rebroadcast the local HD channels in the clear, but if you're buying an HD package from them for ESPN and such, you'll want to connect through their box, because those channels are encrypted.

-Rich
Click to expand...

That part I knew - I didn't realize until last night that the PPV channels were unencrypted. I guess I'll have to send grandma and the kids to bed early, then channel surf!

edit - I just read the Slate article - sounds like exactly what I found.
 
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What Rich said, combined with a request for you to report it to your local Comcast office. A tech can come and adjust the QAM levels at the local node, and keep this from happening. You blocked the one channel, but I assure you that there are more out there.
 
SkyHog said:
What Rich said, combined with a request for you to report it to your local Comcast office. A tech can come and adjust the QAM levels at the local node, and keep this from happening. You blocked the one channel, but I assure you that there are more out there.
Click to expand...

Blocking and Comcast are scary words together. I'd look for all of the QAM channels to start showing artifacts, but then I'm a pessimist.
 
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What's QAM?

With Charter, they show normal movies on all the movie channels until 11PM then about four of them to to soft porn. Contrary to what may be thought, I'm not interested. I wish there was a way to block them out on my favorites list for that type of movie but not block the channel at other times. I can block by content type but then the favorites function still goes that channel and requires a code to enter.
 
SkyHog said:
What Rich said, combined with a request for you to report it to your local Comcast office. A tech can come and adjust the QAM levels at the local node, and keep this from happening. You blocked the one channel, but I assure you that there are more out there.
Click to expand...

Yeah - I have the list of the 'standard' HD programs that are provided by my local Comcast, mainly the local stations. Things like ESPN-HD and Discovery-HD are scrambled and require the HD box so the channel scan skipped them. What it DID lock onto were about a dozen or so channels that had a clear signal, but were blank (nothing showing). I am assuming that those are the OnDemand channels that sometimes will have the 'bonus footage' appear without warning. I'll be going through and deleting anything other than the local stations.

I'll also forward that Slate article to some other folks.

As to KennyFlys question - What's QAM? I can't remember the acronym, but essentially its the decoder that takes the digital signal from the cable and decodes it for the TV. Back in the day, before TVs were cable ready you needed the decoder from a set-top box to convert the signal for the TV onto channel 3 or 4. Then TVs got the analog circuit built into them and could take the cable directly from the wall. Then the digital stations began showing up on cable and once again a set-top box was required and converte the signal into the TV channel 3 or 4. Newer TVs now have the QAM built-in so the set-top box isn't necessary anymore unless you have a premium channel like HBO or Cinemax. Apparently Comcast (and other companies) broadcasts some programs in-the-clear so the set-top box isn't required, as long as you know which channel to tune in.

Of course, I may be completely wrong.


edit - Oh yeah, you might look to see if your TV has a V-chip. If the porn stations are coded with something like TV-MA, the V-chip is supposed to block them out but will still let the shows you want come through without needing an unlock code.

Matt
 
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SkyHog said:
What Rich said, combined with a request for you to report it to your local Comcast office. A tech can come and adjust the QAM levels at the local node, and keep this from happening. You blocked the one channel, but I assure you that there are more out there.
Click to expand...

What on earth for? To screw up the neighborhood's ondemand service? Perhaps Matthew himself would like to use it for one of it's many other offered channels. Bad idea.

-Rich
 
rpadula said:
What on earth for? To screw up the neighborhood's ondemand service? Perhaps Matthew himself would like to use it for one of it's many other offered channels. Bad idea.

-Rich
Click to expand...

Neg. Usually, depending on the market, onDemand is transmitted via 256QAM, and the cable box actually grabs the content directly from a server located at the head end. If the content is displaying on a viewable channel, then something is wrong at that specific node. The content still comes through a specific channel (the one he's viewing), but it should be unviewable by anything but the specific cable box requesting it.
 
Last night I went ahead and deleted any unknown or questionable channels from the list. That leaves me with the local digital and HD stations and nothing more than I expected to get anyway. It was fun while it lasted. I'll probably just end up getting the HD box, we kind of got used to the info/menu/tv-guide/OnDemand services that our older non-hd box provided, also what good is having an HDTV without ESPN-HD?. Then the whole thing becomes a non-issue.

I'll let Comcast know about it, though.

Heh - I still chuckle when I think about my initial reaction!:hairraise:
 
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SkyHog said:
Neg. Usually, depending on the market, onDemand is transmitted via 256QAM,
Click to expand...

256-QAM merely means there are 256 symbols in the constellation, giving you 8 bits per symbol when decoded. The next step down in the US is 64-QAM (only 6 bits per symbol, but you get a better bit error rate for a given power).


SkyHog said:
and the cable box actually grabs the content directly from a server located at the head end. If the content is displaying on a viewable channel, then something is wrong at that specific node. The content still comes through a specific channel (the one he's viewing), but it should be unviewable by anything but the specific cable box requesting it.
Click to expand...

Most of that would be true if Matthew was using his cable box, but he was plugging the coax directly into his TV, which has a QAM tuner. Tune it to a valid QAM channel, and it'll decode a stream of bits. Whether those bits can be turned into a viewable program or not is the question.

Yes, a neighbor on Matthew's node must request an OnDemand program to turn on an unused channel, and as Mattew noted, most of them are dark. But, the program is sent unencrypted at the MPEG transport layer, so everyone on the node with a QAM tuner in their set can see it.

This is a limitation of the current on demand system. It's much easier to encrypt a program once that is being broadcast to everyone (i.e. ESPN). It is not a trivial task to encrypt (usually DES or triple-DES, with AES coming soon) dozens of unique channels that may be rewinding, pausing, etc. That's the kind of thing that needs to be done in real-time with specialized hardware.

Hope this shines some light on the situation.

-Rich
 
It's been a fun experience - the QAM tuner has been like using a metal detector on the beach. You'll never know what you'll find, it'll almost always be junk, but once in a while something very interesting turns up.

All the coding/scrambling issues kind of make sense, the main channels like ESPN-HD get scrambled at the source and unscrambled by the box, that way you have to rent the box, and the rest are secured in the sense that only the receiver knows when or where to grab the signal.

Sure was funny though - "Why are those people in fast-motion? Why are they taking off their clothes in fast motion? Why did it just slow down... wait, huh? Where are the kids? How do I stop this before my wife walks in and whacks me upside the head? Now what? Where'd I drop the remote? It's rewinding and starting again?"
 
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