Digital TV answers
by gmclam - 3/2/09 7:53 AM
In Reply to: Digital box... by cruciatus
> OK, my mom went to the cable company and walked out with 3 digital boxes. Also called converter boxes. ...
> Well, we're worrying. I do understand that we're not OTA and this technically isn't about the digital transition. Anyway...the boxes they gave us are free (for the first 3). ...
> They sent out a letter earlier this year saying that they are going "all digital on April 1, 2009". So, "all digital" means we need this cable box/receiver/Zapper? They never even asked us whether we had digital-ready TVs or not. Just handed over the boxes. Mom tried to get more out of them but they didn't seem to understand it any more than anyone else. Also, we've never had any cable box or anything else before this.
I've found that the average worker at a cable company knows as little as the customers they are there to serve. So don't be surprised that they didn't understand your questions. As broadcasters move their over-the-air (OTA) signals to solely digital, and continue to increase the number of broadcasts in High Definition; cable companies are compelled to carry the HD signals. To make "room" for the HD signals (which take up more bandwidth on the cable) they are eliminating (old fashioned) analog signals. Depending on how much compression is used, a cable company can put 4 to 6 channels in the space of one analog signal.
In cable there are 3 basic aspects of TV signal reception; tuning the correct channel/frequency, demodulating the signal, and authenticating the user. For years cable used the same channels as OTA (2-13), but later added channels 14 and up, which are not the same as 14-83 used OTA. Then came digital where multiple "channels" are within the frequency space originally intended for one channel. Their "converter" handles tuning the correct frequency, determining the channel number, and then whether or not you are authorized to receive that channel.
> I see in your post you mentioned a digital tier. I guess I don't quite understand that. Does that mean that on digital cable some stations are, say, so far off range that my TV doesn't have the ability to receive them?
TVs vary quite a bit as to what they can receive/tune. Original cable ready TVs did nothing more than tune to cable channels 14-"99" (because 14-83 are different frequencies, users had to tell the TV whether you are receiving via antenna or cable). Later TVs came out with QAM tuners in them (in addition to NTSC tuners). When digital OTA was determined, then TVs also came out with ATSC tuners. An entirely different issue has to do with "CableCARDs" which some sets now also have that make authentication work (but not for TV guides and pay-per-view).
When cable started to send digital signals, they initially did it in a manner so as to no disrupt analog channels. At that time it was in fact a "higher" set of channels. But the term "tier" has more to do with how customers are billed - the basic tier, a 2nd tier, the highest tier, etc. It is essentially the 'grouping' of channels that are 'bundled' into a payment level.
> With my cable company, the digital lineup is different than the analog. Local stations are on different channels (which I don't understand--why does CBS have to be channel 9 for analog and channel 5 for digital?). And, obviously, the digital gets, literally, higher stations (100-119 for the basic digital). And if you wanted Digital Premium the stations go all the way up to 300.
Over-the-air, there is your original analog channel, and that was typically carried by the cable company "as is". Then the government loaned every OTA broadcaster with a 2nd channel so they could simultaneously broadcast digitally (ATSC). If a cable company wanted to carry that signal, it would be another channel. However, most will not carry the entire signal; as they strip out only the portions they want to carry and re-modulate the signal as QAM (ATSC uses 8VSB).
Another complexity to the OTA digital transition is the difference between logical channels and physical channels. If your CBS station was 5 analog, then they are known as 5.1, etc via digital. BUT their physical channel could be anywhere (such as channel 9). Cable makes it even more confusing.
> Is this the reason for the box?
Yes. Your cable company will stop broadcasting their signals via analog at some point. The tuners in most TVs will not be able to receive their digital signals AND CONVERTERS INTENDED FOR OTA WILL NOT WORK EITHER.
> If so, does any of this have to do with my TV, specifically?
Yes and no. It depends on your specific TV and how your specific cable company is sending out its signals. The intention of the government is that you should be able to go out and purchase a TV which uses CableCARD, get a CableCARD from your cable company, and not need the converter. The fact your cable company is small tells me they are not yet able to meet the requirements of the law. This is one reason why the converters from them are free.
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