How does DirectTV work??

[Soccerman]

you have a set-top box from your satellite provider, which connects to your dish, and to your TV.

now, my question is this: If I ordered a package from the provider (say I wanted a whole bunch of sports channels), how do they all the sudden permit me to watch? do they send a signal through the satellite which is intended only for that set-top box to recieve, and execute (allowing me access only to those channels)? if so, couldn't u theoretically throw a cover of some sort over the dish when they send the signal to stop letting u access your channels (cause you don't want them anymore, or whatever) to prevent them re-programming the set-top box to do so?

how else could it be? perhaps they use multicasting techniques similar to IP, in that each set top box has a unique identifier and the signal includes all the addresses to be sent to? therefor if your address isn't on the list, your set-top box ignores the signal sortof like IP..

and also, what kind of signal does Digital Cable give u? I mean, do you need a set-top box to de-scramble the digital signal? is the signal transmitted over RF? is it anything similar to HDTV broadcasts (which use the same RF frequencies as TV, just carrying Digital video and audio instead) when it reaches the set-top box?

I have a sister who lives in an apartment, and they get normal cable (not digital or anything). they don't have a set-top box or anything like that, just a cable to the living room (which carries what seems to be signals very similar, if not identical to the signals recieved by a TV antennae for 'farmer vision'). Anywho, I can only presume that there is a decoder somewhere else in the building, or close to it, because AFAIK, these signals are transmitted encoded (and probably digitally via fiber optics, if any typical cable companies boasts are to be considered anywhere near accurate).

are my presumptions correct so far??

 

[atrowe]

Satellite recievers have built-in modems and must be connected to a phone line. The receiver dials into an 800 number at DirecTV/Dish Network, whatever during the middle of the night and exchanges info. Generic receiver firmware updates can come through the satellite feed, but individual box specific data is handled through the modem.

Digital cable travels through the same RF cable that analog cable does. You need a set top receiver because most TVs don't have built-in MPEG decoders. I'd imagine that most digital cable signals are also encrypted to prevent piracy and you would need a set top box to perform decryption. Most digital cable channels aren't in HD because of bandwidth limitations. There's simply not enough bandwidth in an RF cable to support HD signals.

 

[Soccerman]

really! wow, I didn't know they did that..

now, does this happen right away when you order, say, another package?? or what? you're sure that's how they allow your set-top box to recieve channels that it wasn't able to before?

I gotta ask my sister's boyfriend about his experiences with this. AFAIK, he ordered some sort of sporting package for his dad over the phone, and almost immediately (if not immediately) they got access to those channels..

anywho, as for the digital cable thing, you're saying they transmit signals that are the same as HDTV signals? (ie, MPEG2 compressed but these are at 480i).. hmm..

Digital cable travels through the same RF cable that analog cable does. You need a set top receiver because most TVs don't have built-in MPEG decoders. I'd imagine that most digital cable signals are also encrypted to prevent piracy and you would need a set top box to perform decryption. Most digital cable channels aren't in HD because of bandwidth limitations. There's simply not enough bandwidth in an RF cable to support HD signals.

the problem with that is this: HDTV signals can be sent over todays TV frequencies (ie using broadcast TV).. AFAIK, cable RF signals are the same frequencies as broadcast (to allow any TV tuner to connect to cable), so there really isn't a bandwidth limitation (in fact, they can send multiple channels of video within the same frequency spectrum of a normal TV channel when it is Mpeg2 compressed).

I think the maximum bandwidth capability of the spectrum of any TV channel is something like 19.2 megabits a second, which is easily enough for DVD quality video.. I remember readin about all this in a Popular Science a long while back, when the standards were finally finalized..

as for DTV encryption, I think it still uses cable scrambling techniques, like u said, to prevent someone from plugging in 2 TVs without paying (if that's what u mean by 'piracy') for the second TV, or simply tapping into one of their cables and not paying at all..

which brings up another thing: I don't remember properly, but do u need only 1 descrambler for a whole house of TVs? if so, it has to do ALOT of decoding (50+ channels), becuase it must convert ALL the channels at a time, right??

 

[pg22]

I swear no one talks about it..but as piss poor as regular TV looks at times..digital cable is WORSE. Just look at it closely..and you can see artifacts...like..'blocks'.....take an .avi and strehc it to 200% and that's what I mean. It's not THAT bad, but you can deifnietly notice it in the drak colors.

 

[hconnorjr]

dish sat tv does not descramble all channels at once, as far as i know. the stream comes in and only the channel you chose to watch is run through the decoder. this is why you need to set top boxes if you want to watch a program and record one at the same time, real-time.

 

[redls1]

The only reason the phone line is connected is to download all the payper views you bought. Everything else is done through the data stream. Your phone line doesnt even need to be connected if you dont want.

 

[DocDoo]

<< I swear no one talks about it..but as piss poor as regular TV looks at times..digital cable is WORSE. Just look at it closely..and you can see artifacts...like..'blocks'.....take an .avi and strehc it to 200% and that's what I mean. It's not THAT bad, but you can deifnietly notice it in the drak colors. >>


I could not agree more!!! I have had DTV for 4 years and I still hear "amatures" say "ohhh... look how clear and sharp the pictures is." Bahhh... For one thing, it does a poor job at decoding the color RED. You usually get all types of artifacts and as for gradients, its really bad. Its like looking at a .JPG picture that has lots of gradients that was compressed at 50% to 60%. It does a good job with chrome however...

For you audiophiles out there, remember those first generation home CD players. They all suffered from poor DAC, and had inferior (if any) DSP circuitry (hehe, remember those Magnavox ModSquads ). The all had that "typical" digital / synthetic sound. Well, DTV has the same, but for your eyes this time...

redls1 is correct. The analog phone line is only used for PPP. I've had mine disconnected for 3 years.

 

[atrowe]

<< really! wow, I didn't know they did that..

now, does this happen right away when you order, say, another package?? or what? you're sure that's how they allow your set-top box to recieve channels that it wasn't able to before?

I gotta ask my sister's boyfriend about his experiences with this. AFAIK, he ordered some sort of sporting package for his dad over the phone, and almost immediately (if not immediately) they got access to those channels..

anywho, as for the digital cable thing, you're saying they transmit signals that are the same as HDTV signals? (ie, MPEG2 compressed but these are at 480i).. hmm..

Digital cable travels through the same RF cable that analog cable does. You need a set top receiver because most TVs don't have built-in MPEG decoders. I'd imagine that most digital cable signals are also encrypted to prevent piracy and you would need a set top box to perform decryption. Most digital cable channels aren't in HD because of bandwidth limitations. There's simply not enough bandwidth in an RF cable to support HD signals.

the problem with that is this: HDTV signals can be sent over todays TV frequencies (ie using broadcast TV).. AFAIK, cable RF signals are the same frequencies as broadcast (to allow any TV tuner to connect to cable), so there really isn't a bandwidth limitation (in fact, they can send multiple channels of video within the same frequency spectrum of a normal TV channel when it is Mpeg2 compressed).

I think the maximum bandwidth capability of the spectrum of any TV channel is something like 19.2 megabits a second, which is easily enough for DVD quality video.. I remember readin about all this in a Popular Science a long while back, when the standards were finally finalized..

as for DTV encryption, I think it still uses cable scrambling techniques, like u said, to prevent someone from plugging in 2 TVs without paying (if that's what u mean by 'piracy') for the second TV, or simply tapping into one of their cables and not paying at all..

which brings up another thing: I don't remember properly, but do u need only 1 descrambler for a whole house of TVs? if so, it has to do ALOT of decoding (50+ channels), becuase it must convert ALL the channels at a time, right?? >>



You can connect as many TVs as you want to a satellite receiver, but since there is only one receiver decoding the signal, each TV will display the same channel. If you want to watch multiple channels AT THE SAME TIME, you'll need an additional receiver for each channel.

When you sign up for Pay-per-view or some sort of other premium programming, in most cases, the receiver will activate that programming immediately, but it will download a record of that programming to your satellite provider through the modem and you will be billed for it.

RF cable can certainly support HD broadcasts, but you've gotta keep in mind that there is a lot of traffic going through that cable already. You figure the average cable company has 60-80 analog channels, all the cable modem users in your local loop, AND the digital cable traffic all going through a single cable, and there's really not much spectrum left over. Some cable companies are even offering telephone service through cable lines. It would be possible to transmit HD signals over RF, but chances are, they'd have to sacrifice something else to squeeze an HD feed in there.

 

[nightowl]

Soccerman: To anwser your question about how satellite works I think that after you call in to order your programming that they add they card serial # to the data stream coming from space. Then when the signal enters the reciever only the channels that you have paid for can be decoded based on which ones you have paid for. The phone lines only affect the pay-per-view channels and even then you can call in and order them. This is the only logical explanation I can come up with since the receivers we have at home are not connected to the phone line and everthing works fine with the exception of the pay-per-view channels.

 

[sohcrates]

<< I swear no one talks about it..but as piss poor as regular TV looks at times..digital cable is WORSE. Just look at it closely..and you can see artifacts...like..'blocks'.....take an .avi and strehc it to 200% and that's what I mean. It's not THAT bad, but you can deifnietly notice it in the drak colors. >>



The reason for that is the different video compression schemes used to transmit as MANY digital cable channels as possible through the cable "pipe"

There two different basic compressions used: lossless and lossy (duh!)

For important, prime-time events and stuff (aka superbowl) the cable companys are gonna give that transmission some more bandwidth, especially with sports where there is fast movement and what not.

For most everything else, lossy compression is used. Often times, for moving head news or whatever, there is no need to re-transmit the background every second, when it doesn't change...so they cut that out. also, they may take a frame or two out of every second, but since it's refreshing so fast, you most likely won't notice it.

That 'blocky' look is a digital artifact from the compression, and they're hoping you'll overlook it in exchange for having so many more channels.

Same holds true for DirectTV, since bandwidth through satellites is extremely expensive. Next time your watching golf, for instance, look for the cut shots to the ball flying through the air...it most likely will be blocky. this is because golf is not as important as football as far as ratings, so they'll give less bandwidth to a golf satellite uplink...this is ok, though, until the golf ball shots...where the background is moving quickly.

it's all about maximizing profit!

 

[Skud]

The DirecTV card has 25 spots for PPV information. Every time you order a PPV it takes up a spot. If you have your receiver connected to the phone it will send this info to DirecTV. If the line is not connected, the spots will fill up and when you get 25 you won't be able to order any more until they are "Cleaned" off by DirecTV. Unfortunately when DirecTV cleans them off, you get charged for them.

Later
Skud

 

[Soccerman]

I swear no one talks about it..but as piss poor as regular TV looks at times..digital cable is WORSE. Just look at it closely..and you can see artifacts...like..'blocks'.....take an .avi and strehc it to 200% and that's what I mean. It's not THAT bad, but you can deifnietly notice it in the drak colors.

you're no doubt seeing compression artifacts, though most TVs (unless they're capable of real HDTV resolutions, like 1080i or 720p) aren't good enough to see the compression on a DVD, so either your DTV signal is MORE compressed than DVD, or you have a sweet TV.

RF cable can certainly support HD broadcasts, but you've gotta keep in mind that there is a lot of traffic going through that cable already. You figure the average cable company has 60-80 analog channels, all the cable modem users in your local loop, AND the digital cable traffic all going through a single cable, and there's really not much spectrum left over. Some cable companies are even offering telephone service through cable lines. It would be possible to transmit HD signals over RF, but chances are, they'd have to sacrifice something else to squeeze an HD feed in there.

well I guess it depends solely on how the signal gets to your house, more than anything else.. IF your cable provider has a box for your neighborhood where all your houses are connected to, then I can see it being possible that if they're using fiber to the box, and coax to the house, that they could supply whatever type of signal they want. ie, the fiber is capable of handling all of that data, the limit in this case would be the RF. now, if you order DTV, does that mean ALL your channels are digitized? if not, then ya, I can see room running thin on the RF cable, what with the internet, ~80 analogue channels, and whatever else they have going on there..

When you sign up for Pay-per-view or some sort of other premium programming, in most cases, the receiver will activate that programming immediately, but it will download a record of that programming to your satellite provider through the modem and you will be billed for it.

now, I don't own cable or Satellite, so I've no experience doing this, (and almost no knowledge on this topic), so I assume when u talk about Pay Per View programming that it's like a boxing match or a movie, that you pay extra for on top of your normal bill for Cable, right??

and are u sure that your phone line actually DOWNLOADS the program??? or does it download something to decode the incoming satellite feed?

When you sign up for Pay-per-view or some sort of other premium programming, in most cases, the receiver will activate that programming immediately, but it will download a record of that programming to your satellite provider through the modem and you will be billed for it.

I don't quite understand, are u saying the reciever keeps a record of the programming, and than uploads it to the satellite provider?

Soccerman: To anwser your question about how satellite works I think that after you call in to order your programming that they add they card serial # to the data stream coming from space. Then when the signal enters the reciever only the channels that you have paid for can be decoded based on which ones you have paid for.

heh, ok, that's somewhat like what I originally thought...

 

[SNOMANX3]

The satellite tv is just like radio, every channel is in the air. Its just a matter of you pulling it in. When you subscribe they send packets to your CAM(smart card; dtv H,HU dishnet ROM 2,3), these packets will activate your CAM to tell your IRD Receiver to allow decode. Yes your CAM and IRD have unique ID numbers. If you cancel a channel or what ever they send "kill" packets to close your tier so that you will not decode the channel(s) anymore, these kill packets can last for more than a month. The "stream" holds all audio, video, activation & kill packets, and ecm electronic counter measures. The phone line is used to send your location and bill amounts to the SAT offices via phonline. If you order a PPV with your remote(not calling by phone) then go unplug your phoneline to your IRD, you wont be be billed until you plug it in again.

 

[MadRat]

Find a card emulator and look for a pentium-level pc to setup next to the TV. Guess what that can do?

 

[ElFenix]

<< the problem with that is this: HDTV signals can be sent over todays TV frequencies >>

no, they can't. HDTV channels use quite a bit more frequency range per channel than the old analog system. thats the technological limit that kept analog HDTV (invented in japan) from becoming a standard back in the early 90s after the FCC passed a regulation stating HDTV had to work with the legacy system. after some americans came up with digital hdtv in the mid 90s a new frequency range was opened up and sold off to TV stations, who were originally required to give back the analog tv frequency space but that was changed and now they don't have to.

if you're going to cancel directv unhook your receiver from the wall (mine has never been plugged in) and order as many pay-per-views as the card will allow.

 

[Soccerman]

ok well, according to a (I think 2 year old) Popular Science, they can transmit the channel in the broadcast TV frequencies.. I'll have to check again to be sure.

btw, I don't own (nor hope to own) satellite, this all came from a conversation with my sisters boyfriend, who's dad has Satellite..

 

[dszd0g]

As far as PPV goes, the set-top box does not download anything. When you decide to watch a PPV program your set-top box saves the information about your order until the next time it dials out (generally that night). The set-top box only allows you to watch a certain number (that varies) of PPV shows before it has to transmit that information to the company (so you can be billed). If you do not plug in your set-top box to the wall, you will be able to watch that given number of PPV shows and then it won't let you watch any more until you plug it into your phone line at let it transmit the information.

I agree with ElFenix. You obviously have not been following the whole TV frequency conspiracy

North America (and Japan) use NTSC. Television NTSC is broadcast with an RF bandwidth of 6MHz per channel, scanning frequency is 15.734 Hz (color), and an aspect ratio of 4:3. The 6MHz is actually what is allocated. NTSC is 525 lines by 427 pixels, scanned at 29.97 Hz. 525 * 427 * 29.97 / 2 (interlaced?) = 3.35Mhz which is what is used by the video. There are two different HDTV standards to the best of my knowledge. 720p and 1080i. 720p is 1280x720 progressive, and 1080i is 1920x1080 interlaced. 1280 * 720 * 29.97 = 27Mhz. 1920 * 1080 * 29.97 / 2 = 31Mhz. Obviously, these will not directly fit into a 6Mhz signal. The FCC actually allocated more bandwidth to the TV stations a few years ago. I don't remember how much, I think it was 20Mhz. The TV stations decided that it would cost them money to switch to HDTV so decided to just sell off some of the bandwidth the FCC gave them and make a few billions. This pissed off a lot of people, and the FCC has been working to force the TV stations to switch to HDTV. The current HDTV stations are compressing these high bandwidth signals into the 6MHz. I believe they have another 5 years or so till they have to switch to the larger bandwidth signals they were giving. I really haven't been following the politics involving this in a while, so someone else can correct me if I've messed up the details.

 

[ElFenix]

i took a class that outlined the politics of the hdtv frequency selloff, when i get home i'll dig up the notes and summarize them. basically its a huge amount of corporate welfare as no tv station has ever lost money.