How fast is digital sattelite (direct TV) data transmission?

If I understand correctly, it sends video via MPEG2 compression. Since it is giving such high quality live video, it gives me the impression its a pretty fat pipe sending data down to me. How much can it send? Can it be rated in Kilobytes/sec?

Errr… make that Satellite

I just read an article on howstuffworks.com about satellite TV, oddly enough, about 15 minutes ago. IIRC, each channel takes about 10 megabits per second in a compressed mpeg 2 format, plus or minus depending on the amount of motion, etc.

Something weird though - we have both satellite and cable (not my idea :rolleyes: ), and when watching the same program on the satellite and cable, the satellite transmission is a few seconds behind the cable transmission.

Not so weird, Boscibo. They’re probably coming from the same feed. The cable connection is pretty nearly direct, without very much delay, but the satellite connection goes through a lot more on the way. The feed has to be delivered to the uplink station, processed and buffered there (to allow some slack in case of error retransmission or network delays), then sent to the satellite where it’s buffered again, and finally down to your dish. All that extra processing and the lightspeed travel time add up.

If I can add on to the OP… how the hell can we hook that bad boy up to our computers?

[Crap… I’m in GQ… must… sound… smart…]

So, what is preventing us from utilizing this technology (if not the existing satellite system used for TV) in personal computers? I suppose the aforementioned delay would be a problem, notably in realtime chat, but I think it’d be a fair tradeoff, to say the least.

Cost and availability?
Satellite internet service already exists.
http://www.starband.com/

Actually, the delay between [analog] cable and digital satellite has more to do with the set-top box than the propagation delay. I have both digital and analog cable from the same company, and I notice the same delay between the two sources.

Digital TV is delivered (as noted above) in MPEG2 format, and has to be buffered, decompressed and rendered. Those set-top boxes are actually computers (Scientific Georgia’s, IIRC, actually runs BSD). [Non-HD] Digital TV is generally transmitted at about 6 Mbps.

And of course, I meant Scientific-Atlanta.

One obvious difference is that computer users usually want interactive (on-demand) data, not broadcasts. So the satellite needs to send a separate signal to each user. A TV broadcast satellite may be able to send 10 megabit/sec on 200 channels, but if you use such a satellite to provide networking to 10,000 users that’s only 200kbps per user.

Also the equipment to send signals to the satellite is very expensive, and satellites aren’t usually equipped to receive multiple signals. So the satellite link is only good for downlink; you need to use some other method for the uplink. Usually you use a phone line.

**scr4[/b[- Gotcha. Basically, it’d be spreading itself too thin.

As a side note, DirecTV also transmits HD (3 of their channels… HBO, ShowTime, HD.net).

The data rate on these channels is much higher, but I don’t have the specs handy.

Getting back to Troy’s question…since it’s a straight Mpeg2 feed, would it be possible to pump that broadcast directly into your computer, without using a tuner card of some sort? Mostly just curious. Seems like it would be a neat “stupid computer trick.”

Direcway through directv has a two way satellite system. It’s a $579 installation and $60 a month but it’s available if you have the shekels.

Indeed it does. I have Direcway in my house networked to all the machines.

The extra gear cost about $700 or so (including the networking) and took about two hours to install.

It’s damn-all fast. I get speeds past a meg. Worth every penny.

Thanks for all the answers! I have a question about satellite broadband now as well, but instead of hijacking I’ll just start another thread.

Wow! Thanks for the correction. Do you know how big an antenna you need for that? I thought it takes quite a bit of power to transmit to a geosynchronous satellite.

The antenna I have is maybe 18" N-S and 36" E-W. It’s curved kind of oddly but it gets the job done.

It’s not one of those monstrous things.