How digital is digital cable?

[dawks]

Like is it completly digital, and how do they stream such 'high quality' video so consistently? I can also tell its digital at some point because you can occasionally (ie during high action scenes) see the signs of compression...

Is it some kind of IP Multicast system? The picture we get is definitly more clear then that of analog cable, ie, less static.. But video of that quality would be at least 5mbit (with good compression). Perhaps thats possible over the local cable network? I've seen about 4.5mbits from my ISP via standard TCP/IP on the computer..

 

[her209]

Nothing is really digital. Its all really analog. Its the just the way you interpret the signal level that makes it "digital". For example, a voltage reading of 3.3 or higher is consider a logical 1, where as a 2.5 or lower is considered a logical 0. Of course, there are other systems where you have -voltage and +positive voltage also.

 

[kyutip]

For me with Cox,
Not all channel are digital. Only premium channel are digital, others are still crappy analog.

 

[Aves]

It's not transmitted anything like streaming video over the Internet is done. There is no IP used or anything like that because that is way to much over head.

Basically the cable company is constantly broadcasting every signal to all users on the line and because of this there is no need for handshaking or flow-control like with TCP.

What they do is take the analog video signal and compress it into MPEG format, this allows them to broadcast like 10 channels worth of video in the same 6MHz of space that a single analog channel requires.

Since there is ~550MHz of bandwidth available to them on a cable line they can send a tremoundous amount of video data, over 1000 channels.

Because of this you need some kind of MPEG decoder connected to your TV to view anything and that's why it requires a cable box. Most cable companies don't have digital transmissions of all stations, mainly just the Premium channels and the music channels, etc.

 

[Maverick]

not as digital as satellite in most places.

 

[dawks]

excellent aves!

so the same concept as multicast.. kinda?

And yea, not all channels we get are digital.. 2-54 are analog, 55-130 are digital.

My cousin has directtv, and the compression is way more obvious on his dish then my cable. more fuzzy and such..

Partly I guess because he was only getting 75-80% signal at the time.. I guess.

 

[Koing]

All my channels are digital.

I have Sky Digital. The image quality on 99% of the channels is AMAZING and would be very tough to distinguish from DVD quality. I live in England by the way. You do have the odd lower end budget music channel with lots of blocking and artefacts but I don't mind.

 

[Aceshigh]

I have digital cable through Time Warner. I have almost 300 channels, but the quality is the same as it was with normal cable.