April 11th, 2009

flock

It's all bits

Once upon a time, various communications media existed: radio, television, telephone. Each had its own encoding, means of transmission, and its own dedicated hardware and dedicated frequencies to transmit and/or receive and display or play it.

Now, it's all bits. The Internet is a packet-switched network that, given sufficient bandwidth, can move it all.

The problem is this: the folks who have the government-granted monopolies on some of the old communications methods are the ones who control the Internet connections of the vast majority of people, since they have facilities that could be adapted to carry Internet in addition to the old stuff--and they want you to have to pay for both just as long as possible.

Cable TV is highly motivated to make it as hard as possible for you to get your "television" programming via the Internet. All, or most during a transition period, "telephone" communication could be VoIP, but then you wouldn't have to buy phone service. In Canada, Shaw makes no bones about discriminating against those who use VoIP services other than the one they offer; $10 extra per month or they say they can't assure the quality of service needed for that third-party VoIP to work. <bad_mobster_voice>"Nice Vonage setup ya got dere; be a shame if somethin' happened to it..."</bad_mobster_voice> If I could, for a reasonable price, listen to podcasts of my choice or pandora.com while on the road rather than the wasteland that is US commercial radio, I'd do it in a heartbeat.
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    angry angry
flock

Throwing it all (or at least a lot of it) away

So... you have a nice, new digital TV. Perhaps it's capable of doing 1080i or 1080p, the maximum resolution for ATSC television (though in practice 1080p isn't used).

We're in a basement, and have a nice row of trees to the south of us, so we're stuck with cable TV--though I might get an antenna to do an experiment, to wit: suppose I watch CSI in high definition on KCCI as it comes in on cable, and then switch over to it as it comes over the air. I should see the same thing, right?

Wrong.

Digital video is compressed. Not doing so would eat huge quantities of bandwidth. The compression used is like that for JPEG images. It's lossy; what comes out the other end isn't exactly what went in, and like JPEG, the amount of data thrown away can be adjusted. It doesn't change the dimensions of the image in pixels, so one can still boast of a 1080i picture---it's just that it will be blurry, or what should be a smooth color gradient will be a solid square all of the same color. The more data discarded, the less bandwidth needed... and cable TV systems are highly motivated to conserve bandwidth, so they can add to the list of channels they can boast of offering.

Unfortunately, the more data you throw away, the worse the result is. You can see some examples here, from someone who compared streams from different sources and found examples in which the cable company in question (Comcast) threw away 38 percent of the data. Popular Mechanics has a very interesting article on the matter.
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    cranky cranky