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Why is it faster to watch television shows the 'normal way' through something like cable or satellite, compared to watching them over the internet?

This may sound like a funny question, but considering the actual medium may be the same (e.g. you can get the internet over a coax cable in the same way you get the TV) then wouldn't it be closer to the same speed and quality? I don't think my premise is wrong because you can watch 4K TV normally but unless you have a very good internet connection you would probably notice buffering when watching 4K online.

Is it because with the internet there's a lot more overhead (though I would have thought with protocols such as UDP less so)?

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    The medium is not as relevant as you would think. Dial-up and DSL both use the same wire but they work very differently and provide different speeds. – InterLinked Apr 26 '18 at 16:43
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    @InterLinked is correct. The method of transmission and reception is what is important, not the medium they travel on. – Keltari Apr 26 '18 at 19:38
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    With TV the data is sent once and received by everyone at the same time. With the Internet, each viewer gets their own data stream. If 5 people watch the same program at once on the Internet, it has to be sent 5 times. – user20574 Apr 26 '18 at 21:28
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    @northerner Except that: there isn't a large list of clients to receive the same internet TV (how many different people are going to be streaming the same show from the same website?). And network switches normally block multicast traffic unless they specifically allow it through because of the load it has on the switch. When the ISP is the Cable provider they can safely allow their own multicast, but letting any old website's multicast through would probably allow such a multicast storm as to DOS every customer. – Centimane Apr 27 '18 at 10:11
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    Even faster was terrestial broadcast of TV. At the time there was still analog TV broadcast in Germany, the new year countdown looking on a radio controlled clock, watching TV over antenna and watching TV over satellite had a difference of about 1second clock->antenna and about 4-5 seconds clock -> satellite. So I think, it is the additional processing stages which introduces the lag. Not the performance of the medium. – Sunzi Apr 27 '18 at 12:39
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At its core your assumption "over a coax cable in the same way" is false. Cables simply carry an electrical signal. This signal can be encoded many different ways each of which is tailored to a particular usage including encoding schemes that combine multiple uses into a single signal.

"Cable" is fast at providing TV because it is a one way broadcast signal tailored to distributing TV channels to multiple subscribers simultaneously. Everybody gets the same signal at the same time with basically no variation. It is fundamentally one signal to many people.

Watching TV on the Internet is the opposite in almost every regard. It is a two way signal tailored to distributing data to individual subscribers on-demand. Nobody gets the same signal at the same time, and everybody has individual needs. It is fundamentally many signals to many people.

Modern "cable" has changed this by adopting newer bidirectional digital infrastructure influenced by data networks to allow for cable Internet. This further allows for new services like on-demand programming and set top box gaming. This required fundamental changes in the cable network and the electrical signals carried on the cables. Data networks have changed this by adopting multicast protocols to allow for large scale broadcast data to enable IPTV, on-demand programming, and set top box gaming. This also required fundamental changes in the data network.

The convergence will continue until "cable/IPTV" and "Internet" networks are indistinguishable. One day your Internet Service Provider will offer to hook you up with the 10,000 channel YouTube broadcast, and movie studios will broadcast IPTV multicast to the world directly. There still will not be anything to watch on broadcast and there will still be buffering on your personal programming because your favorite cat videos will never be popular enough to make it onto the broadcast schedule.

  • +1 for mentioning multicast, which would allow TV-style broadcast over the Internet if supported by Internet backbones / ISPs. This could massively reduce bandwidth demands for something like the Olympics where many people are watching the same live stream, or have it rewound by under a minute. (In the short-rewind case, the client can just buffer a minute of multicast data before showing it. And if needed, unicast a minute or two of data to catch a user up to the multicast stream after seeking.) – Peter Cordes Apr 28 '18 at 11:17
  • I know this isn't the most up voted answer but I like it the best :) – northerner Nov 22 '18 at 4:08
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For TV and internet video, the problem is the same: you've got to send frames of the video to the viewer. Each approach the problem differently and has advantages and disadvantages.

The frames are really just information, so let's pick an analog. Imagine you want to dictate the GettysBurg Address to 100 people. You've got to get each line of the speech to each person (like the video provider has to get frames to each viewer).

Now Television channels each get an exclusive use of a frequency range on the cable. This is like having exclusive use of a lecture hall. You won't be interrupted by others trying to talk. If you're like a TV channel, you post a time you plan to dictate the speech and when that time comes, you get up on stage and start speaking. Without even checking who is in the audience you just begin:

you send "Four score and seven years ago" to whoeverIsListening
you send "our fathers brought forth on this continent" to whoeverIsListening
you send "a new nation, conceived in Liberty," to whoeverIsListening
you send "and dedicated to the proposition" to whoeverIsListening
you send "that all men are created equal." to whoeverIsListening
...

...
you send "shall not perish from the earth." to whoeverIsListening

You dictate the whole speech without pausing. You spoke each line only once. That wasn't so hard on you. And anyone who was in the hall and listening heard the whole thing with no delays or interruptions. Similarly, Television stations send their signal down the wire just the once, and if you're watching it, it comes through in real time. But also similarly, if you're not at your TV when the show is on, or you have to leave in the middle to go to the bathroom, you miss some of it.

But what if you want to let people hear the play on their own schedule, and you want to make sure everyone hears the entire thing? You invite everyone to visit you in the park whenever they like, and you'll dictate the lines to them individually. This is like making your video available over the internet.

The park is busy, and sometimes you can't speak because it's too noisy. Streaming services share the network with other internet traffic. They have no dedicated frequency. Their packets sometimes have to wait in line.

Person1 shows up, and you start telling them lines:

you send "Four score and seven years ago" to person1
someone sends somethingIrrelevant to someoneElse
you send "our fathers brought forth on this continent" to person1

That wasn't so bad. person1 is still getting the play at a pretty good rate, but then person two shows up, and you promised to start at the beginning for each person, and person 3 shows up soon after, followed by person 1 asking for you to repeat yourself...

you send "a new nation, conceived in Liberty," to person1
you send "Four score and seven years ago" to person2
someone sends somethingIrrelevant to someoneElse
you send "and dedicated to the proposition" to person1
you send "Four score and seven years ago" to person3
person1 sends "what?" to you
you send "our fathers brought forth on this continent" to person2
someone sends somethingIrrelevant to someoneElse
you send "and dedicated to the proposition" to person1
you send "our fathers brought forth on this continent" to person2
someone sends somethingIrrelevant to someoneElse
you send "that all men are created equal." to person1
someone sends somethingIrrelevant to someoneElse
someone sends somethingIrrelevant to someoneElse
you send "our fathers brought forth on this continent" to person3
you send "Four score and seven years ago" to person4
person3 sends "what?" to you
you send "a new nation, conceived in Liberty," to person2
you send "Now we are engaged in a great civil war" to person 1
you send "our fathers brought forth on this continent" to person3
someone sends somethingIrrelevant to someoneElse
someone sends somethingIrrelevant to someoneElse
someone sends somethingIrrelevant to someoneElse
you send "a new nation, conceived in Liberty," to person3
you send "our fathers brought forth on this continent" to person2
you send "a new nation, conceived in Liberty," to person3
you send "our fathers brought forth on this continent" to person4
someone sends somethingIrrelevant to someoneElse
you send "Four score and seven years ago" to person5
you send "Four score and seven years ago" to person6...

and on and on like that, until you've said each line of the speech to each person. When you dictated in the lecture hall, it didn't matter how many people showed up, you still only said things once and they all heard it. But now if thirty people show up at once, or the park gets busier, the rate that each person receives the speech is going to slow to a crawl. Internet video has the advantage that each person can start listening whenever they want, and can even ask to pause and continue later or repeat parts they missed, but the disadvantage that if the network gets crowded or many people are using the same server, the video loads slowly.

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    This is like streaming. Have to be careful with terminology here. Watching a video on Youtube or Netflix isn't really "streaming", it's more a type of downloading (TCP) where multiple users can download the same content any time they like - it is stored locally only temporarily for playback, but it's not like true streaming, which is live, and behaves much like the first case you described. On-demand media can download in bursts - enough to fill a buffer and then not again until the buffer pressure increases. True streaming plays as it streams - typically multicast UDP or the like. – J... Apr 26 '18 at 17:18
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    @Draco18s Unfortunately (to my knowledge) multicast isn’t a thing on the public internet :(. – Jonas Schäfer Apr 26 '18 at 19:43
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    @J... The definitions I am familiar with say streaming is less about the precise timing and more about how the data can be processed. In a stream, each element of the stream can be processed and used without waiting for the rest of the elements to be transmitted, and one processes one element in the stream before moving to the next. There are differing levels of fluidity, ranging from cleverly buffered TCP to multicast UDP to ATM packets over SONET, all the way up to analog. Analog, of course, would be the only true streaming format, by your definition of "plays as it streams." – Cort Ammon Apr 27 '18 at 0:57
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    Oh right. So super simplified TV is faster because there's only one sender in the network so there's no collisions or congestion. – northerner Apr 27 '18 at 8:32
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    @northerner: Yes, but also because everything is sent just once (and everyone listens to it at the same time), instead of sending everything separately to each listener/viewer. – psmears Apr 27 '18 at 10:19
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The actual medium is not the same: TV distributed via dedicated coax works very differently and has a very different infrastructure compared to, say, watching Youtube or Netflix, or anything else over the public internet.

Even if the coax is used to implement IP protocols, and TV content distributed on top of that, you still have total bandwidth control, and can use a dedicated multicast infrastructure (which doesn't work very well over the public internet).

So the answer to your question is: You are comparing apples and oranges, your premise that they are similar is wrong.

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    Digital cable also has bandwidth problems also, which is the reason, every channel isn't in 4k or even HD for that matter. While some of that has to do with the fact, the majority of their customers don't have 4k or HD televisions, the cable industry is not going to solve their bandwidth problems through expensive upgrades until there is a critical moment in demand. Considering their customers are also moving to TV over internet anyways and dropping their traditional television services. – Ramhound Apr 26 '18 at 12:30
  • @Ramhound that's actually what prompted me to ask the question. IMHO the only benefit to having cable TV over e.g. YouTube is there's no loading time. – northerner Apr 26 '18 at 12:47
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    @northerner - Your ISP could make it so there were no loading times on YouTube, by increasing the amount of bandwidth you had access to, but worth pointing out digital cable is encrypted and compressed. Which is then uncompressed and unencrypted at your cable box. While content to YouTube might be encrypted, it isn't compressed typically. While YouTube uses compression within their encoder, I am talking about, how the data is transmitted to the client. The compression is built into the encoder, which is a similar approach, but solves a different problem. – Ramhound Apr 26 '18 at 12:49
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    @ramhound YouTube video is, in fact, compressed. What you call an "encoder" is actually a very sophisticated compression algorithm. Most modern video codecs come from the MPEG family, which combines motion compensation with a DCT-based residual (the latter being very similar to JPEG). Audio compression is also applied within the same stream. Both digital TV/cable and internet video use these codecs, though possibly with different parameters for quality/latency/bandwidth tradeoffs. – Chromatix Apr 27 '18 at 21:42
5

For all dual-purpose providers (e.g. cable with Internet), you can imagine that the traffic going over the wire is like a highway with an express lane, or perhaps even better, an automated highway system. The express lane/automated highway is a dedicated portion of road where everyone is expected to travel at the same speed and have a constant flow. There is never any congestion because it's carefully laid out to allow a specific amount of traffic across it.

The provider allocates all of the channels you can watch to specific frequencies. The traffic is always at a specific bandwidth regardless if anyone is watching that particular channel or not, and everyone gets the same data at the same time. This bandwidth is calculated beforehand, and providers can reliably predict how much bandwidth they have available for those frequencies.

The Internet, on the other hand, is like a normal highway. When it's not utilized very much, everyone can go as fast as they like, but as traffic increases, then some data has to delayed so everyone gets a fair chance. This means that when the Internet bandwidth is nearly saturated, people will start to notice skipping, buffering, distorted audio and video, and so on.

Therefore, the primary reason why cable, satellite, and over-the-air programming is in real time is because it uses dedicated, preallocated bandwidth, which is carefully calculated and measured out to minimize interference, while the Internet is always competing to try and provide a balanced amount of bandwidth for everyone that wants to use it. Once the medium is saturated, everyone starts to feel the effects, from web pages taking longer to load to grainy video streams and distorted audio.

  • I'd say a dedicated line is a highway where everyone is banned from overtaking, while using the internet is consigning all your cars to a shipping company to ship them however they see fit as long as they reach their destination.... – rackandboneman Apr 27 '18 at 21:54
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The simplest explanation is that broadcast video gets a dedicated channel all to itself, with almost no latency and very consistent bandwidth. The data is sent to everyone, regardless of whether they're actually listening or not (which makes it extremely efficient when the expected number of listeners is in the millions), and is deliberately structured so that when someone does start listening, they'll get a keyframe that allows them to start watching within a fraction of a second.

Conversely, internet video has to compete with other traffic sharing various links between routers between the server and your computer, and this causes delays and losses which have to be mitigated. A duplicate copy of the data has to be sent to each listener, which isn't very efficient from the server's point of view and increases the chances of interruptions still further. To cope with the interruptions, your computer waits for several seconds of data to arrive, storing them in a buffer, before it starts playing it.

If the two happen to come over the same physical cable, they're almost certainly modulated onto different carrier frequencies, very much like old-fashioned TV channels.

If you're watching a film or a series episode, the short pause while the buffer fills isn't very noticeable, and the convenience of not having to wait for the TV station to get around to broadcasting it is a compelling advantage for internet video. But for a live sporting or news event, broadcast TV is probably best due to its immediacy.

1

Plenty of good points in the other answers but here is a picture showing how Verizon achieves this over fiber (Verizon FIOS). Every provider is going to have different mechanisms so this is only an example of one such approach. The Internet data and the broadcast video come from two different sources. They are added on close to the last mile by getting transmitted across a different wavelength.

An image showing how video bandwidth is added onto a data stream at an optical coupler by utilizing a third wavelength.  The video circuit uses 1550nm while the voice and data use 1490nm for downstream and 1310nm for upstream.

1

There are several reasons. First, cable/sattelite bandwidth is much higher than you maybe think. Even a quite old coax installation has a total bandwidth that is very competitive to what most average users have for LAN. Same goes for sattelite. Just consider that e.g. on Astra you have some 100+ transponders, each with several channels and each of these with 27.5k symbols per second. That's a huge amount of bandwidth.

Second, data is broadcast, that means it is sent out once to "everybody" (and to nobody in particular), and that's it. Internally, a cable network may have to copy around the raw bits here and there (e.g. to a sattelite, or to your local cable network), but whatever. Everything is just sent once, fire and forget, eat it or die. There is no protocol for transmission errors (well, there is FEC, but that doesn't count, it doesn't communicate back) or any such thing. You get it or you don't, and as time goes by, you care less and less whether you got it, too (the provider doesn't care at all to begin with).
This makes the prerequisites to both the local cable and provider infrastructure a lot less demanding since you only need to transmit a tiny fraction of the data, and you need not worry about getting replies from the client and handling these. The amount of data to be sent through the infrastructure (and also your local cable) depends solely on the number of channels being broadcast, not on the number of people watching them. Since the latter are around a million times as many as the former, that's big win.

There is no HTTPS server involved. No requests being processed, no pulling arbitrary blocks of data at haphazard times, no guarantees, no concurrency/scalability issues. No packets being dropped by intermediate routers, no congestion control (and if packets are lost, nobody cares).

So, all in all, it's a totally different, non-comparable thing.

0

All the information coming into your house on the coax cable occupies a certain bandwidth of the available spectrum. The simple answer to your question is that more of that bandwidth is dedicated to broadcast TV than to general data. You are correct that the overhead of 2-way communication isn't that big a deal as far as what can fit into the available bandwidth on the cable.

Where the difference between broadcast video and on-demand data comes into play is at the provider end where it is easier to provide the same data to everyone (broadcast) than it is to provide specifically requested data to each user. In other words, the provider could allocate more bandwidth to general data but then it would have to cut the number/quality of broadcast channels and provide each user with a bigger pipe to the internet (between their end of your cable and the internet backbone). That is also where the speed based on subscription level comes in: how much you pay dictates how much of their connection to the internet backbone they let you use.

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