Suppose I’m watching the Dallas Cowboys host the New York Giants at AT&T Stadium in Arlington. According to Google Maps, my house is 225 driving miles from the stadium.
The game is being broadcast on Fox. I will be watching the game as broadcast by the Fox affiliate in Austin (KTBC-7). Their offices and studios are in downtown Austin and I believe they broadcast from a tower on Mount Bonnell in West Austin. However, I don’t receive their broadcast over the air. I watch KTBC via Dish Network. I have their Genie DVR and wireless Joey setups.
During the game, Dak Prescott throws a beautiful perfect spiral pass into the loving arms of a Giants defender. My questions:
How many miles has the data comprising the interception traveled to be displayed on my TV?
How long after the actual interception before I am screaming “F**k!” at my TV?
How does Dish receive the signal from KTBC or other local broadcaster stations?
We just discussed this in my work today, and the answer to number 2 was that 30 seconds was still “live,” but it obviously varies a lot, depending on all sorts of things. In my house, I have two different cable boxes from the same provider, and even the same game can be offset by 10-15 seconds due to the signal path taken.
In my case, some of the signals get picked up locally and transported via fiber to the headed - in Atlanta (I am in SoCal) and then transported back to me, through the local headend. I’m sure that Dish does some sort of local collection (in Dallas) and then sends it to their uplink (probably in CO or WY, can’t recall), and then down to you.
But all this happens really fast - I’ve seen my Caller ID flash on the TV screen before the phone itself rang - and this is the switch in OC telling the server in ATL that I’m getting a call, and that server sending a signal to my STB before the switch send the ring to my house.
It is actually becoming a problem in that the Twitter response precedes the broadcast due to all the transport time.
When I watched TV via the cable company, every show on every channel seemed to begin within 2-3 seconds of the scheduled time.
We cut the cord almost a year ago, and now we watch live TV via “Hulu Plus”, and everything seems to be about 2 full minutes late. I don’t watch any sports, but it is pretty annoying to watch the news while I’m getting ready for work, and the time in the corner of the screen is so very delayed.
I don’t know the cause of this delay. If it was circuitry, as the OP seems to presume, it might have affected Cable TV as well, though over-the-air broadcasts would be pretty immune. I can’t help but wonder if my 2-minute delay is built into the contract between Hulu and the tv stations – maybe Hulu would have had to pay more to broadcast truly live?
I have over-the-air, cable, cable app on my phone, and cable on my Roku. If I set all of them to the same OTA channel there’s about a 2-minute difference between OTA and the Roku, with cable and the cable app on my phone being somewhere between.
The answer to OP’s Question #2 must also take into account OP’s reaction time. That, in turn, must take into account how much adult beverage OP has ingested and other similar considerations.
Worth mentioning the huge difference in nature between broadcasting in the days of analog and the digital era.
In days of analog the delay was mostly down to the time of flight as limited by the speed of light. The phosphor dot on your tv screen was scanning in sync with a scanning electron beam in the video tubes in the broadcast cameras. There were clock distribution networks that allowed the broadcaster to keep this synchronised. Atomic clocks were used to allow multiple video sources to be kept in sync.
Now, in the digital age latency creeps in everywhere. Cameras may introduce at least one frame delay before the signal even leaves it. Compression of video signals needs to buffer up enough frames to perform compression. The low bandwidth of broadcast video means aggressive use of inter-frame difference calculations from key frames. So the compression may need to run some frames behind just to work. Format changes may require construction of An entire frame or even sequence of frames before delivering a result. So even more frames of delay. So real time digital video is awful. It is very hard to get latencies down to fractions of a second. And that is with reliable high bandwidth links.
Once you are broadcasting, the links are of poor bandwidth, and of variable reliability. So in order to ensure the viewed video is free of judder one needs to buffer a significant amount of data. So much so that 10 seconds may be considered to be real time. 2 seconds is on the ragged edge. If you are a broadcaster adding a significant amount of fat into the pipe is nowadays cheap (memory is dirt cheap) and makes life vastly easier. A minute or two might be a bit lazy but hardly a surprise.
Last year my dad would sometimes listen to the Yankee game on the radio in one room while I’d be watching the game on TV and on one channel (I don’t remember which one) the delay between hearing the announcers say what happened and then seeing it on TV was 45 seconds! And we’re in NY so it’s not like the signal had far to go.
The countdown clock for the “Opening Bell” (stock exchanges) on CNBC reaches zero almost exactly 15 seconds after my computer shows that the markets have opened (and my clock shows 9:30)…
Possible hijack, but I recall, especially when I was younger, that when you had people on TV taking to each other from the other side of the world, there would be a several second delay. I still see this sometimes but it is rare. Why? I, a regular Joe, can speak to a guy in India and there is no perceptible delay whatsoever.
Time lags that arise for technical reasons have already been mentioned by the others, but I’d like to add that sometimes such lags are introduced intentionally. After the “Nipplegate” incident over Janet Jackson’s halftime performance in the 2004 Super Bowl, many broadcasters have started to delay live transmissions by five seconds, to give directors the time to cut the live programme off in case something happens that would be considered inappropriate to go on air (link).
Before we lived together my now-wife and I used to talk on the phone while watching the Mariners play. She had cable and I had DirecTV. Since my signal went to space and back, she would see a play about 10 seconds before I did. Also, when I flip back and forth between A.M. radio and satellite in my car, there seems to be about a 5 second difference.
I used to work as a Transmission Controller on a satellite TV station. That basically means I was coordinating and monitoring the live output of the station.
I had a large bank of monitors in front of me and one of the two most important ones were arguably the Output and the Return.
The Output was the channel feed as it exited our building and was generally about a single frame behind the server output.
The Return is the feed that everyone at homes sees which we received through a dish like all our customers. If this went blank but our Output remained on then I knew the problem lay outside of my control (although I would still chase it up because I’d be the first person to notice and do something).
The Return was typically about a three-quarters of a second behind our Output. This is the time it takes for the signal to go through our cables, down to a central facility, encoded (I presume) and sent to a satellite before returning back to our dish. If you are watching digitally though an aerial then I think that’s likely to be a bit shorter but your local transmitter has to receive the signal so it might depend on where you are in the country and if the transmitter is a fair distance from the source.
Now that’s for pre-recorded shows played from a server. If we were taking live sports from somewhere then you can probably add up to half a second to that - depending on the route the signal has to go through. If it’s coming from a studio local to me then I’m going to guess at a small fraction of a second. But we can countdown over a coms link to the live studio and they are pretty accurate when cueing up their VTs. Not sure if an engineer maybe syncs things up though. If there are any TV engineers they would know better than me.
This is purely anecdotal but I remember my freshman year in college I lived about two miles from the football stadium (PAC-10 team…it was PAC-10 back then).
When our team scored a touchdown they’d launch a few fireworks. I’d hear the fireworks several seconds before I saw it on TV.
Granted the speed of light is a LOT faster than the speed of sound but apparently all the mucking about the TV signal had to do introduced a noticeable delay for me. That said, I was pretty close to the stadium.
In short, there is a time-lag. It is not a lot considering the distances involved but it is there.
Assuming no artificial delay is introduced (liked some “live” shows do to be able to catch someone swearing and bleep it) I’d guess your delay to be 10-20 seconds. Total guess on my part but it feels like it would be around there.
I have a Sirius/XM satellite radio account; I’ve listened to it in my car for about a decade, but it’s now available on my Amazon Echo, as well.
One of the stations I often listen to is the BBC World Service. When I’m listening in my car, if the feed isn’t precisely on time with their top-of-the-hour signal, it’s really close (i.e., no more than a few seconds off). But, when I listen to it on my Echo, the programming is lagged by about 3 minutes (i.e., the top-of-the-hour signal sounds at 3 minutes after the hour). Weird.
According to space.com, geosynchronous orbit is 22,236 miles above MSL. My thinking in asking this question was,
From stadium to sat
From sat to network office/studio
From network to sat
From sat to Austin affiliate
From Austin affiliate to Dish receiving station (or up to a sat?)
From receiving station to sat
From sat to Dish distribution point
From Dish to sat
From sat to my house
By my count, this is 8 to 10 one-way trips of 22, 236 miles. So, that would be 177,888 to 222,360 miles to get from Arlington to my house. At 186,000 miles per second, this would result in a delay of .9 to 1.2 seconds in travel time, plus whatever delays are introduced intentionally or as an artifact of whatever manipulation of the data takes place at each of its “stops” along the way.
Does that sound reasonable? How does Dish acquire the data from a local affiliate, like KTBC 7 in Austin?
Given equivalent media (over the air/wifi, cable, satellite), online video will always have a longer delay. You aren’t just putting out a signal for anyone to pick up, but sending it to a server that will then negotiate with each client, sending the data separately to each individual connection, which can take time. And then the data stream isn’t constant, but put out in chunks, so you have to wait until the chunk is big enough. The Internet also tends to have a longer travel time, and that time varies depending on the exact route and how congested the traffic is. To deal with that, the video player builds up a buffer. Then there is the encoding and decoding time.
The medium, of course, can add its own latency. Satellite has the longest, and over the air and cable both have to deal with just the speed of the raw signal. In my experience, satellite TV usually has a lag of a few seconds over the other two. But then ping times on satellite Internet are also not great. I’m pretty sure that medium latency is about the same for both direct and Internet broadcasting methods.
For Ashtura : in the 1970s and 1980s, most overseas calls went through a communications satellite. Geostationary satellites are about 30000 km above our heads, so even at the speed of light the signal had to travel for about 1/10 second to reach the satellite. For a normal conversation, the delay between asking a question and hearing the reply was at least 4/10 second (think about it), which was noticeable.
Now, with the development of the Internet, there are fiber optics cables running across most oceans between most countries, and most phone calls are routed through those. There is still a delay but it’s tiny.
2 seconds is on the ragged edge. If you are a broadcaster adding a significant amount of fat into the pipe is nowadays cheap (memory is dirt cheap) and makes life vastly easier. A minute or two might be a bit lazy but hardly a surprise.