Q. for the geeks
Annika1980
interviewed by the CNN anchor back home in the ATL. There is always a
few seconds delay since it takes time for the satellite signal to make
it's way around the world.
OK, so I turn on my Nintendo Wii and I'm playing Mario Kart online
with people from England, Brazil, China, Australia and Japan. I'm
totally kicking ass as we all enjoy a fast-paced game of live racing
action with no delay. How is this possible?
Is it because of the way the WWW is connected? Is it really hard-
wired all the way around? I would think that the signal would have to
hit a satellite at some point.
Doug Payne
> We've all seen TV newscasts that show a reporter live in Iraq being
> interviewed by the CNN anchor back home in the ATL. There is always a
> few seconds delay since it takes time for the satellite signal to make
> it's way around the world.
>
> OK, so I turn on my Nintendo Wii and I'm playing Mario Kart online
> with people from England, Brazil, China, Australia and Japan. I'm
> totally kicking ass as we all enjoy a fast-paced game of live racing
> action with no delay. How is this possible?
>
> Is it because of the way the WWW is connected? Is it really hard-
> wired all the way around?
Yes.
Alan Browne
Networks use satellite for portability reasons. They need a relatively
small number of high bandwidth links that can run out of a truck from
virtually anywhere.
The internet (backbone) uses land/submarine lines (esp. fibre optic) for
international and national connection for reasons of extreme bandwidth,
cost and low latency. Some microwave (tower to tower) for local / rural
connection still at pretty high BW; and copper coax. Low latency is
important for high speed networks.
There are huge fibre optic networks covering the world and if you google
about you'll find maps of them. They carry the major bulk of the
internet traffic.
There are some satellite based internet connections, eg: rural users who
need higher bandwidth than the telephone provides. In these systems,
typically the upload is over the phone (URL's don't need much BW) and
the downlink is over satellite. Though for uploading a large file or
e-mail it will take a while... the performance of these systems on the
downlink side is often less than 1 Mbit/s.
(Vice cable modem service of up to 60 Mbit/s here; and over 100 Mbit/s
fibre to the house service in some countries (S. Korea, Japan, Taiwan...)).
Fred McKenzie
<2f191197-dcc6-4aa7...@m38g2000yqd.googlegroups.com>,
Annika1980 <annik...@aol.com> wrote:
> We've all seen TV newscasts that show a reporter live in Iraq being
> interviewed by the CNN anchor back home in the ATL. There is always a
> few seconds delay since it takes time for the satellite signal to make
> it's way around the world.
It is probably not propagation delay as much as time required for
analog-to-digital and digital-to-analog conversion, perhaps at several
points along the route. At least some of that delay is for error
correction. And what you see is the total delay from the local anchor
to the remote reporter and back again.
I've also noticed a difference in time between a standard FM radio
broadcast and the same program on an HD radio channel.
Now if only they could get the sound to sync with the picture.
David Nebenzahl
> In article
> <2f191197-dcc6-4aa7...@m38g2000yqd.googlegroups.com>,
> Annika1980 <annik...@aol.com> wrote:
>
>> We've all seen TV newscasts that show a reporter live in Iraq being
>> interviewed by the CNN anchor back home in the ATL. There is always a
>> few seconds delay since it takes time for the satellite signal to make
>> it's way around the world.
>
> It is probably not propagation delay as much as time required for
> analog-to-digital and digital-to-analog conversion, perhaps at several
> points along the route.
Hmm; I'm no expert on this, but I don't see why in the world one would
have D-A and A-D conversion on a signal that's in the digital domain and
would be best handled by keeping it there.
> At least some of that delay is for error correction.
Now that makes sense, though I don't know how much ECD and ECC happens
on such signals.
--
Who needs a junta or a dictatorship when you have a Congress
blowing Wall Street, using the media as a condom?
- harvested from Usenet
Alan Browne
> In article
> <2f191197-dcc6-4aa7...@m38g2000yqd.googlegroups.com>,
> Annika1980 <annik...@aol.com> wrote:
>
>> We've all seen TV newscasts that show a reporter live in Iraq being
>> interviewed by the CNN anchor back home in the ATL. There is always a
>> few seconds delay since it takes time for the satellite signal to make
>> it's way around the world.
>
> It is probably not propagation delay as much as time required for
> analog-to-digital and digital-to-analog conversion, perhaps at several
It's prop delay.
Calvin Sambrook
news:fmmck-C24EB8....@nntp.aioe.org...
Twaddle.
Analogue to digital conversion doesn't take significant time at all. In
fact it takes place on a pixel by pixel basis so it's in the 10's to 100's
of MHz region. There shouldn't be much going on anyway as even if the
camera kit is analogue the intermediate systems won't be nor the final
projection display.
Compression and error correction add a frame or two. The most I've ever
seen used is 6 frames although some of the cheaper broadcasters might be
pushing their luck further I guess. That's 120ms in UK speak, a little less
in the US.
No, the bulk of any delay is the round trip to the satellite. Which tends
only to be used when there's no other option.
Eric Stevens
Google has even laid their own submarine cables!
Eric Stevens
John McWilliams
So, might Comcast be using Sat. as well- or what might they use to get
the signal from Philly to SF Bay area? Microwave? - Kinda makes sense,
as friend and I were watching the World Series 'together' in towns 20
miles apart, she on cable, and me on DirecTV, and her signal came in
about two seconds later than mine.
Sad to note that the picture was crumby. Said it was HD, but it was lo-Q
HD at best. Probably 720i overly compressed.
Great bokeh, though!
--
john mcwilliams
Bill Graham
"Annika1980" <annik...@aol.com> wrote in message
news:2f191197-dcc6-4aa7...@m38g2000yqd.googlegroups.com...
I doubt if the delay is there because the satellite signal has to, "make its
way around the world." At 186,000 miles per second, it gets around the world
in .043 seconds. I rather suspect that the delay is due to other, ground
based equipment, or perhaps even built-in political delays.
Alan Browne
> So, might Comcast be using Sat. as well- or what might they use to get
> the signal from Philly to SF Bay area? Microwave? - Kinda makes sense,
> as friend and I were watching the World Series 'together' in towns 20
> miles apart, she on cable, and me on DirecTV, and her signal came in
> about two seconds later than mine.
Television networks insert programming delays for their own reasons
(coordination of commercials across the country, mainly, but
occasionally for "bleep" operators on real time broadcasts like ball games).
Cable operators get some of their signal from local receivers and some
from satellite.
> Sad to note that the picture was crumby. Said it was HD, but it was lo-Q
> HD at best. Probably 720i overly compressed.
I haven't heard of television broadcasts above 720 to date.
John McWilliams
We regularly get programming in 1080 i, also 720 p; it's hard to tell
the difference, esp. so as sources can be so variable. Some VOD is at
1080p, the top of the line so far for consumers in the US. (Blu-ray does
this, and mileage varies according to the source and how well it's
engineered on conversion from the Master.... or not Master, as the case
often seems to be)
However, 720 i sucks badly, more so if the source is lacking or
overcompressed.- as was my feed of the Baseball "World Series".
--
John McWilliams
When asked why he still lives in the UK despite working so much in the
US, John Cleese had this to say:
Number one, we speak English and you don't.
Number two, when we hold a world championship for a particular
sport, we invite teams from other countries.
Number three, when one meets the Head of State in England, one has
to go down on one knee only.
Alan Browne
Got it.
We don't have over the air digital mandates until 2011.08.31 though we
do receive some US channels over the air (digital), cable (analog and
digital). Some stations here do transmit their digital signal already
since they feed that to the cable co's and sat services. I haven't
bothered with the cable subscription for digital as I watch no more than
4 or 5 hours per week (2 hours is more usual) - including the usually
excellent US PBS NOVA at 8 tonight (first of 3 parts on becoming human.
Creationists should watch this.
http://www.pbs.org/wgbh/nova/beta/evolution/becoming-human-part-1.html
David Nebenzahl
> I rather suspect that the delay is due to other, ground based
> equipment, or perhaps even built-in political delays.
"Political delay" like, oh, I don't know, *liberals* intentionally
causing delays so Obama can vet the content? Uh huh.
You're *such* a fucking idiot, Graham.
bo...@nospam.com
There is definitely a delay in satellite TV, I know because I was once at a
demonstration of satellite TV at McGill U. in Montreal, and I got to stand in
front of a camera and wave, and watch myself on the monitor, waving back to
myself a short time later!
Oh, your math is a bit screwy, the satellite is 24,000 miles up, so the full
return trip is around 1/3 second, I guess...
And as for the Internet, there can easily be a 1/3 second delay between
continents, since copper speed is a lot slower than light speed, and there are
lots of "relay stations" providing propagation delay. I used to talk to people
in Oz on Internet phone, and there was a bit of a delay in that.
When I worked in train dispatch, we had a problem with echo on the lines because
the dispatchers are all in Toronto, and the radio towers are in Montreal. Thats
only 320 miles and the delay was at least 100ms.
As for Annikas game server, there may be prop. delay compensation built in
somehow... it only appears to him that there is no delay... it's best to ask the
game operators!
It's funny, I sometimes watch TV on my computer, and if the regular TV is on, I
can see a delay of over 1 second between them. If I miss a sentence, I get to
hear it again a second later!
bo...@nospam.com
<alan....@FreelunchVideotron.ca> wrote:
>
>We don't have over the air digital mandates until 2011.08.31 though we
>do receive some US channels over the air (digital), cable (analog and
>digital). Some stations here do transmit their digital signal already
>since they feed that to the cable co's and sat services. I haven't
>bothered with the cable subscription for digital as I watch no more than
>4 or 5 hours per week (2 hours is more usual) - including the usually
>excellent US PBS NOVA at 8 tonight (first of 3 parts on becoming human.
>
You're so right, Alan, TV here sucks big time! People ask me when I'm getting
digital HD and I answer - "For what?"
Too bad I just saw this post, it's after 8...
tony cooper
>It's funny, I sometimes watch TV on my computer, and if the regular TV is on, I
>can see a delay of over 1 second between them. If I miss a sentence, I get to
>hear it again a second later!
We are on Brighthouse cable. We have a cable convertor/recorder box
in one room, and just cable connections to two other TVs. If I happen
to have two TVs on, the direct cable connected TVs have a slight
delay. Sometimes not more than one complete sentence of dialog.
--
Tony Cooper - Orlando, Florida
Michael
Actually, geostable satellites may be orbiting at 24000 miles up.
That's 48000 miles up and back. So if I send my signal, you get it
48000 miles later. Then your signal does the same, up and back. That is
nearly a half second delay, easily noticeable.
--
Michael
Walter Banks
Doug Payne wrote:
Shortly after communication satellites were launched in geosync
orbits the common carriers decided that quarter second delay
was too much for pleasant conversation. This has meant that c
common carriers and most internet data goes via fibre optic cable
with delays in in the order of 47ms. Satellite phones still have
the quarter second delay.
w..
K W Hart
"Bill Graham" <we...@comcast.net> wrote in message
news:qJidnbH0OMkMMG3X...@giganews.com...
Communications satelites are orbitting (IIRC) at about 22,000 miles above
the equator. The signal has to go up and back down, so each satelite hop is
40,000 miles. To go around the world would requires a minimum of three hops,
which would be about 120,000 miles, or about 2/3 second. There is a lot of
signal processing equipment along the way, causing additional delay.
Bill Graham
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4af0cb5f$0$4062$8226...@news.adtechcomputers.com...
> On 11/3/2009 2:24 PM Bill Graham spake thus:
>
>> I rather suspect that the delay is due to other, ground based
>> equipment, or perhaps even built-in political delays.
>
> "Political delay" like, oh, I don't know, *liberals* intentionally causing
> delays so Obama can vet the content? Uh huh.
>
> You're *such* a fucking idiot, Graham.
I speak of political delays of the type that are involved with editing out
bad language, or verifying clean signal quality, etc. Delays that are not
simply caused by electronic necessity, but which are involved with human
induced quality control.....It is idiotic to jump to conclusions without
knowing anything about what is being discussed.
Bill Graham
<bo...@nospam.com> wrote in message
news:4mn1f559pfo4f1101...@4ax.com...
transmission. It takes time for relays to energize and signal levels to
steady out in capacitive circuits. Also the "political" delays I spoke of
above involved with verification of signal quality and/or content.
Bill Graham
"Michael" <adunc...@mypacks.net> wrote in message
news:2009110400353916807-adunc79617@mypacksnet...
communications......I believe this is due to other factors than satellite
distances.