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uk.tech.digital-tv (Digital TV - General) (uk.tech.digital-tv) Discussion of all matters technical in origin related to the reception of digital television transmissions, be they via satellite, terrestrial or cable. Advertising is forbidden, with no exceptions.

Time delay - Big Ben slow?



 
 
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  #11  
Old January 2nd 12, 05:43 PM posted to uk.tech.digital-tv
Brian Gaff
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Default Time delay - Big Ben slow?

I've also noticed that two freeview boxes are often as much as two seconds
dirfferent. If you really want delay, look at internet streams.
Brian

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"Geoff Pearson" wrote in message
...

"John Aldred" wrote in message
...
I was watching the countdown to the New Year on BBC (Freeview).
As Big Ben struck the hour, my time pieces were indicating about 5 secs
past
midnight.

Our clock is synchronised with the broadcast time signal (NPL MSF), and
the
computer is synchronised with the internet time servers.
Both indicated that Big Ben was slow.

So my question is does it really take about 5 seconds for the TV signal
to
be processed and reach my eyes/ears? Or am I living in a time warp.

--
John


it does take that long - try having a DAB set and an FM set running
together - makes a weird echo.



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  #12  
Old January 2nd 12, 07:46 PM posted to uk.tech.digital-tv
Roger Mills[_2_]
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Default Time delay - Big Ben slow?

On 02/01/2012 13:19, John Aldred wrote:
I was watching the countdown to the New Year on BBC (Freeview).
As Big Ben struck the hour, my time pieces were indicating about 5 secs past
midnight.

Our clock is synchronised with the broadcast time signal (NPL MSF), and the
computer is synchronised with the internet time servers.
Both indicated that Big Ben was slow.

So my question is does it really take about 5 seconds for the TV signal to
be processed and reach my eyes/ears? Or am I living in a time warp.


Probably - particularly if you're watching in HD.

Pre DSO, if we had one of our sets on analog and the other on the same
station but on Freeview, I noticed a 1 - 2 second time difference
between them. Now, after DSO with one set on Freeview-SD via its
internal tuner and the other on Freeview-HD via an HDR-FOX-T2, the one
with HD is a whole sentence - must be upwards of 3 seconds - behind the
other. So Big Ben on that could easily be 5 seconds behind the same
thing on FM radio.
--
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Roger
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  #13  
Old January 2nd 12, 09:55 PM posted to uk.tech.digital-tv
Kennedy McEwen
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Default Time delay - Big Ben slow?

In article , Mark Carver
writes
John Rumm wrote:
I used to note a couple of seconds difference between analogue and
freeview - not sure about 5. Having said that, different boxes
certainly differ in speed by a relatively noticeable amount.


The Beeb may well have been using a satellite link for the OB back to
base, so that's going to add latency too ?

Where's the satellite then? It only takes 2.7sec for a relay on the
moon, half that for Neil Armstrong's one way Apollo broadcasts in 1969,
and I am pretty sure the satellite isn't that far away. Relay to
geostationary orbit is less than 1/10th of that time. Sure, it adds to
the latency, but only 5%.
--
Kennedy
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  #14  
Old January 2nd 12, 10:45 PM posted to uk.tech.digital-tv
Steve Thackery[_2_]
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Default Time delay - Big Ben slow?

Kennedy McEwen wrote:

Relay to
geostationary orbit is less than 1/10th of that time. Sure, it adds to
the latency, but only 5%.


I saw a TV programme about this recently. Apparently it's the
processing delay inside the satellite, not the flight time there and
back.

The programme was talking about the challenges of getting more
processor power within a fairly limited energy budget. There's also
thermal management to deal with when more powerful processors are used.
No air for cooling, you see, it's all done with heat pipes and
radiated heat.

New satellites are much faster.

--
SteveT


  #15  
Old January 2nd 12, 11:14 PM posted to uk.tech.digital-tv
Richard Tobin
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Default Time delay - Big Ben slow?

In article ,
Steve Thackery wrote:

I saw a TV programme about this recently. Apparently it's the
processing delay inside the satellite, not the flight time there and
back.


That's rather surprising. What processing is it doing? And if it's
doing it for seconds, it must be buffering tens of megabytes per
multiplex, which I would have thought was at least as much trouble
as the processing power.

-- Richard
  #16  
Old January 2nd 12, 11:42 PM posted to uk.tech.digital-tv
Paul Ratcliffe
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Default Time delay - Big Ben slow?

On Mon, 02 Jan 2012 14:26:44 +0000, Mark Carver
wrote:

John Rumm wrote:

I used to note a couple of seconds difference between analogue and
freeview - not sure about 5. Having said that, different boxes certainly
differ in speed by a relatively noticeable amount.


The Beeb may well have been using a satellite link for the OB back to base, so
that's going to add latency too ?


Yes, they were. Adds about 2 seconds. Freeview is about 3.
So, to the OP, yes it really does take that long.
  #17  
Old January 2nd 12, 11:44 PM posted to uk.tech.digital-tv
Paul Ratcliffe
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Default Time delay - Big Ben slow?

On Mon, 2 Jan 2012 22:55:01 +0000, Kennedy McEwen
wrote:

The Beeb may well have been using a satellite link for the OB back to
base, so that's going to add latency too ?

Where's the satellite then?


Well, aren't you up yourself? It's in the usual place?

It only takes 2.7sec for a relay on the
moon, half that for Neil Armstrong's one way Apollo broadcasts in 1969,
and I am pretty sure the satellite isn't that far away. Relay to
geostationary orbit is less than 1/10th of that time. Sure, it adds to
the latency, but only 5%.


It's bloody obvious that most of it is MPEG coding and decoding not
the trip to/from the satellite FFS.
  #18  
Old January 2nd 12, 11:47 PM posted to uk.tech.digital-tv
Paul Ratcliffe
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Posts: 2,486
Default Time delay - Big Ben slow?

On Mon, 02 Jan 2012 23:45:17 GMT, Steve Thackery wrote:

Relay to
geostationary orbit is less than 1/10th of that time. Sure, it adds to
the latency, but only 5%.


I saw a TV programme about this recently. Apparently it's the
processing delay inside the satellite, not the flight time there and
back.


That's bull****. A satellite transponder has no significant delay.

The programme was talking about the challenges of getting more
processor power within a fairly limited energy budget. There's also
thermal management to deal with when more powerful processors are used.
No air for cooling, you see, it's all done with heat pipes and
radiated heat.

New satellites are much faster.


Processors? What are you on about? It's just frequency change and
amplification. What do you need a processor for?
It's a bloody analogue radio link.
  #19  
Old January 3rd 12, 12:06 AM posted to uk.tech.digital-tv
Steve Thackery[_2_]
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Posts: 2,552
Default Time delay - Big Ben slow?

Richard Tobin wrote:

That's rather surprising. What processing is it doing? And if it's
doing it for seconds, it must be buffering tens of megabytes per
multiplex, which I would have thought was at least as much trouble
as the processing power.


Dunno. It was one of that short series of programmes about engineering
in the UK. There was one about the Airbus wing, the satellite one, and
a couple of others, I think. Sorry, I can't remember the programme
name or channel. Late 2011, they were broadcast.

Like you, I was surprised. However, this issue with delay was
discussed, and they talked about how much it had been improved in the
later generations of comms satellites.

--
SteveT


  #20  
Old January 3rd 12, 12:09 AM posted to uk.tech.digital-tv
Steve Thackery[_2_]
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Posts: 2,552
Default Time delay - Big Ben slow?

Paul Ratcliffe wrote:

That's bull****. A satellite transponder has no significant delay.


Processors? What are you on about? It's just frequency change and
amplification. What do you need a processor for?
It's a bloody analogue radio link.


Ah, good old Paul! As polite and agreeable as ever.

I'm only reporting what the programme said (sorry, I can't remember
what it was called or the channel). They distinctly mentioned delay,
and how the newer sats are much better.

Hey, Paul: can't you just chill out a bit and have a relaxed genial
chat, like the rest of us? Rather than spraying your coffee
everywhere?

--
SteveT


 




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