Delay on HD channels

BBC HD is currently showing the same as BBC 2, but with a delay of 21
seconds. What causes such a big delay?

-- Richard

On Fri, 7 Sep 2012 17:53:07 +0000 (UTC), Richard Tobin
wrote:

BBC HD is currently showing the same as BBC 2, but with a delay of 21
seconds. What causes such a big delay?

A hard disk.

Richard Tobin wrote:
BBC HD is currently showing the same as BBC 2, but with a delay of 21
seconds. What causes such a big delay?

-- Richard

Because the information density of HD television is higher the signals
interact with the atmosphere rather more. You can visualise it as the
signal having a rougher 'surface' (because there are more bits sticking
out). The effect of this is to delay the speed that the signal travels
through the air. This is what we scientists call 'propagation delay'.

So it might be 21 seconds where you are Richard, but for other viewers
it could be much more or much less.

The effect is much stronger in areas where the air is polluted, so in
Barnsley programmes can arrive several days late. Unfortunately this
effect causes (as Einstein predicted) a 'time dilation'effect, so people
living on the other side of Barnsley (for example) receive signals that
are bent around the Barnsley zone. Since the signals can go around
Barnsley both ways (the new one-way system has no relevance) these
viewers receive their signals twice. This explains all the +1 channels.

Obviously satellite signals have to through a lot of atmosphere since
they are very high up (probably ten miles or more), and this explains
why the men in Top Gear on the satellite channels always have 1970s
haircuts and are testing Ford Cortinas.

There is a related problem called 'phase delay' in which the top of the
picture is delayed more than the bottom. This is why people on
Eastenders sometimes don't seem to know whether they're coming or going.
Luckily the BBC Engineering Dept have found a complete solution to phase
delay, involving a relatively simple alteration to the way television
programmes are made. At first there were problems with the actors'
uniion but these have been settled. Actors are paid to come and paid to
go irrespective of which they do first, but where they are called upon
to come and go simultaneously they get time and a half.

Incidentally I just looked this up on Wikipaedia and found nothing.
That's a gap in human knowledge that needs to be filled, so I'll be
expanding the material I've covered here and making an entry. Can anyone
else contribute to this as I feel that my knowledge, although extensive,
is incomplete.

Bill

On Sep 8, 2:21*am, Bill Wright wrote:
Richard Tobin wrote:
BBC HD is currently showing the same as BBC 2, but with a delay of 21
seconds. *What causes such a big delay?

-- Richard

Because the information density of HD television is higher the signals
interact with the atmosphere rather more. You can visualise it as the
signal having a rougher 'surface' (because there are more bits sticking
out). The effect of this is to delay the speed that the signal travels
through the air. This is what we scientists call 'propagation delay'.

So it might be 21 seconds where you are Richard, but for other viewers
it could be much more or much less.

The effect is much stronger in areas where the air is polluted, so in
Barnsley programmes can arrive several days late. Unfortunately this
effect causes (as Einstein predicted) a 'time dilation'effect, so people
living on the other side of Barnsley (for example) receive signals that
are bent around the Barnsley zone. Since the signals can go around
Barnsley both ways (the new one-way system has no relevance) these
viewers receive their signals twice. This explains all the +1 channels.

Obviously satellite signals have to through a lot of atmosphere since
they are very high up (probably ten miles or more), and this explains
why the men in Top Gear on the satellite channels always have 1970s
haircuts and are testing Ford Cortinas.

There is a related problem called 'phase delay' in which the top of the
picture is delayed more than the bottom. This is why people on
Eastenders sometimes don't seem to know whether they're coming or going.
Luckily the BBC Engineering Dept have found a complete solution to phase
delay, involving a relatively simple alteration to the way television
programmes are made. At first there were problems with the actors'
uniion but these have been settled. Actors are paid to come and paid to
go irrespective of which they do first, but where they are called upon
to come and go simultaneously they get time and a half.

Incidentally I just looked this up on Wikipaedia and found nothing.
That's a gap in human knowledge that needs to be filled, so I'll be
expanding the material I've covered here and making an entry. Can anyone
else contribute to this as I feel that my knowledge, although extensive,
is incomplete.

Bill

It's not April 1st is it?

Bill Wright wrote:
Can anyone
else contribute to this as I feel that my knowledge, although extensive,
is incomplete.

Yes, you forgot to mention that electrons travel backwards in time in
some parts of the country and turn into positrons.

harry wrote:
On Sep 8, 2:21 am, Bill Wright wrote:
Richard Tobin wrote:
BBC HD is currently showing the same as BBC 2, but with a delay of 21
seconds. What causes such a big delay?
-- Richard
Because the information density of HD television is higher the signals
interact with the atmosphere rather more. You can visualise it as the
signal having a rougher 'surface' (because there are more bits sticking
out). The effect of this is to delay the speed that the signal travels
through the air. This is what we scientists call 'propagation delay'.

So it might be 21 seconds where you are Richard, but for other viewers
it could be much more or much less.

The effect is much stronger in areas where the air is polluted, so in
Barnsley programmes can arrive several days late. Unfortunately this
effect causes (as Einstein predicted) a 'time dilation'effect, so people
living on the other side of Barnsley (for example) receive signals that
are bent around the Barnsley zone. Since the signals can go around
Barnsley both ways (the new one-way system has no relevance) these
viewers receive their signals twice. This explains all the +1 channels.

Obviously satellite signals have to through a lot of atmosphere since
they are very high up (probably ten miles or more), and this explains
why the men in Top Gear on the satellite channels always have 1970s
haircuts and are testing Ford Cortinas.

There is a related problem called 'phase delay' in which the top of the
picture is delayed more than the bottom. This is why people on
Eastenders sometimes don't seem to know whether they're coming or going.
Luckily the BBC Engineering Dept have found a complete solution to phase
delay, involving a relatively simple alteration to the way television
programmes are made. At first there were problems with the actors'
uniion but these have been settled. Actors are paid to come and paid to
go irrespective of which they do first, but where they are called upon
to come and go simultaneously they get time and a half.

Incidentally I just looked this up on Wikipaedia and found nothing.
That's a gap in human knowledge that needs to be filled, so I'll be
expanding the material I've covered here and making an entry. Can anyone
else contribute to this as I feel that my knowledge, although extensive,
is incomplete.

Bill

It's not April 1st is it?

I think this is an area of expertise that only Dennis is equipped to
comment on.


--
Ineptocracy

(in-ep-toc’-ra-cy) – a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

Bill



Absolutely brilliant. Well written.

"Bill Wright" wrote in message
...
Richard Tobin wrote:
BBC HD is currently showing the same as BBC 2, but with a delay of 21
seconds. What causes such a big delay?

-- Richard

Because the information density of HD television is higher the signals
interact with the atmosphere rather more. You can visualise it as the
signal having a rougher 'surface' (because there are more bits sticking
out). The effect of this is to delay the speed that the signal travels
through the air. This is what we scientists call 'propagation delay'.

So it might be 21 seconds where you are Richard, but for other viewers it
could be much more or much less.

The effect is much stronger in areas where the air is polluted, so in
Barnsley programmes can arrive several days late. Unfortunately this
effect causes (as Einstein predicted) a 'time dilation'effect, so people
living on the other side of Barnsley (for example) receive signals that
are bent around the Barnsley zone. Since the signals can go around
Barnsley both ways (the new one-way system has no relevance) these viewers
receive their signals twice. This explains all the +1 channels.

Obviously satellite signals have to through a lot of atmosphere since they
are very high up (probably ten miles or more), and this explains why the
men in Top Gear on the satellite channels always have 1970s haircuts and
are testing Ford Cortinas.

There is a related problem called 'phase delay' in which the top of the
picture is delayed more than the bottom. This is why people on Eastenders
sometimes don't seem to know whether they're coming or going. Luckily the
BBC Engineering Dept have found a complete solution to phase delay,
involving a relatively simple alteration to the way television programmes
are made. At first there were problems with the actors' uniion but these
have been settled. Actors are paid to come and paid to go irrespective of
which they do first, but where they are called upon to come and go
simultaneously they get time and a half.

Incidentally I just looked this up on Wikipaedia and found nothing. That's
a gap in human knowledge that needs to be filled, so I'll be expanding the
material I've covered here and making an entry. Can anyone else contribute
to this as I feel that my knowledge, although extensive, is incomplete.

I don't know very much about the technical aspects of digital TV but have an
interest in the subject. Quite a few posts on the newsgroup are
uninteresting but those from Mr Wright are always succint and informative.
Is is rare that someone with such a detailed grasp of things technical can
explain things in a simple manner so that even people such as myself can
begin to understand them. But there is still one thing which I do not
comprehend at all about this. Is it not possible that the revolution of the
sun round the earth may also be causing propagation delays?
--
JohnT

John Legon wrote:
Bill Wright wrote:
Can anyone else contribute to this as I feel that my knowledge,
although extensive, is incomplete.

Yes, you forgot to mention that electrons travel backwards in time in
some parts of the country and turn into positrons.
Ah yes! The 'Norfolk' effect.

Bill

DerbyBorn wrote:
Bill



Absolutely brilliant. Well written.

Thank you. It's pretty easy though. The facts present themselves to me
with crystal clear logic and certainty every Friday night. This is
convenient because I'm usually far to drunk to watch telly, so writing
them down gives me something to do.

I often write letters to the newspapers at the same time, explaining
really obvious ways that all the world's problems could be solved.
Unfortunately vested interests conspire with the editors and my letters
are rarely published.

Bill