Delay

What is digital TV a second or two behind analog? Does it take that
much time to encode and then decode?

Steve

--
Neural Planner Software Ltd http://www.NPSL1.com

On Thu, 26 Mar 2009 15:20:05 +0000, Stephen Wolstenholme
wrote:

What is digital TV a second or two behind analog? Does it take that
much time to encode and then decode?

Steve

Yes

And one day they may get lip sync to work. Mind you I don't care any more!
Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
wrote in message
...
On Thu, 26 Mar 2009 15:20:05 +0000, Stephen Wolstenholme
wrote:

What is digital TV a second or two behind analog? Does it take that
much time to encode and then decode?

Steve

Yes

lid wrote:

On Thu, 26 Mar 2009 15:20:05 +0000, Stephen Wolstenholme
wrote:

What is digital TV a second or two behind analog? Does it take that
much time to encode and then decode?

Steve

Yes

Digital satellite is even further behind digital terrestrial because
of the time it takes the signal to get to and from the satellite. Even
going at the speed of light it takes a bit of time.
--
Phil Cook looking north over the park to the "Westminster Gasworks"

In message , Phil Cook
writes
wrote:

On Thu, 26 Mar 2009 15:20:05 +0000, Stephen Wolstenholme
wrote:

What is digital TV a second or two behind analog? Does it take that
much time to encode and then decode?

Steve

Yes

Digital satellite is even further behind digital terrestrial because
of the time it takes the signal to get to and from the satellite. Even
going at the speed of light it takes a bit of time.

Analogue Sky News time used to be correct. Presumably they set the
clocks about 1 second fast.
--
Ian

On Thu, 26 Mar 2009 17:04:48 +0000, Ian Jackson
wrote:

In message , Phil Cook
writes
wrote:

On Thu, 26 Mar 2009 15:20:05 +0000, Stephen Wolstenholme
wrote:

What is digital TV a second or two behind analog? Does it take that
much time to encode and then decode?

Steve

Yes

Digital satellite is even further behind digital terrestrial because
of the time it takes the signal to get to and from the satellite. Even
going at the speed of light it takes a bit of time.

Analogue Sky News time used to be correct. Presumably they set the
clocks about 1 second fast.

If it was analogue why would they need to do this?

The message
from Stephen Wolstenholme contains these words:

What is digital TV a second or two behind analog? Does it take that
much time to encode and then decode?

Short answer: Yes!

Long answer: Hell, yes!

--
Regards, John.

Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

On Thu, 26 Mar 2009 17:23:50 +0000, Scott
wrote:

On Thu, 26 Mar 2009 17:04:48 +0000, Ian Jackson
wrote:

In message , Phil Cook
writes
wrote:

On Thu, 26 Mar 2009 15:20:05 +0000, Stephen Wolstenholme
wrote:

What is digital TV a second or two behind analog? Does it take that
much time to encode and then decode?

Steve

Yes

Digital satellite is even further behind digital terrestrial because
of the time it takes the signal to get to and from the satellite. Even
going at the speed of light it takes a bit of time.

Analogue Sky News time used to be correct. Presumably they set the
clocks about 1 second fast.

If it was analogue why would they need to do this?

Path delay to satellite and back.

The message
from lid contains these words:

On Thu, 26 Mar 2009 17:23:50 +0000, Scott
wrote:

On Thu, 26 Mar 2009 17:04:48 +0000, Ian Jackson
wrote:

In message , Phil Cook
writes
wrote:

On Thu, 26 Mar 2009 15:20:05 +0000, Stephen Wolstenholme
wrote:

What is digital TV a second or two behind analog? Does it take that
much time to encode and then decode?

Steve

Yes

Digital satellite is even further behind digital terrestrial because
of the time it takes the signal to get to and from the satellite. Even
going at the speed of light it takes a bit of time.

Analogue Sky News time used to be correct. Presumably they set the
clocks about 1 second fast.

If it was analogue why would they need to do this?

Path delay to satellite and back.

A quick (off the top of my head) calculation suggests this will account
for about 250mS delay. Codec delays for a low compression digital stream
in the terrestial distribution network might account for as much as
another 250mS[1] making, at a guess, a maximum propagation delay, studio
to the TV screen, of about half a second.

[1] I suspect the codec delay could be a lot less, I'm not a broadcast
professional. I'm merely surmising that a high bandwidth data link would
employ a less aggressive compression method designed specifically to
minimise codec latency.

--
Regards, John

Scott wrote:

On Thu, 26 Mar 2009 17:04:48 +0000, Ian Jackson
wrote:

Analogue Sky News time used to be correct. Presumably they set the
clocks about 1 second fast.

If it was analogue why would they need to do this?

Because of the time taken for the round trip from ground - satellite -
ground.