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Old December 5th 16, 09:24 AM posted to uk.tech.digital-tv
PeeGee
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Posts: 158
Default Digital drop out.

On 04/12/16 20:41, Roderick Stewart wrote:
On Sun, 04 Dec 2016 16:21:34 +0000 (GMT), Jim Lesurf
wrote:

As I understand it, it is delays due to the processing of the digital
signal. Different sets may have different delays, and radio and TV may
have even more different delays. FM radio would have given you Big Ben
accurately, but nothing digital is likely to have done.


Strictly speaking FM uses NICAM for distribution, and NICAM is "digital".
It does add a delay, but I doubt you'd notice it. So your "nothing" aims at
the wrong target. The cause is the lossy compression schemes employed for
'digital' TV and radio which the systems take some time to process. Not
"digital" per se.


Presumably the compression for video takes considerably longer than
for audio, but the audio part of a television broadcast has to be
delayed to match the picture. Audio on its own, i.e. radio, wouldn't
need so much so the delay wouldn't be noticeable.

I first became aware of how much delay must be in the system on the
day of Princess Diana's funeral, when every channel (except 4) was
broadcasting the same material, and the difference between the latest
and earliest version was about 8 seconds. The only time you can trust
is either a radio controlled clock or the internet. Broadcasting used
to be an authoritative source for everything but not any more.

Rod.


I'm not convinced I trust a radio controlled clock - mine has shown the
time as 36:99 (or some symbols for minutes larger than 100), but usually
during maintenance and at a time when you might want a wake-up alarm. I
don't recall a problem before the change of transmitter location. The
German transmitter is far more reliable!

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