Re: [Phys-l] Digital TV signal delay

["John Clement" <clement@hal-pc.org>]

At the speed of signal propagation in the coaxial cable, and knowing the
length, you can easily determine how much delay is caused by the cable.
Hint: it is a large fraction of the speed of light.

But if the cable introduces reflections that cause signal degradation there
might be a few frames worth of delay for error correction.  The frame rate
is approximately 30fps (30Hz).

HD radio does not have this problem and any 2 HD radios are perfectly synced
due to the necessity of syncing the analog and digital signals.  I suspect
that eventually enough people will complain about the delay issue, and there
may eventually be an industry standard delay for all boxes.  Cable operators
may not respond to complaints about this, and the only solution for cable
users is to ask for identical decoder boxes, or only use the second set to
watch different programs.  That way you can save energy and promote family
togetherness.

John M. Clement
Houston, TX

> Peter Lohstreter wrote:
>
> > Interesting discussion, but I'm not sure it explains an observation I
> made after I had digital cable installed. (FIOS..)
> > One evening, my wife turned on the TV in the den to the same station I
> was watching in my office (30 feet away...) and there was a
> > > > > > > noticeable delay - over a second- between the two signals.  Was
> one of my decoder boxes operating at a higher resolution and needing
> more> >decoding time?
>
> I have noticed the same phenomenon with both our previous Comcast cable
> TV installation between the kitchen and family TV sets and our new FIOS
> installation.  The kitchen and TV sets are on different branches of the
> input cable feed and have different decoder boxes.  Could it be the
> delay in the different lengths of cable (RG-59) and splitters involved?
> I don't have the delay of RG-59 cable handy.  Is there a noticeable
> delay introduced by a TV coax splitter (or amplifier)?