Topband: DSP and Latency

[D Rodman MD]

Everything takes time.  I have a great example of audio latency.  
Kitchen has television with direct cable input and family room has 
digital cable box with HDML to large screen LED set.  When watching 
events, like superbowl, both sets might be on.  It is highly obvious 
which television displays the video and has audio first.  It is the 
kitchen one.

I am not sure how we got a 120msec latency from NYC to NP2.  It is more 
than pinging the route one way.  I have been doing this for over 10 
years.  Latency, for me, is really the total time between the station on 
one end hears a signal, transmits and the station on the other end hears 
the audio.  I can ping within my own network and get times of around 
10msec.  I think 120msec is going to be a one way figure, isn't it?  It 
needs to be doubled to account for the two way internet passage of 
signals both ways and in order to get the true latency add in the 
processing time of the computer or radio at either end (if applicable).

The real killer here can be variation in the internet latency, either at 
the local network or international link.  That variation can negatively 
influence communications and be frustrating.

Moreover, I submit in some circumstances a quarter of a second is plenty 
of time for another station to be first in.  We have all seen that.

-- 
David J Rodman MD
Assistant Clinical Professor
Department of Ophthalmology
SUNY/Buffalo

Office 716-857-8654