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Re: Topband: DSP and Latency

To: topband@contesting.com
Subject: Re: Topband: DSP and Latency
From: D Rodman MD <rodman@buffalo.edu>
Date: Thu, 19 Mar 2015 06:41:38 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
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
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