Re: High Loss% with ThumbDV on DMR


Tom McDermott <tom.n5eg@...>
 

Hi Tom,

In my opinion this is not a hardware issue.  The general problem is that the Internet has
variable latency and variable packet loss.  The software feeding a vocoder has to deal
with it.  The use of TCP to recover from lost packets causes a delay in the received
AMBE frames. 

What to do?   

Brute force would be to just throttle the packets to the DV.  But then the latency would
grow with time, and become unusable.  Another approach is for the software to try
to figure out when arriving internet packets are too late and throw them away.

Real time media devices sometimes use a special protocol such as RTP / RTCP to
balance the tradeoff between loss rate and latency.

If the internet path from the source to the destination (involving a lot of connections,
routers, etc.) has loss and / or latency problems, that sort of has to be fixed first.

-- Tom, N5EG





On Thu, Jan 25, 2018 at 1:39 PM, <tcorcoran@...> wrote:
Tnx Tom,

this is is a thorough diagnosis and resolution of the problem. Is this something that should be fed back to NW? Or is DMR beyond the design spec of the ThumbDV? 

I understand conceptually what you have done but would be unable to build the interface to provide packet limiting on my own. Any "brite force" method of limiting packets? Is this something that the vendor could/should provide? I’m using BlueDV but not implying he should do anything. It’s a NW issue - correct?

Tom VE3NY 
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