Re: High Loss% with ThumbDV on DMR


Hi All,

I will try to explain. 

What happens when you sent to the DMR master/reflector.

Every 20ms I receive a DMR voice frame of 72 bits from the ThumbDV. I wait until I have 3 frames. Then I add some extra spicy saus for DMR data ( 48 bits ) ( EMB etc ).
So when I miss one frame from the AMBE I will wait for the next. This is not a loss what you see on the other end!
The 3*72 bits voice + data 48 bits = 264 bits / 8 = 33 bytes is send to the master/reflector + extra headers ( depends on network ). When this data ( 33 bytes + header) is not received, it is a loss.
When the 72 bits voice is corrupted the BER will be higher. 

It is not normal to use TCP as a transport for voice. When you have loss it will re-transmit. And retransmitting is latency or jitter. Jitter is really bad for voice!
Normally voice is transported by UDP. UDP is like a postcard. You never know if the card is received. In the DMR/DSTAR data we also send a kind of sequence number so we can count the loss and do something with it like filling up with white noise. 

There are several tools on internet to test the latency, loss etc. A good internet connection from end to end is very important for voice!


Greets and 73,
    David PA7LIM

On 25-01-2018 23:24, John D Hays - K7VE wrote:

Tom -- David (PA7LIM), author of BlueDV, participates on this list, so we may hear from him on this topic.

On Thu, Jan 25, 2018 at 2:22 PM, <tcorcoran@...> wrote:

tnx for very constructive advice. I will pursue with s/w author. 

Tom VE3NY 


John D. Hays
Edmonds, WA

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