[VoiceOps] High Quality, Reliable Voice via the Internet / SIPNOC

Alex Balashov abalashov at evaristesys.com
Mon Jun 9 17:43:08 EDT 2014

On 06/09/2014 05:30 PM, PE wrote:

>>2. Increase the ptime from 20 ms to 30-40 ms to reduce packet-drop exposure

> Alex B may be right on this. Hard to speculate without hard evidence
> with lots of volume to back it up. I do know, however, that some
> carriers (Verizon comes to mind) will not support anything other than
> 20ms, so it is easier to standardize on a single ptime rather than try
> to customize each install.

Yeah, it's hard to say. There are lots of variables that could 
potentially pull this in different directions, and possibly still render 
it good advice. For instance, with fewer packets and a constant amount 
of packet loss, a small absolute number of packets get lost. and maybe 
that leads to more reasonable adaptive jitter buffer behaviour that 
introduces less perceived artifacts or loss into the speech path than 
does the loss of a larger amount of packets.

Still, my instinct is that more packets with a smaller payload is better 
in a scenario with packet loss. It certainly seems that online games 
take this view as well, given the enormous amount of position updates 
that first-person shooters send, for instance. The idea is that even if 
some of them don't get there, all is not wholly lost.

Alex Balashov - Principal
Evariste Systems LLC
Tel: +1-678-954-0670
Web: http://www.evaristesys.com/, http://www.alexbalashov.com/

Please be kind to the English language:


More information about the VoiceOps mailing list