Re [Asterisk-Dev] SIP Jitter Buffer Testing

Kevin P. Fleming kpfleming at digium.com
Sat Sep 17 06:29:35 MST 2005


George Pajari wrote:

> It appears to me that, in fact, making modem carriage a design goal can 
> only improve the quality of the voice jitter handling. While one could 
> implement a defective jitterbuffer solution that is not obviously 
> defective during voice testing, it is a tautology that if it passes 
> modem signals it will certainly handle voice.

Well of course! The only way to perfectly handle modem signals is to 
never lose any frames, and to never have them delivered out of order or 
with significantly variable timing. If that were the case, then 
obviously voice connections would be 100% as well.

However, that is an unrealistic goal for a voice-oriented protocol, 
especially over the public Internet and other lossy networks. Packet 
loss concealment can be used to help out voice connections, but is 
anathema for modem connections; not using it would be a ridiculous waste 
of time and energy, when it can be used to great effect for voice.



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