Cut! The SIA indicator, media interworking and call clipping
You surely have experienced this: You call a friend, ringing stops and then there is silence. You say “Hello…?” and immediately your friend responds with “Yes, I’m here, I already said hello!”.
You missed that first “Hello” from your friend which caused an awkward moment.
Why’s that? When you initiate a call, the endpoints will use to the SDP protocol to negotiate which codec to use. Sometimes this negotiation is still ongoing, when the call gets connected. In effect, the endpoints do not know which codec to use & to expect and the first second(s) of speech are clipped.
Voipfuture Qrystal has a special indicator to automatically detect such clipped calls. It’s called “SDP in ACK” or SIA for short. There are call routing scenarios, e.g. involving back-to-back SIP user agents, where the late end of codec negotiation cannot be avoided, and where it’s technically perfectly legal.
However, to the users the clipping effect is a nuisance. You want to know how often it happens and want to eliminate it wherever possible. Qrystal’s SIA indicator is here to help.
Take care, Carsten
Just in case you want to know more: