[Asterisk-Users] A question on codec translation.

WipeOut
Mon, 12 Jan 2004 04:53:43 -0000

Here is the scenario...

SIP UA's can use either GSM or G.711 ( in that order of preference in
the sip.conf )..
Asterisk Server1 is linked to Asterisk Server2 via IAX2 and also
supports GSM and G.711 ( also in that order of preference)..

1. If a call comes in from the UA using GSM and then goes out over the
IAX2 leg, Will Asterisk simply move the GSM encoded data from the SIP
channel to the IAX2 channel and so have very little performance overhead
since it will not be decoding and re-encoding the GSM data? or will it
decode and re-encode the voice data?

2. Assuming that the answer to question1 is that Asterisk will simply
move the encoded data from the SIP channel to the IAX2 channel without
decoding and re-encoding (otherwise the question is irrelevant), would a
call coming in in SIP using G.711 be converted to GSM on the IAX2
channel since it is higher in the order of preference or will it
identify that G.711 is also available on the IAX2 leg and so switch the
call using G.711 to save the performance overhead so that the data does
not have to be decoded and re-encoded?

Thanks..

Later..