Codecs and transcoding

[pcromwell]

I am a little confused regarding transcoding.

1. I assume that if both endpoints are capable of negotitaing and using different codecs, then transcoding is not required. i.e calls between two cisco phones. 1 uses g.711 and the other uses g.729. then the phones will sort out what uses what.

2. If I have a call between 2 sites on the same cluster and they are set to use g.711 locally but across the site g.729. Do I need to use transcoding or will the phones negotiate this themselves?

3. if in the above (point 2) the call passes through each sites voice gateway, would I need transcoding?

any help much appreciated

[gogasca · Accepted solution]

2 no trasncoding as long as both EP support same codec or codec with less BW

example in your case both EP support g729 then it will work without trasncode

3. That will depend which codecs the GW is announcing (MGCP, H323, SIP for these last use voice-class codecs)

Check CallManager fundamentals book it explains MRM layer, also CUCM SRND for MEdia devices for more details