[cisco-voip] Conference with remote resource using G.729

[Robin H]

I have CallManager server at hq site and a WAN/Voice router in branch
office (site1). Site1 phones are using conference and transcoding
resource from CallManager. When I made a call from hq to Site1 (it
uses G729 for VoIP over WAN) and then initiate conference from hq
phone to outside, the conference can be established but it uses G711
for both hq and site1 phone. Is there a way I can force the site1
phone to use G729 even when in conference to save WAN bandwidth? I
read about transcoding feature is to save WAN bandwidth. In this case
How can I use it for site1 phones? Thanks