just something i noticed and though id shoot it out. i recently did an install for a customer. initially, i had them on g711 and although the customer didnt notice anything, i noticed a slight walkie talkie effect (like if we had VAD enabled). i checked though all the normal procedures but nothing seemed out of place (VAD was disabled). i changed to G729 and immediately, the quality was excellent even to this day. i have had not a single report of quality issues.
Now i had another install using 711 and that was fine using CCM 5.0
any reason why? this is CCM 5.1