Asterisk version 11.6.0. We are struggling with changing the ptime from default 20ms to 10 ms, we are using alaw codec. I have set alaw:10 and it works for incoming calls, but not outgoing calls is it anyway that I can force it to be 10ms for outgoing calls?
Have you looked at the autoframing option in sip.conf ?
https://wiki.asterisk.org/wiki/display/AST/RTP+Packetization