Grabacion de llamadas en Asterisk con Mixmonitor()

[monitor]
exten => _8.,1,Answer
exten => _8.,2,set(calltime=${STRFTIME(${EPOCH},,%C%y%m%d%H%M%S)})
exten =>_8.,3,MixMonitor(/var/lib/asterisk/sounds/custom/X${calltime}-${CALLERID(num)}-${EXTEN:3}-.wav)
exten => _8.,4,Dial(SIP/${EXTEN:1}@didlogic,60,tTR)