<condition field="${sip_has_crypto}" expression="^(AES_CM_128_HMAC_SHA1_32|AES_CM_128_HMAC_SHA1_80)$" break="never">
<!-- export sets it local and on export -->
<action application="export" data="sip_secure_media=${sip_has_crypto}"/>
<anti-action application="respond" data="503 TURN ON SRTP"/>
</condition>
You can not accept the call and send it out and get a 415 back and expect to do the process all over again automatically. Once you get the 415 its done.. finished OVER gotta do it again. Remember we are a B2BUA not a proxy... so its all done per leg.
If all else fails just go get libzrtp and install it as per the wiki and enable zrtp support. Then get zfone for your two PC's and you're done. We don't do the trusted man in the middle stuff yet but you can get the same end result.
/b