[Freeswitch-users] Channel Var Codec

Hi what Channel variable should I use to see what Codec the A leg allows? variable_rtp_use_codec_string or variable_ep_codec_string or something else? In the CDR I see this <rtp_use_codec_string>G722,PCMU,PCMA,GSM</rtp_use_codec_string> This looks like what I'm looking for but I need it in the dialplan before the call goes out so I can direct the call where I need it to go. Thanks