FreeSWITCH 1.8

setting channel variables in dialstrings

You can alter this behavior by setting variables in dialstring, using the construct "{variable=value,variable01=value02}dialstring".

In case you want to override outbound_codec_prefs you need to set the "codec-string" variable on the dialstring (note the usage of single quotes to escape value strings containing commas. Comma would delimit variables-values pairs):

   <extension name="bridge_test_02"> 
      <condition field="destination_number" expression="^2908$"> 
        <action application="bridge"  data="{codec_string='PCMA,PCMU,VP8'}user/1011"/> 
      </condition> 
    </extension> 

If instead of changing the preferences list, you want to force FreeSWITCH to use exactly a codec list, and nothing else, you set the "absolute-codec-string": ...