/opt/freeswitch/conf/autoload_configs/opus.conf.xml

<configuration name="opus.conf">
      <settings>
        <param name="use-vbr" value="0"/>
        <param name="use-dtx" value="0"/>
        <param name="complexity" value="10"/>
        <param name="packet-loss-percent" value="8"/>
        <param name="keep-fec-enabled" value="1"/>
        <param name="use-jb-lookahead" value="1"/>
        <param name="advertise-useinbandfec" value="1"/>
        <param name="maxaveragebitrate" value="256000"/>
      </settings>
</configuration>