Here are the solution if you are still interested:

There are multiple built-in codec which can be controlled by the usexxx applet parameters.

Where you can set the values to 0,1,2 or 3,

0 means never
1 means don't offer (but accept it if no other codec found)
2 use with low priority
3 use with high priority

For example to prefer the speex wideband and ultrawideband codecs your applet paramters should look like this:

   -usespeexwb =3
   -usespeexuwb =3
    -useg729=2
    -usepcmu=2
   -usepcma=2
   -usegsm=2
   -usespeex=2