format_
are modules for working with mediafiles, and codec_*
are modules for transcoding human speech.
In general, if we're talking modules, you should enable all codec_
and format_
modules that you have (and then you will enforce the needed codecs via peer configs), because when not used - they basically do nothing. The modules that you shouldn't enable in a bunch are various app_
, cel_
, cdr_
, pbx_
and res_
that you don't use (because these are doing much of unneeded stuff when loaded but not enabled); but you want to have the widest compatibility with incoming/outgoing speech codecs along with on-disk mediafiles formants that you can provide.