i would like to add AGC function to my current asterisk 1.4.28
is that possible?
I think you want the developer mailing list, and also to indicate your level of programming skill.
You may find that support for development for obsolete versions is limited.
It would also be helpful to spell out AGC. I assume you mean automatic gain control.
it seems func_speex for that. but func_speex module not found in 1.4.28
Since this is an old version of Asterisk, the effort of developing new features for it seems like a waste of time.
If you are currently using an old version of Asterisk and you don’t want to upgrade, then try a third-party solution for audio quality improvement (NR,AGC,AEC) like PBXMate.