This is part of the libosmocore "meta"-library. the libosmocore library contains various utility functions that were originally developed as part of the openbsc project, but which are of a more generic nature and thus useful to (at least) other programs that are developed in the sphere of free software / open source mobile communication.

the libosmocodec library in particular contains the implementation of multiple gsm codecs:

- gsm 06.10 - gsm fr codec
- gsm 06.20 - gsm hr codec
- gsm 06.60 - gsm efr codec
- gsm 06.90 - gsm amr codec