slackbuilds_ponce/libraries/opal

The Open Phone Abstraction Library (OPAL) is a C++ multi-platform,
multi-protocol library for Fax, Video & Voice over IP and other
networks.

Opal requires ptlib.  Speex is also recommended, even though Opal 
ships with its own version.  x264 and ffmpeg are optional, but
highly recommended, for video support.

Celt is also optional.