In July 1990, Study Group XV of the then CCITT decided to set up a group to deal with the development of common software tools to help in the development of speech coding standards.
ITU-T G.191 STL MANUAL-2009 Referenced Document
ITU-T G.711 PULSE CODE MODULATION (PCM) OF VOICE FREQUENCIES
ITU-T G.722 7 kHz audio-coding within 64 kbit/s (Study Group 16)