Recommendation ITU-T G.191 provides source code for speech and audio processing modules for narrowband, wideband and super-wideband telephony applications. The set includes codecs, filters, and noise generators.

This edition introduces changes to Annex A, which describes the ITU-T software tools library (STL) containing a high-quality, portable C code library for speech processing applications. This release of the STL, also known as STL2023, incorporates:

An implementation of P.50 fullband modulated noise reference unit (MNRU) as described in Recommendation ITU-T P.810.

A tool for automatic instrumentation of speech and audio codecs to measure their computational complexity and memory.

Recommendation ITU-T G.191 includes an electronic attachment containing STL2023 and a manual.