This revision only introduces changes to ITU-T G.191 Annex A, which describes the ITU-T Software Tools (STL) containing a high-quality, portable C code library for speech processing applications. This new release of the STL dubbed STL2009 incorporates many changes in software and manual. The new sets of tools added are: ITU‑T G.728 fixed-/floating-point executables, basic ITU‑T G.722 frame-erasure concealments (G.722 PLC0 and PLC1), program ROM counting, floating point complexity evaluation, stereo operation and bitstream truncation. There have been also updates such as addition of new filters to rate change tools, more options added for frequency response calculations, adaptation of error-insertion device to embedded-variable bitstream, addition of impulse responses to the reverberation processing tool and update to make ITU‑T G.722/ITU‑T G.192 compliant. Corrections of several known problems have also been implemented. The associated STL user's manual has also been updated.

This Recommendation includes an electronic attachment containing STL2009 Software Tool Library and manual.