Speech quality assessment of CS-ACELP

The CS-ACELP (Conjugate-Structure Algebraic Code-Excited Linear Prediction) algorithm, approved as the standard for 8-kbit/s speech coding in del Recommendation G.729 by the International Telecommunication Union (ITU), is designed to achieve quality no worse than that provided under current Recommendation G.726, Adaptive Differential Pulse Code Modulation (ADPCM), at 32 kbit/s. This paper presents the results of subjective quality tests conducted to characterize the G.729 algorithm using Japanese, English, French, German, and Italian speech. CS-ACELP achieved commercial telephone quality speech under error-free channel conditions and met all requirements under random bit-error conditions for various input levels, including two-stage transcoding. It was also less sensitive than ADPCM to the burst errors that occur in mobile radio channels.