8-KBIT S SHORT AND MEDIUM DELAY SPEECH CODECS BASED ON CELP CODING/

This paper discusses two speech-coding algorithms at around 8 kbit/s. These algorithms both use pre-selection in the codebook search and tra ining for the conjugate structured random codebook. One has short-dela y time that can dispense with echo-control equipment. This algorithm i s robust against channel errors by using LPC analysis separated from p itch excitation, although LPC parameters are derived from the locally decoded signal. The other algorithm has medium-delay time and meets al l the requirements of the ITU-T (formerly CCITT) 8 kbit/s speech codin g standard. The performance of these codecs is evaluated using signal to noise ratio (SNR), pair comparison tests with a modulated noise ref erence unit (MNRU), and Mean Opinion Score (MOS). The major applicatio ns of these codecs are personal handy phone systems and FPLMTS.