A toll quality 8 kb/s speech codec for the personal communicationssystem (PCS)

摘要

A toll quality speech codec at 8 kb/s suitable for the futurenpersonal communications system is presented. The codec is currentlynunder standardization by the ITU-T (successor of CCITT) where the codecnterms of reference were mainly determined considering PCS application.nThe encoding algorithm is based on algebraic code-excited linearnprediction (ACELP) and has a speech frame of 10 ms. Efficient pitch andncodebook search strategies, along with efficient quantizationnprocedures, have been developed to achieve toll quality encoded speechnwith a complexity implementable on current fixed-point DSP chips. Formalnsubjective listening tests, performed by ITU-T SG 12, showed that thencodec quality is equivalent to that of G.726 ADPCM at 32 kb/s innerror-free conditions and it outperforms G.726 under error conditions.nThe codec performs adequately under tandeming conditions, and cannsupport a frame erasure rate up to 3% with a degradation in itsnperformance that is still worse than the ITU-T requirements, and this isnone subject of study for the next phase. The algorithm has beennimplemented on a single fixed-point DSP for the ITU-T subjective rest,nand required about 29 MIPS. An optimized version, however, requires 24nMIPS without any speech quality degradation