Context-based error recovery technique for GSM AMR speech codec

GSM AMR speech codec being used for both Internet and mobile networks, robustness to both frame erasures and random bit errors assumes significance. This paper proposes a new context-based error recovery technique for the CELP-based speech codec accomplishing recovery of erased frames, updating decoder state during erasure spells and reliable estimation of codec parameters in case of bit errors. Previous error concealment techniques do not adequately make use of the context in which concealment is being done. The proposed error concealment technique is intended to retrieve and use contextual information for better performance. The method is solely receiver based, uses no look ahead, makes use of implicitly available codec parameters and buffers for parameter estimation and is hence computationally efficient. Segmental Itakura-Saito measure and MOS scores are used to compare the output speech quality of the proposed technique with those of the basic techniques as recommended by the standard.