Development of a VoIP system implementing a high quality packet loss concealment technique

Speech quality of VoIP (voice over Internet protocol) may potentially be degraded by transmission errors such as packet loss and delay which are basically inevitable in best-effort communications. This study proposes an error concealment technique for such degradation by exploiting a receiver-based technique called pitch waveform replication. For improving the conventional technique, this study investigates a waveform reconstruction technique that also takes account of the pitch variation between the backward and forward frames of gap frames. From experimental results of objective and subjective evaluation, it is indicated that the proposed technique may potentially be useful for improving the speech quality, compared with the conventional technique. In addition, this study has also developed a hardware VoIP system that implements the proposed error concealment technique.