A packet loss recovery method using packet arrived behind the playout time for CELP decoding

This paper proposes a packet loss recovery method using a packet arrived behind the playout time for CELP decoding. The proposed method recovers synchronization of the filter states between encoding and decoding in the period following packet loss. The recovery is performed by replacing the degraded filter states with ones adaptively calculated from the late arrival packet in decoding. When the proposed method is applied to the AMR speech decoder, it improves the segmental SNR by 0.2 to 1.8 dB at packet loss rates of 1 to 10 %, where all the packet losses occur due to their late arrival. The subjective test results show that five-grade mean opinion scores are improved by 0.3 and 0.2 at a packet loss rate of 5 % at speech coding bitrates of 7.95 and 12.2 kbps, respectively.