Perceptually based and embedded wideband CELP coding of speech

This paper presents a novel multi-band CELP coder with the following characteristics: wideband coding (6.5 kHz), variable bit rate (VBR) coding (10-24 kbps), low-delay (10 ms), embeddibility, and perceptually based dynamic bit allocation. The excitation signal of the linear prediction filter is the vector sum of eight off-line pre-filtered bandpass excitation vectors. The eight excitation codebooks are tree structured, providing embeddibility and variable bit rate. The dynamic allocation of the bitstream among the different bands is based on the perceptual importance of each band. The multi-band and perceptual structure of the coding scheme results in graceful degradation with decreasing bit rates both in quiet and in the presence of background noise.