On the Use of Band-Passed Excitation Codebooks for CELP Coding of Speech
Ping Zlieng, Paul G. Mermelstein · 2005
This paper explores the benefits of using multiple band-passed codebooks to replace the single full-band excitation codebook of classical code-excited linear prediction for coding high quality speech in the range of 8-16 kb/s. In the classical method, the residual signal in the LPC frame is divided temporally into subframes and each subframe is coded using a single full-band excitation code book. In this study, we divide the residual signal in the LPC frame into its band-passed components and match each component with an entry from a band-passed code book. Our results indicate objective and subjective advantages for using three codebooks, each with the gain and shape components. In particular, the codebooks required for the frequencies above 1 kHz are very small. Also, by subsampling, the large low frequency (0-1 kHz) codebook can be searched very rapidly resulting in a significant complexity advantage.