Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Research Article Adaptive Long-Term Coding of LSF Parameters Trajectories for Large-Delay/Very- to Ultra-Low Bit-Rate Speech Coding | Hindawi Publishing Corporation EURASIP Journal on Audio Speech and Music Processing Volume 2010 Article ID 597039 13 pages doi 2010 597039 Research Article Adaptive Long-Term Coding of LSF Parameters Trajectories for Large-Delay Very- to Ultra-Low Bit-Rate Speech Coding Laurent Girin Laboratoire Grenoblois des Images de la Parole du Signal et de l Automatique GIPSA-lab ENSE3 961 rue de la Houille Blanche Domaine Universitaire 38402 Saint-Martin d Heres France Correspondence should be addressed to Laurent Girin Received 22 September 2009 Revised 5 March 2010 Accepted 23 March 2010 Academic Editor Dan Chazan Copyright 2010 Laurent Girin. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. This paper presents a model-based method for coding the LSF parameters of LPC speech coders on a long-term basis that is beyond the usual 20-30 ms frame duration. The objective is to provide efficient LSF quantization for a speech coder with large delay but very- to ultra-low bit-rate . below 1 kb s . To do this speech is first segmented into voiced unvoiced segments. A Discrete Cosine model of the time trajectory of the LSF vectors is then applied to each segment to capture the LSF interframe correlation over the whole segment. Bi-directional transformation from the model coefficients to a reduced set of LSF vectors enables both efficient sparse coding using here multistage vector quantizers and the generation of interpolated LSF vectors at the decoder. The proposed method provides up to 50 gain in bit-rate over frame-by-frame quantization while preserving signal quality and competes favorably with 2D-transform coding for the lower range of tested bit rates. Moreover the implicit time-interpolation nature of the long-term coding process provides this technique a high .
