Research On 4kb/s Fast DP-CELP Speech Coding And Bandwidth Extension

Speech coding is the foundation of digital transmission and storage of speech. Recently,there is a great interest in researching 4kb/s toll-quality speech coders and the technology of speech bandwidth extension. A 4kb/s fast speech coding algorithm was proposed, which is based on Dispersed Pulse Code Excited Linear Prediction model, and the speech bandwidth extension technique was researched in this thesis. The main research contents are as follows:Firstly, many methods that can quickly compute Line spectral frequencies of speech were summarized and appraised and one based on Decimation-in-Degree algorithm was applied in the proposed speech coder.Secondly, a general method for establishing the gains codebook is proposed. Using this method, the performance of predictive vector quantizer, where the adaptive codebook gains and fixed codebook gains are quantized with 6 bits, is equal to that of scalar quantization with 8 bits, and the bits are reduced efficiently. Thirdly, according to the phenomenon that the random vector is not described accurately in original algorithm, a fast multi-path searching algorithm based on algebra sub-codebook was presented. The speech quality of 4kb/s CELP speech coding algorithm is improved, and the computing complexity is reduced effectively.Fourthly, a fast method of computing LSFs based on Decimation-in-Degree algorithm was implemented on TMS320C5410 DSP simulator using fixed point assembly language. And a complete Decimation-in-Degree algorithm, whose complexity of fixed point is lower than classic method, is put forward.Finally, basing on the two basic techniques for bandwidth extension of speech, the reconstruction of wideband spectral envelope and the production of wideband excitation, several bandwidth extension methods are summarized and compared. And the approach of bandwidth extension based on Mel frequency cepstral coefficients vector quantization was improved. Then, a new wideband excitation signal producing method is proposed, by which the algorithm of bandwidth extension is...