Low Delay Sparse and Mixed Excitation CELP Coders for Wideband Speech Coding

Przemyslaw Grzegorz Dymarski


Code Excited Linear Prediction (CELP) algorithms
are proposed for compression of speech in 8 kHz band at
switched or variable bit rate and algorithmic delay not exceeding
2 msec. Two structures of Low-Delay CELP coders are analyzed:
Low-delay sparse excitation and mixed excitation CELP. Sparse
excitation is based on MP-MLQ and multilayer models. Mixed
excitation CELP algorithm stems from the narrowband G.728
standard. As opposed to G.728 LD-CELP coder, mixed excitation
codebook consists of pseudorandom vectors and sequences
obtained with Long-Term Prediction (LTP). Variable rate coding
consists in maximizing vector dimension while keeping the
required speech quality. Good speech quality (MOS=3.9
according to PESQ algorithm) is obtained at average bit rate 33.5

Full Text:



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