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

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 Low-Delay CELP coders analyzed: Low-delay sparse excitation mixed CELP. Sparse is based on MP-MLQ multilayer models. Mixed algorithm stems from the narrowband G.728 standard. As opposed to LD-CELP coder, codebook consists pseudorandom vectors sequences obtained with Long-Term (LTP). Variable coding maximizing vector dimension while keeping required quality. Good quality (MOS=3.9 according PESQ algorithm) average 33.5 kbit/sec.