Low-delay 16 kb/s Wideband Speech Coder with Fast Search Methods

In this paper, a low delay 16 kb/s wideband speech coder with a buffering delay of 1.25 ms is introduced. This coder is basically inspired from the G.728 LD-CELP standard for narrowband speech signals. Our main goal is to reduce the implementation complexity of our wideband G728 – like coder, which is mainly due to the search of the optimal excitation (gain-shape) in codebook. For this reason an algebraic codebook is proposed and an exhaustive optimal search and suboptimal full position and Joint Position and Amplitude Search techniques are implemented. Objective and subjective measures on a large corpus of a testing speech database show that the JPAS (Joint Position and Amplitude Search) multistage search technique proposed recently can yield to a very important reduction of coder computational load, without decreasing the perceived quality of wideband speech signals compared to other search techniques.

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