Split Table Extension: A Low Complexity LVQ Extension Scheme in Low Bitrate Audio Coding

Embedded algebraic vector quantization (EAVQ) is a fast and efficient lattice vector quantization (LVQ) scheme used in low-bitrate audio coding. However, a defect of EAVQ is the overload distortion which causes unpleasant noises in audio coding. To solve this problem, specific base codebook extension schemes should be carefully considered. In this letter, we present a novel EAVQ codebook extension scheme-split table extension (STE), which splits a vector into two smaller vectors: one in the base codebook and the other in the split table. The base codebook and the split table are designed according to the appearance probability of quantized vectors in audio segments. Experiments on encoding multiple audio and speech sequences show that, compared with the existed Voronoi extension scheme, STE greatly reduces computation complexity and storage requirement while achieving similar coding quality.