Design Of Lattice Vector Quantization Based On Split Table For Audio Coding

Vector quantization (VQ) based on lattice is a very importantsignal compression method. In many fields of audio signal processing,especially in mobile communication, lattice vector quantization (LVQ)plays an important role. LVQ has low computational complexity andhigh performance so that it can be used for mobile communicationsystem which is considerd to be of high-fidelity and low-bit-rate. Thisarticle applied to design a method of lattice vector quantization basedon split table (STLVQ), which is suitable for low bit rate audio coding.STLVQ has some good features, such as low storage requirements,low computational complexity and high performance.This article firstly introduced the low bit rate audio coding intransform domain and its core technology VQ. Among all the VQtechnologies, LVQ is efficient and attractive due to its highly structurednature of code book generated by certain algebraic rule. A method called embedded algebraic vector quantization (EAVQ) and anextension method called Voronoi extension are very popular in today’saudio coding technology.With the existing theory, this article has designed a new LVQsystem based on split table. We designed a base codebook with23leaders which are chosen from the Gauss lattice RE8. And we alsodesigned the encoding methods using base codebook, including directencoding, odd encoding of2D8data, and fast encoding of some normalvectors using cache.In order to resolve the overload distortion problem in LVQ, thisarticle designed an extension method utilizing split table. According tothe characteristics of the base codebook, we designed a split table andalso the encoding method based on it. The encoding method has twolevels, which are called the first-level extension encoding and thesecond-level extension encoding. The first one is applied to smalloverload vectors while the second one is applied to larger ones.Finally, this article described the software realization of the STLVQsystem based on the codec of AVS P10. Then we give the subjectivetests and objective tests performances of the new LVQ system, so as its storage requirement and computational complexity. Testing andanalysis show that STLVQ has almost equal performance with theclassic LVQ using Voronoi extension (VELVQ), but with less storagerequirement and much lower computational complexity.The method of STLVQ designed in this article has accepted byAVS group, and it has become a part of the mobile speech and audiocoding standard AVS P10.