An efficient code structure and search strategy for stochastic coding at 8 kb/s

Methods of increasing the performance of two components of stochastic coding, the codebook excitation search and the long-term synthesis filter, while maintaining or reducing complexity are discussed. A flexible tree-coding technique is introduced that significantly lowers the complexity of the codebook search with very little loss in quality. An efficient method of performing a three-tap long-term prediction analysis in a closed loop is developed. It improves perceptual quality and requires little additional complexity. The result is a stochastic coder which produces high-quality speech at 8 kb/s with manageable computational complexity