Low-complexity multi-mode VXC using multi-stage optimization and mode selection [speech coding]

The authors propose an algorithm in which multi-mode coding is a transparent adaptation of multi-stage VXC (vector excitation coding) requiring almost zero additional computation. In the process, it is shown how the cost of the jointly optimized multi-stage VXC can be minimized using a backward-transform implementation of the perceptually orthogonal VXC (POVXC) algorithm previously proposed by the authors. It is shown that the performance of such a coder, while not as good as that of a normal multi-mode coder, is noticeably better than that of a normal POVXC