Multi-channel audio signal encoding and decoding method and the system for the same

A method and an apparatus for decoding and encoding a multi-channel audio signal are provided to map spatial information, extracted from a QMF(Quadrature Mirror Filter) filter bank, with a multi-channel signal applied with the spatial information or sub-band signals on frequency index of a down-mix signal. A down-mix signal is converted into a QMF domain through at least two QMF analysis filter banks(40). The converted sub-band signals are up-mixed to a multi-channel signal by using spatial information(50). After that, the multi-channel signal is converted into a time domain(60). In the above second step, spatial information applied to a neighboring band sub-band signal is used if a sub-band signal band boundary is inconsistent with a band boundary applied with the spatial information.