Estimating spatial cues for audio coding in MDCT domain

Although widely used otherwise, MDCT is excluded in the current scheme for spatial cues representation, due to its lacking of phase information and energy conservation. But combining MDCT with MDST overcomes the difficulties. Moreover, MDST spectra can be built perfectly from neighboring MDCT spectra. The MDCT-MDST conversion, in matrix form, is approximating to a banded sparse matrix. When applied to spatial audio coding using MDCT based core coders, this method avoids separate transforming for cues representation and saves significant computation. Listening tests also show that it has same audio quality as other complex transform based methods.