MDCT spectrum separation: Catching the fine spectral structures for stereo coding

The spectrum of a sinusoid using the Modified Discrete Cosine Transform (MDCT), when separated into an even subspectrum and an odd subspectrum by bin parity, gives rise to a distinctive property-subspectral shapes are independent of the sinusoid phase, which contributes only to scaling. Based on this finding, we propose an Even-Odd (EO) scheme for stereo coding: partitioning the even and odd subspectra separately into subbands to capture the fine spectral structures of sinusoidal and rich tone signals. The scheme reduces the coding noises by 0-20 dB for music signals. When integrated into a MDCT domain KLT-based stereo coder, the scheme boosts subjective listening test (MUSHRA) scores. This coder, called KLT-EO, competes the Parametric Stereo (PS) in quality by a slightly higher bitrate but without the algorithmic delay of 20 ms resulted from the stereo processing.