Combined spectral envelope normalization and subtraction of sinusoidal components in the ODFT and MDCT frequency domains

Recent research in high-quality audio coding seeks not only improved coding gains but also new functionalities such as easy semantic access to compressed audio material and audio modification in the compressed domain. These objectives imply the decomposition of the audio signal into several components of specific semantic value, such as sinusoidal components, that take advantage of selective coding and parametrization tools. We presume an MDCT based audio coding environment and present a new technique combining spectral envelope normalization with accurate subtraction of sinusoidal components in the MDCT frequency domain. It is shown how a parametrization of L stationary sinusoids in the complex ODFT spectrum can lead to the effective subtraction, in the real MDCT spectrum, of 3L spectral lines. A demonstration of the implementation of the technique is available on the Internet (see http://www.inescn.pt/~ajf/waspaa01/flattening.html.)