SCALABLE SPEECH AND AUDIO ENCODING USING COMBINATORIAL ENCODING OF MDCT SPECTRUM

PROBLEM TO BE SOLVED: To provide an efficient technique for encoding/decoding of MDCT (or similar transform-based) spectrum in scalable speech and audio compression algorithms.SOLUTION: A residual signal which is a difference between an original audio signal and a reconstructed version of the original audio signal is obtained from a Code Excited Linear Prediction (CELP)-based encoding layer and is transformed at a discrete cosine transform (DCT)-type transform layer to obtain a corresponding transform spectrum having a plurality of spectral lines. The transform spectrum spectral lines are transformed using a combinatorial position coding technique. The combinatorial position coding technique generates a lexicographical index for a selected subset of spectral lines, where each lexicographic index represents one of a plurality of possible binary strings representing the positions of the selected subset of spectral lines.