SCALABLE MULTI-CHANNEL AUDIO CODING

摘要

An audio encoder adapted to encode a multi-channel audio signal, the encoder comprising an encoder combination module (ECM) for generating a dominant signal part (m) and a residual signal part (s) being a combined representation of first and second audio signals (xl, x2), the dominant and residual signal parts (m, s) being obtained by applying a mathematical procedure to the first and second audio signals (xl, x2), wherein the mathematical procedure involves a first spatial parameter (SPl) comprising a description of spatial properties of the first and second audio signals (xl, x2), a parameter generator (PG) for generating a first parameter (PSl) set comprising a second spatial parameter (SP2), and a second parameter (PS2) set comprising a third spatial parameter (SP3), and an output generator for generating an encoded output signal comprising a first output part (OPl) comprising the dominant signal part (m) and the first parameter set (PSl), and a second output part (OP2) comprising the residual signal part (s) and the second parameter set (PS2). In preferred embodiments the mathematical procedure includes a two-dimensional signal rotation, and the third spatial parameter (SP3) comprises a difference between the second spatial parameter (SP2) and the first spatial parameter (SPl). Preferred embodiments include a plurality of interconnected encoder combination module, so that e.g. six independent 5.1 format audio signals can be encoded to a single or two dominant signal parts and a number of parameter sets and residual signal parts. In an output bit stream the first output part is included in a base layer, while the second output part is included in a refinement layer. A transparent audio signal quality can be obtained by a decoder utilizing both layers, while an acceptable quality can be obtained by a decoder using only the base layer data. Thus, a scalable spatial audio coding has been provided.