Koninklijke Philips Corporation N.v.

Coding Technologies Ab

Machiel Willem Van Loon

Dirk Jeroen Breebaart

Gerard Herman Hotho

Heiko Purnhagen

Erik Gosuinus Petrus Schuijers

Karl Jonas Roeden

Karl Jonas Roden

Erik G P Schuijers

Method for processing a stereo signal includes encoding an N-channel audio signal in a stereo signal (Lo, Ro) and spatial parameters (wl, wr), processing the stereo signal using the spatial parameters for generating a processed stereo signal (low, Row). The matrix of the processed stereo signal is described as the matrix of the stereo signal, multiplied by a filter matrix (H) having element that are filter functions (H1, H2, H3, H4) operated with spatial parameters (wl, wr) and a constant (a). The filter functions are time invariant and selected so that the matrix is invertible.

Method, device, encoder apparatus, decoder apparatus and audio system

Techniques are described for combining parametric multi-channel audio coding with matrixing, reconstructing a full-quality multi-channel, independent of the decoder. A stereo signal is obtained from encoding an N-channel audio signal into spatial parameters and a stereo down-mix signal having first and second stereo signals, including adding a first signal and a third signal to obtain a first output signal, the first signal having the first stereo signal modified by a first complex function, the third signal having the second stereo signal modified by a third complex function. A second signal and fourth signal are similarly added to obtain a second output signal. Complex functions are chosen such that an energy value of the difference between first signal and the second signals (fourth signal and third signals) is larger than or equal to the energy value of the sum of the first and the second signal (fourth signal and third signal).

A method and a device are described for processing a stereo signal obtained from an encoder, which encodes an N-channel audio signal into spatial parameters (P) and a stereo down-mix comprising first and second stereo signals (L, R). A first signal and a third signal are added in order to obtain a first output signal (L), wherein the first signal (L) comprises the first stereo signal (L) modified by a first complex function (g), and the third signal (L) comprises the second stereo signal (R) modified by a third complex function (g). A second signal and a fourth signal are added to obtain a second output signal (R). The fourth signal (R) comprises the second stereo signal (R) modified by a fourth complex function (g), and the second signal (R) comprises the first stereo signal (L) modified by a second complex function (g). The complex functions (g, g, g, g) are functions of the spatial parameters (P) and are chosen to be such that an energy value of the difference (L,R) between the first signal and the second signal is larger than or equal to the energy value of the sum (L+R) of the first and the second signal, and the energy value of the difference (R&#x2212;L) between the fourth signal and the third signal is larger than or equal to the energy value of the sum (R+L) of the fourth signal and the third signal.

A device () for enhancing a multi-channel (e.g. stereo) audio signal has a parameter adjustment unit () for adjusting an original parameter (&#x3b1;, ILD, ICC) which represents an original inter-channel property of the audio signal. The device further comprises a processing unit () for processing the audio signal so as to produce an enhanced audio signal having the adjusted parameter (&#x3b1;', ILD&#x2032;, ICC&#x2032;). The device allows stereo widening or other multi-channel signal enhancements without introducing artifacts.

Audio signal enhancement

There is described a multi-channel encoder () for processing input signals conveyed in N input channels to generate corresponding output signals conveyed in M output channels together with complementary parametric data; M and N are integers wherein N&#x3e;M. The encoder () includes a down-mixer for down-mixing the input signals to generate the corresponding output signals, the encoder also comprising an analyser for processing the input signals to generate the parameter data, said parametric data describing mutual differences between the N channels of input signal to allow for regenerating during decoding one or more of the N channels of input signals from the M channels of output signal. Such an encoder () is capable of providing highly efficient data encoding and also of being backwards compatibility with relatively simpler decoders having fewer than N decoding output channels. The invention also concerns decoders () compatible with such a multi-channel encoder ().

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Eindhoven, Netherlands

Machiel Willem Van Loon