Koninklijke Philips Corporation N.v.

Coding Technologies Ab

Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V.

Dolby International Ab

Other

Koninklijke Philips Electronics N.v.

Dolby Sweden Ab

Gerard Herman Hotho

Dirk Jeroen Breebaart

Heiko Purnhagen

Erik Gosuinus Petrus Schuijers

Albertus Cornelis Den Brinker

Machiel Willem Van Loon

Lars Villemoes

Sascha Disch

Juergen Herre

Matthias Neusinger

Karl Jonas Roden

Kristofer Kjoerling

Karl Jonas Roeden

Andreas Johannes Gerrits

Jeroen Dirk Breebaart

Francois Philippus Myburg

Evgeny Verbitskiy

Holger Horich

Arnoldus Werner Johannes Oomen

Holger Hoerich

Jonas Roeden

Wolfgang Alexander Schildbach

Erik G P Schuijers

Hans Magnus Kristofer Kjorling

Hans Magnus Kristofer Kjoerling

Christophe Alain Bernard Hoeppe

Karl J Rödén

Karl J Roeden

Hans M Kjoerling

Karl J Röden

Wolfgang A Schildbach

Lars F Villemoes

Machiel W Van Loon

Dirk J Breebart

Erik G P Schuiers

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

A selected channel of a multi-channel signal which is represented by frames composed from sampling values having a high time resolution can be encoded with higher quality when a wave form parameter representation representing a wave form of an intermediate resolution representation of the selected channel is derived, the wave form parameter representation including a sequence of intermediate wave form parameters having a time resolution lower than the high time resolution of the sampling values and higher than a time resolution defined by a frame repetition rate. The wave form parameter representation with the intermediate resolution can be used to shape a reconstructed channel to retrieve a channel having a signal envelope close to that one of the selected original channel. The time scale on which the shaping is performed is shorter than the time scale of a framewise processing, thus enhancing the quality of the reconstructed channel. On the other hand, the shaping time scale is larger than the time scale of the sampling values, significantly reducing the amount of data needed by the wave form parameter representation.

Temporal and spatial shaping of multi-channel audio signal

Temporal and spatial shaping of multi-channel audio signals

An audio encoder () has a hierarchical encoding structure and generates a data stream comprising one or more audio channels as well as parametric audio encoding data. The encoder () comprises an encoding structure processor () which inserts decoder tree structure data into the data stream. The decoder tree structure data comprises at least one data value indicative of a channel split characteristic for an audio channel at a hierarchical layer of the hierarchical decoder structure and may specifically specify the decoder tree structures to be applied by a decoder. A decoder () comprises a receiver () which receives the data stream and a decoder structure processor () for generating the hierarchical decoder structure in response to the decoder tree structure data. A decode processor () then generates output audio channels from the data stream using the hierarchical decoder structure.

Audio encoding and decoding

For a multi-channel reconstruction of audio signals based on at least one base channel, an energy measure is used for compensating energy losses due to an predictive upmix. The energy measure can be applied in the encoder or the decoder. Furthermore, a decorrelated signal is added to output channels generated by an energy-loss introducing upmix procedure. The energy of the decorrelated signal is smaller than or equal to an energy error introduced by the predictive upmix. Thus, problems occurring for prediction based up-mix methods such as up-mixing signals that are coded with High Frequency Reconstruction techniques are solved, so that the correct correlation between the up-mixed channels is obtained or the up-mix is adapted to arbitrary down-mixes.

Methods for improved performance of prediction based multi-channel reconstruction

A multi-channel audio encoder () for encoding a multi-channel audio signal (), e.g. a 5.1 channel audio signal, into a spatial down-mix (), e.g. a stereo signal, and associated parameters (). The encoder () comprises first and second units (). The first unit () encodes the multi-channel audio signal () into the spatial down-mix () and parameters (). These parameters () enable a multi-channel decoder () to reconstruct the multi-channel audio signal () from the spatial down-mix (). The second unit () generates, from the spatial down-mix (), parameters () that enable the decoder to reconstruct the spatial down-mix () from an alternative down-mix (), e.g. a so-called artistic down-mix that has been manually mixed in a sound studio. In this way, the decoder () can efficiently deal with a situation in which an alternative down-mix () is received instead of the regular spatial, down-mix (). In the decoder (), first the spatial down-mix () is reconstructed from the alternative down-mix () and the parameters (). Next, the spatial down-mix () is decoded into the multi-channel audio signal ().

Multi-channel audio coding

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.

In a method of encoding input signals (CHto CHto) in a multi-channel encoder () to generate corresponding output data having down-mix output signals () together with complementary parametric data (), the method includes a first step of down-mixing input signals (CHto CHto) to generate the corresponding down-mix output signals (), and a second step of processing the input signals (CHto CHto) during down-mixing to generate the parametric data () complementary to the down-mix output signals (). Processing of the input signals (CHto CHto) involves including information in the down-mix signals () which is useable during subsequent decoding of the down-mix output signals () and the parametric data () to determine at least some parameter data and thereby enabling representations of the input signals (CHto CHto) to be subsequently regenerated.

Multi-channel encoder

A selected channel of a multi-channel signal represented by frames composed from sampling values having a high time resolution is provided that can be encoded with higher quality when a wave form parameter representation representing a wave form of an intermediate resolution representation of the selected channel is derived. The wave form parameter representation with the intermediate resolution can be used to shape a reconstructed channel to retrieve a channel having a signal envelope close to a selected original channel. The time scale on which the shaping is performed is shorter than the time scale of a framewise processing, thus enhancing the quality of the reconstructed channel. On the other hand, the shaping time scale is larger than the time scale of the sampling values, significantly reducing the amount of data needed by the wave form parameter representation.

Method and apparatus for generating a number of output audio channels

A multi-channel audio encoder () encodes an N-channel audio signal. A first unit () generates a first encoded M-channel signal, e.g. a spatial stereo down-mix, for the N-channel signal (N&#x3e;M). Down-mixers () generate first enhancement data for the signal relative to the N-channel audio signal. A second M-channel signal, such as an artistic stereo mix, is generated for the N-channel signal. A processor () then generates second enhancement data for the second M-channel signal relative to the first M-channel signal. A second unit () generates an output signal comprising the second M-channel signal, the first enhancement data and the second enhancement data. The generator () can dynamically select between generating the second enhancement data as absolute enhancement data or as relative enhancement data relative to the second encoded M-channel signal. A decoder () can perform the inverse operation and can apply the second enhancement data as absolute or relative enhancement depending on an indication in the received bit-stream.

There is described a method of encoding input signals (CHI to CHto) in a multi-channel encoder () to generate corresponding output data comprising down-mix output signals () together with complementary parametric data (). The method includes a first step of down-mixing input signals (CHI to CHto) to generate the corresponding down-mix output signals (), and a second step of processing the input signals (CHI to CHto) during down-mixing to generate said parametric data () complementary to the down-mix output signals (). Processing of the input signals (CHI to CHto) involves including information in the down-mix signals () which is useable during subsequent decoding of the down-mix output signals () and the parametric data () to determine at least some parameter data and thereby enabling representations of the input signals (CHI to CHto) to be subsequently regenerated. Coders for use in the encoder () for performing essential signal processing operations therein are also elucidated.

An encoding device () for converting a first number (M) of input audio channels into a second, smaller number (N) of output audio channels comprises at least one conversion unit () for converting a first signal (Lf; Rf; Co) and a second signal (Lr; Rr; Le) into a third signal (L; R; C) and a fourth signal (Ls; Rs; Cs). The third, dominant signal contains most of the signal energy of the first and second signals, while the fourth, residual signal contains the remainder of said signal energy. The encoding device is arranged for using the third signal (L; R; C) to produce an output signal and for outputting the fourth signal (Ls; Rs; Cs). A decoding device () for converting a first number (N) of input audio channels into a second, larger number (M) or output audio channels comprises at least one conversion unit () for converting a first signal (L; R; C) and a second signal (Ld; Rd; Ld) into a third signal (Lf, Rf; Co) and a fourth signal (Lr; Rr; Le). The first, dominant signal contains most of the signal energy of the third and fourth signal, while the second, residual signal contains the remainder of said signal energy. The encoding device is arranged for receiving at least one-second signal (Ld; Rd; Cd).

Encoding and decoding of multi-channel audio signals

A multi-channel synthesizer for generating at least three output channels using an input signal having at least one base channel, the base channel being derived from the original multi-channel signal, the input signal further including at least two different up-mixing parameters, and an up-mixer mode indication indicating, in a first state that a first up-mixing rule is to be performed, and, indicating, in a second state, that a different second up-mixing rule is to be performed, uses an up-mixer for up-mixing the at least one base channel using the at least two different up-mixing parameters based on the first or the second up-mixing rule in response to the up-mixer mode indication so that the at least three output channels are obtained.

Multi parametrisation based multi-channel reconstruction

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Eindhoven, Netherlands

Gerard Herman Hotho