Telefonaktiebolaget Lm Ericsson (publ)

France Telecom

Orange

Manuel Briand

Anisse Taleb

Gustaf Ullberg

Tomas Jansson Toftgård

David Virette

Arnault Nagle

Tomas Jansson

Auréllen Sollaud

A method for spectrum recovery in spectral decoding of an audio signal, comprises obtaining of an initial set of spectral coefficients representing the audio signal, and determining a transition frequency. The transition frequency is adapted to a spectral content of the audio signal. Spectral holes in the initial set of spectral coefficients below the transition frequency are noise filled and the initial set of spectral coefficients are bandwidth extended above the transition frequency. Decoders and encoders being arranged for performing part of or the entire method are also illustrated.

Adaptive transition frequency between noise fill and bandwidth extension

A method and device are disclosed for determining an inter-channel time difference of a multi-channel audio signal having at least two channels. A determination is made at a number of consecutive time instances, inter-channel correlation based on a cross-correlation function involving at least two different channels of the multi-channel audio signal. Each value of the inter-channel correlation is associated with a corresponding value of the inter-channel time difference. An adaptive inter-channel correlation threshold is adaptively determined based on adaptive smoothing of the inter-channel correlation in time. A current value of the inter-channel correlation is then evaluated in relation to the adaptive inter-channel correlation threshold to determine whether the corresponding current value of the inter-channel time difference is relevant. Based on the result of this evaluation, an updated value of the inter-channel time difference is determined.

Determining the inter-channel time difference of a multi-channel audio signal

Disclosed methods and apparatuses determine an inter-channel time difference of a multi-channel audio signal by determining a set of local maxima of a cross-correlation function involving at least two different channels of the multi-channel audio signal, for positive and negative time-lags and associating each local maximum with a corresponding time-lag. Local maximums for the positive and negative time-lags are selected from the set as respective positive and negative time-lag inter-channel correlation candidates. Processing also includes evaluating whether there is an energy-dominant channel, when the absolute value of a difference in amplitude between the inter-channel correlation candidates is smaller than a first threshold, and, when there is an energy-dominant-channel, identifying the sign of the inter-channel time difference and extracting a current value of the inter-channel time difference based on the time-lag corresponding to the positive or negative time-lag inter-channel correlation candidate.

There is provided a method and device for determining an inter-channel time difference of a multi-channel audio signal having at least two channels. A set of local maxima of a cross-correlation function involving at least two different channels of the multi-channel audio signal is determined (S) for positive and negative time-lags, where each local maximum is associated with a corresponding time-lag. From the set of local maxima, a local maximum for positive time-lags is selected as a so-called positive time-lag inter-channel correlation candidate and a local maximum for negative time-lags is selected as a so-called negative time-lag inter-channel correlation candidate (S). When the absolute value of a difference in amplitude between the inter-channel correlation candidates is smaller than a first threshold, it is evaluated whether there is an energy-dominant channel (S). When there is an energy-dominant-channel, the sign of the inter-channel time difference is identified and a current value of the inter-channel time difference is extracted based on either the time-lag corresponding to the positive time-lag inter-channel con-elation candidate or the time-lag corresponding to the negative time-lag inter-channel correlation candidate (S).

There is provided a method and device for determining an inter-channel time difference of a multi-channel audio signal having at least two channels. A determination is made, at a number of consecutive time instances, of inter-channel correlation based on a cross-correlation function involving at least two different channels of the multi-channel audio signal. Each value of the inter-channel correlation is associated with a corresponding value of the inter-channel time difference. An adaptive inter-channel correlation threshold is adaptively determined based on adaptive smoothing of the inter-channel correlation in time. A current value of the inter-channel correlation is then evaluated in relation to the adaptive inter-channel correlation threshold to determine whether the corresponding current value of the inter-channel time difference is relevant. Based on the result of this evaluation, an updated value of the inter-channel time difference is determined.

A method for spectrum recovery in spectral decoding of an audio signal, comprises obtaining () of an initial set of spectral coefficients representing the audio signal, and determining () a transition frequency. The transition frequency is adapted to a spectral content of the audio signal. Spectral holes in the initial set of spectral coefficients below the transition frequency are noise filled () and the initial set of spectral coefficients are bandwidth extended () above the transition frequency. Decoders and encoders being arranged for performing part of or the entire method are also illustrated.

In a method of perceptual transform coding of audio signals in a telecommunication system, performing the steps of determining transform coefficients representative of a time to frequency transformation of a time segmented input audio signal; determining a spectrum of perceptual sub-bands for said input audio signal based on said determined transform coefficients; determining masking thresholds for each said sub-band based on said determined spectrum; computing scale factors for each said sub-band based on said determined masking thresholds, and finally adapting said computed scale factors for each said sub-band to prevent energy loss for perceptually relevant sub-bands.

Transform coding of speech and audio signals

A method for perceptual spectral decoding includes decoding of spectral coefficients recovered from a binary flux into decoded spectral coefficients of an initial set of spectral coefficients. The initial set of spectral coefficients are spectrum filled. The spectrum filling includes noise filling of spectral holes by setting spectral coefficients in the initial set of spectral coefficients not being decoded from the binary flux equal to elements derived from the decoded spectral coefficients. The set of reconstructed spectral coefficients of a frequency domain formed by the spectrum filling is converted into an audio signal of a time domain.

Methods and systems for perceptual spectral decoding

A method of determining a spatial coding mode for audio data sent by a sender entity () to a receiver terminal () adapted to receive said audio data in one or more sound reproduction formats. The method comprises the steps of the receiver terminal () indicating () to the sender entity () said reproduction format(s) in a given order of preference and the sender entity () determining a mode of spatial coding of the audio data compatible with a reproduction format taken in the order of preference and indicating () said reproduction format to the receiver terminal (). Application to Voice over IP services.

Method for determining an audio data spatial encoding mode

A system and a method for coding by principal component analysis (PCA) of a multi-channel audio signal comprising the following steps: decomposing at least two channels (L, R) of said audio signal into a plurality of frequency sub-bands (I(b), . . . , I(b), r(b), . . . , r(b)), calculating at least one transformation parameter (&#x3b8;(b), . . . , &#x3b8;(b)) as a function of at least some of said plurality of frequency sub-bands, transforming at least some of said plurality of frequency sub-bands into a plurality of frequency sub-components as a function of said at least one transformation parameter (&#x3b8;(b), . . . , &#x3b8;(b)), said plurality of frequency sub-components comprising principal frequency sub-components (CP(b), . . . , CP(b)), combining at least some of said principal frequency sub-components (CP(b), . . . , CP(b)) in order to form a principal component (CP), and defining a coded audio signal (SC) representing said multi-channel audio signal (C, . . . , C), said coded audio signal (SC) comprising said principal component (CP) and said at least one transformation parameter (&#x3b8;(b), . . . , &#x3b8;(b)).

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Djursholm, Sweden

Manuel Briand