Apparatus, method and computer program for obtaining a parameter describing a variation of a signal characteristic of a signal

A method for acquiring one or more model parameters describing a variation of a signal characteristic for an audio signal on the basis of actual transform-domain parameters describing the audio signal in a transformed domain, the method comprising:

• determining one or more model parameters of a transform-domain variation model, the variation model describing an evolution of transform-domain parameters in dependence on the one or more model parameters, such that a model error, representing a deviation between a modeled temporal evolution of the transform-domain parameters and an evolution of the actual transform-domain parameters, is brought below a predetermined threshold value or minimized;
• wherein first transform domain information comprising a first set of transform domain parameters and describing the audio signal for a first time interval for a plurality of different values of a transform variable, and second transform domain information comprising a second set of transform domain parameters and describing the audio signal for a second time interval for the different values of the transform variable are acquired as the actual transform-domain parameters;
• wherein a temporal variation between the first transform domain information and the second transform domain information is evaluated for a plurality of different values of the transform variable, to acquire temporal variation information,
• wherein a local variation of the transform domain information over the transform variable is estimated for a plurality of different values of the transform variable, to acquire a local variation information;
• wherein the temporal variation information and the local variation information are combined, to acquire a frequency variation model parameter;
• wherein the frequency variation model parameter is acquired using a transform domain variation model comprising the frequency variation model parameter and representing a compression or expansion of the transform domain representation of the audio signal with respect to the transform variable assuming a smooth frequency variation of the audio signal;
• and
• wherein the frequency variation model parameter is determined such that the parameterized transform-domain variation model is adapted to the first set of transform domain parameters and the second set of transform domain parameters.

An apparatus for acquiring one or more model parameters describing a variation of a signal characteristic of an audio signal on the basis of actual transform domain parameters of a transform domain representation of the audio signal describing the audio signal in a transform domain, the apparatus comprising:

• a parameter determinator configured to determine one or more model parameters of a transform-domain variation model, the variation model describing an evolution of transform domain parameters in dependence on the one or more model parameters, such that a model error, representing a deviation between a modelled evolution of the transform domain parameters and an evolution of the actual transform domain parameters, is brought below a predetermined threshold value or minimized;
• wherein the apparatus is configured to acquire autocovariance information describing an autocovariance of the audio signal for a single autocovariance window but for different autocovariance lag values,
• to evaluate, for a plurality of different pairs of autocovariance lag values, weighted differences between the pairs of autocovariance values,
• wherein the weight is chosen in dependence on a difference of the lag values of the respective pairs of lag values, and in dependence on a variation of the autocovariance values over lag,
• to sum-combine different weighted difference values, to acquire a combination value, and
• to acquire the model parameters on the basis of the combination value.

A method for acquiring one or more model parameters describing a variation of a signal characteristic for an audio signal on the basis of actual transform-domain parameters of a transform-domain representation of the audio signal describing the audio signal in a transformed domain, the method comprising:

• determining one or more model parameters of a transform-domain variation model, the transform-domain variation model describing an evolution of transform-domain parameters in dependence on the one or more model parameters, such that a model error, representing a deviation between a modeled temporal evolution of the transform-domain parameters and an evolution of the actual transform-domain parameters, is brought below a predetermined threshold value or minimized;
• wherein an autocovariance information describing an autocovariance of the audio signal for a single autocovariance window but for different autocovariance lag values is acquired;
• wherein weighted differences between pairs of autocovariance values are evaluated for a plurality of different pairs of autocovariance lag values,
• wherein the weight is chosen in dependence on a difference of the lag values of the respective pairs of lag values, and in dependence on a variation of the autocovariance values over lag,
• wherein different weighted difference values are sum-combined, to acquire a combination value;
• and
• wherein the one or more model parameters are acquired on the basis of the combination value.

An apparatus for acquiring one or more model parameters describing a variation of a signal characteristic of an audio signal on the basis of actual transform domain parameters of a transform-domain representation of the audio signal describing the audio signal in a transform domain, the apparatus comprising:

• a parameter determinator configured to determine one or more model parameters of a transform-domain variation model, the variation model describing an evolution of transform domain parameters in dependence on the one or more model parameters, such that a model error, representing a deviation between a modeled evolution of the transform domain parameters and an evolution of the actual transform domain parameters, is brought below a predetermined threshold value or minimized;
• wherein the apparatus is configured to acquire a model parameter describing a temporal variation of an envelope of the audio signal,
• wherein the parameter determinator is configured to acquire a plurality of transform-domain parameters describing a signal power of the audio signal for a plurality of time intervals,
• wherein the parameter determinator is configured to acquire the envelope variation model parameter using a representation of a parameterized transform-domain variation model comprising the envelope variation model parameter and representing a temporal increase in power or a temporal decrease in power of the transform-domain representation of the audio signal assuming a smooth envelope variation of the audio signal, and
• wherein the parameter determinator is configured to determine the envelope variation model parameter such that the parameterized transform-domain variation model is adapted to the transform-domain parameters;
• and
• wherein the parameter determinator is configured to acquire a plurality of autocorrelation parameters or autocovariance parameters for a given autocorrelation lag or autocovariance lag, and
• wherein the parameter determinator is configured to determine a plurality of polynomial parameters of a polynomial envelope variation model.

A method for acquiring one or more model parameters describing a variation of a signal characteristic for an audio signal on the basis of actual transform-domain parameters of a transform-domain representation of the audio signal describing the audio signal in a transformed domain, the method comprising:

• determining one or more model parameters of a transform-domain variation model, the variation model describing an evolution of transform-domain parameters in dependence on the one or more model parameters, such that a model error, representing a deviation between a modeled temporal evolution of the transform-domain parameters and an evolution of the actual transform-domain parameters, is brought below a predetermined threshold value or minimized;
• wherein a plurality of transform-domain parameters describing a signal power of the audio signal for a plurality of time intervals is acquired;
• wherein a plurality of polynomial parameters of a polynomial envelope variation model are determined,
• wherein the envelope variation model parameters are acquired using a representation of a parameterized transform-domain variation model comprising the envelope variation model parameters and representing a temporal increase in power or a temporal decrease in power of the transform-domain representation of the audio signal assuming a smooth envelope variation of the audio signal,
• wherein the envelope variation model parameters are determined such that the parameterized transform-domain variation model is adapted to the transform-domain parameters,
• wherein a plurality of autocorrelation parameters or autocovariance parameters are acquired for a given autocorrelation lag or autocovariance lag.

An apparatus for acquiring one or more model parameters describing a variation of a signal characteristic of an audio signal on the basis of actual transform domain parameters of a transform domain representation of the audio signal describing the audio signal in a transform domain, the apparatus comprising:

• a parameter determinator configured to determine one or more model parameters of a transform-domain variation model, the variation model describing an evolution of transform domain parameters in dependence on one or more model parameters, such that a model error, representing a deviation between a modelled evolution of the transform domain parameters and an evolution of the actual transform domain parameters, is brought below a predetermined threshold value or minimized;
• wherein the apparatus comprises a formant-structure-reducer configured to preprocess an input audio signal, to acquire a formant-structure-reduced audio signal;
• wherein the apparatus is configured to acquire the actual transform-domain parameter on the basis of the formant-structure-reduced audio signal;
• wherein the formant-structure-reducer is configured to estimate parameters of a linear-predictive model of the input audio signal on the basis of a high-pass filtered version of the input audio signal, and
• to filter a broad band version of the input audio signal on the basis of the estimated parameters of the linear-predictive model,
• to acquire the formant-structure-reduced audio signal such that the formant-structure-reduced audio signal comprises a low-pass characteristic.

A method for acquiring one or more model parameters describing a variation of a signal characteristic for an audio signal on the basis of actual transform-domain parameters of a transform-domain representation of the audio signal describing the audio signal in a transformed domain, the method comprising:

• determining one or more model parameters of a transform-domain variation model, the variation model describing an evolution of transform-domain parameters in dependence on one or more model parameters, such that a model error, representing a deviation between a modeled temporal evolution of the transform-domain parameters and an evolution of the actual transform-domain parameters, is brought below a predetermined threshold value or minimized;
• wherein an input audio signal is preprocessed, to acquire a formant-structure-reduced audio signal;
• wherein the actual transform-domain parameter is acquired on the basis of the formant-structure-reduced audio signal;
• wherein parameters of a linear-predictive model of the input audio signal are estimated on the basis of a high-pass filtered version of the input audio signal;
• wherein a broad band version of the input audio signal is filtered on the basis of the estimated parameters of the linear-predictive model, to acquire the formant-structure-reduced audio signal such that the formant-structure-reduced audio signal comprises a low-pass characteristic.