US 7,003,448 B1Granted

Method and device for error concealment in an encoded audio-signal and method and device for decoding an encoded audio signal

AssigneeFraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.

InventorsPierre Lauber, Martin Dietz, Juergen Herre, Reinhold Boehm, Ralph Sperschneider, Daniel Homm

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Abstract

In a method for concealing an error in an encoded audio signal a set of spectral coefficients is subdivided into at least two sub-bands (14), whereupon the sub-bands are subjected to a re-verse transform (16). A specific prediction is performed (18) for each quasi time signal of a sub-band to obtain an estimated temporal representation for a sub-band of a set of spectral coefficients following the current set. A forward transform (20) of the time signal of each sub-band provides estimated spectral coefficients which can be used (28) instead of erroneous spectral coefficients of a following set of spectral coefficients, e.g. in order to conceal transmission errors. Transforming at the sub-band level provides independence from transform characteristics such as block length, window type and MDCT algorithm while at the same time preserving spectral processing for error concealment. Thus the spectral characteristics of audio signals can also be taken into account during error concealment.

Claims13

Dependent claims

A method for concealing an error in an encoded audio signal, where the encoded audio signal has successive sets of spectral coefficients, where a set of spectral coefficients is a spectral representation for a set of audio sampled values, comprising the following steps:

subdividing a current set of spectral coefficients into at least two sub-bands with different frequency ranges, where one sub-band of the at least two sub-bands has at least two spectral coefficients;
reverse transforming the spectral coefficients of the one sub-band to obtain a temporal representation of the at least two spectral coefficients of the one sub-band;
performing a prediction using the temporal representation of the at least two spectral coefficients of the one sub-band to obtain an estimated temporal representation for a sub-band of a set following the current set, where the sub-band of the following set has the same frequency range as the sub-band of the current set;
forward transforming the estimated temporal representation to obtain at least two estimated spectral coefficients for the sub-band of the following set;
determining whether a spectral coefficient of the sub-band of the following set is erroneous;
and
as reaction to the step of determining, if there is an erroneous spectral coefficient, using an estimated spectral coefficient instead of an erroneous spectral coefficient of the following set so as to conceal the erroneous spectral coefficient of the following set.

4 more elements

A method for decoding an encoded audio signal which comprises successive sets of spectral coefficients, wherein a set of spectral coefficients is a spectral representation for a set of audio sampled values:

receiving a current set of spectral coefficients;
subdividing a current set of spectral coefficients into at least two sub-bands with different frequency ranges, where one sub-band of the at least two sub-bands has at least two spectral coefficients;
reverse transforming the spectral coefficients of the one sub-band to obtain a temporal representation of the at least two spectral coefficients of the one sub-band;
performing a prediction using the temporal representation of the at least two spectral coefficients of the one sub-band to obtain an estimated temporal representation for a sub-band of a set following the current set, where the sub-band of the following set has the same frequency range as the sub-band of the current set;
forward transforming the estimated temporal representation to obtain at least two estimated spectral coefficients for the sub-band of the following set;
receiving a following set of spectral coefficients and subdividing the following set into sub-bands which cover the same frequency range as the sub-bands of the current set;
determining whether a spectral coefficient of the sub-band of the following set is erroneous;
as reaction to the step of determining, if there is an erroneous spectral coefficient, using an estimated spectral coefficient instead of an erroneous spectral coefficient of the following set so as to conceal the erroneous spectral coefficient of the following set;
and
processing the following set using the estimated spectral coefficient used in the step of using to obtain the following set of audio sampled values.

7 more elements

Dependencies are inferred from the claim text.