Apparatus and method for decoding and encoding an audio signal using adaptive spectral tile selection

Patent metadata

Field	Value
Publication number	US-2016140973-A1
Application number	US-201615003334-A
Country	US
Kind code	A1
Filing date	Jan 21, 2016
Priority date	Jul 22, 2013
Publication date	May 19, 2016
Grant date	—

Abstract

An apparatus for decoding an encoded signal includes: an audio decoder for decoding an encoded representation of a first set of first spectral portions to obtain a decoded first set of first spectral portions; a parametric decoder for decoding an encoded parametric representation of a second set of second spectral portions to obtain a decoded representation of the parametric representation, wherein the parametric information includes, for each target frequency tile, a source region identification as a matching information; and a frequency regenerator for regenerating a target frequency tile using a source region from the first set of first spectral portions identified by the matching information.

First claim

1 . Apparatus for decoding an encoded signal, comprising:
an audio decoder for decoding an encoded representation of a first set of first spectral portions to acquire a decoded first set of first spectral portions; a parametric decoder for decoding an encoded parametric representation of a second set of second spectral portions to acquire a decoded representation of the parametric representation, wherein the decoded representation of the parametric representation comprises, for each target frequency tile, a source region identification as a matching information; and a frequency regenerator for regenerating a target frequency tile using a source region from the first set of first spectral portions identified by the matching information, wherein the frequency regenerator comprises a controllable whitening filter, wherein the decoded representation of the parametric representation comprises a whitening information, wherein the frequency regenerator is configured for applying the whitening filter to a source region selected in accordance with the matching information before performing a spectral envelope adjustment, when the whitening information for the source region indicates that the source region is to be whitened, and wherein applying the whitening filter is performed so that a coarse envelope information is removed and a spectral fine structure is emphasized or wherein applying the whitening filter comprises calculating a spectral envelope estimate of the source region and dividing a spectrum of the source region by a spectral envelope indicated by the spectral envelope estimate.

2 . Apparatus of claim 1 , wherein the audio decoder is a spectral domain audio decoder, and
wherein the apparatus further comprises a spectrum-time converter for converting a spectral representation of the first spectral portions and reconstructed second spectral portions into a time representation.

3 . Apparatus of claim 1 , wherein the whitening information comprises for a tile or a group of tiles, a whitening level information indicating a whitening level to be applied to a source frequency tile when regenerating the target frequency tile, and
wherein the frequency regenerator is configured for applying a whitening filter selected from a group of different whitening filters in response to the whitening information.

4 . Apparatus in accordance with claim 1 ,
wherein the frequency regenerator comprises a source region modifier, wherein the decoded representation of the parametric representation comprises, in addition to the source region identification , a sign information, and wherein the source region modifier is configured for applying an operation to acquire a phase shift of the source region spectral values in accordance with the sign information.

5 . Apparatus in accordance with claim 1 ,
wherein the frequency regenerator comprises a tile modulator, wherein the decoded representation of the parametric representation comprises a correlation lag in addition to the source region identification, and wherein the tile modulator is configured for applying a tile modulation in accordance with the correlation lag associated with the source region identification.

6 . Apparatus in accordance with claim 1 ,
wherein the frequency regenerator comprises a tile modulator, wherein the decoded representation of the parametric representation comprises a correlation lag in addition to the source region identification, and wherein the tile modulator is configured for applying a tile modulation using an alternating temporal sequence of −1/1 when the correlation lag is an odd number.

7 . Apparatus for encoding an audio signal, comprising:
a time-spectrum converter for converting an audio signal into a spectral representation; a spectral analyzer for analyzing the spectral representation to determine a first set of first spectral portions to be encoded with a first spectral resolution, and a second set of second spectral portions to be encoded with a second spectral resolution, wherein the second spectral resolution is lower than the first spectral resolution; a parameter calculator for calculating similarities between predefined source regions and target regions, a source region comprising spectral portions and a target region comprising second spectral portions, wherein the parameter calculator is configured for comparing matching results for different pairs of a first spectral portion and a second spectral portion to determine a selected matching pair and for providing matching information identifying the matching pair; and a core coder for encoding the first set of first spectral portions, wherein the first set of first spectral portions comprises the predefined source regions and spectral portions different from the predefined source regions, wherein the parameter calculator is configured to copy a source tile multiple times into a target tile until the target tile is filled up with multiple copies of the source tile, when the target tile is greater than the source tile, or wherein the parameter calculator is configured for spectrally whitening the first or the second spectral portion of the pairs before performing a correlation processing to acquire the matching identification, wherein the spectrally whitening is performed so that a coarse envelope information is removed and a spectral fine structure is emphasized or wherein spectrally whitening comprises calculating a spectral envelope estimate of the first or the second spectral portion and dividing a spectrum of the first or the second spectral portion, respectively, by a spectral envelope indicated by the spectral envelope estimate.

8 . Apparatus of claim 7 , wherein the parameter calculator is configured for using predefined target regions in the second set of second spectral portions or predefined source regions in the first set of first spectral portions.

9 . Apparatus of claim 7 , wherein the parameter calculator is configured so that the predefined target regions are non-overlapping, or the predefined source regions are overlapping, or wherein the predefined source regions are a subset of the first set of the first spectral portions below a gap filling start frequency, or wherein a predefined target region covers a lowest spectral region coinciding with the gap filling start frequency.

10 . Apparatus in accordance with claim 7 ,
wherein the parameter calculator is configured for comparing pairs of a target region and a source region and a pair of the target region and the same source region, wherein the same source region is shifted by a correlation lag to provide information on the correlation lag of a selected pair as an additional matching information.

11 . Audio encoder of claim 7 ,
wherein the parameter calculator is configured for performing a correlation processing to acquire a matching result for a pair of the first spectral portion and the second spectral portion, the matching result having a negative sign, and wherein the parameter calculator is configured to provide an information on the negative sign as additional matching information.

12 . Audio encoder of claim 7 ,
wherein the parameter calculator is configured to determine an integer number of target tiles and to determine a plurality of equally sized source tiles for each target tile.

13 . Apparatus of claim 7 ,
wherein the parameter calculator is configured for calculating the spectral envelope of the first spectral portion or the second spectral portion using at least one of the following procedures: transforming the spectrum with a discrete cosine transform (DCT), retaining lower frequency DCT coefficients by settin

Assignees

• Fraunhofer Ges Forschung

Inventors

• Neukam Christian
• Disch Sascha
• Nagel Frederik
• Niedermeier Andreas
• Schmidt Konstantin
• Thoshkahna Balaji Nagendran

Classifications

• G10L25/06

  the extracted parameters being correlation coefficients · CPC title

• G10L19/022

  Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring · CPC title

• G10L19/06

  Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients · CPC title

• G10L19/0204 Primary

  using subband decomposition · CPC title

• G10L19/008 Primary

  Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing · CPC title