Apparatus and method for encoding or decoding an audio signal with intelligent gap filling in the spectral domain

Patent metadata

Field	Value
Publication number	US-2016133265-A1
Application number	US-201615002370-A
Country	US
Kind code	A1
Filing date	Jan 20, 2016
Priority date	Jul 22, 2013
Publication date	May 12, 2016
Grant date	—

Abstract

An apparatus for decoding an encoded audio signal, includes a spectral domain audio decoder for generating a first decoded representation of a first set of first spectral portions, the decoded representation having a first spectral resolution; a parametric decoder for generating a second decoded representation of a second set of second spectral portions having a second spectral resolution being lower than the first spectral resolution; a frequency regenerator for regenerating every constructed second spectral portion having the first spectral resolution using a first spectral portion and spectral envelope information for the second spectral portion; and a spectrum time converter for converting the first decoded representation and the reconstructed second spectral portion into a time representation.

First claim

1 . Apparatus for decoding an encoded audio signal, comprising:
a spectral domain audio decoder configured for generating a first decoded representation of a first set of first spectral portions, the decoded representation comprising a first spectral resolution; a parametric decoder configured for generating a second decoded representation of a second set of second spectral portions, the second decoded representation comprising spectral envelope information comprising a second spectral resolution being lower than the first spectral resolution; a frequency regenerator configured for regenerating a reconstructed second spectral portion comprising the first spectral resolution using a first spectral portion and the spectral envelope information for a second spectral portion from the second set of second spectral portions; and a spectrum time converter configured for converting the first decoded representation and the reconstructed second spectral portion into a time representation, wherein the spectral domain audio decoder is configured to generate the first decoded representation so that the first decoded representation comprises a Nyquist frequency defining a sampling rate being equal to a sampling rate of the time representation generated by the spectrum-time converter, or wherein the spectral domain audio decoder is configured to generate the first decoded representation so that a first spectral portion is placed, with respect to frequency, between two second spectral portions.

2 . Apparatus of claim 1 , wherein the parametric decoder is configured for generating the second decoded representation comprising matching information on a first spectral portion indicating that the first spectral portion matches with a second spectral portion, and
wherein the frequency regenerator is configured for regenerating the reconstructed second spectral portion using the first spectral portion identified by the matching information.

3 . Apparatus of claim 1 , wherein the spectral domain audio decoder is configured to output a sequence of decoded frames of spectral values, a decoded frame being the first decoded representation, wherein the frame comprises spectral values for the first set of spectral portions and zero indications for the second set of second spectral portions,
wherein the apparatus for decoding further comprises a combiner for combining spectral values generated by the frequency regenerator for the second set of second spectral portions and spectral values of the first set of first spectral portions in a reconstruction band to acquire a reconstructed spectral frame comprising spectral values for the first set of the first spectral portions and the second set of second spectral portion, and wherein the spectrum-time converter is configured to convert the reconstructed spectral frame into the time representation.

4 . Apparatus of claim 1 , wherein the spectrum-time converter is configured to perform an inverse modified discrete cosine transform, and further comprises an overlap-add stage for overlapping and adding subsequent time domain frames, each subsequent time domain frame originating from a spectrum representation comprising the first decoded representation and the reconstructed second spectral portion.

5 . Apparatus of claim 1 , wherein a maximum frequency represented by a spectral value for the maximum frequency in the first decoded representation is equal to a maximum frequency comprised in the time representation generated by the spectrum-time converter, wherein the spectral value for the maximum frequency in the first representation is zero or different from zero.

6 . Apparatus of claim 1 ,
wherein the encoded audio signal comprises the first encoded representation being a frequency domain encoded version of the first set of first spectral portions and an encoded version of the second set of second spectral portions, wherein the apparatus further comprises a data stream parser for extracting the first encoded representation and for forwarding the encoded representation to the spectral domain audio decoder and for extracting the second encoded representation and for forwarding the second encoded representation to the parametric decoder.

7 . The apparatus in accordance with claim 1 , wherein the encoded audio signal further comprises an encoded representation of the third set of third spectral portions to be reconstructed by noise filling, further comprising:
a noise filler for extracting noise filling information from the encoded representation of the third set of third spectral portions and for applying a noise filling operation in the third set of third spectral portions without using a first spectral portion in a different frequency range to generate a reconstructed third spectral portion, wherein the spectrum-time converter is configured for additionally converting the third spectral portion into the time representation.

8 . Apparatus in accordance with claim 1 ,
wherein the spectral domain audio decoder is configured to generate the first decoded representation comprising the first spectral portions with frequency values being greater than a frequency being equal to a frequency in a middle of a frequency range covered by the time representation output by the spectrum-time converter.

9 . Apparatus of claim 1 ,
wherein the frequency regenerator is configured to generate a reconstruction band comprising a spectral portion of the first set of spectral portions at a frequency in the reconstruction band being different from a center frequency of the reconstruction band, wherein the reconstruction band is a scale factor band, for which an energy value indicating the spectral envelope information is comprised in the second set of second spectral portions comprising the second spectral resolution.

10 . Apparatus for encoding an audio signal, comprising:
a time-spectrum converter configured for converting an audio signal comprising a sampling rate into a spectral representation; a spectral analyzer configured for analyzing the spectral representation for determining a first set of first spectral portions to be encoded with a first spectral resolution and a different second set of second spectral portions to be encoded with a second spectral resolution, the second spectral resolution being smaller than the first spectral resolution, wherein a first spectral portion is placed, with respect to frequency, between two second spectral portions; a spectral domain audio encoder configured for generating a first encoded representation of the first set of spectral portions comprising the first spectral resolution; and a parametric coder configured for calculating spectral envelope information for the second set of second spectral portions, the spectral envelope information comprising the second spectral resolution.

11 . Apparatus of claim 10 , wherein the parameter coder is configured for calculating similarities between source ranges comprising first spectral portions and target ranges comprising second spectral portions and for determining, based on calculated similarities, for a second spectral portion, a first spectral portion matching with the second spectral portion and for providing the matching information on the first spectral portion matching with the second spectral portion into an encoded representation.

12 . Apparatus of claim 10 ,
wherein the spectral analyzer is configured for analyzing the spectral representation up to a maximum analysis frequency being at least one quarter of a sampling frequency of the audio signal.

13 . Apparatus of claim 10 ,
wherein the time-spectrum converter is configured for windowing the audio

Assignees

• Fraunhofer Ges Forschung

Inventors

• Disch Sascha
• Nagel Frederik
• Erlangen Ralf
• Thoshkahna Balaji
• Schmidt Konstantin
• Bayer Stefan
• Neukam Christian
• Edler Bernd
• Helmrich Christian

Classifications

• H04S1/007

  in which the audio signals are in digital form (data reduction aspects thereof based on psychoacoustics G10L19/02) · CPC title

• G10L21/0388 Primary

  Details of processing therefor · CPC title

• G10L19/02 Primary

  using spectral analysis, e.g. transform vocoders or subband vocoders · CPC title

• G10L19/0208

  Subband vocoders · CPC title

• H03M7/30

  Compression (speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N); Expansion; Suppression of unnecessary data, e.g. redundancy reduction · CPC title