Audio encoder, audio decoder and related methods using two-channel processing within an intelligent gap filling framework

Patent metadata

Field	Value
Publication number	US-10134404-B2
Application number	US-201615000902-A
Country	US
Kind code	B2
Filing date	Jan 19, 2016
Priority date	Jul 22, 2013
Publication date	Nov 20, 2018
Grant date	Nov 20, 2018

Abstract

An apparatus for generating a decoded two-channel signal includes: an audio processor for decoding an encoded two-channel signal to obtain a first set of first spectral portions; a parametric decoder for providing parametric data for a second set of second spectral portions and a two-channel identification identifying either a first or a second different two-channel representation for the second spectral portions; and a frequency regenerator for regenerating a second spectral portion depending on a first spectral portion of the first set of first spectral portions, the parametric data for the second portion and the two-channel identification for the second portion.

First claim

The invention claimed is:

1. Audio decoder for generating a decoded two-channel audio signal, the audio decoder comprising:
an audio processor configured for decoding an encoded two-channel audio signal to obtain a first set of first spectral portions;
a parametric decoder configured for providing parametric data for a second set of second spectral portions and a two-channel identification for a second spectral portion of the second set of second spectral portions identifying either a first two-channel audio representation for the second spectral portion of the second set of second spectral portions or a second different two-channel audio representation for the second spectral portion of the second set of second spectral portions; and
a frequency regenerator configured for regenerating the second spectral portion of the second set of second spectral portions depending on a first spectral portion of the first set of first spectral portions, the parametric data for the second spectral portion of the second set of second spectral portions and the two-channel identification for the second spectral portion of the second set of second spectral portions to obtain a regenerated second spectral portion of the second set of second spectral portions, wherein the decoded two-channel audio signal comprises the regenerated second spectral portion of the second set of second spectral portions,
wherein the audio processor is configured to decode the first set of first spectral portions in accordance with a further two-channel identification for the first set of first spectral portions, the further two-channel identification identifying either a first two-channel audio representation for a first spectral portion of the first set of first spectral portions or a second different two-channel audio representation for the first spectral portion of the first set of first spectral portions, and to transform the first set of first spectral portions so that the first two-channel audio representation of the first spectral portions of the first set of first spectral portions and the second two-channel audio representation of the first spectral portions of the first set of first spectral portions are obtained, and
wherein the frequency regenerator is configured to use either the first two-channel audio representation of the first set of first spectral portions or the second two-channel audio representation of the first set of first spectral portions as indicated in the two-channel identification for the second spectral portion of the second set of second spectral portions, and
wherein one or more of the audio processor, the parametric decoder, and the frequency regenerator is implemented, at least in part, by one or more hardware elements of the audio decoder.

2. Audio decoder of claim 1 , wherein the two-channel identification identifies either a separate processing of two channels of the encoded two-channel audio signal or a joint processing of the two channels of the encoded two-channel audio signal, and
wherein the frequency regenerator is configured for regenerating the second spectral portion of the second set of second spectral portions for a first channel of the two channels and the second spectral portion of the second set of second spectral portions for a second channel of the two channels using the first portion of the first channel and the first portion of the second channel, wherein the first portion of the first channel and the first portion of the second channel are in a two-channel audio representation identified by the two-channel identification for the second spectral portion of the second set of second spectral portions.

3. Audio decoder of claim 1 ,
wherein the two-channel identification identifies either a separate processing of two channels of the encoded two-channel audio signal or a joint processing of the two channels of the encoded two-channel audio signal, and
wherein the frequency regenerator is configured for regenerating a joint representation of the two channels in the second spectral portion of the second set of second spectral portions as identified by the two-channel identification, and
wherein the frequency regenerator further comprises a representation transformer for transforming the joint representation of the second spectral portion of the second set of second spectral portions into a separate representation for the second spectral portion of the second set of second spectral portions.

4. Audio decoder of claim 3 , wherein the representation transformer uses additional joint representation parameters for the representation transformation.

5. Audio decoder of claim 3 , wherein the joint representation is a mid/side representation, and wherein the representation transformer is configured to operate based on the following equation:
leftTile=0.5*(midTile+sideTile)
rightTile=0.5*(midTile−sideTile)

wherein leftTile and rightTile are the separate representation for the second spectral portion of the second set of second spectral portions, and wherein midTile and sideTile are the joint representation for the second spectral portion of the second set of second spectral portions.

6. Audio decoder of claim 3 , wherein the joint representation is a representation comprising an additional prediction coefficient, and wherein the representation transformer is configured to operate based on the following equation:
sideTile[ k ]=sideTile[ k ]−predictionCoeff·midTile[ k]

leftTile[ k ]=midTile[ k ]+sideTile[ k]
rightTile[ k ]=midTile[ k ]−sideTile[ k]

when a prediction direction is from mid to side, or
midTile1[ k ]=midTile[ k ]−predictionCoeff·sideTile[ k]

leftTile[ k ]=midTile1[ k ]−sideTile[ k]

rightTile[ k ]=midTile1[ k ]+sideTile[ k]

when a prediction direction is indicated from side to mid,
wherein leftTile and rightTile are the separate representation for the second spectral portion of the second set of second spectral portions, and wherein midTile and sideTile are the joint representation for the second spectral portion of the second set of second spectral portions, and wherein predictionCoefficient is the additional prediction coefficient.

7. Audio decoder of claim 1 ,
wherein the parametric data for the second set of second spectral portions is separately given for each channel of the two-channel audio representation, and
wherein the frequency regenerator is configured for transforming the parametric data for the second spectral portion of the second set of second spectral portions into a joint representation for the second spectral portion of the second set of second spectral portions and for applying the parametric data to a joint representation of the first spectral portion of the first set of first spectral portions, when the two-channel identification identifies the joint representation for the second spectral portion of the second set of second spectral portions.

8. Audio decoder of claim 1 , wherein the second spectral portions of the second set of second spectral portions correspond to frequency bands, and wherein the two-channel identification is an array of flags, one flag for each frequency band, and wherein the parametric decoder is configured to check, whether the flag is set or not and to control the frequency regeneration in accordance with the flag to use either a first two channel representation or a second two channel representation of the first spectral portion of the first set of first spectral portions of the encoded two-channel audio signal.

9. Audio decoder of claim 1 , wherein the parametric decoder is configured to provide the further two-channel identification for the first set of first spectral portions indicating either a first or a second different two-chann

Assignees

• Fraunhofer Ges Forschung

Inventors

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

Classifications

• 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

• G10L25/06

  the extracted parameters being correlation coefficients · CPC title

• G10L19/0204

  using subband decomposition · CPC title

• G10L19/03 Primary

  Spectral prediction for preventing pre-echo; Temporary noise shaping [TNS], e.g. in MPEG2 or MPEG4 · CPC title

• G10L19/022

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