Device and method for improved magnitude response and temporal alignment in a phase vocoder based bandwidth extension method for audio signals

Patent metadata

Field	Value
Publication number	US-9905235-B2
Application number	US-201615071569-A
Country	US
Kind code	B2
Filing date	Mar 16, 2016
Priority date	Mar 9, 2010
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

An apparatus for generating a bandwidth extended audio signal from an input signal, includes a patch generator for generating one or more patch signals from the input signal, wherein the patch generator is configured for performing a time stretching of subband signals from an analysis filterbank, and wherein the patch generator further includes a phase adjuster for adjusting phases of the subband signals using a filterbank-channel dependent phase correction.

First claim

The invention claimed is:

1. An apparatus for generating a bandwidth extended audio signal from an input audio signal, comprising:
a patch generator configured for generating one or more patch signals from the input audio signal, wherein a patch signal comprises a patch center frequency being different from a patch center frequency of a different patch or from a center frequency of the input audio signal,
wherein the patch generator is configured for performing a time stretching of subband audio signals from an analysis filterbank, and
wherein the patch generator comprises a phase adjuster configured for adjusting phases of the subband audio signals using a filterbank-channel dependent phase correction, wherein one or more of the patch generator, and the phase adjuster is implemented, at least in part, by one or more hardware elements of the apparatus.

2. The apparatus in accordance with claim 1 , in which the phase adjuster is configured to select the filterbank-channel dependent phase correction so that an amplitude variation of a signal introduced by a design of the filterbank is reduced or eliminated.

3. The apparatus in accordance with claim 1 , in which the phase adjuster is configured for applying the filterbank-channel dependent phase correction, wherein the filterbank-channel dependent phase correction being independent on the subband audio signals.

4. The apparatus in accordance with claim 1 , in which the phase adjuster is configured to additionally apply a signal-dependent phase correction depending on an applied transposition factor.

5. The apparatus in accordance with claim 1 ,
wherein the patch generator is configured for performing the time stretching using a first block advance value,
wherein the patch generator is configured for performing a block-wise processing and comprises:
a block extractor configured for extracting subsequent blocks of values from the subband audio signal using a block advance value;
the phase adjuster; and
an overlap-add processor, wherein the overlap-add processor is configured for applying a second block advance value being larger than the first block advance value used by the patch generator.

6. The apparatus in accordance with claim 5 , in which the block extractor is configured to additionally perform a decimation operation dependent on the transposition factor T and to perform an interpolation in case of a non-integer decimation operation.

7. The apparatus in accordance with claim 5 , in which the patch generator further comprises a windower configured for windowing a block using a window function.

8. The apparatus in accordance with claim 1 , further comprising:
a high frequency reconstruction processor configured for applying high frequency reconstruction parameters to the subband audio signals subsequent to the adjusting the phases of the subband audio signals using the filterbank-channel dependent phase correction.

9. The apparatus in accordance with claim 1 , further comprising a synthesis filterbank comprising a subband spacing being greater than a subband spacing of the analysis filterbank.

10. The apparatus in accordance with claim 1 ,
in which the patch generator comprises the analysis filterbank configured for generating the subband audio signals from a lowband signal, wherein the analysis filter bank is a Quadrature Mirror Filterbank comprising phase twiddling,
wherein the patch generator is configured to apply a transposition factor to generate the one or more patch signals, and
wherein the filterbank-channel dependent phase correction depends on the applied transposition factor.

11. The apparatus in accordance with claim 1 ,
wherein the patch generator is configured to apply a transposition factor to generate the one or more patch signals
wherein the patch generator comprises the analysis filterbank configured for generating the subband audio signals from a lowband signal,
wherein the analysis filterbank is a QMF filterbank configured to apply a phase twiddling, and
wherein the filterbank-channel dependent phase correction is independent from a transposition factor used for generating the one or more patch signal.

12. The apparatus in accordance with claim 1 , in which the patch generator comprises a time stretcher, and in which the time stretcher comprises a block extractor using an extraction advance value.

13. The apparatus in accordance with claim 1 , in which the patch generator comprises a time stretcher, wherein the time stretcher comprises a block extractor, a windower, or a phase adjuster and the overlap-adder for at least two different channels comprising different channel numbers of an analysis filterbank,
wherein the windower or phase adjuster for each of the at least two channels is configured for applying a phase adjustment for each channel, the phase adjustment depending on the channel number.

14. The apparatus in accordance with claim 1 , in which the patch generator is configured to generate the one or more patch signals so that a time disalignment between the input audio signal and the one or more patch signals or a time disalignment between different patch signals is reduced or eliminated.

15. The apparatus in accordance with claim 1 , wherein the patch generator comprises the analysis filterbank configured for generating the subband audio signals from the input audio signal.

16. The apparatus in accordance with claim 1 , in which the patch generator is configured to generate a plurality of patch signals, and comprises:
at least one patcher comprising a decimating functionality;
a time stretcher configured for performing the time stretching of the subband audio signals from the analysis filterbank; and
a patch corrector configured for applying a time correction to the plurality of patch signals to reduce or eliminate a time disalignment between the plurality of patch signals occurring without any time correction applied.

17. A method of generating a bandwidth extended audio signal from an input audio signal, comprising:
generating one or more patch signals from the input audio signal, wherein a patch signal comprises a patch center frequency being different from a patch center frequency of a different patch or from a center frequency of the input audio signal,
wherein a time stretching of subband audio signals from an analysis filterbank is performed, and
wherein phases of the subband audio signals are adjusted using a filterbank-channel dependent phase correction,
wherein one or more of generating one or more patch signals, and adjusting phases of the subband audio signal is implemented, at least in part, by one or more hardware elements of an audio signal processing device.

18. A non-transitory storage medium having stored thereon a computer program comprising a program code for performing, when running in a computer, the method of generating a bandwidth extended audio signal from an input audio signal, the method comprising:
generating one or more patch signals from the input audio signal, wherein a patch signal comprises a patch center frequency being different from a patch center frequency of a different patch or from a center frequency of the input audio signal,
wherein a time stretching of subband audio signals from an analysis filterbank is performed, and
wherein phases of the subband audio signals are adjusted using a filterbank-channel dependent phase correction.

Assignees

• Fraunhofer Ges Forschung
• Dolby Int Ab

Inventors

• Disch Sascha
• Nagel Frederik
• Wilde Stephan
• Villemoes Lars
• Ekstrand Per

Classifications

• G10L19/0208 Primary

  Subband vocoders · CPC title

• G10L19/022

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

• G10L19/16

  Vocoder architecture · CPC title

• G10L21/038 Primary

  using band spreading techniques · CPC title

• G10L19/26

  Pre-filtering or post-filtering · CPC title