Apparatus, method and computer program for manipulating an audio signal comprising a transient event

Patent metadata

Field	Value
Publication number	US-9230557-B2
Application number	US-201113191780-A
Country	US
Kind code	B2
Filing date	Jul 27, 2011
Priority date	Jan 30, 2009
Publication date	Jan 5, 2016
Grant date	Jan 5, 2016

Abstract

An apparatus for manipulating an audio signal comprising a transient event has a transient signal replacer configured to replace a transient signal portion, comprising the transient event of the audio signal, with a replacement signal portion adapted to signal energy characteristics of one or more transient signal portions of the audio signal, or to signal energy characteristics of the transient signal portion, to obtain a transient-reduced audio signal. The apparatus also has a signal processor configured to process the transient-reduced audio signal to obtain a processed version of the transient-reduced audio signal. The apparatus also has a transient-signal-re-inserter configured to combine the processed version of the transient-reduced audio signal with a transient signal representing, in an original or processed form, a transient content of the transient signal portion.

First claim

The invention claimed is:

1. An apparatus for manipulating an audio signal comprising a transient event, the apparatus comprising:
a transient signal replacer configured to replace a transient signal portion, comprising the transient event, of the audio signal with a replacement signal portion adapted to signal energy characteristics of one or more non-transient signal portions of the audio signal, or to a signal energy characteristic of the transient signal portion, to acquire a transient-reduced audio signal;
a signal processor configured to process the transient-reduced audio signal, to acquire a processed version of the transient-reduced audio signal; and
a transient signal re-inserter configured to combine the processed version of the transient-reduced audio signal with a transient signal representing, in an original or processed form, a transient content of the transient signal portion, to obtain a processed signal;
wherein the transient signal replacer is configured to extrapolate amplitude values of one or more signal portions preceding the transient signal portion, to acquire amplitude values of the replacement signal portion, and
wherein the transient signal replacer is configured to extrapolate phase values of one or more signal portions preceding the transient signal portion to acquire phase values of the replacement signal portion.

2. The apparatus according to claim 1 , wherein the transient signal replacer is configured to provide the replacement signal portion such that the replacement signal portion represents a time signal comprising a smoothened temporal evolution when compared to the transient signal portion, such that a deviation between an energy of the replacement signal portion and an energy of a non-transient signal portion of the audio signal preceding the transient signal portion or following the transient signal portion is smaller than a predetermined threshold value.

3. The apparatus according to claim 1 , wherein the transient signal replacer is configured to apply a weighted noise to acquire the amplitude values of the replacement signal portion, or
to apply a weighted noise to acquire the phase values of the replacement signal portions.

4. The apparatus according to claim 1 , wherein the transient signal replacer is configured to combine non-transient components of the transient signal portion with the extrapolated or interpolated values, to acquire the replacement signal portion.

5. The apparatus according to claim 1 , wherein the transient signal replacer is configured to acquire replacement signal portions of variable length in dependence on a length of the present transient signal portion.

6. The apparatus according to claim 1 , wherein the signal processor is configured to process the transient-reduced audio signal such that a given temporal signal portion of the processed version of the transient-reduced audio signal is dependent on a plurality of temporally shifted temporal signal portions of the transient-reduced audio signal.

7. The apparatus according to claim 1 , wherein the signal processor is configured to perform a time-block-based processing of the transient-reduced audio signal, to acquire the processed version of the transient-reduced audio signal; and
wherein the transient signal replacer is configured to adjust the duration of the transient signal portion to be replaced by the replacement signal portion with a temporal resolution which is finer than the duration of a time block, or to replace a transient signal portion comprising a temporal duration smaller than the duration of the time block with a replacement signal portion comprising a temporal duration smaller than the duration of the time block.

8. The apparatus according to claim 1 , wherein the signal processor is configured to process the transient-reduced audio signal in a frequency-dependent way, so that the processing introduces transient-degrading frequency-dependent phase shifts into the transient-reduced audio signal.

9. The apparatus according to claim 1 , wherein the transient signal replacer comprises a transient detector, wherein the transient detector is configured to provide a time-varying detection threshold for the detection of the transient in the audio signal such that the detection threshold follows an envelope of the audio signal with on adjustable smoothing time constant, and
wherein the transient detector is configured to change the smoothing time constant in response to the detection of a transient and/or in dependence on a temporal evolution of the audio signal.

10. The apparatus according to claim 1 , wherein the apparatus comprises a transient processor configured to receive a transient information and to acquire, on the basis of the transient information, a processed transient signal in which tonal components are reduced, and
wherein the transient signal re-inserter is configured to combine the processed version of the transient-reduced audio signal with the processed transient signal provided by the transient processor.

11. The apparatus according to claim 1 ,
wherein the transient signal replacer comprises a transient detector configured to detect a transient signal portion of the audio signal on the basis of a monitoring of the audio signal, or on the basis of a side information accompanying the audio signal, and to determine a length of the transient signal portion;
wherein the transient signal replacer is configured to take into account the length of the transient signal portion determined by the transient detector;
wherein the transient signal replacer is configured to extrapolate, in a time-frequency domain, complex-valued time-frequency-domain coefficients associated with a non-transient signal portion of the audio signal preceding the transient signal portion, to acquire time-frequency domain coefficients of the replacement signal portion, or
wherein the transient signal replacer is configured to interpolate, in a time-frequency domain, between complex-valued time-frequency-domain coefficients associated with a non-transient signal portion of the audio signal preceding the transient signal portion, and complex-valued time-frequency domain coefficients associated with a non-transient signal portion of the audio signal following the transient signal portion, to acquire time-frequency domain coefficients of the replacement signal portion;
wherein the signal processor is configured to perform a transient-degrading audio signal processing by time stretching or time compression, such that the processed signal provided by the signal processor comprises a duration greater than, or smaller than, a duration of the unprocessed signal received by the audio signal processor; and
wherein the apparatus is configured to adapt a time-scaling or sample rate of the signal acquired by the transient signal re-inserter such that at least non-transient components of the signal acquired by the transient signal re-inserter are frequency-transposed when compared to the audio signal input into the transient signal replacer.

12. The apparatus according to claim 1 , wherein the a transient signal re-inserter is configured to cross-fade the processed version of the transient-reduced audio signal with a transient signal representing, in an original or processed form, a transient content of the transient signal portion.

13. The apparatus according to claim 1 , wherein the apparatus is configured to obtain the processed signal such that the processed signal comprises an unprocessed transient, or wherein the apparatus comprises a transient processor which is configured to derive the transient signal from a transient information using a transie

Assignees

• Nagel Frederik
• Walther Andreas
• Fuchs Guillaume
• Lecomte Jeremie
• Popp Harald
• Wik Tilo
• Fraunhofer Ges Forschung

Inventors

• Nagel Frederik
• Walther Andreas
• Fuchs Guillaume
• Lecomte Jeremie
• Popp Harald
• Wik Tilo

Classifications

• G10L19/028

  Noise substitution, i.e. substituting non-tonal spectral components by noisy source (comfort noise for discontinuous speech transmission G10L19/012) · CPC title

• G10L21/04 Primary

  Time compression or expansion · CPC title

• G10L19/025

  Detection of transients or attacks for time/frequency resolution switching · CPC title

• G10L19/02 Primary

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

• G10L19/00

  Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis (in musical instruments G10H) · CPC title