System and method for reducing temporal artifacts for transient signals in a decorrelator circuit

Patent metadata

Field	Value
Publication number	US-9747909-B2
Application number	US-201414907542-A
Country	US
Kind code	B2
Filing date	Jul 23, 2014
Priority date	Jul 29, 2013
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

Embodiments are directed to a method for processing an input audio signal, comprising: splitting the input audio signal into at least two components, in which the first component is characterized by fast fluctuations in the input signal envelope, and a second component that is relatively stationary over time; processing the second, stationary component by a decorrelation circuit; and constructing an output signal by combining the output of the decorrelator circuit with the input signal and/or the first component signal.

First claim

What is claimed is:

1. A method for processing an input audio signal, comprising:
separating the input audio signal into a transient component characterized by fast fluctuations in the input signal envelope and a continuous component characterized by slow fluctuations in the input signal envelope;
processing the continuous component in a decorrelation circuit to generate a decorrelated continuous signal, wherein the decorrelated continuous signal is scaled with a time-varying scaling function, dependent on the envelope of the input audio signal and the output of the decorrelation circuit; and
combining the decorrelated continuous signal with the transient component to construct an output signal.

2. The method of claim 1 , wherein the fluctuations are measured with respect to time and the transient component is identified by a time-varying characteristic that exceeds a pre-defined threshold value distinguishing the transient component from the continuous component.

3. The method of claim 2 wherein the time-varying characteristic is selected from the group consisting of amplitude, energy, loudness, and spectral coherence.

4. The method of claim 3 further comprising:
estimating the envelope of the input audio signal; and
analyzing the envelope of the input audio signal for changes in the time-varying characteristic relative to the pre-defined threshold value to identify the transient component.

5. The method of claim 2 further comprising performing at least one of: pre-filtering the input audio signal to enhance or attenuate certain frequency bands of interest, and estimating at least one sub-band envelope of the envelope of the input audio signal to detect one or more transients in the at least one sub-band envelope and combining the sub-band envelope signals together to generate wide-band continuous and wide-band transient signals.

6. The method of claim 1 further comprising applying weighting values to at least one of the transient component, the continuous component, the input signal, and the decorrelated continuous signal, wherein the weighting values comprise mixing gains.

7. The method of claim 1 wherein the decorrelation circuit comprises a plurality of all-pass delay sections.

8. The method of claim 6 wherein an envelope of the decorrelated continuous signal is predicted from an envelope of the continuous component.

9. The method of claim 1 further comprising filtering at least one of the continuous component and the decorrelated continuous signal to obtain a frequency-dependent correlation in the output signals.

10. The method of claim 6 wherein the input audio signal comprises an object-based audio signal having spatial reproduction data, and in wherein the weighting values depend on the spatial reproduction data.

11. The method of claim 10 wherein the spatial reproduction data comprises at least one of: object width, object size, object correlation, and object diffuseness.

12. An apparatus for processing an input audio signal, comprising:
a transient processor separating the input audio signal into a transient component characterized by fast fluctuations in the input signal envelope and a continuous component characterized by slow fluctuations in the input signal envelope;
a decorrelation circuit coupled to the transient processor and decorrelating the continuous component to generate a decorrelated continuous signal;
an output stage coupled to the decorrelation circuit and transient processor combining the decorrelated continuous signal transient component to construct an output signal; and
a gain circuit associated with the output stage and configured to apply weighting values to at least one of the transient component, the continuous component, the input signal, and the decorrelated continuous signal, wherein the weighting values comprise mixing gains, and further wherein the decorrelated continuous signal is scaled with a time-varying scaling function, dependent on the envelope of the input audio signal and the output of the decorrelation circuit.

13. The apparatus of claim 12 , wherein the fluctuations are measured with respect to time and the transient component is identified by a time-varying characteristic that exceeds a pre-defined threshold value distinguishing the transient component from the continuous component, and wherein the time-varying characteristic is selected from the group consisting of amplitude, energy, loudness, and spectral coherence.

14. The apparatus of claim 13 further comprising an envelope processor coupled to the transient processor and configure to estimate the envelope of the input audio signal, and analyze the envelope of the input audio signal for changes in the time-varying characteristic relative to the pre-defined threshold value to identify the transient component.

15. The apparatus of claim 14 further comprising:
a pre-filter stage pre-filtering the input audio signal to enhance or attenuate certain frequency bands of interest; and
a sub-band processor estimating at least one sub-band envelope of the envelope of the input audio signal to detect one or more transients in the at least one sub-band envelope and combining the sub-band envelope signals together to generate wide-band continuous and wide-band transient signals.

16. The apparatus of claim 12 wherein the decorrelation circuit comprises a plurality of all-pass delay sections.

17. The apparatus of claim 12 further comprising an envelope predictor coupled to the transient processor, and configured to predict an envelope of the decorrelated continuous signal from an envelope of the continuous component.

18. The apparatus of claim 12 further comprising a filter stage filtering at least one of the continuous component and the decorrelated continuous signal to obtain a frequency-dependent correlation in the output signals.

19. The apparatus of claim 12 wherein the input audio signal comprises an object-based audio signal having spatial reproduction data, and in wherein the weighting values depend on the spatial reproduction data, and wherein the spatial reproduction data comprises at least one: object width, object size, object correlation, and object diffuseness.

20. A method for processing an input signal, comprising:
analyzing a signal envelope of the input signal to identify a continuous component of the input signal from a transient component of the input signal;
decorrelating the continuous component to generate a decorrelated continuous signal passing the transient component to an output stage;
combining the transient component and the decorrelated continuous signal in the output stage to generate an output signal;
generating two envelope estimates calculated with different integration times of the input signal; and
using a ratio of the two envelope estimates to distinguish the transient component from the continuous component.

21. The method of claim 20 further comprising estimating an envelope of the input signal using one of a Hilbert transform, a peak detection process, or a short-term RMS process.

22. The method of claim 20 the fluctuations are measured with respect to time and the transient component is identified by a time-varying characteristic that exceeds a pre-defined threshold value distinguishing the transient component from the continuous component, and further wherein the transient component characterized by fast fluctuations in the input signal envelope and a continuous component characterized by slow fluctuations in the input s

Assignees

• Dolby Laboratories Licensing Corp
• Dolby Int Ab

Inventors

• Breebaart Dirk Jeroen
• Lu Lie
• Mateos Sole Antonio
• Tsingos Nicolas R

Classifications

• G10L19/06

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

• G10L19/02

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

• G10L19/26

  Pre-filtering or post-filtering · 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