SIGNAL PROCESSING METHOD

• US 20120140598A1
• Filed: 11/17/2011
• Published: 06/07/2012
• Est. Priority Date: 12/02/2010
• Status: Active Grant

• Current Assignee: Fujitsu Ten Limited (DENSO Corporation)
• Original Assignee: Fujitsu Ten Limited (DENSO Corporation)
• Inventors: WAKABAYASHI, Isao
• Granted Patent: US 9,305,566 B2
• Time in Patent Office: Days
• US Class Current: 367/135
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: G10L 25/06 the extracted parameters being correlation coefficients
• CPC Class Codes: H04R 2499/13 Acoustic transducers and sound field adaptation in vehicles
• CPC Class Codes: H04S 1/007 in which the audio signals are in digital form data reduction aspects thereof based on psychoacoustics G10L19/02
• CPC Class Codes: H04S 2400/05 Generation or adaptation of centre channel in multi-channel audio systems
• CPC Class Codes: H04S 5/00 Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation

Abstract

A computing part computes a correlation coefficient representing a level of correlation among acoustic signals for a plurality of channels. A filtering part smoothes a time variation of the correlation coefficient computed. A center component reducer reduces a correlation component that is common in the acoustic signals by using the correlation coefficient. Then, the correlation component extracted by the reducer is reduced from each of the acoustic signals.

Claims

1. A signal processing method that processes a signal, the method comprising the steps of:

(a) computing a first correlation coefficient that represents a level of correlation among acoustic signals for a plurality of channels;

(b) deriving a second correlation coefficient by smoothing a time variation of the first correlation coefficient; and

(c) extracting a correlation component that is common in the acoustic signals by using the second correlation coefficient, and reducing the correlation component from each of the acoustic signals.

2. The signal processing method according to claim 1, further comprising the step of

(1) prior to the step (a), converting each of the acoustic signals into a signal consisting of a real part and an imaginary part, and wherein

the step (a) computes the first correlation coefficient based on the signal consisting of the real part and the imaginary part.

3. The signal processing method according to claim 2, wherein

the step (1) shifts a phase of a signal corresponding to the real part of each of the acoustic signals by 90 degrees and then generates a signal corresponding to the imaginary part of each of the acoustic signals.

4. The signal processing method according to claim 2, wherein

the step (a) computes a square value of a vector corresponding to each of the acoustic signals, then computes a specific correlation coefficient by which a value of the imaginary part in a first power is weighted, based on a value of the first power obtained by summing the square values computed and a value of an inner product of the vector, further computes a value of a second power by weighting the value of the imaginary part in the first power by using the specific correlation coefficient, and then computes the first correlation coefficient based on the value of the second power and the value of the inner product.

5. The signal processing method according to claim 4, wherein

the step (a) computes the first correlation coefficient based on the value of the real part in the second power and the value of the inner product.

6. The signal processing method according to claim 1, wherein

the step (b) derives the second correlation coefficient by using a low pass filter.

7. A signal processing apparatus that processes a signal, the apparatus comprising:

a computing part that computes a first correlation coefficient representing a level of correlation among acoustic signals for a plurality of channels;

a deriving part that derives a second correlation coefficient by smoothing a time variation of the first correlation coefficient; and

a reducer that extracts a correlation component that is common in the acoustic signals by using the second correlation coefficient, and that reduces the correlation component from each of the acoustic signals.

8. The signal processing apparatus according to claim 7, further comprising

a converter that converts each of the acoustic signals into a signal consisting of a real part and an imaginary part, and wherein

the computing part computes the first correlation coefficient based on the signal consisting of the real part and the imaginary part.

9. The signal processing apparatus according to claim 8, wherein

the converter shifts a phase of a signal corresponding to the real part of each of the acoustic signals by 90 degrees and then generates a signal corresponding to the imaginary part of each of the acoustic signals.

10. The signal processing apparatus according to claim 8, wherein

the computing part computes a square value of a vector corresponding to each of the acoustic signals, then computes a specific correlation coefficient by which a value of the imaginary part in a first power is weighted, based on a value of the first power obtained by summing the square values computed and a value of an inner product of the vector, further computes a value of a second power by weighting the value of the imaginary part in the first power by using the specific correlation coefficient, and then computes the first correlation coefficient based on the value of the second power and the value of the inner product.

11. The signal processing apparatus according to claim 10, wherein

the computing part computes the first correlation coefficient based on the value of the real part in the second power and the value of the inner product.

12. The signal processing apparatus according to claim 7, wherein

the deriving part derives the second correlation coefficient by using a low pass filter.

13. A reproduction apparatus that reproduces an acoustic signal, the reproduction apparatus comprising;

a computing part that computes a first correlation coefficient representing a level of correlation among acoustic signals for a plurality of channels;

a deriving part that derives a second correlation coefficient by smoothing a time variation of the first correlation coefficient;

an extracting part that extracts a correlation component that is common in the acoustic signals, by using the second correlation coefficient;

an adjuster that adjusts a ratio of the correlation component and a decorrelation component in the acoustic signals; and

a reproduction part that reproduces each of the acoustic signals in which the ratio has been adjusted.