Apparatus and method for center signal scaling and stereophonic enhancement based on a signal-to-downmix ratio

Patent metadata

Field	Value
Publication number	US-9743215-B2
Application number	US-201514880065-A
Country	US
Kind code	B2
Filing date	Oct 9, 2015
Priority date	Apr 12, 2013
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

An apparatus for generating a modified audio signal having two or more modified audio channels from an audio input signal comprising two or more audio input channels is provided. The apparatus has an information generator for generating signal-to-downmix information. The information generator is adapted to generate signal information by combining a spectral value of each of the two or more audio input channels in a first way. The information generator is adapted to generate downmix information by combining the spectral value of each of the two or more audio input channels in a second way being different from the first way. Furthermore, the information generator is adapted to combine the signal information and the downmix information to obtain signal-to-downmix information. The apparatus has a signal attenuator for attenuating the two or more audio input channels depending on the signal-to-downmix information to obtain the two or more modified audio channels.

First claim

The invention claimed is:

1. An apparatus for generating a modified audio signal comprising two or more modified audio channels from an audio input signal comprising two or more audio input channels, wherein the apparatus comprises:
an information generator for generating signal-to-downmix information, wherein the information generator is adapted to generate signal information by combining a spectral value of each of the two or more audio input channels in a first way, wherein the information generator is adapted to generate downmix information by combining the spectral value of each of the two or more audio input channels in a second way being different from the first way, and wherein the information generator is adapted to combine the signal information and the downmix information to acquire signal-to-downmix information, and
a signal attenuator for attenuating the two or more audio input channels depending on the signal-to-downmix information to acquire the two or more modified audio channels,
wherein the information generator is configured to generate the signal information Φ 1 (m, k) according to the formula:
Φ 1 ( m,k )=ε{ WX ( m,k )( WX ( m,k )) H },

wherein the information generator is configured to generate the downmix information Φ 2 (m, k) according to the formula:
Φ 2 ( m,k )=ε{ VX ( m,k )( VX ( m,k )) H }, and

wherein the information generator is configured to generate a signal-to-downmix ratio as the signal-to-downmix information R g (m, k, β) according to the formula:

R
g

⁡

(

m
,
k
,
β

)

=

(

tr
⁢

{

Φ
1

⁡

(

m
,
k

)

β

}

tr
⁢

{

Φ
2

⁡

(

m
,
k

)

β

}

)

1

2
⁢
β

-
1

wherein X(m, k) indicates the audio input signal, wherein
X ( m,k )=[ X 1 ( m,k ) . . . X N ( m,k )] T ,

wherein N indicates the number of audio input channels of the audio input signal,
wherein m indicates a time index, and wherein k indicates a frequency index,
wherein X 1 (m, k) indicates the first audio input channel, wherein X N (m, k) indicates the N-th audio input channel,
wherein V indicates a matrix or a vector,
wherein W indicates a matrix or a vector,
wherein H indicates the conjugate transpose of a matrix or a vector,
wherein ε{•} is an expectation operation,
wherein β is a real number with β>0, and
wherein tr{ } is the trace of a matrix.

2. The apparatus according to claim 1 , wherein V is a row vector of length N whose elements are equal to one and W is the identity matrix of size N×N.

3. The apparatus according to claim 1 , wherein V=[1, 1], wherein W=[1, −1] and wherein N=2.

4. The apparatus according to claim 1 , wherein the number of the modified audio channels is equal to the number of the audio input channels, or wherein the number of the modified audio channels is smaller than the number of the audio input channels.

5. The apparatus according to claim 1 ,
wherein the information generator is configured to process the spectral value of each of the two or more audio input channels to acquire two or more processed values, and wherein the information generator is configured to combine the two or more processed values to acquire the signal information, and
wherein the information generator is configured to combine the spectral value of each of the two or more audio input channels to acquire a combined value, and wherein the information generator is configured to process the combined value to acquire the downmix information.

6. The apparatus according to claim 5 , wherein the information generator is configured to process the combined value by determining a power spectral density of the combined value.

7. The apparatus according to claim 6 , wherein the information generator is configured to use
s ( m,k ,β)=Σ i=1 N Φ i,i ( m,k ) β

to acquire the signal information,
wherein Φ i,i (m, k) indicates the auto power spectral density of the spectral value of the i-th audio signal channel.

8. The apparatus according to claim 7 ,
wherein the information generator is configured to determine

R
⁡

(

m
,
k
,
β

)

=

(

∑

i
=
1

N

⁢

⁢

Φ

i
,
i

⁡

(

m

Assignees

• Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E V

Inventors

• Uhle Christian
• Prokein Peter
• Hellmuth Oliver
• Scharrer Sebastian
• Habets Emanuel

Classifications

• H04S3/00

  Systems employing more than two channels, e.g. quadraphonic (H04S5/00, H04S7/00 take precedence) · CPC title

• H04S7/307 Primary

  Frequency adjustment, e.g. tone control (H04S7/301 takes precedence) · CPC title

• H04S3/02

  of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other · CPC title

• H04S2400/01

  Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved · CPC title

• H04S2400/03

  Aspects of down-mixing multi-channel audio to configurations with lower numbers of playback channels, e.g. 7.1 -> 5.1 (H04S2400/01 takes precedence) · CPC title