# US 2014/0192987 A1 · Matrix encoder with improved channel separation

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- Number: US 2014/0192987 A1
- Document ID: US20140192987A1
- Status: Published application
- Kind: A1
- Application number: 14/124,161
- Filed: 2012-06-04
- Published: 2014-07-10
- Earliest claimed: 2011-06-06
- Assignees: Reality IP Pty Ltd
- Inventors: Charlie Van Dongen
- Web page: https://patentgrep.com/patent/US20140192987A1

## CPC

- G10L 19/008: Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
- H04S 3/02: 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
- H04S 2400/01: Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- H04S: STEREOPHONIC SYSTEMS

## Abstract

An encoder is disclosed for use in a surround sound system wherein at least four audio input signals (FL, FR, RL, RR) representing an original sound field are encoded into two channel signals (L, and the encoded two channel signals are decoded into at least four audio output signals (FL′, FR′, RL′, RR′) corresponding to the four audio input signals. The encoder includes matrix means connected to receive the four audio input signals for encoding the four input signals into two channel (L and R) output signals. The matrix means includes means responsive to the four input signals for producing Lenc and Renc output signals as follows: Lenc=FL+kFR+jRL+jkRR Renc=FR+kFL−jRR−jkRL wherein k denotes a transformation or matrix coefficient having a value that is steered dynamically based on level of rear signal (RL+RR) content relative to front signal (FL+FR) content. An encoding method for use in a surround sound system is also disclosed.

## Claims

### Claim 1

An encoder for use in a surround sound system wherein at least four audio input signals (FL, FR, RL, RR) representing an original sound field are encoded into two channel signals (L, R) and said encoded two channel signals are decoded into at least four audio output signals (FL′, FR′, RL′, RR′) corresponding to said four audio input signals, said encoder including:
matrix means connected to receive said four audio input signals for encoding said four input signals into two channel (L and R) output signals, said matrix means including means responsive to said four input signals for producing Lenc and Renc output signals as follows:
Lenc=FL+kFR+jRL+jkRR
Renc=FR+kFL−jRR−jkRL
wherein k denotes a transformation or matrix coefficient having a value substantially 0.207 and j denotes a 90 degree phase shift.

### Claim 2

An encoder for use in a surround sound system wherein at least four audio input signals (FL, FR, RL, RR) representing an original sound field are encoded into two channel signals (L, R) and said encoded two channel signals are decoded into at least four audio output signals (FL′, FR′, RL′, RR′) corresponding to said four audio input signals, said encoder including:
matrix means connected to receive said four audio input signals for encoding said four input signals into two channel (L and R) output signals, said matrix means including means responsive to said four input signals for producing Lenc and Renc output signals as follows:
Lenc=FL+kFR+jRL+jkRR
Renc=FR+kFL−jRR−jkRL
wherein k denotes a transformation or matrix coefficient having a value that is steered dynamically based on level of rear signal (RL+RR) content relative to front signal (FL+FR) content.

### Claim 3 (depends on 2)

An encoder according to claim 2 wherein the coefficient k is steered from a first value to a second value.

### Claim 4 (depends on 3)

An encoder according to claim 3 wherein the coefficient k is steered between said first and second values substantially linearly.

### Claim 5 (depends on 2)

An encoder according to claim 2 wherein the coefficient k has a first value that is substantially 0.1.

### Claim 6 (depends on 2)

An encoder according to claim 2 wherein the coefficient k has a second value that is substantially 0.414.

### Claim 7 (depends on 1)

An encoder according to claim 1 wherein said matrix means includes a plurality of components selected from adders, multipliers, 90° phase shifters and comparators.

### Claim 8

An encoding method for use in a surround sound system wherein at least four audio input signals (FL, FR, RL, RR) representing an original sound field are encoded into two channel signals (L, R) and said encoded two channel signals are decoded into at least four audio output signals (FL′, FR′, RL′, RR′) corresponding to said four audio input signals, said method including:
processing said four audio input signals into two channel (L and R) output signals by matrix means responsive to said four input signals for producing Lenc and Renc output signals as follows:
Lenc=FL+kFR+jRL+jkRR
Renc=FR+kFL−jRR−jkRL
wherein k denotes a transformation or matrix coefficient having a value approximately 0.207 and j denotes a 90 degree phase shift.

### Claim 9

An encoding method for use in a surround sound system wherein at least four audio input signals (FL, FR, RL, RR) representing an original sound field are encoded into two channel signals (L, R) and said encoded two channel signals are decoded into at least four audio output signals (FL′, FR′, RL′, RR′) corresponding to said four audio input signals, said method including:
processing said four audio input signals into two channel (L and R) output signals by matrix means responsive to said four input signals for producing Lenc and Renc output signals as follows:
Lenc=FL+kFR+jRL+jkRR
Renc=FR+kFL−jRR−jkRL
wherein k denotes a transformation or matrix coefficient and wherein said processing includes steering the value of coefficient k based on level of rear signal (RL+RR) content relative to front signal (FL+FR) content.

### Claim 10 (depends on 9)

An encoding method according to claim 9 wherein the coefficient k is steered from a first value to a second value.

### Claim 11 (depends on 10)

An encoding method according to claim 10 wherein the coefficient k is steered between said first and second values substantially linearly.

### Claim 12 (depends on 9)

An encoding method according to claim 9 wherein the coefficient k has a first value that is substantially 0.1.

### Claim 13 (depends on 9)

An encoding method according to claim 9 wherein the coefficient k has a second value that is substantially 0.414.

### Claim at position 14

14-15. (canceled)

### Claim 16 (depends on 2)

An encoder according to claim 2 wherein said matrix means includes a plurality of components selected from adders, multipliers, 90° phase shifters and comparators.