Method for apparatus for audio matrix decoding

• US 20040125960A1
• Filed: 02/25/2003
• Published: 07/01/2004
• Est. Priority Date: 08/31/2000
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Vernon, Stephen D., Andersen, Robert L., Fosgate, James W.
• Granted Patent: US 7,280,664 B2
• Time in Patent Office: Days
• US Class Current: 381/20
• CPC Class Codes: 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

Abstract

A method derives at least three audio signals, each associated with a direction, from two input audio signals. In response to the two input signals, a passive matrix generates a plurality of passive matrix audio signals, including two pairs of passive matrix audio signals, a first pair of passive amtrix audio signals represent directions lying on a first axis and a second pair of passive matrix audio signals represent direction lying on a second axis, the first and second aces being substantially at ninety degrees to ach other. The pairs of passive matrix audio signals are processed to derive a plurality of matrix coefficients therefrom, The processing includes deriving a pair of intermediate signals and urging each pair of intermediate signals toward equality in response to a respective error signal. At least three output signals are produced by matrix multiplying the two input signals by the matrix coefficients.

Claims

1. A method for deriving at least three audio signals, each associated with a direction, from two input audio signals, comprising

generating with a passive matrix in response to said two input audio signals a plurality of passive matrix audio signals including two pairs of passive matrix audio signals, a first pair of passive matrix audio signals representing directions lying on a first axis and a second pair of passive matrix audio signals representing directions lying on a second axis, said first and second axes being substantially at ninety degrees to each other,

processing each of said pairs of passive matrix audio signals to derive a plurality of matrix coefficients therefrom, said processing including deriving a pair of intermediate signals [(1−

gL)*Lt′ and

(1−

gR)*Rt′

, (1−

gF)*Ft and (1−

gB)*Bt] from each pair of passive matrix audio signals, respectively, and urging each pair of intermediate signals toward equality in response to a respective error signal, and

producing at least three output signals by matrix multiplying said two input signals by said matrix coefficients.

2. The method of claim 1 wherein each error signal is generated in response to the relative magnitudes of the pair of intermediate signals with which it is associated.

3. The method of claim 1 or claim 2 wherein said plurality of matrix coefficients are derived from said error signals.

4. The method of claim 1 or claim 2 wherein said plurality of matrix coefficients are derived from control signals generated by said processing in response to said error signals.

5. The method of claim 1 wherein the method derives four audio output signals associated with the directions left, center, right, and surround.

6. The method of claim 1 wherein the method derives six audio output signals associated with the directions left, center, right, left surround, back surround and right surround.

7. The method of claim 1 wherein the method derives five audio output signals associated with the directions left, center, right, left surround and right surround.

8. The method of any one of claims 1-7 wherein the method is implemented in the digital domain.

9. The method of claim 8 wherein at least a portion of said processing is downsampled.

10. The method of claim 9 wherein said matrix coefficients are upsampled.

11. The method of claim 9 as dependent on claim 3 wherein said error signals are upsampled.

12. The method of claim 9 as dependent on claim 4 wherein said control signals are upsampled.

13. The method of claim 8 further comprising delaying said input signals to produce delayed input signals and wherein said producing produces at least three output signals by matrix multiplying said delayed input signals by said matrix coefficients.

14. The method of claim 13 wherein said delaying delays said input signals by about 5 ms.