Stereo decoding system

• US 9,374,117 B2
• Filed: 07/24/2012
• Issued: 06/21/2016
• Est. Priority Date: 07/25/2011
• Status: Active Grant

• Current Assignee: Harman Becker Automotive Systems GmbH (Samsung Electronics Co. Ltd.)
• Original Assignee: Harman Becker Automotive Systems GmbH (Samsung Electronics Co. Ltd.)
• Inventors: Gierl, Stefan, Benz, Christoph, Krner, Andreas, Becker, Karl-Anton
• Primary Examiner(s): Lee, Ping
• Application Number:
  US13/557,028
• Publication Number:
  US 20130028425A1
• Time in Patent Office: 1,428 Days
• Field of Search: 381/1, 381/12, 381/13, 381/2, 381/3, 381/11
• US Class Current: 1/1
• CPC Class Codes: H04B 1/1676 of the sum or difference signal

Abstract

A system for decoding a stereo multiplex signal, including one or more devices operable to convert the stereo multiplex signal into a sum signal (L+R) and a difference signal (L−R). The sum signal and the difference signal may be derived from a left stereo signal (L) and right stereo signal (R). The system may also be operable to determine a first transfer function H_L(f) and a second transfer function (H_R(f)) from the sum signal (L+R) and the difference signal (L−R). Further, the system may be operable to filter the sum signal (L+R) according to the first transfer function to provide the left stereo signal (L), and filter the sum signal (L+R) according to the second transfer function to provide the right stereo signal (R).

Claims

1. A method for decoding a stereo multiplex signal, comprising:

converting the stereo multiplex signal into a sum signal (L+R) and a difference signal (L−

R), where the sum signal and the difference signal are derived from a left stereo signal (L) and right stereo signal (R);

determining a first transfer function H_L(f) and a second transfer function H_R(f) from the sum signal (L+R) and the difference signal (L−

R), wherein the first transfer function H_L(f) and the second transfer function H_R(f) are each variable and adjustable;

adaptively filtering the sum signal (L+R) by modifying first filter coefficients according to the first transfer function to provide the left stereo signal (L); and

adaptively filtering the sum signal (L+R) by modifying second filter coefficients according to the second transfer function to provide the right stereo signal (R).

2. The method of claim 1, where the second transfer function is defined by

3. The method of claim 1, where the first transfer function H_L(f)=1 the second transfer function H_r(f).

4. The method of claim 1, further comprising:

decoding the sum signal (L+R) and the difference signal (L−

R) with a stereo matrix; and

providing decoded signals from the decoded sum signal (L+R) and the decoded difference signal (L−

R).

5. The method of claim 4, further comprising filtering the decoded sum signal (L+R) and the decoded difference signal (L−

R) according to a third transfer function, where the decoded signals include the left stereo signal (L) and the right stereo signal (R).

6. The method of claim 5, where the third transfer function includes a unity function.

7. The method of claim 4, further comprising filtering one of the decoded sum signal (L+R) and the decoded difference signal (L−

R) according to the first transfer function and filtering the other decoded signal according to the second transfer function, where the decoded signals include a part of to the sum signal (L+R).

8. The method of claim 7, further comprising

switching or fading the decoded sum signal (L+R) and the decoded difference signal (L−

R) to the filtered decoded sum signal (L+R) and filtered decoded the difference signal (L−

R), respectively.

9. The method of claim 1, further comprising noise reducing the sum signal (L+R) and the difference signal (L−

R).

10. The method of claim 9, where the noise reducing includes spectral subtracting.

11. The method of claim 1, further comprising delaying the stereo multiplex signal.

12. A system for decoding a stereo multiplex signal, comprising:

a stereo decoder that converts the stereo multiplex signal into a sum signal (L+R) and a difference signal (L−

R);

a first filter that is connected to the stereo decoder and that is operable to filter the sum signal (L+R) according to a first transfer function to provide a left stereo signal (L);

a second filter that is connected to the stereo decoder and that is operable to filter the sum signal (L+R) according to a second transfer function to provide a right stereo signal (R); and

a filter control unit that is connected to the stereo decoder and that is operable to control the first filter and the second filter by providing modified filter coefficients as control signals representing the first transfer function and the second transfer function, respectively,

wherein the first filter and the second filter are adaptive, and

wherein the first transfer function and the second transfer function are each variable and adjustable.

13. The system of claim 12, further comprising:

a receiver front end unit that is connected upstream of the stereo decoder and that is configured to receive the stereo multiplex signal and a quality signal representing the quality of the stereo multiplex signal with respect to at least one of signal strength or noise level;

a mono/stereo switch that is connected to the receiver front end unit and that is configured to evaluate the quality signal with respect to at least one of the signal strength or the noise level and provide a mode control signal indicating a mono mode or a stereo mode; and

a stereo matrix unit that is connected to the stereo decoder and the first and the second filter, the stereo matrix unit configured to provide to decoded signals, where the decoded signals represent the left stereo signal (L) and the right stereo signal (R) due to the quality signal indicating a high quality signal, and where the decoded signals represent the sum signal (L+R) due to the quality signal indicating a low quality signal.

14. The system of claim 13, where the stereo matrix unit is operable to filter the decoded signals according to a third transfer function, in response to the decoded signals representing the left stereo signal (L) and the right stereo signal (R).

15. The system of claim 14, where the third transfer function includes a unity function.

16. The system of claim 13, further comprising an intermediate frequency (IF) processing unit that is connected downstream of the receiver front end unit and that is configured to delay the stereo multiplex signal.

17. The system of claim 13, where the stereo matrix unit is operable to filter one of the decoded signals according to the first transfer function and filter another decoded signal according to the second transfer function, in response to the decoded signals representing the sum signal (L+R).

18. The system of claim 17, where the stereo matrix unit is operable to switch or fade the decoded sum signal (L+R) and the decoded difference signal (L−

R) to the filtered decoded sum signal (L+R) and the filtered decoded difference signal (L−

R), respectively.

19. The system of claim 12, further comprising a noise reduction unit that is connected downstream of the stereo decoder and is configured to reduce noise contained in the sum signal (L+R) and the difference signal (L−

R).

20. A non-transitory computer readable storage medium storing computer readable instructions executable by a processor to decode a stereo multiplex signal, the computer readable medium comprising instructions to:

convert the stereo multiplex signal into a sum signal (L+R) and a difference signal (L−

R), where the sum signal and the difference signal are derived from a left stereo signal (L) and right stereo signal (R);

determine a first transfer function H_L(f) and a second transfer function (H_R(f)) from the sum signal (L+R) and the difference signal (L−

R), wherein the first transfer function H_L(f) and the second transfer function H_R(f) are each variable and adjustable;

adaptively filter the sum signal (L+R) by modifying first filter coefficients according to the first transfer function to provide the left stereo signal (L); and

adaptively filter the sum signal (L+R) by modifying second filter coefficients according to the second transfer function to provide the right stereo signal (R).