Audio signal processing

• US 7,490,044 B2
• Filed: 06/08/2004
• Issued: 02/10/2009
• Est. Priority Date: 06/08/2004
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Kulkarni, Abhijit
• Primary Examiner(s): Vo; Huyen X.
• Application Number:
  US10/863,931
• Publication Number:
  US 20050271215A1
• Time in Patent Office: 1,708 Days
• Field of Search: 704500-504, 704/228, 704/278, 381/27, 381/22
• US Class Current: 704/501
• 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
• CPC Class Codes: H04S 5/005 of the pseudo five- or more-channel type, e.g. virtual surround

Abstract

An audio system for processing two channels of audio input to provide more than two output channels. The input may be conventional stereo material or compressed audio signal data. The audio processing includes separating the input signals into frequency bands and processing the frequency bands according to processes which may differ from band to band. The audio processing includes no processing of L−R signals.

Claims

1. A method for processing two input audio channel signals to provide n output audio channel signals where n>

2, comprising;

dividing the first input channel signal and the second input channel signal into a plurality of corresponding non-bass frequency bands;

measuring the amplitude of the audio signal in the two input channels in one of the frequency bands to provide a first channel first frequency band audio signal and a second channel first frequency band audio signal to provide a first channel first frequency band audio signal amplitude and a second channel first frequency band audio signal amplitude;

determining the correlation between the first channel first frequency band audio signal and the second channel first frequency band audio signal to provide a first frequency band correlation;

scaling the first channel first frequency band audio signal by a first factor (a(first)) related to the first frequency band correlation and further related to the first channel first frequency band audio signal amplitude and the second channel first frequency band audio signal amplitude, the scaling to provide a first scaled first output channel first frequency band audio signal first portion;

scaling the second channel first frequency band audio signal by a second factor (a(second)) related to the first frequency band correlation and further related to the first channel first frequency band audio signal amplitude and the second channel first frequency band audio signal amplitude, the scaling to provide a first scaled first output channel first frequency band audio signal second portion; and

combining the first scaled first channel first frequency band audio signal first portion and the first scaled first channel first frequency band audio signal second portion to provide a first frequency band portion of a center channel output audio signal.

2. A method for processing two input audio channel signals in accordance with claim 1, further comprising:

scaling the first channel first frequency band audio signal by a third factor (a(third)) to provide a first frequency band portion of a left channel output audio signal.

3. A method for processing two input audio channel signals in accordance with claim 2, wherein a(third)=√

{square root over (1−

a(first)²)}.

4. A method for processing two input audio channel signals in accordance with claim 2, further comprising:

combining the first frequency band portion of the left channel output audio signal with a second frequency band portion of the first channel audio signal to provide a left non-bass audio signal.

5. A method for processing two input audio channel signals in accordance with claim 1, where the frequency bands are time varying.

6. A method for processing two input audio channel signals in accordance with claim 1, where the first frequency bands is the speech band.

7. A method for processing two input audio channel signals in accordance with claim 1, wherein the two input audio channel signals comprise compressed audio signal data.

8. A method for processing two input audio channels signals in accordance with claim 7, wherein the compressed audio signals are in a non-reconstructable data format.

9. A method for processing two input audio channel signals in accordance with claim 1, wherein the input signals are compressed according to the MP3 format.