MULTI-CHANNEL AUDIO ENHANCEMENT SYSTEM FOR USE IN RECORDING PLAYBACK AND METHODS FOR PROVIDING SAME

• US 20090190766A1
• Filed: 01/30/2009
• Published: 07/30/2009
• Est. Priority Date: 11/07/1996
• Status: Active Grant

• Current Assignee: DTS, Inc. (Adeia Inc.)
• Original Assignee: SRS Labs Incorporated (Adeia Inc.)
• Inventors: Kraemer, Alan D., Klayman, Arnold I.
• Granted Patent: US 8,472,631 B2
• Time in Patent Office: Days
• US Class Current: 381/18
• CPC Class Codes: 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
• CPC Class Codes: H04S 2420/01 Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]
• CPC Class Codes: H04S 3/002 Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution control circuits for electronic adaptation of the sound field H04S7/30
• CPC Class Codes: H04S 3/008 in which the audio signals are in digital form, i.e. employing more than two discrete digital channels data reduction aspects thereof based on psychoacoustics G10L19/02

Abstract

An audio enhancement system and method for use receives a group of multi-channel audio signals and provides a simulated surround sound environment through playback of only two output signals. The multi-channel audio signals comprise a pair of front signals intended for playback from a forward sound stage and a pair of rear signals intended for playback from a rear sound stage. The front and rear signals are modified in pairs by separating an ambient component of each pair of signals from a direct component and processing at least some of the components with a head-related transfer function. Processing of the individual audio signal components is determined by an intended playback position of the corresponding original audio signals. The individual audio signal components are then selectively combined with the original audio signals to form two enhanced output signals for generating a surround sound experience upon playback.

Claims

1. A method of processing a plurality of audio input signals to create two audio output signals, the method comprising:

receiving a left front input signal and a right front input signal, each of the left and right front input signals comprising first audio information;

processing, with one or more processors, at least a portion of one or both of the left and right front input signals with a first filter to produce one or more processed front signals;

receiving a left rear input signal and a right rear input signal, each of the left and right rear input signals comprising second audio information;

using the one or more processors to process at least a portion of the left and right rear input signals with a second filter to produce processed left and right rear signals, the second filter having a different frequency response than the first filter;

providing a left output signal comprising a combination of at least a portion of the one or more processed front signals and at least a portion of the processed left rear signal; and

providing a right output signal comprising a combination of at least a portion of the one or more processed front signals and at least a portion of the processed right rear signal.

2. The method of claim 1, wherein:

the first filter has a first frequency response comprising a first peak, a first trough at a higher frequency than the first peak, and a second peak at a higher frequency than the first trough; and

the frequency response of the second filter comprises a third peak, a second trough at a higher frequency than the third peak, and a fourth peak at a higher frequency than the second trough.

3. The method of claim 2, wherein the second peak is greater in magnitude than the fourth peak.

4. The method of claim 2, wherein a gain difference between the third and fourth peaks is greater than a gain difference between the first and second peaks.

5. The method of claim 4, wherein a gain difference between the third and fourth peaks is about 9 dB.

6. The method of claim 2, wherein the first peak occurs at a frequency of about 125 Hz, the first trough occurs at a frequency of about 1.5 kHz to 2.5 kHz and the second peak occurs at a frequency of about 15 kHz to 20 kHz.

7. The method of claim 2, wherein the third peak occurs at a frequency of about 125 Hz, the second trough occurs at a frequency of about 1.5 kHz to 2.5 kHz, and the fourth peak occurs at a frequency of about 10.5 kHz to 11.5 kHz.

8. The method of claim 1, wherein using the one or more processors to process at least a portion of the left and right rear input signals comprises separately processing monophonic and ambient portions of the left and right rear input signals.

9. The method of claim 1, wherein using the one or more processors to process at least a portion of the left and right rear input signals comprises phase shifting at least a portion of the left and right rear input signals.

10. A system for combining a plurality of audio input signals to create two audio output signals, the system comprising:

at least one processor operative to;

receive a plurality of audio signals comprising first and second front audio signals and one or more surround audio signals;

process at least a portion of one or both of the first and second front audio signals with a first audio filter to produce one or more processed front audio signals;

process at least a portion of the at least one surround audio signal with a second audio filter to produce at least one processed surround audio signal, the second audio filter having a different frequency response from the first audio filter;

provide a left output signal comprising at least a portion of the one or more processed front audio signals and at least a first portion of the at least one processed surround audio signal; and

provide a right output signal comprising at least a portion of the one or more processed front audio signals and at least a second portion of the at least one processed surround audio signal.

11. The system of claim 10, wherein:

the first audio filter has a first frequency response comprising a first peak, a first trough at a higher frequency than the first peak, and a second peak at a higher frequency than the first trough; and

the frequency response of the second audio filter comprises a third peak, a second trough at a higher frequency than the third peak, and a fourth peak at a higher frequency than the second trough.

12. The system of claim 11, wherein the second peak is greater in magnitude than the fourth peak.

13. The system of claim 11, wherein a gain difference between the third and fourth peaks is greater than a gain difference between the first and second peaks.

14. The system of claim 13, wherein a gain difference between the third and fourth peaks is about 9 dB.

15. The system of claim 11, wherein the first peak occurs at a frequency of about 125 Hz, the first trough occurs at a frequency of about 1.5 kHz to 2.5 kHz, and the second peak occurs at a frequency of about 15 kHz to 20 kHz.

16. The system of claim 11, wherein the third peak occurs at a frequency of about 125 Hz, the second trough occurs at a frequency of about 1.5 kHz to 2.5 kHz, and the fourth peak occurs at a frequency of about 10.5 kHz to 11.5 kHz.

17. The system of claim 10, wherein the at least one surround audio signal comprises left and right surround audio signals.

18. The system of claim 17, wherein the at least one processor is further operative to process at least a portion of the at least one surround audio signal by at least separately processing monophonic and ambient portions of the left and right surround audio signals.

19. The system of claim 17, wherein the at least one processor is further operative to process at least a portion of the at least one surround audio signal by at least phase shifting at least a portion of the left and right rear input signals.