Upmixing method and system for multichannel audio reproduction

Patent metadata

Field	Value
Publication number	US-9307338-B2
Application number	US-201313923608-A
Country	US
Kind code	B2
Filing date	Jun 21, 2013
Priority date	Sep 6, 2010
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

An audio signal enhancing device, and a corresponding method of enhancing stereophonic signals, is provided which generates an enhanced signal with improved spatial sound image quality for upmixing a stereophonic input signal. When used in combination with a centre channel processor or LFE processor, an improved processing of the input signals is provided resulting in final centre channel and at least one LFE sub-woofer channel wherein the problems and disadvantages of the prior art are resolved. The result is a centre and LFE signal that contains a stable, non time-smeared image with a high quality natural-sounding fidelity. These advantages are achieved especially for time-delayed or phase-panned stereo input signals, independently of whether they are matrix encoded or non-matrix encoded input signals.

First claim

The invention claimed is:

1. An audio signal enhancing device for upmixing a stereophonic input signal comprising two audio signals, the device comprising:
signal enhancement means for processing the two input signals to generate at least one enhanced signal, the signal enhancement means comprising:
two parallel processing lines comprising two parallel processing branches each;
the first processing branch comprising adaptive filter means; and
the second processing branch comprising means for delaying a signal;
means for combining the output signal of the first processing branch of the first processing line with the output signal of the second processing branch of the second processing line to generate a first enhanced signal;
means for combining the output signal of the first processing branch of the second processing line with the output signal of the second processing branch of the first processing line to generate a second enhanced signal;
means for combining the first and second enhanced signals to generate a third enhanced signal;
means for determining a dominant image direction of the third enhanced signal to determine a centre channel weighting coefficient that determines an output level of a centre channel to create a perception of sound location as in the direction of a single front side loudspeaker; and
control means for controlling the signal enhancement means.

2. The audio signal enhancing device of claim 1 , wherein the control means is adapted:
to analyse the input signals, the output of the first and second processing branches of the first and second processing lines, the at least one enhanced signal, the first, second and third enhanced signals; and
to dynamically vary the gain and delay coefficients of the signal enhancement means.

3. The audio signal enhancing device of claim 2
wherein each of the means for combining comprise respective weighted summing operations.

4. The audio signal enhancing device of claim 2 wherein the adaptive filter means comprises adaptive filter coefficient setting means and wherein the adaptive filter coefficients are set by the control means.

5. The audio signal enhancing device of claim 2 wherein the second processing branch further comprises multiplying means for applying at least one gain coefficient to the third and fourth signals and wherein the at least one gain coefficient and the amount of delay for the means for delaying the signal is set by the control means.

6. The audio signal enhancing device of claim 2 further comprising: multiplying means for applying at least one gain coefficient to the first and second enhanced signals and wherein the at least one gain coefficient is set by the control means; and
first and second adaptive filters wherein the dominant image direction is calculated as an average of the filter coefficients of both the first and second adaptive filters.

7. The audio signal enhancing device of claim 2 further comprising centre channel signal generating means for generating a centre channel signal from the third enhanced signal, the centre channel signal generating means comprising centre channel weighting means and multiplying means for applying the centre channel weighting coefficient to the third enhanced signal and wherein the centre channel signal generating means is controlled by the control means.

8. The audio signal enhancing device of claim 2 further comprising low frequency effects subwoofer signal generating means for generating at least one low frequency effects subwoofer signal from the at least one enhanced signal, the low frequency effects subwoofer signal generating means comprising low pass filter means and wherein the low frequency effects subwoofer signal generating means is controlled by the control means.

9. The audio signal enhancing device of claim 2 wherein the dominant direction is calculated as a level ratio of two filters, and wherein a centre channel weighting coefficient corresponding to the level ratio may range from zero indicating a perceived sound location from one of a sin le front left or front right loudspeaker, to a value greater than zero indicating at least a portion of the perceived sound location from a center loudspeaker in addition to the sin be front side loudspeaker.

10. A method for enhancing a stereophonic input signal comprising two audio signals for upmixing, the method comprising:
processing the two input signals to generate at least one enhanced signal in two parallel processing lines comprising two parallel processing branches each;
the first processing branch comprising adaptive filtering the signals; and
the second processing branch comprising delaying the signals;
the processing the two input signals comprising:
combining the output signal of the first processing branch of the first processing line with the output signal of the second processing branch of the second processing line to generate a first enhanced signal;
combining the output signal of the first processing branch of the second processing line with the output signal of the second processing branch of the first processing line to generate a second enhanced signal;
combining the first and second enhanced signals to generate a third enhanced signal;
determining a dominant image direction of the third enhanced signal to determine a centre channel weighting coefficient that determines an output level of a centre channel to create a perception of sound location as in the direction of a single front side loudspeaker ;and
controlling the processing to generate at least one enhanced signal.

11. The method of claim 10 , wherein controlling the processing comprises analyzing the input signals, the output of the first and second processing branches of the first and second processing lines, the at least one enhanced signal, the first, second and third enhanced signals; and
dynamically varying the gain and delay coefficients of the signal enhancement means, and wherein each of the combining steps comprise respective weighted summing operations.

12. The method of claim 11 further comprising adding a portion of the first input signal to the second input signal to generate a third signal for feeding into the first processing line and adding a portion of the second input signal to the first input signal to generate a fourth signal for feeding into the second processing line.

13. The method of claim 11 further comprising generating a centre channel signal from the third enhanced signal by determining a centre channel weighting coefficient and multiplying the third enhanced signal by the centre channel weighting coefficient to generate a centre channel signal for output through a centre channel speaker, and wherein the dominant direction is calculated as a level ratio of two filters, and wherein a centre channel weighting coefficient corresponding to the level ratio may range from zero indicating a perceived sound location from one of a single front left or front right loudspeaker, to a value greater than zero indicating at least a portion of the perceived sound location from a center loudspeaker in addition to the single front side loudspeaker.

14. The method of claim 11 further comprising generating at least one low frequency effects subwoofer signal from the at least one enhanced signal comprising low pass filtering the input signals and the at least one enhanced signal, and further comprising first and second adaptive filters, wherein the dominant image direction is calculated as an average of the filter coefficients of both the first and second adaptive filters.

15. A centre channel generation device for generatin

Assignees

• Dolby Int Ab

Inventors

• Usher John
• Sole Antonio

Classifications

• H04S2400/07

  Generation or adaptation of the Low Frequency Effect [LFE] channel, e.g. distribution or signal processing · CPC title

• H04S5/005

  of the pseudo five- or more-channel type, e.g. virtual surround · CPC title

• H04S2400/05

  Generation or adaptation of centre channel in multi-channel audio systems · CPC title

• H04S1/002 Primary

  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 title

• H04S5/00 Primary

  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 title