Configurable multi-band compressor architecture with advanced surround processing

• US 10,652,689 B2
• Filed: 01/04/2018
• Issued: 05/12/2020
• Est. Priority Date: 01/04/2017
• Status: Active Grant

• Current Assignee: THAT Corporation
• Original Assignee: THAT Corporation
• Inventors: Easley, Matthew, Oda, Mikio
• Primary Examiner(s): Goins, Davetta W
• Assistant Examiner(s): Ganmavo, Kuassi A
• Application Number:
  US15/862,045
• Publication Number:
  US 20180192229A1
• Time in Patent Office: 859 Days
• CPC Class Codes: H03G 11/00 Limiting amplitude; Limiting rate of change of amplitude ; Clipping in general
• CPC Class Codes: H03G 5/165 Equalizers; Volume or gain control in limited frequency bands
• CPC Class Codes: H03G 9/025 frequency-dependent volume compression or expansion, e.g. multiple-band systems H03G9/10, H03G9/18 take precedence
• CPC Class Codes: H04R 3/04 for correcting frequency response
• CPC Class Codes: H04R 3/14 Cross-over networks
• CPC Class Codes: H04S 1/002 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 1/007 in which the audio signals are in digital form data reduction aspects thereof based on psychoacoustics G10L19/02
• CPC Class Codes: H04S 2400/13 Aspects of volume control, not necessarily automatic, in stereophonic sound systems
• CPC Class Codes: H04S 2420/07 Synergistic effects of band splitting and sub-band processing
• CPC Class Codes: H04S 7/30 Control circuits for electronic adaptation of the sound field
• CPC Class Codes: H04S 7/307 Frequency adjustment, e.g. tone control H04S7/301 takes precedence

Abstract

Audio processing architectures are described for implementing a multi-band audio compression algorithm with advanced surround processing. Exemplary architectures can improve the fidelity and perceived sound field spread of inexpensive, cabinet mounted, stereo speakers such as those that might be found in televisions, wireless speaker systems and sound bars. Embodiments of the present disclosure can improve inexpensive, cabinet mounted, stereo speakers by providing, e.g., (i) an Advanced Surround algorithm that adds depth and height to the left/right/center sound field images, (ii) a Soft Clip algorithm to minimize the perceived artifacts caused by compressor overshoot, (iii) configurable crossover filter order adjustment to allow better isolation between bands, (iv) a compressor maximum gain adjustment to reduce overshoot and minimize noise boost, and/or (v) a center gain adjustment to emphasize the perception of the center image (dialog) in high ambient noise situations.

Claims

1. A system for enhancing a perception of a center image in stereo audio, while maintaining a defined limit of a difference to sum ratio ((L−

R)/(L+R)) based upon a threshold setting of a difference channel, the system comprising;

a dual processing protection (DPP) processor operative to receive left (L) and right (R) signals from left (L) and right (R) audio channels, respectively, as inputs and configured to limit the audio difference to sum ratio ((L−

R)(L+R)) by attenuating the audio difference signal, thereby producing an attenuated difference signal, and increasing the level of the sum signal, wherein the level of the sum signal represents center gain, wherein the DPP processor is operative to produce left and right output signals;

a first crossover network configured to receive the left and right output signals from the DPP processor as input signals and to separate each of the left and right input signals into a plurality of frequency bands, including a high band and a low band, wherein the crossover network produces left and right output signals for each band and wherein the crossover network is configurable by a user to set a crossover frequency and filter order of the first crossover network;

first and second compressors, wherein the first compressor is configured to receive the left and right high band output signals from the first crossover network and to produce compressed left and right high band output signals corresponding to the high band, and wherein the second compressor is configured to receive the left and right low band output signals from the first crossover network and to produce compressed left and right low band output signals corresponding to the low band, and wherein the first and second compressors are configured to limit a maximum loudness of the high and low bands;

a two channel surround processor configurable to receive the outputs from the first and second compressors and set the amount of perceived sound field spread in multiple dimensions by calculating the attenuated difference signal (L−

R) resulting from processing of the DPP processor and to generate left and right output signals;

a stereo equalizer configured to receive the left and right audio output signals from the two channel surround processor and shape the spectral characteristics such that the overall bandwidth of the audio material is not compromised when subjected to the playback on system speakers, wherein the stereo equalizer is configured to produce left and right output signals;

a soft clipper operative to receive as inputs compressed stereo left and right input signals, wherein the soft clipper is configured to limit the perceived distortion of left and right signals that briefly exceed a full scale output when subjected to the center gain, and dynamics of the first and second compressors, and to produce a stereo output.

2. The system of claim 1, wherein the system is configurable to produce desired sound listening modes.

3. The system of claim 2, further comprising a second crossover network configured to receive the left and right output signals from the stereo equalizer as left and right input signals, and to separate each of the left and right input signals into a plurality of frequency bands, including a high band and a low band, wherein the second crossover network produces left and right output signals for each band.

4. The system of claim 3, further comprising a third compressor configured to receive the left and right output of the second crossover network and to limit the amount of low frequency audio energy in a band defined by a system speaker low frequency response and configured to dynamically boost the audio level when the audio level is below the limit threshold, wherein the system is configured for bass-enhanced music listening.

5. The system of claim 1, wherein the filter order of the at least one crossover network is 4^th order.

6. The system of claim 1, further comprising a volume control configured to produce a volume control setting to adjust a level of a stereo input signal.

7. The system of claim 6, wherein the volume control is configured to receive a stereo input and to feed the volume control setting forward to at least one of the stereo compressors.

8. The system of claim 6, wherein the volume control is configured to receive a stereo input and to feed the volume control setting back to at least one of the stereo compressors.