# US 12,010,501 B2 · Method and apparatus for decoding stereo loudspeaker signals from a higher-order Ambisonics audio signal

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- Number: US 12,010,501 B2
- Document ID: US12010501B2
- Status: Granted
- Kind: B2
- Application number: 17/521,762
- Filed: 2021-11-08
- Published: 2022-06-09
- Granted: 2024-06-11
- Earliest claimed: 2012-03-28
- Assignees: Dolby International AB
- Applicants: Dolby International AB
- Inventors: Johannes Boehm; Florian Keiler
- Web page: https://patentgrep.com/patent/US12010501B2

## CPC

- 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)}
- G10L 19/00: Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis (in musical instruments G10H)
- 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)}
- H04S 1/007: {in which the audio signals are in digital form (data reduction aspects thereof based on psychoacoustics G10L19/02)}
- H04S 3/02: of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other
- H04S 7/30: {Control circuits for electronic adaptation of the sound field}
- 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
- H04S 2400/11: Positioning of individual sound objects, e.g. moving airplane, within a sound field (H04S2420/13 takes precedence)
- H04S 2420/11: Application of ambisonics in stereophonic audio systems
- H04S: STEREOPHONIC SYSTEMS
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

Decoding of Ambisonics representations for a stereo loudspeaker setup is known for first-order Ambisonics audio signals. But such first-order Ambisonics approaches have either high negative side lobes or poor localisation in the frontal region. The invention deals with the processing for stereo decoders for higher-order Ambisonics HOA.

## Claims

### Claim 1

A method for decoding a Higher-Order Ambisonics (HOA) audio signal, the method comprising:
receiving the HOA audio signal;
determining a matrix G of panning function values, wherein the matrix G contains, for each of a number S of virtual sampling points on a sphere, gain vectors g1 . . . gs, wherein at least a first panning function value for a first virtual sampling point located opposite to a loudspeaker position approaches zero, and at least a second panning function value for a second source located close to the loudspeaker position has a value not approaching zero; and
determining a decoding matrix based on the matrix G; and
rendering, by at least one processor, the HOA audio signal to stereo loudspeaker signals based on the decoding matrix.

### Claim 2 (depends on 1)

The method of claim 1, wherein the matrix G has a size L×S, wherein L corresponds to a number of loudspeakers.

### Claim 3 (depends on 2)

The method of claim 2, wherein the gain vectors g1 . . . gs, are directed to achieve a panned mix in S directions of the L loudspeakers.

### Claim 4 (depends on 1)

A non-transitory computer-readable medium having stored thereon instructions, that when executed by one or more processors, cause one or more processors to perform the method of claim 1.

### Claim 5

An apparatus for decoding a Higher-Order Ambisonics (HOA) audio signal, the apparatus comprising:
a first receiver configured to receive the HOA audio signal;
a first processor for determining a matrix G of panning function values, wherein the matrix G contains, for each of a number S of virtual sampling points on a sphere, gain vectors g1 . . . gs, wherein at least a first panning function value for a first virtual sampling point located opposite to a loudspeaker position approaches zero, and at least a second panning function value for a second source located close to the loudspeaker position has a value not approaching zero;
a second processor for determining a decoding matrix based on the matrix G; and
a renderer for rendering the HOA audio signal to stereo loudspeaker signals based on the decoding matrix.