# US 9,883,310 B2 · Obtaining symmetry information for higher order ambisonic audio renderers

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- Number: US 9,883,310 B2
- Document ID: US9883310B2
- Status: Granted
- Kind: B2
- Application number: 14/724,615
- Filed: 2015-05-28
- Published: 2015-11-26
- Granted: 2018-01-30
- Earliest claimed: 2013-02-08
- Assignees: QUALCOMM Incorporated
- Applicants: QUALCOMM Incorporated
- Inventors: Nils Günther Peters; Dipanjan Sen; Martin James Morrell
- Web page: https://patentgrep.com/patent/US9883310B2

## CPC

- 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}
- G10L 19/008: Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
- H04S 7/301: {Automatic calibration of stereophonic sound system, e.g. with test microphone}
- H04S 2420/03: Application of parametric coding in stereophonic audio systems
- 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

In general, techniques are described for obtaining audio rendering information in a bitstream. A device configured to render higher order ambisonic coefficients comprising a processor and a memory may perform the techniques. The processor may be configured to obtain sign symmetry information indicative of sign symmetry of a matrix used to render the higher order ambisonic coefficients to generate a plurality of speaker feeds. The memory may be configured to store the sparseness information.

## Claims

### Claim 1

A device configured to reconstruct a matrix to render a plurality of speaker feeds, the device comprising:
one or more processors configured to:
obtain, from a bitstream that includes an encoded version of higher order ambisonic coefficients, sparseness information that indicates a sparseness of the matrix used to render the plurality of speaker feeds;
obtain, from the bitstream, sign symmetry information indicative of sign symmetry of the matrix;
obtain, from the bitstream, an indication of a number of bits used to represent the matrix;
reconstruct, based on the sparseness information, the sign symmetry information, and the indication of the number of bits, the matrix;
output the plurality of speaker feeds based on the reconstructed matrix; and
a memory coupled to the one or more processors, and configured to store the sign symmetry information.

### Claim 2 (depends on 1)

The device of claim 1, wherein the one or more processors are further configured to determine a speaker layout for which the matrix is to be used to render the plurality of speaker feeds from the encoded version of the higher order ambisonic coefficients.

### Claim 3 (depends on 1)

The device of claim 1, further comprising a speaker configured to reproduce a soundfield represented by the encoded version of the higher order ambisonic coefficients based on the plurality of speaker feeds.

### Claim 4 (depends on 1)

The device of claim 1, wherein the one or more processors are further configured to obtain audio rendering information indicative of a signal value identifying an audio renderer used when generating the plurality of speaker feeds, and render the plurality of speaker feeds based on the audio rendering information.

### Claim 5 (depends on 4)

The device of claim 4,
wherein the signal value includes the matrix used to render the plurality of speaker feeds, and
wherein the one or more processors are configured to render the plurality of speaker feeds based on the matrix included in the signal value.

### Claim 6

A method of reconstruct a matrix to render a plurality of speaker feeds, the method comprising:
obtaining, from a bitstream that includes an encoded version of higher order ambisonic coefficients, sparseness information that indicates a sparseness of the matrix used to render the plurality of speaker feeds;
obtaining, from the bitstream, sign symmetry information indicative of sign symmetry of the matrix; obtaining, from the bitstream, an indication of a number of bits used to represent the matrix;
reconstructing, based on the sparseness information, the sign symmetry information, and the indication of the number of bits, the matrix; and
outputting the plurality of speaker feeds based on the reconstructed matrix.

### Claim 7 (depends on 6)

The method of claim 6, further comprising determining a speaker layout for which the matrix is to be used to render the multi-channel audio data from the encoded version of the higher order ambisonic coefficients.

### Claim 8 (depends on 6)

The method of claim 6, further comprising reproducing a soundfield represented by the encoded version of the higher order ambisonic coefficients based on the plurality of speaker feeds.

### Claim 9 (depends on 6)

The method of claim 6, further comprising:
obtaining audio rendering information indicative of a signal value identifying an audio renderer used when generating the plurality of speaker feeds; and
rendering the plurality of speaker feeds based on the audio rendering information.

### Claim 10 (depends on 9)

The method of claim 9,
wherein the signal value includes the matrix used to render the plurality of speaker feeds, and
wherein method further comprises rendering the plurality of speaker feeds based on the matrix included in the signal value.

### Claim 11

A device configured to produce a bitstream, the device comprising:
a memory configured to store a matrix used to render a plurality of speaker feeds; and
one or more processors coupled to the memory, and configured to:
obtain sign symmetry information indicative of sign symmetry of the matrix;
obtain sparseness information that indicates a sparseness of the matrix;
based on the sign symmetry information and the sparseness information, determine an indication of a number of bits used to represent the matrix in the bitstream; and
generate the bitstream to include an encoded version of higher order ambisonic coefficients, the sign symmetry information, the sparseness information, and the indication of the number of bits.

### Claim 12 (depends on 11)

The device of claim 11, wherein the one or more processors are further configured to determine a speaker layout for which the matrix is to be used to render the plurality of speaker feeds from the encoded version of the higher order ambisonic coefficients.

### Claim 13 (depends on 11)

The device of claim 11, further comprising a microphone configured to capture a soundfield represented by the encoded version of the higher order ambisonic coefficients.

### Claim 14

A method of producing a bitstream, the method comprising:
obtaining, by one or more processors, sparseness information indicative of a sparseness of a matrix used to render a plurality of speaker feeds;
obtaining, by the one or more processors, sign symmetry information indicative of sign symmetry of the matrix;
determining, by the one or more processors and based on the sign symmetry information and the sparseness information, an indication of a number of bits used to represent the matrix in the bitstream; and
generating, by the one or more processors, the bitstream to include an encoded version of higher order ambisonic coefficients, the sign symmetry information, the sparseness information, and the indication of the number of bits.

### Claim 15 (depends on 14)

The method of claim 14, further comprising determining a speaker layout for which the matrix is to be used to render the multi-channel audio data from the encoded version of the higher order ambisonic coefficients.

### Claim 16 (depends on 14)

The method of claim 14, further comprising capturing a soundfield represented by the encoded version of the higher order ambisonic coefficients.

### Claim 17 (depends on 1)

The device of claim 1,
wherein the one or more processors are further configured to render, from the higher order ambisonic coefficients and based on the matrix, the plurality of speaker feeds, and
wherein the device further comprises one or more loudspeakers coupled to the one or more processors, and configured to reproduce a soundfield based on the plurality of speaker feeds.

### Claim 18 (depends on 11)

The device of claim 11, further comprising a microphone coupled to the one or more processors, and configured to capture audio data indicative of the higher order ambisonic coefficients.