Reducing correlation between higher order ambisonic (hoa) background channels

Patent metadata

Field	Value
Publication number	US-2016007132-A1
Application number	US-201514789961-A
Country	US
Kind code	A1
Filing date	Jul 1, 2015
Priority date	Jul 2, 2014
Publication date	Jan 7, 2016
Grant date	—

Abstract

In general, techniques are described for compression and decoding of audio data are generally disclosed. An example device for compressing audio data includes one or more processors configured to apply a decorrelation transform to ambient ambisonic coefficients to obtain a decorrelated representation of the ambient ambisonic coefficients, the ambient HOA coefficients having been extracted from a plurality of higher order ambisonic coefficients and representative of a background component of a soundfield described by the plurality of higher order ambisonic coefficients, wherein at least one of the plurality of higher order ambisonic coefficients is associated with a spherical basis function having an order greater than one.

First claim

What is claimed is:

1 . A method comprising:
obtaining a decorrelated representation of ambient ambisonic coefficients having at least a left signal and a right signal, the ambient ambisonic coefficients having been extracted from a plurality of higher order ambisonic coefficients and representative of a background component of a soundfield described by the plurality of higher order ambisonic coefficients, wherein at least one of the plurality of higher order ambisonic coefficients is associated with a spherical basis function having an order greater than one; and generating a speaker feed based on the decorrelated representation of the ambient ambisonic coefficients.

2 . The method of claim 1 , further comprising applying a recorrelation transform to the decorrelated representation of the ambient ambisonic coefficients to obtain a plurality of correlated ambient ambisonic coefficients.

3 . The method of claim 2 , wherein applying the recorrelation transform comprises applying an inverse phase-based transform to the ambient ambisonic coefficients.

4 . The method of claim 3 , wherein the inverse phase-based transform has been normalized according to one of N3D (full three-D) normalization.

5 . The method of claim 3 , wherein the inverse phase-based transform has been normalized according to SN3D normalization (Schmidt semi-normalization).

6 . The method of claim 3 , wherein the ambient ambisonic coefficients are associated with spherical basis functions having an order of zero or an order of one, and wherein applying the inverse phase-based transform comprises performing a scalar multiplication of the phase-based transform with respect to the decorrelated representation of the ambient ambisonic coefficients.

7 . The method of claim 1 , further comprising obtaining an indication that the decorrelated representation of ambient ambisonic coefficients was decorrelated with a decorrelation transform.

8 . The method of claim 1 , further comprising obtaining one or more spatial components defining spatial characteristics of foreground components of the sound field, the spatial components defined in a spherical harmonic domain and generated by performing a decomposition with respect to the plurality of higher order ambisonic coefficient,
wherein generating the speaker feed comprises combining the correlated ambient ambisonic coefficients with one or more foreground channels obtained based on the one or more spatial components.

9 . A method comprising:
applying a decorrelation transform to ambient ambisonic coefficients to obtain a decorrelated representation of the ambient ambisonic coefficients, the ambient HOA coefficients having been extracted from a plurality of higher order ambisonic coefficients and representative of a background component of a soundfield described by the plurality of higher order ambisonic coefficients, wherein at least one of the plurality of higher order ambisonic coefficients is associated with a spherical basis function having an order greater than one.

10 . The method of claim 9 , wherein applying the decorrelation transform comprises applying a phase-based transform to the ambient ambisonic coefficients.

11 . The method of claim 10 , further comprising normalizing the phase-based transform according to N3D (full three-D) normalization.

12 . The method of claim 10 , further comprising normalizing the phase-based transform according to SN3D normalization (Schmidt semi-normalization).

13 . The method of claim 10 , wherein the ambient ambisonic coefficients are associated with spherical basis functions having an order of zero or an order of one, and wherein applying the phase-based transform to the ambient ambisonic coefficients comprises performing a scalar multiplication of the phase-based transform with respect to at least a subset of the ambient ambisonic coefficients.

14 . The method of claim 10 , further comprising signaling an indication of the decorrelation transform having been applied to the ambient ambisonic coefficients.

15 . A device for processing audio data, the device comprising:
a memory configured to store at least a portion of the audio data to be processed; and one or more processors configured to:
obtain a decorrelated representation of ambient ambisonic coefficients having at least a left signal and a right signal, the ambient ambisonic coefficients having been extracted from a plurality of higher order ambisonic coefficients and representative of a background component of a soundfield described by the plurality of higher order ambisonic coefficients, wherein at least one of the plurality of higher order ambisonic coefficients is associated with a spherical basis function having an order greater than one; and
generate a speaker feed based on the decorrelated representation of the ambient ambisonic coefficients.

16 . The device of claim 15 , wherein, to generate the speaker feed, the one or more processors are configured to generate, for output by a stereo reproduction system, a left speaker feed based on the left signal and a right speaker feed based on the right signal.

17 . The device of claim 15 , wherein, to generate the speaker feed, the one or more processors are configured to use the left signal as a left speaker feed and the right signal as a right speaker feed without applying a recorrelation transform to the right and left signals.

18 . The device of claim 15 , wherein, to generate the speaker feed, the one or more processors are configured to mix the left signal and the right signal for output by a mono audio system.

19 . The device of claim 15 , wherein, to generate the speaker feed, the one or more processors are configured to combine the correlated ambient ambisonic coefficients with one or more foreground channels.

20 . The device of claim 15 , wherein the one or more processors are further configured to determine that no foreground channels are available with which to combine the correlated ambient ambisonic coefficients.

21 . The device of claim 15 , wherein the one or more processors are further configured to:
determine that the soundfield is to be output via a mono-audio reproduction system; and decode at least a subset of the decorrelated ambient ambisonic coefficients that include data for output by the mono-audio reproduction system.

22 . The device of claim 15 , wherein the one or more processors are further configured to obtain an indication that the decorrelated representation of ambient ambisonic coefficients was decorrelated with a decorrelation transform.

23 . The device of claim 15 , further comprising a loudspeaker configured to output the speaker feed generated based on the decorrelated representation of the ambient ambisonic coefficients.

24 . A device for compressing audio data, the device comprising:
a memory configured to store at least a portion of the audio data to be compressed; and one or more processors configured to:
apply a decorrelation transform to ambient ambisonic coefficients to obtain a decorrelated representation of the ambient ambisonic coefficients, the ambient HOA coefficients having been extracted from a plurality of higher order ambisonic coefficients and representative of a background component of a soundfield described by the plurality of higher order ambisonic coefficients, wherein at least one of the plurality of higher order ambisonic coefficients is associated with a spherical basis functio

Assignees

• Qualcomm Inc

Inventors

• Peters Nils Günther
• Sen Dipanjan
• Morrell Martin James

Classifications

• H04S2420/11

  Application of ambisonics in stereophonic audio systems · CPC title

• H04R5/04

  Circuit arrangements, {e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments (combinations of amplifiers H03F3/68; stereophonic systems H04S)} · CPC title

• H04S3/008

  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) · CPC title

• G10L19/008 Primary

  Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing · 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