Method for compressing a higher order ambisonics (hoa) signal, method for decompressing a compressed hoa signal, apparatus for compressing a hoa signal, and apparatus for decompressing a compressed hoa signal

Patent metadata

Field	Value
Publication number	US-2017180902-A1
Application number	US-201515127577-A
Country	US
Kind code	A1
Filing date	Mar 20, 2015
Priority date	Mar 21, 2014
Publication date	Jun 22, 2017
Grant date	—

Abstract

A method for compressing a HOA signal being an input HOA representation with input time frames (C(k)) of HOA coefficient sequences comprises spatial HOA encoding of the input time frames and subsequent perceptual encoding and source encoding. Each input time frame is decomposed ( 802 ) into a frame of predominant sound signals (X PS (k−1)) and a frame of an ambient HOA component (C AMB (k−1)). The ambient HOA component (C AMB (k−1)) comprises, in a layered mode, first HOA coefficient sequences of the input HOA representation (c n (k−1)) in lower positions and second HOA coefficient sequences (C AMB,n (k−1)) in remaining higher positions. The second HOA coefficient sequences are part of an HOA representation of a residual between the input HOA representation and the HOA representation of the predominant sound signals.

First claim

1 - 21 . (canceled)

22 . A method of decoding a compressed Higher Order Ambisonics (HOA) representation of a sound or a soundfield, the method comprising:
receiving a bit stream containing the compressed HOA representation; determining whether there are multiple layers relating to the compressed HOA representation; decoding, based on a determination that there are multiple layers, the compressed HOA representation from the bitstream to obtain a sequence of decoded HOA representations, wherein a first subset of the sequence of decoded HOA representations corresponds to a first set of indices and a second subset of the sequence of decoded HOA representations corresponds to a second set of indices, wherein the first set of indices is based on O MIN channels, wherein, for each index in the first set of indices, a corresponding decoded HOA representation in the first subset is determined based on only a corresponding ambient HOA component, and wherein the second set of indices is determined based on at least one of the multiple layers.

23 . The method of claim 22 , wherein the first set of indices are determined based on 1≦n≦0 MIN and the second set of indices are determined based on 0 MIN +1≦n≦0, wherein 0 indicates a total number of channels and 0 MIN indicates a number between 1 and 0.

24 . The method of claim 22 , wherein, for an index n and a frame k, when n is in the first set of indices, the first subset is determined based on a corresponding ambient sound component ĉ AMB,n (k−1) and, when n is in the second set of indices, the second subset is determined based on an addition of a corresponding predominant sound component ĉ n,PS (k−1) and a corresponding ambient sound component ĉ n,AMB (k−1), and wherein the decoded HOA representations are represented at least in part by

c
^

~

n



(

k
-
1

)

=

{

c
^

AMB
,
n



(

k
-
1

)

c
^

n



(

k
-
1

)

=

c
^

PS
,
n



(

k
-
1

)

+

c
^

AMB
,
n



(

k
-
1

)

,

for n in the first set of indices
for n in the second set of indices

25 . The method of claim 22 , wherein 0 MIN =(N MIN +1) 2 with N MIN ≦N, wherein N is an order of input frames of the encoded HOA representation.

26 . The method of claim 22 , wherein an indication of multiple layers is signalled in the bitstream.

27 . The method of claim 22 , wherein the multiple layers include a base layer and at least an enhancement layer.

28 . The method of claim 22 , wherein, for a frame k, the sequence of decoded HOA representations is determined based on an ambient assignment vector (v AMB,ASSIGN (k)) and a first tuple set DIR (k+1), comprising an index of a directional representation and a respective quantized direction and a second tuple set VEC (k+1)) comprising an index of a vector based representation and a vector defining the directional distribution of the vector based representation.

29 . The method of claim 22 , further comprising generating, during channel reassignment, a third set of indices ( AMB,ACT (k)) of coefficient sequences that are active in frame k, and a second set of indices ( E (k−1), D (k−1), U (k−1)) of coefficient sequences of that have to be enabled, disabled and to remain active, respectively, in a frame (k−1).

30 . The method of claim 22 , further determining, based on a determination that there are not multiple layers, that there is a single layer, and, based on the determination of the single layer, determining, for a frame k, a single layer decoded HOA representation based on an addition of a corresponding predominant HOA sound component (Ĉ PS (k−1)) and a corresponding ambient HOA component ({tilde over (Ĉ)} AMB (k−1)).

31 . An apparatus for decoding a compressed Higher Order Ambisonics (HOA) representation of a sound or a soundfield, the apparatus comprising:
a receiver for receiving a bit stream containing the compressed HOA representation; an a

Assignees

• Dolby Int Ab

Inventors

• Kordon Sven
• Krueger Alexander
• Wuebbolt Oliver

Classifications

• H04S2420/11

  Application of ambisonics in stereophonic audio systems · 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

• H04S2400/01

  Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved · CPC title

• H04S3/008 Primary

  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

• G10L19/24

  Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding · CPC title