Methods and apparatus for decoding a compressed HOA signal
Methods and apparatus for decoding a compressed Higher Order Ambisonics (HOA) representation of a sound or soundfield. The method may include receiving a bit stream containing the compressed HOA representation and 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. A first subset of the sequence of decoded HOA representations is determined based only on corresponding ambient HOA components. A second subset of the sequence of decoded HOA representations is determined based on corresponding ambient HOA components and corresponding predominant sound components. For a frame k, the sequence of decoded HOA representations are represented at least in part by c ^ ~ n ( k - 1 ) = { c ^ A M B , n ( k - 1 ) for n in the first subset c ^ n ( k - 1 ) = c ^ P S , n ( k - 1 ) + c ^ A M B , n ( k - 1 ) , for n in the second subset where ĉ AMB,n (k−1) corresponds to the corresponding ambient HOA components and ĉ PS,n (k−1) corresponds to the corresponding predominant sound components.
1. A method of decoding a compressed Higher Order Ambisonics (HOA) representation of a sound or soundfield, the method comprising:
receiving a bit stream containing the compressed HOA representation;
generating, during channel reassignment, indices AMB,ACT (k)) of coefficient sequences that are active in a frame k; and
decoding, based on a determination that there are multiple layers, the compressed HOA representation from a bitstream to obtain a sequence of decoded HOA representations,
wherein the decoding is based on the indices of coefficient sequences,
wherein a first subset of the sequence of decoded HOA representations is determined based only on corresponding ambient HOA components,
wherein a second subset of the sequence of decoded HOA representations is determined based on corresponding ambient HOA components and corresponding predominant sound components,
wherein, for a frame k, the sequence of decoded HOA representations are represented at least in part by
c
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~
n
(
k
-
1
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=
{
c
ˆ
A
M
B
,
n
(
k
-
1
)
for
n
in
the
first
subset
c
ˆ
n
(
k
-
1
)
=
c
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S
,
n
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+
c
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A
M
B
,
n
(
k
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,
for
n
in
the
second
subset
wherein ĉ AMB,n (k−1) corresponds to the corresponding ambient HOA components and ĉ PS,n (k−1) corresponds to the corresponding predominant sound components,
wherein an indication of the multiple layers is signalled in the bitstream, and wherein the multiple layers include a base layer and at least an enhancement layer that are independently decodable of one another, and
wherein the first subset is determined based on 1≤n≤O MIN and the second subset is determined based on O MIN +1≤m≤0, wherein O indicates a total number of channels and O MIN indicates a number between 1 and O.
2. The method of claim 1 , 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 ( AMB (k−1)).
3. 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;
a processor for generating, during channel reassignment, indices AMB,ACT (k)) of coefficient sequences that are active in a frame k; and
an audio decoder for decoding, based on a determination that there are multiple layers, the compressed HOA representation from a bitstream to obtain a sequence of decoded HOA representations,
wherein the decoding is based on the indices of coefficient sequences,
wherein a first subset of the sequence of decoded HOA representations is determined based only on corresponding ambient HOA components,
wherein a second subset of the sequence of decoded HOA representations is determined based on corresponding ambient HOA components and corresponding predominant sound components,
wherein, for a frame k, the sequence of decoded HOA representations are represented at least in part by
c
ˆ
~
n
(
k
-
1
)
=
{
c
ˆ
A
M
B
,
n
(
k
-
1
)
for
n
in
the
first
subset
c
ˆ
n
(
k
-
1
)
=
c
ˆ
P
S
,
n
(
k
-
1
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+
c
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A
M
B
,
n
(
k
-
1
)
,
for
n
in
the
second
subset
wherein ĉ AMB,n (k−1) corresponds to the corresponding ambient HOA components and ĉ PS,n (k−1) corresponds to the corresponding predominant sound components, wherein an indication of the multiple layers is signalled in the bitstream, and wherein the multiple layers include a base layer and at least an enhancement layer that are independently decodable of one another, and
wherein the first subset is determined based on 1≤n≤O MIN and the second subset is determined based on O MIN +1≤m≤O, wherein O indicates a total number of channels and O MIN indicates a number between 1 and O.
4. The apparatus of claim 3 , wherein the audio decoder is further configured to determine, 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 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 ( AMB (k−1)).
5. A non-transitory computer readable storage medium containing instructions that when executed by a processor perform the method of claim 1 .