US2016155450A1PendingUtilityA1
Audio Encoding/Decoding based on an Efficient Representation of Auto-Regressive Coefficients
Est. expiryNov 2, 2031(~5.3 yrs left)· nominal 20-yr term from priority
G10L 19/032G10L 19/038G10L 19/0204G10L 21/038G10L 19/06G10L 2019/001
52
PatentIndex Score
0
Cited by
0
References
0
Claims
Abstract
An encoder for encoding a parametric spectral representation (f) of auto-regressive coefficients that partially represent an audio signal. The encoder includes a low-frequency encoder configured to quantize elements of a part of the parametric spectral representation that correspond to a low-frequency part of the audio signal. It also includes a high-frequency encoder configured to encode a high-frequency part (f H ) of the parametric spectral representation (f) by weighted averaging based on the quantized elements ({circumflex over (f)} L ) flipped around a quantized mirroring frequency ({circumflex over (f)} m ), which separates the low-frequency part from the high-frequency part, and a frequency grid determined from a frequency grid codebook in a closed-loop search procedure. Described are also a corresponding decoder, corresponding encoding/decoding methods and UEs including such an encoder/decoder.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1 . A method of encoding a parametric spectral representation (f) of auto-regressive coefficients (a) that partially represent an audio signal, the method comprising:
encoding a low-frequency part (f L ) of the parametric spectral representation (f) by quantizing coefficients of the parametric spectral representation that correspond to a low-frequency part of the audio signal; and encoding a high-frequency part (f H ) of the parametric spectral representation (f) by weighted averaging based on the quantized coefficients ({circumflex over (f)} L ) flipped around a quantized mirroring frequency ({circumflex over (f)} m ), which separates the low-frequency part from the high-frequency part, and a frequency grid (g opt ) determined from a frequency grid codebook in a closed-loop search procedure.
2 . The method of claim 1 , further comprising the step of quantizing the mirroring frequency {circumflex over (f)} m in accordance with:
{circumflex over (f)} m =Q ( f ( M/ 2)−{circumflex over ( f )}( M/ 2−1))+{circumflex over ( f )}( M/ 2−1),
where
Q denotes quantization of the expression in the adjacent parenthesis,
M denotes the total number of coefficients in the parametric spectral representation,
f(M/2) denotes the first coefficient in the high-frequency part, and
{circumflex over (f)}(M/2−1) denotes the last quantized coefficient in the low-frequency part.
3 . The method of claim 2 , further comprising the step of flipping the quantized coefficients of the low frequency part (f L ) of the parametric spectral representation (f) around the quantized mirroring frequency {circumflex over (f)} m in accordance with:
f flip ( k )=2 {circumflex over (f)} m −{circumflex over (f)} ( M/ 2−1− k ), 0≦ k≦M/ 2−1.
where {circumflex over (f)}(M/2−1−k) denotes quantized coefficient M/2−1−k.
4 . The method of claim 3 , further comprising the step of rescaling the flipped coefficients f flip (k) in accordance with:
f
~
flip
(
k
)
=
{
(
f
flip
(
k
)
-
f
flip
(
0
)
)
·
(
f
max
-
f
^
m
)
/
f
^
m
+
f
flip
(
0
)
,
f
^
m
>
0.25
f
flip
(
k
)
,
otherwise
.
5 . The method of claim 4 , further comprising the step of rescaling the frequency grids g i from the frequency grid codebook to fit into the interval between the last quantized coefficient {circumflex over (f)}(M/2−1) in the low-frequency part and a maximum grid point value g max in accordance with:
{tilde over (g)} i ( k )= g i ( k )·( g max −{circumflex over (f)} ( M/ 2−1))+{circumflex over ( f )}( M/ 2−1).
6 . The method of claim 5 , including the step of weighted averaging of the flipped and rescaled coefficients {tilde over (f)} flip (k) and the rescaled frequency grids {tilde over (g)} i (k) in accordance with:
f smooth i ( k )=[1−λ( k )] {tilde over (f)} flip ( k )+λ( k ) {tilde over (g)} i ( k )
where λ(k) and [1−λ(k)] are predefined weights.
7 . The method of claim 6 , further comprising the step of selecting a frequency grid g opt , where the index opt satisfies the criterion:
opt
=
arg
min
i
(
∑
k
=
0
M
/
2
-
1
(
f
smooth
i
(
k
)
-
f
H
(
k
)
)
2
)
where f H (k) is a target vector formed by the coefficients of the high-frequency part of the parametric spectral representation.
8 . The method of claim 7 , wherein M=10, g max =0.5, and the weights λ(k) are defined as
λ={0.2, 0.35, 0.5, 0.75, 0.8}.
9 . The method of claim 1 , wherein the encoding of the parametric spectral representation (f) of auto-regressive coefficients is performed on a line spectral frequencies representation of the auto-regressive coefficients.
10 . A method of decoding an encoded parametric spectral representation ({circumflex over (f)}) of auto-regressive coefficients (a) that partially represent an audio signal, said method including the steps of:
decoding coefficients ({circumflex over (f)} L ) of a low-frequency part (f L ) of the parametric spectral representation (f) corresponding to a low-frequency part of the audio signal from at least one quantization index (I f L ) encoding that part of the parametric spectral representation; decoding coefficients ({circumflex over (f)} H ) of a high-frequency part (f H ) of the parametric spectral representation by weighted averaging based on the decoded coefficients ({circumflex over (f)} L ) flipped around a decoded mirroring frequency ({circumflex over (f)} m ), which separates the low-frequency part from the high-frequency part, and a decoded frequency grid (g opt ).
11 . The method of claim 10 , further comprising the step of flipping the decoded coefficients ({circumflex over (f)} L ) of the low-frequency part around the mirroring frequency {circumflex over (f)} m in accordance with:
f flip ( k )=2 {circumflex over (f)} m −{circumflex over (f)} ( M/ 2−1− k ), 0≦ k≦M/ 2−1
where
M denotes the total number of coefficients in the parametric spectral representation, and
{circumflex over (f)}(M/2−1−k) denotes decoded coefficient M/2−1−k.
12 . The method of claim 11 , further comprising the step of rescaling the flipped coefficients f flip (k) in accordance with:
f
~
flip
(
k
)
=
{
(
f
flip
(
k
)
-
f
flip
(
0
)
)
·
(
f
max
-
f
^
m
)
/
f
^
m
+
f
flip
(
0
)
,
f
^
m
>
0.25
f
flip
(
k
)
,
otherwise
.
13 . The method of claim 12 , further comprising the step of rescaling the decoded frequency grid g opt to fit into the interval between the last quantized coefficient {circumflex over (f)}(M/2−1) in the low-frequency part and a maximum grid point value g max in accordance with:
{tilde over (g)} opt ( k )= g opt ( k )·( g max −{circumflex over (f)} ( M/ 2−1))+{circumflex over ( f )}( M/ 2−1).
14 . The method of claim 13 , further comprising the step of weighted averaging of the flipped and rescaled coefficients {tilde over (f)} flip (k) and the rescaled frequency grid {tilde over (g)} opt (k) in accordance with:
f smooth ( k )=[1−λ( k )] {tilde over (f)} flip ( k )+λ( k ) {tilde over (g)} opt ( k ).
where λ(k) and [1−λ(k)] are predefined weights.
15 . The method of claim 14 , wherein M=10, g max =0.5, and the weights λ(k) are defined as
λ={0.2, 0.35, 0.5, 0.75, 0.8}.
16 . The method of claim 10 , wherein the decoding is performed on a line spectral frequencies representation of the auto-regressive coefficients.
17 . An encoder for encoding a parametric spectral representation (f) of auto-regressive coefficients (a) that partially represent an audio signal, said encoder including:
a low-frequency encoder configured to encode a low-frequency part (f L ) of the parametric spectral representation (f) by quantizing coefficients of the parametric spectral representation that correspond to a low-frequency part of the audio signal; a high-frequency encoder configured to encode a high-frequency part (f H ) of the parametric spectral representation (f) by weighted averaging based on the quantized coefficients ({circumflex over (f)} L ) flipped around a quantized mirroring frequency ({circumflex over (f)} m ), which separates the low-frequency part from the high-frequency part, and a frequency grid (g opt ) determined from a frequency grid codebook in a closed-loop search procedure.
18 . The encoder of claim 17 , wherein the high-frequency encoder includes a mirroring frequency calculator configured to calculate the quantized mirroring frequency {circumflex over (f)} m in accordance with:
{circumflex over (f)} m =Q ( f ( M/ 2)−{circumflex over ( f )}( M/ 2−1))+{circumflex over ( f )}( M/ 2−1),
where
Q denotes quantization of the expression in the adjacent parenthesis,
M denotes the total number of coefficients in the parametric spectral representation,
f(M/2) denotes the first coefficient in the high-frequency part, and
{circumflex over (f)}(M/2−1) denotes the last quantized coefficient in the low-frequency part.
19 . The encoder of claim 18 , wherein the high-frequency encoder includes a quantized low-frequency subvector flipping unit configured to flip the quantized coefficients of the low frequency part (f L ) of the parametric spectral representation (f) around the quantized mirroring frequency {circumflex over (f)} m in accordance with:
f flip ( k )=2 {circumflex over (f)} m −{circumflex over (f)} ( M/ 2−1− k ), 0≦ k≦M/ 2−1.
where {circumflex over (f)}(M/2−1−k) denotes quantized coefficient M/2−1−k.
20 . The encoder of claim 19 , wherein the high-frequency encoder includes a flipped coefficient rescaler configured to rescale the flipped coefficients f flip (k) in accordance with:
f
~
flip
(
k
)
=
{
(
f
flip
(
k
)
-
f
flip
(
0
)
)
·
(
f
max
-
f
^
m
)
/
f
^
m
+
f
flip
(
0
)
,
f
^
m
>
0.25
f
flip
(
k
)
,
otherwise
.
21 . The encoder of claim 20 , wherein the high-frequency encoder includes a frequency grid rescaler configured to rescale the frequency grids g i from the frequency grid codebook to fit into the interval between the last quantized coefficient {circumflex over (f)}(M/2−1) in the low-frequency part and a maximum grid point value g max in accordance with:
{tilde over (g)} i ( k )= g i ( k )·( g max −{circumflex over (f)} ( M/ 2−1))+{circumflex over ( f )}( M/ 2−1).
22 . The encoder of claim 21 , wherein the high-frequency encoder includes a weighting unit configured to perform weighted averaging of the flipped and rescaled coefficients {tilde over (f)} flip (k) and the rescaled frequency grids {tilde over (g)} i (k) in accordance with:
f smooth i ( k )=[1−λ( k )] {tilde over (f)} flip ( k )+λ( k ) {tilde over (g)} i ( k )
where λ(k) and [1−λ(k)] are predefined weights.
23 . The encoder of claim 22 , wherein the high-frequency encoder includes a frequency grid search unit configured to select a frequency grid g opt , where the index opt satisfies the criterion:
opt
=
arg
min
i
(
∑
k
=
0
M
/
2
-
1
(
f
smooth
i
(
k
)
-
f
H
(
k
)
)
2
)
where f H (k) is a target vector formed by the coefficients of the high-frequency part of the parametric spectral representation.
24 . The encoder of claim 23 , wherein M=10, g max =0.5, and the weights λ(k) are defined as
λ={0.2, 0.35, 0.5, 0.75, 0.8}.
25 . The encoder of claim 18 , wherein the encoder is configured to perform the encoding on a line spectral frequencies representation of the auto-regressive coefficients.
26 . A user equipment including the encoder of with claim 17 .
27 . A decoder for decoding an encoded parametric spectral representation ({circumflex over (f)}) of auto-regressive coefficients (a) that partially represent an audio signal, said decoder including:
a low-frequency decoder configured to decode coefficients ({circumflex over (f)} L ) of a low-frequency part (f L ) of the parametric spectral representation (f) corresponding to a low-frequency part of the audio signal from at least one quantization index (I f L ) encoding that part of the parametric spectral representation; a high-frequency decoder configured to decode coefficients ({circumflex over (f)} H ) of a high-frequency part (f H ) of the parametric spectral representation by weighted averaging based on the decoded coefficients ({circumflex over (f)} L ) flipped around a decoded mirroring frequency ({circumflex over (f)} m ), which separates the low-frequency part from the high-frequency part, and a decoded frequency grid (g opt ).
28 . The decoder of claim 27 , wherein the high-frequency decoder includes a quantized low-frequency subvector flipping unit configured to flip the decoded coefficients ({circumflex over (f)} L ) of the low-frequency part around the mirroring frequency {circumflex over (f)} m in accordance with:
f flip ( k )=2 {circumflex over (f)} m −{circumflex over (f)} ( M/ 2−1− k ), 0≦ k≦M/ 2−1
where
M denotes the total number of coefficients in the parametric spectral representation, and
{circumflex over (f)}(M/2−1−k) denotes decoded coefficient M/2−1−k.
29 . The decoder of claim 28 , wherein the high-frequency decoder includes a flipped coefficient rescaler configured to rescale the flipped coefficients f flip (k) in accordance with:
f
~
flip
(
k
)
=
{
(
f
flip
(
k
)
-
f
flip
(
0
)
)
·
(
f
max
-
f
^
m
)
/
f
^
m
+
f
flip
(
0
)
,
f
^
m
>
0.25
f
flip
(
k
)
,
otherwise
.
30 . The decoder of claim 29 , wherein the high-frequency decoder includes a frequency grid rescaler configured to rescale the decoded frequency grid g opt to fit into the interval between the last quantized coefficient {circumflex over (f)}(M/2−1) in the low-frequency part and a maximum grid point value g max in accordance with:
{tilde over (g)} opt ( k )= g opt ( k )·( g max −{circumflex over (f)} ( M/ 2−1))+{circumflex over ( f )}( M/ 2−1).
31 . The decoder of claim 30 , wherein the high-frequency decoder includes a weighting unit configured to perform weighted averaging of the flipped and rescaled coefficients {tilde over (f)} flip (k) and the rescaled frequency grid {tilde over (g)} opt (k) in accordance with:
f smooth ( k )=[1−λ( k )] {tilde over (f)} flip ( k )+λ( k ) {tilde over (g)} opt ( k ).
where λ(k) and [1−λ(k)] are predefined weights.
32 . The decoder of claim 31 , wherein M=10, g max =0.5, and the weights λ(k) are defined as
λ={0.2, 0.35, 0.5, 0.75, 0.8}.
33 . The decoder of claim 27 , wherein the decoder is configured to perform the decoding of the encoded parametric spectral representation ({circumflex over (f)}) of auto-regressive coefficients (a) on a line spectral frequencies representation of the auto-regressive coefficients.
34 . A user equipment including the decoder of claim 27 .
35 . A method of encoding a parametric spectral representation (f) of auto-regressive coefficients (a) that partially represent an audio signal, the method comprising:
encoding a low-frequency part (f L ) of the parametric spectral representation (f) by quantizing coefficients of the parametric spectral representation that correspond to a low-frequency part of the audio signal; and encoding a high-frequency part (f H ) of the parametric spectral representation (f) by weighted averaging based on the quantized coefficients ({circumflex over (f)} L ) flipped around a quantized mirroring frequency ({circumflex over (f)} m ), which separates the low-frequency part from the high-frequency part, and a frequency grid codebook obtained in a closed-loop search procedure.
36 . An encoder for encoding a parametric spectral representation (f) of auto-regressive coefficients (a) that partially represent an audio signal, said encoder including:
a low-frequency encoder configured to encode a low-frequency part (f L ) of the parametric spectral representation (f) by quantizing coefficients of the parametric spectral representation that correspond to a low-frequency part of the audio signal; a high-frequency encoder configured to encode a high-frequency part (f H ) of the parametric spectral representation (f) by weighted averaging based on the quantized coefficients ({circumflex over (f)} L ) flipped around a quantized mirroring frequency ({circumflex over (f)} m ), which separates the low-frequency part from the high-frequency part, and a frequency grid codebook obtained in a closed-loop search procedure.Join the waitlist — get patent alerts
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