Audio decoder, audio object encoder, method for decoding a multi-audio-object signal, multi-audio-object encoding method, and non-transitory computer-readable medium therefor
An audio decoder for decoding a multi-audio-object signal having an audio signal of a first type and an audio signal of a second type encoded therein is described, the multi-audio-object signal having a downmix signal and side information, the side information having level information of the audio signals of the first and second types in a first predetermined time/frequency resolution, and a residual signal specifying residual level values in a second predetermined time/frequency resolution, the audio decoder having a processor for computing prediction coefficients based on the level information; and an up-mixer for up-mixing the downmix signal based on the prediction coefficients and the residual signal to obtain a first up-mix audio signal approximating the audio signal of the first type and/or a second up-mix audio signal approximating the audio signal of the second type.
1. An audio decoder for decoding a multi-audio-object signal comprising an audio signal of a first type and an audio signal of a second type encoded therein, the multi-audio-object signal comprising a downmix signal d=(d 1 , d 2 ) comprising right and left downmix channels and side information, wherein the audio signal of the first type comprises a stereo audio signal comprising right and left input channels, the side information comprising level information OLD R , OLD L and OLD F of the right and left channels of audio signal of the first type and a channel of the audio signal of the second type, respectively, and an inter-correlation information IOC LR defining level similarities between the right and left input channels in a first predetermined time/frequency resolution, and a downmix prescription for the channel of the audio signal of the second type describing as to how the channel of the audio signal of the second type is downmixed into the right and left channels of the downmix signal, and a residual signal specifying residual level values in a second predetermined time/frequency resolution, the audio decoder comprising
a processor for computing prediction coefficients based on the level information and the inter-correlation information according to C=(c 1 ,c 2 ) with
c
1
=
P
LoF
P
Ro
-
P
RoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
and
c
2
=
P
RoF
P
Lo
-
P
LoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
with
P
Lo
=
OLD
L
+
m
F
2
OLD
F
,
P
Ro
=
OLD
R
+
n
F
2
OLD
F
,
P
LoRo
=
IOC
LR
OLD
L
OLD
R
+
m
F
n
F
OLD
F
,
P
LoF
=
m
F
OLD
L
+
n
F
IOC
LR
OLD
L
OLD
R
-
m
F
OLD
F
,
P
RoF
=
n
F
OLD
R
+
m
F
IOC
LR
OLD
L
OLD
R
-
n
F
OLD
F
with values m F and n F depending on the downmix prescription; and
an up-mixer for up-mixing the downmix signal based on the prediction coefficients, using C·d, and the residual signal to acquire a first up-mix audio signal approximating the audio signal of the first type and/or a second up-mix audio signal approximating the audio signal of the second type.
2. The audio decoder according to claim 1 , wherein the downmix prescription varies in time within the side information.
3. The audio decoder according to claim 2 , wherein the downmix prescription varies in time within the side information at a time resolution coarser than a frame-size.
4. The audio decoder according to claim 2 , wherein the downmix prescription indicates the weighting by which the downmix signal has been mixed-up based on the audio signal of the first type and the audio signal of the second type.
5. The audio decoder according to claim 1 , wherein the first and third time/frequency resolutions are determined by a common syntax element within the side information.
6. The audio decoder according to claim 1 , wherein the processor and the up-mixer are configured such that the up-mixing is representable by an appliance of a vector composed of the downmix signal and the residual signal, to a sequence of a first and a second matrix, the first matrix being composed of the prediction coefficients and the second matrix being defined by a downmix prescription according to which the audio signal of the first type and the audio signal of the second type are downmixed into the downmix signal, and which is also comprised by the side information.
7. The audio decoder according to claim 6 , wherein the processor and the up-mixer are configured such that the first matrix maps the vector to an intermediate vector comprising a first component for the audio signal of the first type and/or a second component for the audio signal of the second type and being defined such that the downmix signal is mapped onto the first component 1-to-1, and a linear combination of the residual signal and the downmix signal is mapped onto the second component.
8. The audio decoder according to claim 1 , wherein the multi-audio-object signal comprises a plurality of audio signals of the second type and the side information comprises one residual signal per audio signal of the second type.
9. The audio decoder according to claim 1 , wherein the second predetermined time/frequency resolution is related to the first predetermined time/frequency resolution via a residual resolution parameter comprised in the side information, wherein the audio decoder is configured to derive the residual resolution parameter from the side information.
10. The audio decoder according to claim 9 , wherein the residual resolution parameter defines a spectral range over which the residual signal is transmitted within the side information.
11. The audio decoder according to claim 10 , wherein the residual resolution parameter defines a lower and an upper limit of the spectral range.
12. The audio decoder according to claim 1 , wherein the multi-audio-object signal comprises spatial rendering information for spatially rendering the audio signal of the first type onto a predetermined loudspeaker configuration.
13. The audio decoder according to claim 1 , wherein the upmixer is configured to spatially render the first up-mix audio signal separated from the second up-mix audio signal, spatially render the second up-mix audio signal separated from the first up-mix audio signal, or mix the first up-mix audio signal and the second up-mix audio signal and spatially render the mixed version thereof onto a predetermined loudspeaker configuration.
14. An audio object encoder comprising:
a processor for computing level information OLD R , OLD L and OLD F of right and left channels of an audio signal of the first type and a channel of an audio signal of the second type, respectively, and an inter-correlation information IOC LR defining level similarities between the right and left input channels in a first predetermined time/frequency resolution;
a processor for computing prediction coefficients based on the level information and the inter-correlation information according to C=(c 1 ,c 2 ) with
c
1
=
P
LoF
P
Ro
-
P
RoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
and
c
2
=
P
RoF
P
Lo
-
P
LoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
with
P
Lo
=
OLD
L
+
m
F
2
OLD
F
,
P
Ro
=
OLD
R
+
n
F
2
OLD
F
,
P
LoRo
=
IOC
LR
OLD
L
OLD
R
+
m
F
n
F
OLD
F
,
P
LoF
=
m
F
OLD
L
+
n
F
IOC
LR
OLD
L
OLD
R
-
m
F
OLD
F
,
P
RoF
=
n
F
OLD
R
+
m
F
IOC
LR
OLD
L
OLD
R
-
n
F
OLD
F
with values m F and n F depending on the downmix prescription;
a downmixer for downmixing the audio signal of the first type and the audio signal of the second type to acquire a downmix signal d=(d 1 , d 2 ) comprising right and left downmix channels, wherein a downmix prescription for the channel of the audio signal of the second type describes as to how the channel of the audio signal of the second type is downmixed into the right and left channels of the downmix signal;
a setter for setting a residual signal specifying residual level values at a second predetermined time/frequency resolution such that up-mixing the downmix signal based on both the prediction coefficients, using C·d, and the residual signal results in a first up-mix audio signal approximating the audio signal of the first type and a second up-mix audio signal approximating the audio signal of the second type, the approximation being improved compared to the absence of the residual signal;
the level information, the inter-correlation information, the downmix prescription and the residual signal being comprised by a side information forming, along with the downmix signal, a multi-audio-object signal.
15. The audio object encoder according to claim 14 , further comprising
a decomposer for spectrally decomposing the audio signal of a first type and the audio signal of a second type.
16. A method for decoding a multi-audio-object signal comprising an audio signal of a first type and an audio signal of a second type encoded therein, the multi-audio-object signal comprising a downmix signal d=(d 1 , d 2 ) comprising right and left downmix channels and side information, wherein the audio signal of the first type comprises a stereo audio signal comprising right and left input channels, the side information comprising level information OLD R , OLD L and OLD F of the right and left channels of audio signal of the first type and a channel of the audio signal of the second type, respectively, and an inter-correlation information IOC LR defining level similarities between the right and left input channels in a first predetermined time/frequency resolution, and a downmix prescription for the channel of the audio signal of the second type describing as to how the channel of the audio signal of the second type is downmixed into the right and left channels of the downmix signal, and a residual signal specifying residual level values in a second predetermined time/frequency resolution, the method comprising
computing prediction coefficients based on the level information and the inter-correlation information according to C=(c 1 ,c 2 ) with
c
1
=
P
LoF
P
Ro
-
P
RoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
and
c
2
=
P
RoF
P
Lo
-
P
LoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
with
P
Lo
=
OLD
L
+
m
F
2
OLD
F
,
P
Ro
=
OLD
R
+
n
F
2
OLD
F
,
P
LoRo
=
IOC
LR
OLD
L
OLD
R
+
m
F
n
F
OLD
F
,
P
LoF
=
m
F
OLD
L
+
n
F
IOC
LR
OLD
L
OLD
R
-
m
F
OLD
F
,
P
RoF
=
n
F
OLD
R
+
m
F
IOC
LR
OLD
L
OLD
R
-
n
F
OLD
F
with values m F and n F depending on the downmix prescription; and
up-mixing the downmix signal based on the prediction coefficients, using C·d, and the residual signal to acquire a first up-mix audio signal approximating the audio signal of the first type and/or a second up-mix audio signal approximating the audio signal of the second type.
17. A multi-audio-object encoding method, comprising:
computing level information OLD R , OLD L and OLD F of right and left channels of an audio signal of the first type and a channel of an audio signal of the second type, respectively, and an inter-correlation information IOC LR defining level similarities between the right and left input channels in a first predetermined time/frequency resolution;
computing prediction coefficients based on the level information and the inter-correlation information according to C=(c 1 ,c 2 ) with
c
1
=
P
LoF
P
Ro
-
P
RoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
and
c
2
=
P
RoF
P
Lo
-
P
LoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
with
P
Lo
=
OLD
L
+
m
F
2
OLD
F
,
P
Ro
=
OLD
R
+
n
F
2
OLD
F
,
P
LoRo
=
IOC
LR
OLD
L
OLD
R
+
m
F
n
F
OLD
F
,
P
LoF
=
m
F
OLD
L
+
n
F
IOC
LR
OLD
L
OLD
R
-
m
F
OLD
F
,
P
RoF
=
n
F
OLD
R
+
m
F
IOC
LR
OLD
L
OLD
R
-
n
F
OLD
F
with values m F and n F depending on the downmix prescription;
downmixing the audio signal of the first type and the audio signal of the second type to acquire a downmix signal d=(d 1 , d 2 ) comprising right and left downmix channels, wherein a downmix prescription for the channel of the audio signal of the second type describes as to how the channel of the audio signal of the second type is downmixed into the right and left channels of the downmix signal;
setting a residual signal specifying residual level values at a second predetermined time/frequency resolution such that up-mixing the downmix signal based on both the prediction coefficients, using C·d, and the residual signal results in a first up-mix audio signal approximating the audio signal of the first type and a second up-mix audio signal approximating the audio signal of the second type, the approximation being improved compared to the absence of the residual signal,
the level information, the inter-correlation information, the downmix prescription and the residual signal being comprised by a side information forming, along with the downmix signal, a multi-audio-object signal.
18. A non-transitory computer-readable medium having stored thereon a computer program with a program code for executing, when running on a processor, a method for decoding a multi-audio-object signal comprising an audio signal of a first type and an audio signal of a second type encoded therein, the multi-audio-object signal comprising a downmix signal d=(d 1 , d 2 ) comprising right and left downmix channels and side information, wherein the audio signal of the first type comprises a stereo audio signal comprising right and left input channels, the side information comprising level information OLD R , OLD L and OLD F of the right and left channels of audio signal of the first type and a channel of the audio signal of the second type, respectively, and an inter-correlation information IOC LR defining level similarities between the right and left input channels in a first predetermined time/frequency resolution, and a downmix prescription for the channel of the audio signal of the second type describing as to how the channel of the audio signal of the second type is downmixed into the right and left channels of the downmix signal, and a residual signal specifying residual level values in a second predetermined time/frequency resolution, the method comprising
computing prediction coefficients based on the level information and the inter-correlation information according to C=(c 1 ,c 2 ) with
c
1
=
P
LoF
P
Ro
-
P
RoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
and
c
2
=
P
RoF
P
Lo
-
P
LoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
with
P
Lo
=
OLD
L
+
m
F
2
OLD
F
,
P
Ro
=
OLD
R
+
n
F
2
OLD
F
,
P
LoRo
=
IOC
LR
OLD
L
OLD
R
+
m
F
n
F
OLD
F
,
P
LoF
=
m
F
OLD
L
+
n
F
IOC
LR
OLD
L
OLD
R
-
m
F
OLD
F
,
P
RoF
=
n
F
OLD
R
+
m
F
IOC
LR
OLD
L
OLD
R
-
n
F
OLD
F
with values m F and n F depending on the downmix prescription; and
up-mixing the downmix signal based on the prediction coefficients, using C·d, and the residual signal to acquire a first up-mix audio signal approximating the audio signal of the first type and/or a second up-mix audio signal approximating the audio signal of the second type.
19. A non-transitory computer-readable medium having stored thereon a computer program with a program code for executing, when running on a processor, a multi-audio-object encoding method, comprising:
computing level information OLD R , OLD L and OLD F of right and left channels of an audio signal of the first type and a channel of an audio signal of the second type, respectively, and an inter-correlation information IOC LR defining level similarities between the right and left input channels in a first predetermined time/frequency resolution;
computing prediction coefficients based on the level information and the inter-correlation information according to C=(c 1 ,c 2 ) with
c
1
=
P
LoF
P
Ro
-
P
RoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
and
c
2
=
P
RoF
P
Lo
-
P
LoF
P
LoRo
P
Lo
P
Ro
-
P
LoRo
2
with
P
Lo
=
OLD
L
+
m
F
2
OLD
F
,
P
Ro
=
OLD
R
+
n
F
2
OLD
F
,
P
LoRo
=
IOC
LR
OLD
L
OLD
R
+
m
F
n
F
OLD
F
,
P
LoF
=
m
F
OLD
L
+
n
F
IOC
LR
OLD
L
OLD
R
-
m
F
OLD
F
,
P
RoF
=
n
F
OLD
R
+
m
F
IOC
LR
OLD
L
OLD
R
-
n
F
OLD
F
with values m F and n F depending on the downmix prescription;
downmixing the audio signal of the first type and the audio signal of the second type to acquire a downmix signal d=(d 1 , d 2 ) comprising right and left downmix channels, wherein a downmix prescription for the channel of the audio signal of the second type describes as to how the channel of the audio signal of the second type is downmixed into the right and left channels of the downmix signal;
setting a residual signal specifying residual level values at a second predetermined time/frequency resolution such that up-mixing the downmix signal based on both the prediction coefficients, using C·d, and the residual signal results in a first up-mix audio signal approximating the audio signal of the first type and a second up-mix audio signal approximating the audio signal of the second type, the approximation being improved compared to the absence of the residual signal,
the level information, the inter-correlation information, the downmix prescription and the residual signal being comprised by a side information forming, along with the downmix signal, a multi-audio-object signal.