Method for representing multi-channel audio signals
A multi-channel input signal having at least three original channels is represented by a parameter representation of the multi-channel signal. A first balance parameter, a first coherence parameter, or a first inter-channel time difference between a first channel pair and a second balance parameter, or a second coherence parameter, or a second inter-channel time difference parameter between a second channel pair are calculated. This set of parameters is the parameter representation of the original signals. The first channel pair has two channels, which are different from two channels of a second channel pair. Furthermore, each channel of the two channel pairs is one of the original channels, or a weighted combination of the original channels, and the first channel pair and the second channel pair include information on the three original channels. For multi-channel reconstruction purposes, the parameters are used in addition to down-mixing information to generate a selectable number of output channels in a scalable fashion.
1. An apparatus for generating a parameter representation of a multi-channel input signal having original channels, the original channels including a left channel, a right channel, a rear left channel, and a rear right channel, comprising:
a surround encoder configured for generating a downmix of the original channels;
a parameter generator configured for generating a first balance parameter between a first channel pair, for generating a second balance parameter between a second channel pair and for generating a third balance parameter, wherein the balance parameters form the parameter representation,
wherein the third balance parameter is a center balance parameter and a third channel pair includes, as a first channel, the center channel and, as a second channel, a channel combination including the left channel and the right channel,
in which the parameter generator is operative to calculate the center balance parameter in accordance with the following equation:
r
2
=
γ
2
2
C
α
2
(
B
+
D
)
wherein r 2 is the center balance parameter, wherein C represents the centre channel, wherein B represents the left channel, wherein D represents the right channel, and wherein γ and α represent down-mixing factors,
wherein the first balance parameter is a left single-sided front/back balance parameter, and wherein the first channel pair includes, as a first channel, the rear left channel and, as a second channel, the left channel, and
wherein the second balance parameter is a right single-sided front/back balance parameter and wherein the second channel pair has, as a first channel, the rear right channel and, as a second channel, the right channel; and
a multiplexer for multiplexing the downmix and the parameter representation into an output bitstream.
2. An apparatus for generating a reconstructed multi-channel representation of an original multi-channel signal, the apparatus comprising:
a demultiplexer configured for demultiplexing a bit-stream into a downmix comprising one or more base channels and a parameter representation comprising a first balance parameter, a second balance parameter, and a third balance parameter;
an up-mixer configured for generating a number of reconstructed channels, the number of reconstructed channels being greater than the number of base channels and smaller than or forming equal to a number of original channels forming the one or more base channels generated using a down-mixing scheme,
wherein the up-mixer is operative to generate the reconstructed channels based on information on the down-mixing scheme and using the first balance parameter, the second balance parameter and the third balance parameter,
wherein the first balance parameter is a left single-sided front/back balance parameter, wherein the second balance parameter is a right single-sided front/back balance parameter, and wherein the third balance parameter is a center balance parameter that is based on:
r
2
=
γ
2
2
C
α
2
(
B
+
D
)
wherein r 2 is the center balance parameter, wherein C represents a center channel, wherein B represents a left channel, wherein D represents a right channel, and wherein γ and α represent down-mixing factors,
wherein the up-mixer is operative to generate a reconstructed left channel and a reconstructed rear left channel based on the first balance parameter, and
wherein the up-mixer is operative to reconstruct a reconstructed right channel and a reconstructed rear right channel based on the second balance parameter.
3. A method of generating a parameter representation of a multi-channel input signal having original channels, the original channels including a left channel, a right channel, a rear left channel, and a rear right channel, comprising:
generating, by a surround encoder, a downmix of the original channels;
generating, by a parameter generator, a first balance parameter between a first channel pair;
generating, by the parameter generator, a second balance parameter between a second channel pair; and generating, by the parameter generator, a third balance parameter, wherein the balance parameters form the parameter representation,
wherein the first balance parameter is a left single-sided front/back balance parameter, and wherein the first channel pair includes, as a first channel, the rear left channel and, as a second channel, the left channel, and
wherein the second balance parameter is a right single-sided front/back balance parameter and wherein the second channel pair has, as a first channel, the rear right channel and, as a second channel, the right channel,
wherein the third balance parameter is a center balance parameter and a third channel pair includes, as a first channel, the center channel and, as a second channel, a channel combination including the left channel and the right channel,
in which the center balance parameter is calculated in accordance with the following equation:
r
2
=
γ
2
2
C
α
2
(
B
+
D
)
wherein r 2 is the center balance parameter, wherein C represents the centre channel, wherein B represents the left channel, wherein D represents the right channel, and wherein γ and α represent down-mixing factors,
multiplexing, by a multiplexer, the downmix and the parameter representation into an output bitstream,
wherein at least one of the surround encoder, the parameter generator and the multiplexer comprises a hardware implementation.
4. A method of generating a reconstructed multi-channel representation of an original multi-channel signal, comprising:
demultiplexing, by a demultiplexer, a bitstream into a downmix comprising one or more base channels and a parameter representation comprising a first balance parameter and a second balance parameter; and
generating, by an upmixer, a number of reconstructed channels, the number of reconstructed channels being greater than the number of base channels and smaller than or equal to a number of original channels forming the one or more base channels generated using a down-mixing scheme;
wherein the generating comprises:
generating the reconstructed channels based on information on the down-mixing scheme and using the first balance parameter, the second balance parameter, and a third balance parameter,
wherein the first balance parameter is a left single-sided front/back balance parameter, wherein the second balance parameter is a right single-sided front/back balance parameter, and wherein a third balance parameter is a center balance parameter that is based on:
r
2
=
γ
2
2
C
α
2
(
B
+
D
)
wherein r 2 is the center balance parameter, wherein C represents the center channel, wherein B represents the left channel, wherein D represents the right channel, and wherein γ and α represent down-mixing factors;
generating a reconstructed left channel and a reconstructed rear left channel based on the first balance parameter, and
generating a reconstructed right channel and a reconstructed rear right channel based on the second balance parameter;
wherein at least one of the demultiplexer and the upmixer comprises a hardware implementation.
5. A non-transitory storage medium having stored thereon a computer program having machine-readable instructions for performing, when running on a computer, a method of generating a parameter representation of a multi-channel input signal having original channels, the original channels including a left channel, a right channel, a rear left channel, and a rear right channel, the method comprising:
generating a downmix of the original channels;
generating a first balance parameter between a first channel pair;
generating a second balance parameter between a second channel pair; and generating a third balance parameter, wherein the balance parameters form the parameter representation,
wherein the first balance parameter is a left single-sided front/back balance parameter, and wherein the first channel pair includes, as a first channel, the rear left channel and, as a second channel, the left channel, and
wherein the second balance parameter is a right single-sided front/back balance parameter and wherein the second channel pair has, as a first channel, the rear right channel and, as a second channel, the right channel
wherein the third balance parameter is a center balance parameter and a third channel pair includes, as a first channel, the center channel and, as a second channel, a channel combination including the left channel and the right channel,
in which the center balance parameter is calculated in accordance with the following equation:
r
2
=
γ
2
2
C
α
2
(
B
+
D
)
wherein r 2 is the center balance parameter, wherein C represents the centre channel, wherein B represents the left channel, wherein D represents the right channel, and wherein γ and α represent down-mixing factors, and
multiplexing the downmix and the parameter representation into an output bitstream.
6. A non-transitory storage medium having stored thereon a computer program having machine-readable instructions for performing, when running on a computer, a method of generating a reconstructed multi-channel representation of an original multi-channel signal, the method comprising:
demultiplexing a bitstream into a downmix comprising one or more base channels and a parameter representation comprising a first balance parameter, a second balance parameter and a third balance parameter; and
generating a number of reconstructed channels, the number of reconstructed channels being greater than the number of base channels and smaller than or equal to a number of original channels using the one or more base channels generated using a down-mixing scheme;
wherein the generating comprises:
generating the reconstructed channels based on information on the down-mixing scheme and using the first balance parameter, the second balance parameter, and the third balance parameter,
wherein the first balance parameter is a left single-sided front/back balance parameter, wherein the second balance parameter is a right single-sided front/back balance parameter, and wherein a third balance parameter is a center balance parameter that is based on:
r
2
=
γ
2
2
C
α
2
(
B
+
D
)
wherein r 2 is the center balance parameter, wherein C represents the center channel, wherein B represents the left channel, wherein D represents the right channel, and wherein γ and α represent down-mixing factors;
generating a reconstructed left channel and a reconstructed rear left channel based on the first balance parameter, and
generating a reconstructed right channel and a reconstructed rear right channel based on the second balance parameter.