Multi-channel decorrelator, multi-channel audio decoder, multi channel audio encoder, methods and computer program using a premix of decorrelator input signals
A multi-channel decorrelator for providing a plurality of decorrelated signals on the basis of a plurality of decorrelator input signals is configured to premix a first set of N decorrelator input signals into a second set of K decorrelator input signals, wherein K<N. The multi-channel decorrelator is configured to provide a first set of K′ decorrelator output signals on the basis of the second set of K decorrelator input signals. The multi-channel decorrelator is further configured to upmix the first set of K′ decorrelator output signals into a second set of N′ decorrelator output signals, wherein N′>K′. The multi-channel decorrelator can be used in a multi-channel audio decoder. A multi-channel audio encoder provides complexity control information for the multi-channel decorrelator.
1. A multi-channel decorrelator apparatus for providing a plurality of decorrelated audio signals on the basis of a plurality of decorrelator input audio signals, comprising:
a premixer configured to premix a first set {circumflex over (Z)} of N decorrelator input audio signals into a second set {circumflex over (Z)} mix of K decorrelator input audio signals, wherein K<N;
a multi-channel decorrelator configured to decorrelate the second set {circumflex over (Z)} mix of K decorrelator input audio signals to provide a first set {tilde over (Z)} mix dec of K′ decorrelator output audio signals; and
an upmixer configured to upmix the first set {circumflex over (Z)} mix dec of K′ decorrelator output audio signals into a second set W of N′ decorrelator output audio signals, wherein N′>K′;
wherein the premixer is configured to premix the first set {circumflex over (Z)} of N decorrelator input audio signals into the second set {circumflex over (Z)} mix of K decorrelator input audio signals using a premixing matrix M pre according to
{circumflex over (Z)} mix =M pre {circumflex over (Z)}
wherein the multi-channel decorrelator is configured to acquire the first set {circumflex over (Z)} mix dec of K′ decorrelator output audio signals on the basis of the second set {circumflex over (Z)} mix of K decorrelator input audio signals, and
wherein the upmixer is configured to upmix the first set {circumflex over (Z)} mix dec of K′ decorrelator output audio signals into the second set W of N′ decorrelator output audio signals using a postmixing matrix M post according to
W=M post {circumflex over (Z)} mix dec ;
wherein the multi-channel decorrelator is configured to acquire the postmixing matrix M post according to
M past =M pre H ( M pre M pre H ) −1 ;
wherein the multi-channel-decorrelator apparatus is implemented using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.
2. A method for providing a plurality of decorrelated audio signals on the basis of a plurality of decorrelator input audio signals, the method comprising:
premixing a first set {circumflex over (Z)} of N decorrelator input audio signals into a second set {circumflex over (Z)} mix of K decorrelator input audio signals, wherein K<N;
decorrelating the second set {circumflex over (Z)} mix of K decorrelator input audio signals to provide a first set {circumflex over (Z)} mix dec of K′ decorrelator output audio signals; and
upmixing the first set {circumflex over (Z)} mix dec of K′ decorrelator output audio signals into a second set W of N′ decorrelator output audio signals, wherein N′>K′;
wherein the first set {circumflex over (Z)} of N decorrelator input audio signals is premixed into the second set of {circumflex over (Z)} mix decorrelator input audio signals using a premixing matrix M pre according to
{circumflex over (Z)}=M pre {circumflex over (Z)}
wherein the first set {circumflex over (Z)} mix dec of K′ decorrelator output audio signals is acquired on the basis of the second set {circumflex over (Z)} mix of K decorrelator input audio signals, and
wherein the first set {circumflex over (Z)} mix dec of K′ decorrelator output audio signals is upmixed into the second set W of N′ decorrelator output audio signals using a postmixing matrix M post according to
W=M post {circumflex over (Z)} mix dec ;
wherein the postmixing matrix M post is acquired according to
M post =M pre H ( M pre M pre H ) −1 .
3. A non-transitory digital storage medium having stored thereon a computer program for performing the method of claim 2 when said computer program is run by a computer.