Compatible multi-channel coding/decoding by weighting the downmix channel

Method of processing a multi-channel audio signal, the multi-channel audio signal having at least three original channels, the original channels including a center channel, the method comprising:

• providing a first downmix channel and a second downmix channel, the first and the second downmix channels being derived from the original channels;
• combining the first downmix channel and the second downmix channel to obtain a combined downmix channel;
• calculating channel side information for a selected original channel of the original signals such that a downmix channel or the combined downmix channel including the first and the second downmix channel, when weighted using the channel side information, results in an approximation of the selected original channel, wherein the channel side information for the center channel as the selected original channel is calculated, and wherein the channel side information for the center channel is calculated such that the combined downmix channel, when weiqhted using the channel side information, results in an approximation of the original center channel;
• and
• generating output data, the output data including the channel side information.

Apparatus for inverse processing of input data, the input data including channel side information, a first downmix channel or a signal derived from the first downmix channel and a second downmix channel or a signal derived from the second downmix channel, wherein the first downmix channel and the second downmix channel are derived from at least three original channels of a multi-channel audio signal, and wherein the channel side information are calculated such that a downmix channel or a combined downmix channel including the first downmix channel and the second downmix channel, when weighted using the channel side information, results in an approximation of the selected original channel, the apparatus comprising:

• an input data reader for reading the input data to obtain the first downmix channel or a signal derived from the first downmix channel and the second downmix channel or a signal derived from the second downmix channel and the channel side information;
• a channel reconstructor for reconstructing the approximation of the selected original channel using the channel side information and the downmix channel or the combined downmix channel to obtain the approximation of the selected original channel;
• and
• the channel reconstructor being operative to reconstruct an approximation for the center channel using channel side information for the center channel and the combined downmix channel.

Method of inverse processing of input data, the input data including channel side information, a first downmix channel or a signal derived from the first downmix channel and a second downmix channel or a signal derived from the second downmix channel, wherein the first downmix channel and the second downmix channel are derived from at least three original channels of a multi-channel audio signal, and wherein the channel side information are calculated such that a downmix channel or a combined downmix channel including the first downmix channel and the second downmix channel, when weighted using the channel side information, results in an approximation of the selected original channel, the method comprising:

• reading the input data to obtain the first downmix channel or a signal derived from the first downmix channel and the second downmix channel or a signal derived from the second downmix channel and the channel side information;
• reconstructing the approximation of the selected original channel using the channel side information and the downmix channel or the combined downmix channel to obtain the approximation of the selected original channel;
• and
• the reconstructing step further including reconstructingan approximation for the center channel using channel side information for the center channel and the combined downmix channel.

A computer implemented method of processing a multi-channel audio signal, the multi-channel audio signal having at least three original channels, the original channels including a center channel, the method comprising:

• providing a first downmix channel and a second downmix channel, the first and the second downmix channels being derived from the original channels;
• combining the first downmix channel and the second downmix channel to obtain a combined downmix channel;
• calculating channel side information for a selected original channel of the original signals such that a downmix channel or the combined downmix channel including the first and the second downmix channel, when weighted using the channel side information, results in an approximation of the selected original channel, wherein the channel side information for the center channel as the selected original channel is calculated, and wherein the channel side information for the center channel is calculated such that the combined downmix channel when weighted using the channel side information results in an approximation of the original center channel;
• and
• generating output data, the output data including the channel side information.

A computer implemented method for inverse processing of input data, the input data including channel side information, a first downmix channel or a signal derived from the first downmix channel and a second downmix channel or a signal derived from the second downmix channel, wherein the first downmix channel and the second downmix channel are derived from at least three original channels of a multi-channel audio signal, and wherein the channel side information are calculated such that a downmix channel or a combined downmix channel including the first downmix channel and the second downmix channel, when weighted using the channel side information, results in an approximation of the selected original channel, the method comprising:

• reading the input data to obtain the first downmix channel or a signal derived from the first downmix channel and the second downmix channel or a signal derived from the second downmix channel and the channel side information;
• reconstructing the approximation of the selected original channel using the channel side information and the downmix channel or the combined downmix channel to obtain the approtimation of the selected original channel;
• and
• the reconstructing step further including reconstructingan approximation for the center channel using channel side information for the center channel and the combined downmix channel.

An apparatus for processing a multi-channel audio signal having at least three original channels, including a left channel, a left surround channel a right channel and a right surround channel, the apparatus comprising:

• means for providing a first downmix channel and a second downmix channel, the first and the second downmix channels being derived from the original channels;
• said means for providing being operative to provide the first downmix channel as a left downmix channel and to provide the second downmix channel as a right downmix channel, the left and the right downmix channels being formed such that are sult, when played, is a stereo representation of the multi-channel audio signal;
• means for calculating channel. side information for a selected original channel of the original signals, the means for calculating being operative to calculate the channel side information such that a downmix channel or a combined downmix channel including the first and the second downmix channel, when weighted using the channel side information, results in an approximation of the selected original channel;
• said means for calculating being operative to:
• calculate the channel side information for the left channel as the selected original channel using the left downmix channel;
• calculate the channel side information for the right channel as the selected original channel using the right downmix channel;
• calculate the channel side information for the left surround channel as the selected original channel using the left downmix channel;
• and
• calculate the channel side information for the right surround channel as the selected original channel using the right downmix channel;
• and
• means for generating output data, the output data including the channel side information.

An apparatus for processing a multi-channel audio signal, the multi-channel audio signal having at least three original channels, the original channels including a center channel, the apparatus comprising:

• means for providing a first dowrxmix channel and a second downmix channel, the first and the second downmix channels being derived from the original channels;
• a combiner for combining the first downmix channel and the second downmix channel to obtain a combined downmix channel;
• means for calculating channel side information for a selected original channel of the original signals, the means for calculating being operative to calculate the channel side information such that a downmix channel or the combined downmix channel including the first and the second downmix channels, when weighted using the channel side information, results in an approximation of the selected original channel, wherein the means for calculating the channel side information is operative to calculate the channel side information for the center channel as the selected original channel, and wherein the means for calculating the channel side information is operative to calculate the channel side information for the center channel such that the combined downmix channel, when weighted using the channel side information, results in an approximation of the original center channel;
• and
• means for generating output data, the output datain cluding the channel side information.

A method of processing a multi-channel audio signal, the multi-channel audio signal having at least three original channels, the multi-channel audio signal including a left channel, a left surround channel, a right channel and a right surround channel, the method comprising:

• providing a first downmix channel and a second downmix channel, the first and the second downmix channels being derived from the original channels, wherein the first downmix channel is provided as a left downmix channel and the second downmix channel is provided as a right downmix channel, the left and the right downmix channels being formed such that a result, when played, is a stereo representation of the multi-channel audio signal;
• calculating channel side information for a selected original channel of the original signals such that a downmix channel or a combined downmix channel including the first and the second downmix channel, when weighted using the channel side information, results in an approximation of the selected original channel,
• wherein the step of calculating farther includes:
• calculating the channel side information for the left channel as the selected original channel using the left downmix channel;
• calculating the channel side information for the right channel as the selected original channel using the right downmix channel;
• calculating the channel side information for the left surround channel as the selected original channel using the left downmix channel;
• and
• calculating the channel side information for the right surround channel as the selected original channel using the right downmix channel;
• and
• generating output data, the output data including the channel side information.

A method of processing a multi-channel audio signal, the multi-channel audio signal having at least three original channels, the method comprising:

• providing a first downmix channel and a second downmix channel, the first and the second downmix channels being derived from the original channels;
• calculating channel side information for a selected original channel of the original signals such that a downmix channel or a combined downmix channel including the first and the second downmix channel, when weighted using the channel side information, results in an approximation of the selected original channel;
• the calculating step further including performing joint stereo coding using a downmix channel as a carrier channel and using, as an input channel, the selected original channel, togenerate joint stereo parameters as channel side information for the selected original channel;
• and
• generating output data, the output data including the channel side information.