Compatible multi-channel coding/decoding

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

• providing, by a provider, a first downmix channel and a second downmix channel, the first and the second downmix channels being derived from the original channels;
• calculating, by a calculator, channel side information for a selected original channel of the original signals such that a downmix channel or a combined downmix channel comprising the first and the second downmix channel, when weighted using the channel side information, results in an approximation of the selected original channel;
• and
• generating, by a generator, output data, the output data comprising the channel side information;
• wherein the provider, the calculator or the generator comprises a hardware implementation.

An apparatus for inverse processing of input data, the apparatus comprising:

• an input data reader for reading the input data, the input data comprising 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 channel side information are calculated such that a downmix channel or a combined downmix channel comprising the first downmix channel and the second downmix channel, when weighted using the channel side information, results in an approximation of a selected original channel, wherein the input data reader is configured 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;
• and
• 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,
• wherein at least one of the input data reader and the channel reconstructor comprises a hardware implementation.

A method of inverse processing of input data, the method comprising:

• reading, by an input data reader, the input data, the input data comprising 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, w wherein the channel side information are calculated such that a downmix channel or a combined downmix channel comprising the first downmix channel and the second downmix channel, when weighted using the channel side information, results in an approximation of a selected original channel;
• and
• reconstructing, by a reconstructor, 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,
• wherein at least one of the input data reader and the reconstructor comprises a hardware implementation.

A non-transitory storage medium having stored thereon a computer program having a program code for performing a method of processing a multi-channel audio signal, the multi-channel audio signal having at least three original channels, 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 comprising the first and the second downmix channel, when weighted using the channel side information, results in an approximation of the selected original channel;
• and
• generating output data, the output data comprising the channel side information.