Audio encoder and decoder

A method for reconstructing an audio object of a time frame comprising a plurality of frequency bands, comprising:

• receiving M>1 downmix signals, each being a combination of a plurality of audio objects including the audio object,
• receiving indicators comprising first indicators that indicate which N of the M downmix signals to be used and not to be used in the plurality of frequency bands when reconstructing the audio object, wherein N is less than or equal to M,
• wherein, in a first decoding mode, each of the first indicators indicates a downmix signal to be used for all of the plurality of frequency bands when reconstructing the audio object,
• receiving first parameters each associated with a frequency band and a downmix signal indicated by the first indicators for that frequency band,
• reconstructing the audio object of the plurality of frequency bands by, for each frequency band of the plurality of frequency bands, forming a weighted sum of at least the downmix signals indicated by the first indicators for the frequency band, wherein each downmix signal is weighted according to its associated first parameter.

A decoder for reconstructing an audio object of a time frame comprising a plurality of frequency bands, comprising:

• a receiving stage configured for:
• receiving M>1 downmix signals, each being a combination of a plurality of audio objects including the audio object,
• receiving indicators comprising first indicators that indicate which of the M downmix signals to be used and not to be used in the plurality of frequency bands when reconstructing the audio object, wherein, in a first decoding mode, each of the first indicators indicates a downmix signal to be used for all of the plurality of frequency bands when reconstructing the audio object, and
• receiving first parameters each associated with a frequency band and a downmix signal indicated by the indicators for that frequency band,
• a reconstruction stage configured for reconstructing the audio object of the plurality of frequency bands by, for each frequency band of the plurality of frequency bands, forming a weighted sum of the downmix signals indicated by the first indicators for the frequency band, wherein each downmix signal is weighted according to its associated first parameter.

A method for encoding an audio object of a time frame comprising a plurality of frequency bands, comprising:

• determining M>1 downmix signals, each being a combination of a plurality of audio objects including the audio object,
• in a first encoding mode,
• selecting a subset comprising N downmix signals of the M downmix signals to be used when reconstructing the audio object in a decoder in a audio coding system, wherein N is less than or equal to M, and
• representing each downmix signal in the subset of the M downmix signals by an indicator identifying the downmix signal to be used and not to be used among the M downmix signals, and by a plurality of parameters, one for each of the plurality of frequency bands, and each one associated with a frequency band, wherein each parameter of the plurality of parameters represents a weight for the downmix signal when reconstructing the audio object for the associated frequency band.