Audio decoder for interleaving signals

A decoder for a multi-channel audio processing system for reconstructing M encoded channels, wherein M>2, comprising:

• a first receiving stage configured to receive N waveform-coded downmix signals comprising spectral coefficients corresponding to frequencies between a first and a second cross-over frequency, wherein N<M;
• a second receiving stage configured to receiving M waveform-coded signals comprising spectral coefficients corresponding to a respective one of the M encoded channels;
• a frequency reconstructing stage configured to perform frequency reconstruction to determine N reconstructed downmix signals, wherein the frequency reconstruction determines the N reconstructed downmix signals corresponding to a frequency range above the second cross-over frequency based on the N waveform-coded downmix signals;
• an upmix stage downstreams of the frequency reconstructing stage configured to perform a parametric upmix of the N frequency reconstructed downmix signals into M upmix signals;
• and
• an interleaver stage downstreams of the upmix stage and the second receiving stage configured to interleave the M upmix signals from the upmix stage with the M waveform-coded signals received by the second receiving stage.

A non-transitory computer-readable medium having stored thereon instructions, that when executed by one or more processors, cause the one or more processors to perform operations comprising:

• receiving N waveform-coded downmix signals comprising spectral coefficients corresponding to frequencies between a first and a second cross-over frequency, wherein N<M;
• receiving M waveform-coded signals comprising spectral coefficients corresponding to a respective one of the M encoded channels;
• performing frequency reconstruction to determine N reconstructed downmix signals, wherein the frequency reconstruction determines the N reconstructed downmix signals corresponding to a frequency range above the second cross-over frequency based on the N waveform-coded downmix signals;
• performing a parametric upmix of the N frequency reconstructed downmix signals into M upmix signals;
• and interleaving the M upmix signals with the M waveform-coded signals.