Methods and apparatus for decoding encoded audio signal(s)

An apparatus for decoding a plurality of audio signals, the apparatus comprising:

• a receiver for receiving a first audio signal, the first audio signal being a mid-signal and for receiving a second audio signal corresponding to the mid-signal, the second audio signal being a side signal;
• and
• a decoder for decoding the second audio signal and its corresponding mid-signal so as to generate a stereo signal including a first stereo signal and a second stereo audio signal which are suitable for playback on two channels of a speaker configuration,
• wherein the received second audio signal is a waveform-coded signal comprising spectral data corresponding to frequencies up to a first frequency, and the corresponding mid-signal is a waveform-coded signal comprising spectral data corresponding to frequencies up to a frequency which is larger than the first frequency, and
• wherein the decoding of the second audio signal and its corresponding mid-signal comprises upmixing the mid-signal and the side-signal so as to generate the stereo signal, wherein for frequencies below the first frequency the upmixing comprises performing an inverse sum-difference transformation of the side signal and the mid signal, and for frequencies above the first frequency the upmixing comprises performing parametric upmixing of the mid signal.