Patent ID: 7519538

Claim:
A method of encoding an audio signal, the audio signal comprising a first audio channel and a second audio channel, the method comprising: subband filtering each of the first audio channel and the second audio channel in a complex modulated filterbank to provide a first plurality of subband signals for the first audio channel and a second plurality of subband signals for the second audio channel; downsampling each of the subband signals to provide a first plurality of downsampled subband signals and a second plurality of downsampled subband signals; further subband filtering at least one of the downsampled subband signals in a further filterbank in order to provide a plurality of sub-subband signals, wherein a number of downsampled subband signals subjected to the further subband filtering is smaller than a total number of downsampled subband signals so that downsampled subband signals that are not further subband filtered remain; deriving spatial parameters from the sub-subband signals and from the downsampled subband signals that are not further subband filtered; and deriving a single channel audio signal comprising derived subband signals derived from the first plurality of downsampled subband signals and the second plurality of downsampled subband signals.