Advanced processing based on a complex-exponential-modulated filterbank and adaptive time signalling methods

A multi-channel decoder for decoding a mono signal and an associated inter-channel coherence measure, the inter-channel coherence measure representing a coherence between a plurality of original channels, the mono signal being derived from the plurality of original channels, comprising:

• a generator for generating a decorrelation signal from the mono signal comprising a provider for providing a plurality of subband signals, wherein a subband signal includes a sequence of at least two subband samples, the sequence of the subband samples representing a bandwidth of the subband signal, which is smaller than a bandwidth of the input signal, wherein the provider is operative to provide a subband signal such that when the input signal includes a block having a predetermined number of input samples, the number of subband samples in a subband signal is smaller than the number of input samples;
• and a filter for filtering each subband signal using a reverberation filter to obtain a plurality of reverberated subband signals, wherein a plurality of reverberated subband signals together represent the decorrelation signal;
• a mixer for mixing the mono signal and the decorrelation signal in accordance with a first mixing mode to obtain a first decoded output signal and in accordance with a second mixing mode to obtain a second decoded output signal, wherein the mixer is operative to determine the first mixing mode and the second mixing mode based on the inter-channel coherence measure.

A method of multi-channel decoding for decoding a mono signal and an associated inter-channel coherence measure, the inter-channel coherence measure representing a coherence between a plurality of original channels, the mono signal being derived from the plurality of original channels, comprising:

• generating a decorrelation signal from the mono signal comprising:
• providing a plurality of subband signals, wherein a subband signal includes a sequence of at least two subband samples, the sequence of the subband samples representing a bandwidth of the subband signal, which is smaller than a bandwidth of the input signal, wherein the step of providing is performed such that when the input signal includes a block having a predetermined number of input samples, the number of subband samples in a subband signal is smaller than the number of input samples;
• and filtering each subband signal using a reverberation filter to obtain a plurality of reverberated subband signals, wherein a plurality of reverberated subband signals together represent the decorrelation signal;
• mixing the mono signal and the decorrelation signal in accordance with a first mixing mode to obtain a first decoded output signal and in accordance with a second mixing mode to obtain a second decoded output signal, wherein the mixer is operative to determine the first mixing mode and the second mixing mode based on the inter-channel coherence measure.

An apparatus for encoding a stereo signal to obtain a mono output signal and a stereo parameter set, comprising:

• a calculator for calculating the mono signal by combining a left and a right channel of the stereo signals;
• a generator for generating a first stereo parameter set using a portion of the left channel and a portion of the right channel, the portion starting at a first time border;
• a determiner for determining a validity of the first stereo parameter set for subsequent portions of the left channel and the right channel, wherein the determiner for determining is operative to:
• generate second time border, and
• activate the generator for generating, when it is determined that the stereo parameter set is not valid anymore so that a second stereo parameter set for portions of the left and right signals starting at the second time border is generated;
• and
• an outputter for outputting the mono signal and the first stereo parameter set and the first time border associated with the first parameter set, and the second stereo parameter set and the second time border associated with the second stereo parameter set.

A method of encoding a stereo signal to obtain a mono output signal and a stereo parameter set, comprising:

• calculating the mono signal by combining a left and a right channel of the stereo signals;
• generating a first stereo parameter set using a portion of the left channel and a portion of the right channel, the portion starting at a first time border;
• determining a validity of the first stereo parameter set for subsequent portions of the left channel and the right channel, by
• generating a second time border, and
• conducting the step of generating, when it is determined that the stereo parameter set is not valid anymore so that a second stereo parameter set for portions of the left and right signals starting at the second time border is generated;
• and
• outputting the mono signal and the first stereo parameter set and the first time border associated with the first parameter set, and the second stereo parameter set and the second time border associated with the second stereo parameter set.