Source coding enhancement using spectral-band replication

A decoder for decoding

• an encoded signal, the encoded signal being derived from an original signal and representing only a portion of frequency bands included in the original signal, comprising:
• a provider for providing subband samples for a plurality of subbands or a plurality of spectral coefficients, the subband samples or spectral coefficients, the subband samples or spectral coefficients representing the encoded signal;
• a transposer for transposing subband samples or spectral coefficients, which represent source frequencies to corresponding destination frequencies in a reconstruction frequency band which is included in the original signal and which is not included in the encoded signal,
• wherein a destination frequency is related to a corresponding source frequency by means of the following equation:
• fdest=fsource·M±Δfsource,
• wherein fdest is a destination frequency, fsource is a source frequency corresponding to the destination frequency, M is a transposition factor not equal to one, and Δfsource is a deviation from an exact transposition being greater than or equal to zero and smaller than 5 percent of a bandwidth of a critical band, in which the destination frequency is located,
• wherein, for each subband or frequency coefficient for a certain destination frequency, phase information for respective subband samples or a respective frequency coefficient is derived only from phase information from subband samples or a frequency coefficient for a certain source frequency which corresponds to the certain destination frequency,
• wherein the subband samples or spectral coefficients are adjusted using spectral envelope information derived from the original signal or the encoded signal to obtain adjusted transposed subband samples or adjusted transposed spectral coefficients, before or after the step of transposing;
• and
• a combiner for combining the subband samples and the adjusted transposed subband samples or the spectral coefficients and the adjusted transposed spectral coefficients, such that a decoded output signal is obtained.

Computer program product including computer readable instructions for performing, when processed by a computer, a method of decoding an encoded signal, the encoded signal being derived from an original signal and representing only a portion of frequency bands included in the original signal, the method comprising:

• providing subband samples for a plurality of subbands or a plurality of spectral coefficients, the subband samples or spectral coefficients representing the encoded signal;
• transposing subband samples or spectral coefficients, which represent source frequencies to corresponding destination frequencies in a reconstruction frequency band which is included in the original signal and which is not included in the encoded signal,
• wherein a destination frequency is related to a corresponding source frequency by means of the following equation:
• fdest=fsource·M±Δfsource,
• wherein fdest is a destination frequency, fsource is a source frequency corresponding to the destination frequency, M is a transposition factor not equal to one, and Δfsource is a deviation from an exact transposition being greater than or equal to zero and smaller than 5 percent of a bandwidth of a critical band, in which the destination frequency is located,
• wherein, for each subband or frequency coefficient for a certain destination frequency, phase information for respective subband samples or a respective frequency coefficient is derived only from phase information from subband samples or a frequency coefficient for a certain source frequency which corresponds to the certain destination frequency,
• wherein the subband samples or spectral coefficients are adjusted using spectral envelope information derived from the original signal or the encoded signal to obtain adjusted transposed subband samples or adjusted transposed spectral coefficients, before or after the step of transposing;
• and
• combining the subband samples and the adjusted transposed subband samples or the spectral coefficients and the adjusted transposed spectral coefficients such that a decoded output signal is obtained.