Source coding enhancement using spectral-band replication

The present invention proposes a new method and apparatus for the enhancement of source coding systems. The invention employs bandwidth reduction prior to or in the encoder, followed by spectral-band replication at the decoder. This is accomplished by the use of new transposition methods, in combination with spectral envelope adjustments. Reduced bitrate at a given perceptual quality or an improved perceptual quality at a given bitrate is offered. The invention is preferably integrated in a hardware or software codec, but can also be implemented as a separate processor in combination with a codec. The invention offers substantial improvements practically independent f codec type and technological progress.