Patent ID: 8428941

Claim:
A method for lossless encoding of a source signal, using a lossy encoded data stream and a lossless extension data stream which together form a lossless encoded data stream for said source signal, said method comprising the steps: lossy encoding said source signal, wherein said lossy encoding provides said lossy encoded data stream as well as spectral whitening data; correspondingly lossy decoding said lossy encoded data, thereby reconstructing a standard decoded signal and, using said spectral whitening data, constructing from said standard decoded signal a superior quality decoded signal; forming a difference signal between said source signal and said superior quality decoded signal and lossless encoding said difference signal; packing said encoded difference signal together with said spectral whitening data to form said lossless extension data stream, wherein said spectral whitening data are generated by: processing said source signal in an analysis filter bank and quantizing its output signal and forming the difference signal between the analysis filter bank output signal and the quantization output signal, wherein said quantizing is controlled by a perceptual model calculator; quantizing said difference signal thereby controlling this further quantization such that the difference signal between the input and the output of said further quantization approaches a white spectrum, whereby the output signal of said further quantization forms said spectral whitening data, and wherein said further quantization is controlled by an adaptation controller that checks the current bit rate of said spectral whitening data and, if said current bit rate exceeds a pre-determined threshold value, sets an escape signal; and wherein said lossless encoding of said difference signal uses an entropy encoder, the input signal of which passes through an LPC de-correlator only if said escape signal is set.