DIGITAL SIGNAL COMPRESSION ENCODING WITH IMPROVED QUANTISATION

摘要

In compression encoding of a digital signal, such as MPEG2, transform coefficients are quantised with the lower bound of each interval being controlled by a parameter lambda . In the MPEG2 reference coder, for example, lambda =0.75. Because the quantised coefficients are variable length coded, improved quality or reduced bit rates can be achieved by controlling lambda so as to vary dynamically the bound of each interval with respect to the associated representation level. The parameter lambda can vary with coefficient amplitude, with frequency, with quantisation step size. In a transcoding operation, lambda can also vary with parameters in the initial coding operation.