| 摘要 |
In compression encoding of a digital signal, such as MPEG 2, transform coefficients are quantised with the lower bound of each interval being controlled by a parameter #. In the MPEG 2 reference coder, for example, # = 0.75. Because the quantised coefficients are variable length coded, improved quality or reduced bit rates can be achieved by controlling # so as to vary dynamically the bound of each interval with respect to the associated representation level. The parameter # can vary with coefficient amplitude, with frequency, with quantisation step size. In a transcoding operation, # can also vary with parameters in the initial coding operation. |
