Block adaptive quantisation

摘要

A block adaptive quantisation device processes blocks of sample pairs to determine an aggregate or average value at 18. The average or aggregate value is applied to each of a number of exponent look up tables 22 to 26, which output an exponent value (E) dependent on the extent of compression required. The exponent value is split by an exponent splitter into a remainder value (R) and a shift value (S). The remainder value is used to select one of a number of divide look up tables to which the unsigned data sample is applied, and the shift value is used to apply a variable bit shift to the data sample (either before or after the division operation). <??>The divide code tables are grouped, and within each group the code tables are spaced logarithmically, as are the groups themselves. This arrangement considerably reduces the number of look up tables required for a given processor, reducing memory requirement and increasing speed. <IMAGE>