METHOD FOR DATA CODING

Numerical data in a two-dimensional distribution for encoding picture data or voice data at high efficiency is divided into blocks being not equal in length depending on an amount of variation of each numeric data. The numeric data within the divided blocks is converted into data corresponding to an apex of each block, and the converted data is encoded into tree-structure data. Image data is divided into blocks being not equal in length depending on amount of variation of brightness, and the brightness within the divided blocks is converted into data corresponding to an apex of each block, and the converted data is encoded into tree-structure data. Range of values to be taken by data is divided into a range of normal values and a range of abnormal values, and a short bit number is assigned to the quantizing level in the range of normal values and a long bit number is assigned to quantizing level of other data, thereby the variable length coding at two steps is performed.