Information signal encoding apparatus, encoding method thereof, information signal decoding method, and information signal record medium thereof

An information signal encoding apparatus for generating at least first hierarchical data and second hierarchical data by an input digital information signal, encoding the first hierarchical data and the second hierarchical data, and transmitting the encoded data, the apparatus comprising:

• means for forming the second hierarchical data with a resolution lower than the first hierarchical data;
• means for predicting the first hierarchical data by the second hierarchical data;
• means for forming difference signals representing differences between the predicted data and the first hierarchical data;
• means for block segmenting the difference signals;
• means for detecting a maximum value and a minimum value of the difference signals of each block;
• mode determining means for determining whether or not the range of levels of the difference signals of each block crosses 0 corresponding to the maximum value and the minimum value, assigning a first quantizing mode when the range of the levels crosses 0, and assigning a second quantizing mode when the range of the levels does not cross 0;
• quantizing means for quantizing the difference signals with a predetermined number of bits smaller than the original number of bits in the first quantizing mode and for quantizing the difference signals with a predetermined number of bits smaller than the original number of bits and performing a code conversion for decreasing the number of bits in the second quantizing mode;
• and
• transmitting means for transmitting information identifying the first quantizing mode and the second quantizing mode and output data of said quantizing means.