Apparatus and method for variable-length coding

摘要

A variable-length coding apparatus for dividing an input signal into a plurality frequency bands, each comprising coefficient data, quantizing the coefficient data for each frequency band, and coding the quantized coefficient. This apparatus comprises a zero judge means for judging whether each coefficient data is zero or not; a code table storing code words used whens coding of the coefficient data is performed; a coefficient coding means for coding the coefficient data using the code table when the zero judge means judges that the coefficient data is not zero; a zero counting means for counting the number of successive zero, when the zero judge means judges that the coefficient data is zero, until the zero judge means judges that the coefficient data is not zero; a group table for managing successive zero lengths (zerorun lengths) of all coefficient data in each frequency band, wherein one table number is assigned to one zerorun length and one table number is assigned to one group of a plurality of zerorun lengths; a zerorun grouping means for deciding a group number corresponding to the successive zero number counted by the zero counting means, using the group table; and a zerorun coding means for coding the successive zero number, using the group number decided by the zerorun grouping means, and the code table. In operation, the coefficient data to be zeroruns are classified into groups according to the data size, using the group table and, thereafter, the coefficient data are coded. Therefore, even a long zerorun can be compressed with high efficiency using a small-sized zerorun table.