APPARATUS FOR ACCESSING CONTEXT MEMORY IN JBIG DECODER

摘要

PURPOSE: An apparatus for accessing a Context memory in a JBIG decoder is provided to obtain a Context value between the two extracted context values before previous pixel decoding, thereby minimizing time spent in decoding a pixel. CONSTITUTION: The apparatus for accessing a Context memory in a JBIG(Joint bi-level image experts group) decoder comprises: a Context memory which accesses a probability estimation table using a Context value of 9 bit input from a decoder and a Context value of a predictable 10th bit and outputs an MPS(More probable symbol) and ST having different values from each other, the MPS and ST having a number corresponding to a kind of the predictable 10th bit; a first multiplexer which selects and outputs an MPS value corresponding to a Context value of 10th bit input from the decoder among the MPS values provided from the Context memory; a second multiplexer which selects and outputs an ST value corresponding to a Context value of 10th bit input from the decoder among the ST values provided from the Context memory; and a ROM(Read only memory) which accesses an inner table using the ST value output from the second multiplexer and outputs an LSZ(Less probable symbol size) to the decoder.