| 摘要 |
A prediction bit pattern consisting of selected bits of the instantaneous and preceding raster scanning lines and a method for predicting a number of bits per clock pulse are described. In general, a prediction device is used before data decoding in order to increase the compression. The instantaneous bit in a bit sequence is compared with the predicted value and a one is output when the two values are not equal. An effective prediction device reduces the number of ones in a bit sequence which increases the number of zero-chain lengths which increases the performance of a run-length coding system. The bit pattern described contains bits which are close to the instantaneous bit in order to effectively predict half-tone data and neglects a number of intermediate bits in order to reduce the hardware costs. A two-stage method is also described which provides for the parallel prediction of a number of bits. A circuit for carrying out this method comprises a buffer (15) for storing the data of the preceding line and of the current line, two registers (LR1, LR2, LR3, LR4, R0, R1 and R2) for holding or storing the prediction data patterns for the preceding and instantaneous line and two PROMs (16, 17) for carrying out the two-stage prediction. <IMAGE>
|
