| 摘要 |
For selectively carrying out predictive encoding of an original pattern of a first tone on a background of a second tone and a thinned pattern having, in effect, the first tone on its background corresponding to the second tone, a device comprises a predictor responsive to a set of sample pulses representative of a few picture elements selected from those sampled from the original pattern and its background for producing each of prediction error pulses of a sequence, another predictor responsive to a set of pre-processed pulses representative of several picture elements selected from those sampled, in effect, from the thinned pattern and its background for producing each of error pulses of another sequence, a selector for selecting one of the original and the thinned patterns and consequently one of the predictors to produce a selection code indicative of the selected predictor, and an encoder for encoding the error pulses produced by the selected predictor into an encoded signal including the selection code. Preferably, each predictor is operable to produce for each error pulse a mode code indicative of one of two or more groups into which all allowable permutations of at least one of the two tones of the selected picture elements are classified and, in comsideration of which, codes are predetermined for all possible durations of same error pulse. The encoder uses the mode code for the respective error pulses in selecting some or all of the predetermined codes and arranges the selected codes in a predetermined order.
|
