Showing papers on "Run-length encoding published in 1980"

Method and apparatus for adaptive facsimile compression using a two dimensional maximum likelihood predictor

Abstract: Data compression, for either a storage or transmission, of facsimile information is effected employing a two dimensional, non-contiguous prediction matrix. A data stream representing the data to be compressed is input to a buffer which is of a size to store sufficient information for prediction purposes. A predictor is responsive to the buffer for producing a predicted data representation from a plurality of data units comprising a two dimensional matrix. A selector is responsive to the data unit employed in the prediction process for making a select/non-select determination. For those data units which are selected, a comparator compares the predicted status of the data unit with the actual status of the data unit. At least one run length encoder is responsive to the comparator for run length encoding successive correct predictions and a following incorrect prediction. An output buffer is provided for storing the run length encoded output of the run length encoder as well as representations of the non-selected data units. By using plural run length encoders, each can be optimized for the encoded data by correlating prediction difficulty with code length, i.e., easy predictions are encoded by long code words and hard predictions are encoded with short words. Further, the unselected class data units correspond to most difficult predictions and these are not coded.

Data decompressor circuit

Abstract: A circuit and method for decompressing video subsequent to its prior compression for transmission or storage. The circuit assumes that the original video generated by a raster input scanner was operated on by a two line one shot predictor, coded using run length encoding into code words of four, eight, or twelve bits and packed into sixteen bit data words. This described decompressor, then, unpacks the data by joining together the sixteen bit data words and then separately the individual code words, converts the code words into a number of all zero four bit nibbles and a terminating nibble containing one or more one bits which constitutes decoded data, inspects the actual video of the preceeding scan line and the previous video bits of the present line to produce depredictor bits and compares the decoded data and depredictor bits to produce the final actual video.