Abstract: Black terminated white runs of a binary video signal having a raster scan format with some scan lines of difference modulated picture elements and other scan lines of unmodulated picture elements are run length encoded using a block length multiple plus run length residue code format, whereby runs in excess of a predetermined block length are represented by block length multiple codes plus, for any runs which are not integer multiples of the block length, run length residue codes. Shorter black terminated white runs are converted into run length residue codes, and unterminated white runs are converted into end-of-line codes which distinguish between scan lines of difference modulated and unmodulated picture elements.

Abstract: A binary video signal having a raster scan format is fractionally difference modulated to limit the inter-scan line propagation of decoding errors. The fractionally difference modulated video signal is then encoded using different end-of-line message codes to distinguish between unterminated white runs of difference modulated and unmodulated picture elements, thereby providing a scan line-by-scan line indication of whether the picture elements are difference modulated or not and avoiding the need for distinguishing between the difference modulated and unmodulated picture elements while converting black terminated white runs and non-terminating black picture elements into run length message codes and individual message bits, respectively.

Abstract: A fractionally difference modulated binary video signal having a raster scan format and containing some scan lines of difference modulated picture elements and other scan lines of unmodulated picture elements is compressed by a truncated run length encoder which converts black terminated white runs into run length message codes, non-terminating black picture elements into individual message bits, and unterminated white runs into end-of-line message codes. No distinction is made between the difference modulated and unmodulated picture elements while generating the run length message codes and the individual message bits, but different end-of-line message codes are generated in response to the unterminated white runs of difference modulated and unmodulated picture elements, thereby providing a scan line-by-scan line indication of whether the picture elements are difference modulated or not.