Abstract: An improved video display system is provided in which two color images are combinable in a dynamic and self-determining fashion to provide improved contrast, comprehension and display versatility. Two separate video signals that are to be used in generating a single display are converted into sequences of digitally encoded picture elements (pixels). Control signals are generated that are dependent upon the data content of the elements in at least one of the sequences, and these signals are used to govern the mode of combination of the two video signals for individual pixel sets. For example a first video signal of digital character and having varying pixel intensity may be transformed into color values for a first pseudocolor display. A second video signal, derived from an analog source, is digitized and is also transformed into pseudocolor, concurrent with the dynamic generation in real time of the data dependent control signals.

Abstract: There is disclosed a method and means for compacting (encoding) and decompacting (decoding) binary bit strings which avoids the blocking of string elements required by Huffman coding and the ever increasing memory as is the case in simple enumerative coding. The method and means arithmetically encodes successive terms or symbols in a symbol string s=a.sub.i a.sub.j . . . , in which each new term a.sub.k in a source alphabet of N symbols gives rise to a new encoded string C(sa.sub.k) and a new length indicator L(sa.sub.k). The method and means comprises the steps of forming L(sa.sub.k) from the recursion L(sa.sub.k)=L(s)+l(a.sub.k), where l(a.sub.k) is a rational approximation of log.sub.2 1/p(a.sub.k), p(a.sub.k) being the a'priori probability of occurrence of a.sub.k, and l(a.sub.k) being so constrained that the Kraft inequality is satisfied: ##EQU1## AND FORMING C(sa.sub.k) from the recursion C(s)+[P.sub.k-1 2.sup.L(sa.sbsp.k.sup.) ],where: ##EQU2## AND WHERE P.sub.