A new high-speed digital interface for transmitting video information over various transmission media including terminated copper wires such as twisted-pair wires and fiber optical cable is described. The significance of this new interface is that (1) it only uses a small number of data channels with all timing and control data embedded in data transmission, (2) it uses a transition controlled binary DC balanced coding for reliable, low-power and high-speed data transmission, (3) it uses low-swing differential voltage which minimizes EMI, and (4) it can be implemented in low-cost scaleable CMOS technology as a megacell or standard IC. The high-speed digital interface incorporates a method and apparatus for producing a transition-controlled, DC-balanced sequence of characters from an input sequence of data bytes. The bits in each of the data bytes are selectively complemented in accordance with the number of logical transitions in each data byte in order to produce selectively complemented data blocks. A cumulative disparity is then determined between the logical values of different type included within ones of the selectively complemented data blocks previously encoded into characters. In addition, a current disparity in a candidate character associated with a current one of the selectively complemented data blocks being encoded is also determined. The candidate character is assigned to the current one of the selectively complemented data blocks if the current disparity is of a polarity opposite to a first polarity of the cumulative disparity. Alternately, the complement of the candidate character is assigned to the current one of the selectively complemented data blocks if the current disparity is of the first polarity. In a high-transition mode of operation, the bits within data blocks including less than a minimum number of logical transitions are selectively complemented so that each such selectively complemented data block includes in excess of the minimum number of logical transitions. In a low-transition mode of operation, the bits within data blocks having more than a predefined number of logical transitions are selectively complemented so that each such selectively complemented data block includes less than the maximum number of logical transitions.