Dynamic bit inversion for reduced overhead dc-balanced coding

Abstract

Embodiments of the present disclosure relate to dynamic bit inversion for reduced overhead DC balanced coding. A computed polarity bit controls whether or not bits are inverted and is inserted in the data stream whenever DC balancing is triggered. Fixed overhead codes are commonly used to provide DC balance. However, one can do much better than a fixed overhead code by observing that many data streams are inherently DC balanced, and a random data stream does not need a correction to its disparity every byte. For example, a string of alternating 1s and 0s is naturally DC balanced. The dynamic bit inversion code has the property that overhead is inserted only when needed. For a string of alternating 1s and 0s there is no overhead. In an example, the overhead is about 4%, about ⅓ that of a fixed overhead 8 bit/9 bit code with the same maximum output disparity.