Information recording and reproducing apparatus for reducing average DC level variation

摘要

An information recording method and apparatus records information signals having data signals and synchronizing signal patterns inserted at predetermined intervals of the data signals on a recording medium with a binary level by using a coding rule without a DC free property. The synchronizing signal patterns are inserted into the data at intervals of a fixed block length and are supplied to a recording apparatus as a mark/space pattern (record signal pattern). The data are converted into the same pattern as the mark/space pattern and an accumulated value (corresponding to the average DC value) for each block length is counted. The sum and the difference of an output of a memory which stores the accumulated values from the head of the sector to the (N-1)-st block, and the accumulated value of the N-th block, are compared with each other in absolute value. When the difference is smaller than the sum, a pattern inversion circuit is operated at the head of the N-th block of the record code string to invert the polarity of the record signal pattern, and when the sum is smaller than the difference, the pattern inversion circuit is not operated and the polarity of the record signal pattern is not inverted.