in digital signal recording apparatus using i - nrzi modulation for recording , the need for intermittently reading or intermittently writing buffer storage is eliminated by using parallel - bit precoding to generate the channel words that are selected between for recording . the precoders perform preceding on an accelerated basis using ripple - through integration of the alternate successive bits used to form each channel word . two precoders generate - parallel - bit channel words at a channel word rate slower by a factor of than the rate of a system clock for the i - nrzi modulation . this leaves additional time during each channel word interval to carry out a decision procedure , which determines which of the channel words generated by the two precoders is to be selected for recording . there is also sufficient additional time for completing a subsequent updating procedure , in which preceding information stored in the precoder that did not generate the selected channel word is altered , to conform to precoding information stored in the precoder that did generate the selected channel word . the parallel - bit channel words from the precoders are converted to serial - bit format for recording with a bit rate equal to that of the system clock . the parallel - bit channel words from the precoders are converted to serial - bit format with an effective bit rate that is substantially higher than that of the system clock , to provide signal for timely implementing the decision and updating procedures .