8-9 Block Code: A DC-Free Channel Code for Digital Magnetic Recording

Author(s): H. Yoshida ; Y. Hashimoto ; T. Shimada
Publisher: Society of Motion Picture and Television Engineers
Publication Date: 1 February 1983
Conference Location: San Francisco, CA, USA
Conference Date: 4 February 1983
Page(s): 184 - 195
ISBN (Paper): 978-1-61482-913-3
DOI: 10.5594/M00605



Channel coding is generally employed in digital magnetic recording to match certain properties of the coded sequence to the channel characteristics of the recorder. Since magnetic recorders are incapable of reproducing very low frequencies or dc content, dc-free channel codings have been primarily employed in the digital VTR's, for example 8-10 block code [1], M2 [2], interleaved NRZI* [3,4], tri-level code [5] and so on. This paper describes the dc-free 8-9 block coding. The coding strategy is discussed in detail with examples of three practical methods. The properties of the 8-9 block code have been investigated both by hardware experiments and by computer simulation. The performance of this channel code is found to be better than that of the 8-10 block code when it is applied to an experimental digital VTR without any major modification to the recording and playback circuits.