Eight-to-Fourteen Modulation

What Does Eight-to-Fourteen Modulation Mean?

Eight-to-fourteen modulation (EFM) is a data encoding technique invented by Kees A. Schouhamer Immink, which makes CDs and Hi-MD MiniDiscs highly resilient to dust, fingerprints and tiny scratches. Prior to the creation of this data encoding technique, these imperfections negatively affected retrieved data.


Techopedia Explains Eight-to-Fourteen Modulation

Eight-to-fourteen modulation modifies binary code data and allows 17 bits of data space to be used to encode 8 bits of data. The 8-bit block of data is replaced by a 14-bit codeword using a lookup table. This requires more space for data, but assures that imperfections and foreign material do not cause critical data to be missed by the optical pickup in the playback mechanism. This involves two extra zeros placed between two consecutive ones (Ten consecutive zeros are the maximum allowed between consecutive zeros.) Consistently applied, the data can be read accurately even with the disc imperfections and foreign material present. For DVDs and SACDs, a channel code called EFMPlus is used, which translates 8-bit words into 16-bit code words. This results in a 6.25 percent increase in storage capacity above that achieved by classic EFM.


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Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…