Eight-to-Fourteen Modulation, or EFM as it is abbreviated, is an encoding
technique used by
CDs and provides a way of
countering errors by encoding a
byte into 2 bytes. Using
EFM the
data is broken into 8-
bit
blocks (bytes). Each 8-bit block is translated into a corresponding 14-bit
codeword using a predefined lookup table. The 14-bit codeword are chosen so that
binary ones are always separated by a minimum of two
and a maximum of ten binary zeroes. EFM maximizes the number of transitions
possible with an arbitrary pit and land length which is determined by the
wavelength of the laser light used to read the data. Eight-to-Fourteen
Modulation uses an
RLL encoding
scheme.
