In the EFM process, 8 bits are converted into a bit pattern of 14 bits, with a minimum of three and a maximum of eleven zeros between the two ones. Fourteen bits are required for this concept, in which a byte with its 256 possible combinations is represented without two ones following each other.
The EFM method is implemented in CD drives. A variant of this method is EFM-Plus (EFM+), which is used in DVDs and uses 16-bit words and low frequency suppression for increased data security. EFM-Plus has 3 control bits per byte.