Cross-interleaved Reed–Solomon coding

In thecompact discsystem,cross-interleaved Reed–Solomon code(CIRC) provides error detection anderror correction.CIRC adds to every three databytesoneredundantparitybyte.

Overview

Reed–Solomon codesare specifically useful in combating mixtures of random and bursterrors.CIRC correctserror burstsup to 4000 data bits in sequence (2.5 mm in length as seen on CD surface) and compensates for error bursts up to 12,000 bits (7.5 mm) that may be caused by minor scratches.

Characteristics

• High random error correctability
• Long burst error correctability
• In case the burst correction capability is exceeded,interpolationmay provide concealment by approximation
• Simple decoder strategy possible with reasonably-sized externalrandom access memory
• Very high efficiency
• Room for future introduction of four audio channels without major changes in the format (as of 2024, this has not been implemented).

Interleave

Errors found incompact discs(CDs) are a combination of random and burst errors. In order to alleviate the strain on the error control code, some form of interleaving is required. The CD system employs twoconcatenatedReed–Solomon codes, which areinterleaved cross-wise.Judicious positioning of thestereochannels as well as the audio samples on even or odd-number instants within the interleaving scheme, provide the error concealment ability, and the multitude of interleave structures used on the CD makes it possible to correct and detect errors with a relatively low amount of redundancy.

See also

• Multiplexing
• Parity (mathematics)
• Parity (telecommunication)
• Checksum