Editing Reed–Solomon error correction (section)

===Data storage===
Reed–Solomon coding is very widely used in mass storage systems to correct
the burst errors associated with media defects.

Reed–Solomon coding is a key component of the [[compact disc]]. It was the first use of strong error correction coding in a mass-produced consumer product, and [[digital audio tape|DAT]] and [[DVD]] use similar schemes. In the CD, two layers of Reed–Solomon coding separated by a 28-way [[convolution]]al [[interleaver]] yields a scheme called Cross-Interleaved Reed–Solomon Coding ([[Cross-interleaved Reed–Solomon coding|CIRC]]). The first element of a CIRC decoder is a relatively weak inner (32,28) Reed–Solomon code, shortened from a (255,251) code with 8-bit symbols. This code can correct up to 2 byte errors per 32-byte block. More importantly, it flags as erasures any uncorrectable blocks, i.e., blocks with more than 2 byte errors. The decoded 28-byte blocks, with erasure indications, are then spread by the deinterleaver to different blocks of the (28,24) outer code. Thanks to the deinterleaving, an erased 28-byte block from the inner code becomes a single erased byte in each of 28 outer code blocks. The outer code easily corrects this, since it can handle up to 4 such erasures per block.

The result is a CIRC that can completely correct error bursts up to 4000 bits, or about 2.5&nbsp;mm on the disc surface. This code is so strong that most CD playback errors are almost certainly caused by tracking errors that cause the laser to jump track, not by uncorrectable error bursts.<ref>{{Citation |first=K. A. S. |last=Immink |author-link=Kees Immink |contribution=Reed–Solomon Codes and the Compact Disc |editor1-first=Stephen B. |editor1-last=Wicker |editor2-first=Vijay K. |editor2-last=Bhargava |title=Reed–Solomon Codes and Their Applications |publisher=[[IEEE Press]] |year=1994 |isbn=978-0-7803-1025-4 }}</ref>

DVDs use a similar scheme, but with much larger blocks, a (208,192) inner code, and a (182,172) outer code.

Reed–Solomon error correction is also used in [[parchive]] files which are commonly posted accompanying multimedia files on [[USENET]]. The distributed online storage service [[Wuala]] (discontinued in 2015) also used Reed–Solomon when breaking up files.