Block Error Rate QA measurement for CD s, which, according to the Red Book, must be not more than 220 block errors per second.

The “raw” digital error rate, usually measured off media before any error correction, which indicates the number of data blocks that have any bad symbols (bytes) at the C1 error-correction stage. The reason that BLER is a good indicator of overall disc quality is that it essentially indicates the number of errors of all types, since errors that are uncorrectable at C1 get passed to C2 for possible interpolation. The Red Book specifies a maximum BLER of 220 per second, averaged over 10 seconds. Top-quality discs used as masters for replication, should have an average BLER of below 10. A peak of 100 bad-data blocks per second is acceptable for CD-ROM, but an average BLER of 50 per second over the entire disc is a good cut-off point to ensure data integrity. Audio CDs may play with a high BLER, but when such discs are used as masters for replication purposes, these initial media errors are passed on to the final pressed discs, compounding error correction problems, a factor in reproduced sound quality. A high BLER indicates that their longevity may be limited, and that there may be problems in playing reliably on all types of readers. (See CIRC)

Block Error Rate. A measure of the average number of raw channel errors when reading or writing a disc.