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Member
Audio
Engineering
Society |
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| digital Errors And cd
Quality |
Write
Errors
Write errors can result in CD failure. CD
manufacturers will reject a master disc if write errors
exceed their specifications.
There are three common errors types that affect CD
quality. They are C1, C2, and CU.
C1
Errors
C1 Errors refer to the block error rate (BLER), which
consists of bit errors at the lowest level. C1
errors are always expressed
in errors per second. All CDs and CDRs contain C1
errors. They are a normal result of the write
process. However, the
maximum C1 error rate for a
quality recording is an average of 220 errors per second
based on 10 second samples.
C2
Errors
C2 Errors refer to bytes in a frame (24 bytes per
frame, 98 frames per block) and is an indication of a CD
player's attempt to
use error correction to recover lost
data. C2 errors can be serious. In theory, a CD player
should correct them. C2 errors
are usually an indication of poor media quality,
or the failure of a CD burner to produce a quality burn (see
conclusion).
CU
Errors
CU Errors refer to uncorrectable errors that are
present after error correction. No CU errors are
allowed in a recorded disc.
Generally, discs with CU
errors will not play properly because they contain data
that cannot be recovered.
When errors are the result of physical damage to the disc,
CIRC Logic - Cross Interleaved Reed-Solomon Code, is used
to
identify and correct random errors, which allows some
damaged CDs to play without any distinguishable
difference.
Conclusion
CD replicators consider a disc with an average
of 220 C1 errors per second, "a good quality
disc." Typically, our masters
average
less than 1 C1 error per second with absolutely no C2 or
CU errors. We have our own standard which states
that in
addition to no C2 or CU errors, we will not ship
any disc that averages more than 2 C1 errors per
second. That's .009% of the
maximum allowed for a
good quality disc. This provides you with an
excellent master of the highest quality. If you're
going to
have your CD professionally replicated, there
is no substitute for a quality master provided by a
professional mastering facility.
While mastering is about
EQ, dynamics, song levels, etc., it's also about
providing you with a low error master that will be
accepted by CD replicators. We test each master for
errors before it leaves our facility to insure disc
quality. |
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