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| Explaining Common CD Errors |
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By
Mastering Engineer, Bob Speer
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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. BLER is
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 BLER 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. A CD player may correct
them, then again, it may not.
C2 errors are usually an indication of poor media quality,
or a CD writer's failure to produce a quality burn (see
conclusion).
CU Errors.
CU Errors refer to uncorrectable errors that are present
after C2 error correction. No CU errors are allowed in
a recorded disc. Generally, discs with CU errors cannot be
played at all 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 10
C1 errors per second. That's 4.5% 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. Mastering isn't just 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 and
provide you with full documentation on it's quality |
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