Feurio Frequently Asked Questions - Definition:
C2 Errors
- What are C2 errors?
CD-ROMs have different levels of error recognition and correction. One level
of error correction is the "C2 error correction". C2 errors can usually correctable
, i.e. the CD-ROM itself is capable of fixing a certain number of C2 errors.
If to many C2 errors occur, the CD-ROM will interpolate the missing data (i.e.
it "guesses" the bad data). Usually correctable C2 errors are not reported (because
the errors should usually have been fixed). If to many C2 errors occur (i.e.
the errors are not further correctable), most CD-ROMs report a read error. (Some
CD-ROMs interpolate silently and only if bigger parts are not readable they will
report a read error). There are CD-ROMs that can return additional information
where C2 errors occurred and if they were corrected by the CD-ROM.
- What does C2 errors mean?
As described above C2 errors normally are correctable error - they are no "real"
errors then rather "warnings". On one hand C2 errors are warnings, that there
is something wrong with the inserted CD, i. e. the CD is probably dirty or scratched.
In most cases it helps cleaning the CD and the C2 errors will disappear. If the
C2 errors do NOT disappear this usually means that the CD is slowly "ceasing"
- it is strongly recommended to backup the CD!
On the other hand some CD-ROMs do NOT report normal error messages even if the
data haven't been fixed correctly. In this case C2 errors are warnings for possible
incorrect (or rather: no longer matching the original) data. Furthermore the
error correction - as every error correction - can only fix errors correctly
with a certain probability - so if too many errors do occur the error correction
might fix an error incorrectly (although this is very unlikely).
Summary: C2 errors are a sign for a damaged or dirty CD; depending on the CD-ROM
C2 errors can also indicate possible wrong data.
- Counting C2 errors:
The C2 error correction works byte-per-byte, that is: 1 C2 error per byte - 4
C2 errors per sample - 2352 C2 errors per sector and a maximum of 176.400 C2
errors per second.
- C2 errors and Feurio:
Feurio!® can - if supported by the CD-ROM - read C2 error information from
the CD-ROM and analyse it. Feurio! can report a C2 error immediately or display
the number of C2 errors after the track/ image is read. Analysing C2 errors can
be activated under: "Program" -> "Program Parameters" -> "Device Parameters"
-> "Special Parameters" -> "C2 Error Messages".
- C2 errors with data CDs
The above statements and texts ONLY apply to audio CDs! Data CDs have an additonal
error correction level; a C2 error correction is performed as well, but of course
incorrect data will not be interpolated. The C2 error information are used as
a evidence for possible errors for the "higher" levels of error correction. The
"higher" error correction is much more expensive than the C2 error correction
and can correct substantial more errors with higher certainty; from there a data
CD has a maximum size of 650 MB instead of 750 MB (for an audio CD) - the remaining
100 MB are error correction information. Therefore analysing C2 error correction
for data CDs would be a silly thing, because errors can be detected and fixed
much better by the "higher" levels of the error correction. From there reading
C2 error information with data tracks is not intended for Feurio!®.
- Which drives support reading C2 error information?
Unfortunately only a few drives support reading C2 error information correctly.
You can find a list of CD-ROMs on the Feurio! homepage on the page "Supported
CD-ROMs" ( HYPERLINK "http://www.feurio.com/English/cd_roms/" 00d0c9ea79f9bace118c8200aa004ba90b02000000170000002700000068007400740070003a002f002f007700770077002e00660065007500720069006f002e0063006f006d002f0045006e0067006c006900730068002f00630064005f0072006f006d0073002f000000e0c9ea79f9bace118c8200aa004ba90b4e00000068007400740070003a002f002f007700770077002e00660065007500720069006f002e0063006f006d002f0045006e0067006c006900730068002f00630064005f0072006f006d0073002f000000http://www.feurio.com/English/cd_roms/);
all CD-ROMs that have a "Yes" in the column "C2 error" can read C2 errors. Note:
CD-ROMs that have a "No" in this column might support reading C2 errors as well
- simply try it. Important: We've already found CD-ROMs that are capable of reading
C2 errors, but return faulty audio data when the C2 error correction is activated
- of course this is not the object of the exercise. Obviously some CD-ROMs still
have bugs in the firmware. If the C2 error correction is used with an unknown
CD-ROM, the reading quality should be checked once more (device test).
Who wants to be sure should read the track without C2 error correction first
and with activated C2 error correction afterwards and then compare the two tracks
with each other. Unfortunately some CD-ROMs do not support reading C2 errors
according to the appropiate standards. We got the following answer from a manufacturer
to our question about reading C2 errors: "You can return all errors. But the
codes are top secret and I would have to kill you if I tell you." So if you should
attach great importance to "perfect audio reading" with C2 errors, you have to
chose a CD-ROM that is marked as "C2 error capable" in the list at the moment.
- Automatic recovery/ Reducing the read speed after C2 errors?
For additional information see: "Automatic recovery/
reducing the read speed after C2 errors?"
For additional information see:
Frequently asked questions - Definitions
Frequently asked questions - Main page
You are the 521. visitor of this page (today: 1)