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Method for Determining Compact Disk-Recordable/Compact Disk-Read Only Memory Quality During Verify

IP.com Disclosure Number: IPCOM000118490D
Original Publication Date: 1997-Feb-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Coburn, GH: AUTHOR [+3]

Abstract

Disclosed is a method for determining the quality of a written Compact Disk-Recordable (CD-R) or a Compact Disk-Read Only Memory (CD-ROM) during read verify by measuring the time to read the disc or data rate compared to the expected time or data rate. The ratio or difference of the measured to expected time or data rate gives a measure of the quality of the disc.

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Method for Determining Compact Disk-Recordable/Compact Disk-Read
Only Memory Quality During Verify

      Disclosed is a method for determining the quality of a written
Compact Disk-Recordable (CD-R) or a Compact Disk-Read Only Memory
(CD-ROM) during read verify by measuring the time to read the disc or
data rate compared to the expected time or data rate.  The ratio or
difference of the measured to expected time or data rate gives a
measure of the quality of the disc.

      By doing a read or Cyclic Redundancy check of a CD-R or CD-ROM
on an inexpensive player, it is very difficult to tell what the
quality of that disc is in terms of readability.  This is because
there are powerful error correction and retry algorithms built into
the system that are invoked when errors are detected, and this allows
the drive to read the disc even when the quality is very bad.

      An objective measure of the quality of the disc for readability
is obtained by measuring the time it takes to read the disc or parts
of the disc and comparing this to the expected time.  The expected
time is calculated by dividing the amount of data read by the rate of
the drive, which is a fixed rate depending on the model of the drive.
The actual time for the read is measured by the computer by simply
timing from the command issued by the computer to the reader to read
the data  to the time when the read of the data is complete.

      The ratio of the measured time divided by the expected...