MIL-HDBK-9660B
realign the heads due to physical changes in the drive platters caused by heat expansion. During t-cal, all drive activity stops and the drive does a series of seeks. If this happens while a CD-R is being written, the disc is ruined. Some software utilities can turn t-cal off on some drives.
T-cal has become less of a problem as newer CD-R devices have larger buffers.
6. Buy the premastering software designed to go with the recorder being purchased. Premastering software converts files to the desired format (CD-A, ISO 9660 CD-ROM, etc.) and creates an image of the compact disc which is to be written. Make sure the software purchased supports the format(s) wanted.
7. Make a physical ISO image (a bit-for-bit copy of the finished CD) on a hard drive before writing rather than a virtual one (virtual requires the hard drive to not only maintain a sufficient transfer rate, but to spend time seeking files that may be on different parts of the hard disk).
8. Disable screen savers. Screen savers can interrupt the flow of data and trash the disc. Close any competing applications.
A.5.3.2 Problems with Writing to CD-R.
1. Bugs in the CD-R products themselves (not so much a problem today).
2. Finding enough conventional memory (some CD-R programs require a minimum amount of
450 KB).
3. Buffer Underrun Errors - Buffer underruns are the number one cause for creating "coffee coasters" out of blank CD-Rs. These are errors that occur when the data rate falls below the minimum during a write operation. Buffer underruns can be caused by the cache buffer not being kept full, if t-cal occurs, by screen savers, background applications, and by network activity. Packet writing curtails the occurrence of buffer underruns when recording, files to be written are grouped into packets, with each packet equal to or smaller than the recorder's buffer.
A.5.4 Final word on CD-R. Complaints continue that CD-R discs simply cannot be read. CD-R products appeared in the marketplace before the Orange Book standard was finalized. This allowed for many vendor interpretations of the CD-WO specifications. The Orange Book Part II defines the medium only, not the drives used to record it or play it. Therefore, a CD-WO drive using CD-R media not specifically designed for it may or may not be able to read the disc or append to it. This problem will continue until older model devices and early software versions have been replaced or upgraded.
A.6. CD-RW (COMPACT DISC-REWRITABLE)
Compact Disc-Rewritable (CD-RW) discs support the CD-UDF file format and have a capacity of 650
MB. An estimated 1,000 direct overwrites are possible, using phase change rewritability (PCR). Part 3 of the Orange Book specifications (released in 1994) pertains to CD-RW. CD-RW drives can read CD- ROMs, read and write CD-Rs, and read/write/overwrite CD-RWs. However, due to the medium's lower reflectivity, a disc created on a CD-RW drive can only be played on CD-RW drives, new generation CD- ROM drives, or on DVD-ROM drives. CD-RW drives cost around $1,000, with speeds beginning at 6X. Media costs average $20-$25. Due to the random overwrite function, ISO 9660 is inadequate for CD- RW.
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