Copyright OSTA 2001
All rights reserved.


Author's Notes
Physical, Logical and File
System Standards

> Recording Hardware
Recording Software
Recording Speed
Physical Compatibility
Disc Size and Capacity
Audio Recording
Digital Pictures on CD
Duplication, Replication
and Publishing
Disc Labeling
Disc Handling, Storage
and Disposal

Disc Longivity
Disc Testing and

Disc Construction and

Appendix A - Further
Reading and Resources

Appendix B - Industry
and Product Contacts
About OSTA
About the Author

  CD-Recordable Glossary


  White Papers

  Archived Storage (COSA)

  Optical Websites


What types of devices write CD-R and CD-RW discs?
All CD-R and CD-R/RW recorders write CD-R discs but only CD-R/RW recorders write both CD-R and CD-RW discs. Many DVD recorders also come combined with CD-R and CD-RW writing functions but be aware that there are exceptions. If in doubt, consult with the hardware manufacturer.

Are there audio CD recorders available that connect to stereo systems?
Several manufacturers offer consumer and professional audio CD recorders that connect, like cassette decks, to conventional stereo systems. Typically, they will record to CD-R or CD-R and CD-RW discs from either digital (CD, DAT, MD, etc.) or analog (cassette, vinyl record, radio, etc.) sources.

What do the numbers describing a CD-R or CD-R/RW recorder mean?
Manufacturers typically use a sequence of two, three or four numbers to express the maximum writing and reading speeds of a recorder. The generally accepted industry convention for a CD-R recorder has been for the first figure to indicate CD-R writing speed followed by CD reading speed for CD-R and prerecorded (pressed) data CDs. For a CD-R/RW recorder the first number usually indicates CD-R writing speed followed by CD-RW writing speed and then by the CD reading speed. In the case of a combination recorder a fourth number is included to indicate DVD reading speed. As examples, 8x12 usually means 8x CD-R write and 12x CD read while 48x12x48 typically indicates 48x CD-R write, 12x CD-RW write and 48x CD read. And for a combination recorder 24x10x40x12 denotes 24x CD-R write, 10x CD-RW write, 40x CD read, and 12x DVD read.

What types of CD-R and CD-R/RW recorder configurations are available?
Whether for PC, Mac or UNIX computers in desktop, laptop or notebook form, CD-R and CD-R/RW recorders are available in a wide variety of configurations to suit most needs. Several industry standard interfaces are available including SCSI, EIDE/ATAPI, Parallel, USB and IEEE 1394 for either internal or external recorder connection.

The Enhanced Integrated Drive Electronics/ATA Packet Interface (EIDE/ATAPI) is the most popular method for connecting CD and DVD-ROM drives and hard disks as well as CD-R and CD-R/RW recorders to a computer. Since most computers already have EIDE/ATAPI built-into their motherboards no additional interface card is necessary. These devices are normally installed internally but many external recorders are actually EIDE/ATAPI models that use bridge technology to convert them to SCSI, USB or IEEE 1394 interfaces.

The Small Computer Systems Interface (SCSI) or “scuzzy” interface is a high performance and flexible method of connecting to a computer many peripherals including scanners, CD and DVD-ROM and hard drives as well as CD-R and CD-R/RW recorders. In addition to long cable lengths, SCSI allows for both internal and external attachments. Some computers already have SCSI built-into their motherboards, but, more often than not, a SCSI interface card is required. Depending upon the specific product, a SCSI card may or may not be included with the CD-R/RW recorder bundle.

CD-R/RW recorders that make use of a parallel interface connect to the computer using the same parallel port used by a printer and can only be installed externally. Depending upon the product, some recorders have pass-through arrangements allowing both a printer and recorder to be connected to the computer at the same time.

The Universal Serial Bus (USB) is used to connect many types of peripherals to a computer including joysticks, mice, keyboards, printers, scanners and external CD-R and CD-R/RW recorders. Since USB is a plug and play interface computers do not have to be rebooted when a recorder is attached as these devices are automatically recognized by the system. And USB has been updated several times to accommodate the demands of increasingly faster peripherals. USB 1.1 interfaces are built into the motherboards of many systems and generally permit up to 4x CD-R/RW writing and 6x reading speeds. USB version 2.0 is an updated version of the specification allowing greater performance but typically requires an additional interface card. Most USB 2.0 CD-R/RW recorders are backward compatible and can operate at reduced speed when connected to older USB 1.1 systems.

IEEE 1394
Popularly known by trade names such as FireWire and i.LINK, IEEE 1394 is a high performance plug and play interface commonly used to connect computers to external hard disk drives and CD-R and CD-R/RW recorders as well as consumer electronics devices like digital camcorders, televisions and game consoles. IEEE 1394 interfaces come standard on many Macintosh systems and on some brands of PCs but, more often than not, an interface card is required.

What is buffer underrun?
An important point to remember about CD-R and CD-RW recording is that information must be written to a blank disc in a continuous stream. To help smooth out the flow in the data transfer rate from the computer, the recorder employs a memory buffer which, like a reservoir storing water for use when it is needed, caches data for when it is required by the recorder. As with a water reservoir, the key is to always have enough data in the buffer to satisfy the demands of the recorder, even if, from time to time, the computer can’t supply the needed amount of information. If the buffer runs dry (a “buffer underrun”) the disc is ruined.

How can buffer underrun be prevented?
Most current computer recorders incorporate advanced buffer underrun protection technology to eliminate buffer underruns but for units not so equipped there are a variety of common sense techniques that can be used to help minimize the possibility. These include ensuring that the recorder and writing software are properly configured, defragmenting the operating system and data source hard disk partitions, disconnecting from any networks, closing all other programs and disabling background tasks such as power managers and anti-virus software. In more stubborn cases additional measures to be considered include reducing writing speed as well as enabling the recording software to build a temporary image on the hard disk drive before recording.

What is buffer underrun protection?
In order to keep pace with the demands of ultra speed writing, recorder manufacturers have created new technologies for preventing buffer underruns. A recent innovation now known by a multitude of different trade names, buffer underrun protection utilizes a combination of recorder hardware, firmware and writing software to accomplish its task.

Buffer underrun protection functions by constantly monitoring the amount of data in the recorder’s buffer during the writing of a disc and suspends recording if the amount available falls below a predetermined threshold. Once the buffer again accumulates sufficient data the recorder resumes writing precisely where it left off. Obviously, it’s critical to leave as small a gap as possible between the previous and newly recorded sections so as to avoid producing an unreadable segment on the disc. Generally speaking, the gap length has been found to be well within the error correction capabilities of CD and DVD-ROM drives and players. As the technology matures the gap will continue to shrink.