CD CD-R CD-RW writing
CD-Recordable is compact disc technology that allows users to create their own CDs. This is done by means of a recording system that uses “write once” optical discs standardized by Philips and Sony and a CD recording device that is connected to a host system. The recording process is controlled by software.
The principal purpose of multiple sessions is to allow additional data to be appended to a previously recorded disc. A session is defined as a data section including lead-in, program data and lead-out. A CD-R recorder that supports multisession can write a disc that will have multiple sessions linked together so that any multisession supported CD reader can access the data, whether it was written in the first session or subsequent session. The number of sessions per disc is limited to 99. The benefit of multisession CD writing is that you can fully use the total available space on the CD.
The birth of the Compact Disc was made possible in 1982 by Philips and Sony. This was primarily an Audio CD for digital audio. The Redbook (Philips & Sony 1982) defines the Audio CD (CD-DA), the Yellowbook (Philips & Sony 1984) defines the specifications of the CD-ROM. For the use of audio, video and animation in programs the specifications were extended to CD-i.
The Photo CD was developed by Kodak and Philips. To read a PhotoCD requires a special PhotoCD player, a CD-i player or a CD-ROM drive in a computer.
The VideoCD requires a CD-ROM/XA drive. A CD-ROM can hold around 70 minutes or more of video footage. The VideoCD standard for linear video was defined in 1993 by Philips, Sony and JVC. This standard is the successor of JVC KaraokeCD. In 1994 Philips, Sony, Matsushita and JVC defined the VideoCD version 2.0 format. This specification allows more interactivity and is suitable for interactive applications.
There are two types of Read/Write disc: WORM (Write Once/Read Many) and CD-RW (CD Re-Writeable).
The recording speed of a CD-R
The speed measurement of a CD recorder is how fast it can record data to blank CD-R media. Speed designators such as “4x” “20x” and “50x” are multiples of the original playback speeds of first generation CD-ROM players. For a CD-ROM player or CD recorder, a 1x speed translates to 153,600 bytes per second. This is rounded to 150K per second. So a “2x” recorder records at 300K per second, and a “50x” records at 7500K per second. There are some variations in measuring speed because there are no recording modes that provide more than 2048 data bytes per frame (audio is recorded at 2352 bytes per frame). Some CD recorders have a different reading speed than their recording speed. For instance a “10x/25x” CD recorder can write at 10x speed (1500K/sec) and read back at 25x speed (3750K/sec).
The recording speed is independent of playback speed. It is generally better to record at higher speeds. The physics, chemistry and thermodynamics of the recording process produce more consistent and readable marks within the CD-R recording layer.
The CD recorder manufacturers that provide recommendations regarding the type of PC you need to successfully record CD-R media and the type of CD-R media that you should use in their CD recorder. If you follow these recommendations, the speed that you record with produces an identical CD. If your PC cannot support the data throughput required to drive the CD-Recorder at its rated speed, then recording at a lower speed is necessary.
|Compact Disc Average Transfer Rates
The normal CD transfer rate from the disc is 75 blocks per second, the average transfer rates shown are in bytes per second. Source: Craig Schwarz, Eastman Kodak Company.
|(2352 b/b)||(2048 b/b)||(2336 b/b)||(2048 b/b)||(2324 b/b)|
The difference between CD-R fixation and finalization
Fixation is the process of writing the lead-in and lead-out information to the disc. This process finishes a writing session and creates a table of contents. Fixation is required for a CD-ROM or CD Audio player to play the disc. Discs which are fixated for append can have additional sessions recorded, with their own session lead-in and lead-out, thus creating a multisession disc. When a disc is finalized, the absolute lead-in and lead-out for the entire disc is written, along with information which tells the reader not to look for subsequent sessions. This final table of contents (TOC) conforms to the ISO 9660 standard. CD-R writers support incremental packet writing. Using this mode data can be saved to a CD without finalizing a session or the CD so more data can be added to the CD at a later time. The CD can not be read in a CD-ROM player until it has been finalized.
Disc at Once (DAO)
Disc at Once is a writing mode that requires lead-in, program data and lead-out to be written in one write event. Another name for this is single session recording. All of the necessary information you wish to record needs to be on your harddisk prior to recording in Disc at Once mode. This mode is usually necessary for discs that are sent to a CD replication facility for CD-ROM replication where the CD-R is the original source. By recording in the Disc at Once mode, you eliminate the linking, run-in, and run-out blocks associated with multisession and packet recording modes which often are interpreted as uncorrectable errors during the glass mastering process.
Track at Once (TAO)
Track at Once is a writing mode that allows a session to be written in a number of discrete write events. The disc may be removed from the writer and read in another writer before the session is fixated. The sessions written contain complete tracks of information.
Incremental or packet writing
Track at Once writing is a form of incremental writing which mandates a minimum track length of 300 blocks and a maximum of 99 tracks per disc. A Track at Once written track has 150 blocks of overhead for run-in, run-out, pre-gap and linking. Packet writing is a method whereby several write events are allowed within a track, thus reducing the overhead. These packets are bounded by 7 blocks for run-in (4), run-out (2) and link (1).
Cleaning CD-R media
You can tell if a disc has been written to just by looking at it (compare with an empty disc). The CD-R media should always be handled by the edges or the center hole. You can also handle the disc by grasping it inside of the center hub stacking ring. CDs should always be stored in jewel cases or CD caddies to prevent scratches. CDs should be stored so that they are not exposed to direct sunlight or heat. The read laser will focus beyond the disc surface so that fingerprints and minor scratches do not affect the data integrity. A dusty disc can be cleaned so that the dust does not enter the drive mechanism or ends up on the reader mirror or lens. If you wipe the surface, do so with a lens tissue and wipe gently in a radial direction.
Writing on a CD-R
Using a water-based felt tip pen is the best way to label a CD-R. Never use a ballpoint pen or any other sharp object to label your discs. The safest area to label your CD-R is within the center stacking ring that surrounds the center hub hole. Never use a permanent marker pen that contains a solvent.
Always use a label positioning device to stick on labels. If you misalign the label or you don’t get it smooth (air bubbles under the surface), you run the risk of having your CD-R spinning out of balance which could cause read and tracking problems. If you try to reposition the label after it is partially stuck, you run the risk of damaging the CD-R.
There are really only two capacities on CD-R: 63 and 74 minutes. These time capacities can be translated to bytes of data by multiplying the CD delivery rate of 75 frames per second and 60 seconds per minute. Each frame is 2048 bytes, so a 74 minute CD-R disc contains 333,000 frames and 681,984,000 bytes. This translates to 650 MB. The 63 minute CD-R holds 283,500 frames or 580,608,000 bytes, which is about 553 MB. You will also see disc capacities rated as 780 MB, which refers to how much digital audio (PCM) data can be carried on the disc. Audio discs require less error correction data and so each frame has 2352 bytes of data giving a 74 minute disc 783,216,000 bytes of digital audio (PCM) data or 746 MB capacity.
|Compact Disc Capacities (based on Playing Time)
The normal CD transfer rate from the disc is 75 blocks per second. Capacities shown in bytes. Source: Craig Schwarz, Eastman Kodak Company
|Disc Size & Playing Time||Audio
|(2048 b/b)||(2336 b/b)||(2048 b/b)||(2324 b/b)|
There are two basic types of discs that you can buy for CD burners, CD-R (one bottom layer) and CD-RW (three bottom layers). CD-R is the cheapest and most used, but can only be burned one time. CD-RW allows you to erase discs and reuse them, much like a harddisk. New recorders support both CD-R and CD-RW. CD-RW is the best choice if you need a backup disc that is going to be updated often. It is reliable and offers large disc space, but you will have to use it in a CD-RW drive all the time, they cannot be read by ordinary CD-ROM drives. If the data is not going to be updated for a while, it is better to opt for the CD-R disc and to make the disc readable for CD-ROM drives. This way you can read the disc on all computers that have an ordinary CD-ROM drive.
In general the CD-R will offer the best quality of reading in other CD-ROM drives. Also recording a CD at a lower write speed will render a more consistent quality. CD-ROM drives that support the MultiRead standard can read CD-RW discs as well. Drives that support this standard should have a MultiRead logo on the packaging or on the CD-ROM drive itself.
You may also find newer types of discs, such as the CD Music discs. They are made for CD drives inside stereos. Avoid using them for discs you make using your computer.
|Disc Readable Formats||
CD-ROM (Mode 1 & 2) CD-ROM/XA (Mode 2, Form 1 & 2) CD-R, CD-RW, CD-Extra (CD+) Photo-CD (Single & Multi-Sessions) Video CD, Karaoke CD CD-I/MPEG, CD-WO, I-TRAX CD
|Sustained Data Transfer Rate||8.1 MB/s MAX|
|Eject Button||Motorized Eject button, Emergency button
|Headphone Jack||Stereo 3.5mm mini-Jack|
|Volume Control||Wheel knob|
|Interface Connector||40-pin EIDE header|
|CD-Audio Analog Out||Supported|
|Digital Audio Out||Supported|
|EIDE Settings||(E)IDE drives have Master/Slave jumpers.|
|Power Supply||DC+5V ,1.2A ,1.5A peak
DC+12V, 0.5A, 1.5A peak
|MTBF||100,000 Power On Hours|
|Warranty||One year warranty|
The DVD-ROM has also made its entrance, and as such will most likely replace the CD altogether in the (near) future. In purchasing a CD writer, you may look for a drive that offers DVD-ROM, CD-R and CD-RW all in one device. DVD-ROM drives are capable of reading audio CDs and CD-ROMs which are commercially produced. Only some of the DVD-ROM drives will read the CD-R/CD-RW disks recorded by you.
According to the manufacturers of CD-recordable discs, the green discs last up to 75 years, gold colored discs last up to 100 years and platinum colored discs last up to 200 years.