Everything you Wanted to Know About CDs

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Everything you Wanted to Know About CDs

Physical and Logical Properties of CDs | Audio Recording CDs | Difference Between Disks and Standard CDs | FAQ

Understanding CD-R and CD-RW

PHYSICAL, LOGICAL AND FILE SYSTEM STANDARDS

What is the Orange Book?
Orange Book is the set of specifications created by Philips and Sony to define the optical signal characteristics, physical arrangement, writing methods and testing conditions for CD-R (Orange Book Part II) and CD-RW (Orange Book Part III) discs. First released in 1990, Orange Book originally dealt with only single speed CD-R recording but, with rapid advances since made in hardware and media technology, the specification grew to include CD-RW in 1996. Higher writing speeds continue to be incorporated as the industry evolves.

What are the different sections of CD-R and CD-RW discs?
Orange Book organizes CD-R and CD-RW discs into various sections serving distinct purposes. The Information Area is most fundamental and consists of a shallow spiral groove (pregroove) extending from the discs’ inside to outside diameter. Encoded in the structure of this pregroove are speed control and Absolute Time In Pregroove (ATIP) time code information as well as other parameters critical for recorders to correctly write a disc. Several regions within this pregroove are reserved exclusively for recorder use.

The first is the Power Calibration Area (PCA), located in the inner portion of the disc, which is employed while determining the correct power level for the writing laser. Due to physical and practical design limitations on rotational velocity it is, generally speaking, not possible to conduct power calibrations at the inner diameter of the disc at speeds above 16x. A process of extrapolation is therefore used to determine suitable writing power for those higher speeds. Recently, Orange Book has designated the addition of another PCA located in the Lead-Out Area at the outer portion of the disc to provide the space necessary to conduct actual high speed write power calibrations.

Following the first PCA is the Program Memory Area (PMA) which is used as intermediate storage to record track information for all sessions written to the disc. Typically, the PMA is first followed by the Lead-In Area, containing table of contents information, followed by the Program Area which holds the written data tracks and finally the Lead-Out Area which indicates to a reading device that the end of the data has been reached.

What is a Multisession CD-R or CD-RW disc?
Multisession recording allows additional data to be written to a previously partially recorded CD-R or CD-RW disc. Each session on the multisession disc has its own Lead-In Area, Program Area and Lead-Out Area and may be connected to other sessions to function as a single volume (linked) or operate independently (multi-volume). In addition to being written by a recorder the first session of a multisession disc can be, alternatively, prerecorded (stamped) at the factory.

What is the difference between fixation and finalization?
Fixation is the process of completing a CD-R or CD-RW disc session by writing Lead-In (table of contents) and Lead-Out information. Once a disc is fixated it can then be played back in CD and DVD-ROM drives and recorders and consumer electronics devices compatible with the particular disc type and format. It is also possible to record additional information later to create a multisession disc. Finalization, on the other hand, completely closes the disc so no further material can be added.

What are the different writing modes?
CD-R and CD-R/RW recorders employ several different writing modes including Disc-At-Once (DAO), Track-At-Once (TAO), Session-At-Once (SAO), and packet writing. Be aware that not all recorders and software support all writing modes. If in doubt, consult with the product manufacturer.

During DAO recording the Lead-In Area, Program Area and Lead-Out Area of a CD-R or CD-RW disc are consecutively written in a single uninterrupted operation. DAO recording is only possible using a blank disc and, after recording is completed, no additional information can be written. Typically, DAO is used to write CD audio, CD-Text and discs destined for mass replication.

In contrast to DAO, TAO operates by turning the writing laser on and off at the beginning and end of each track and writes the Program Area of a disc before its Lead-In and Lead-Out Areas. It is possible to use a recorder to read from (or write additional tracks to) a TAO disc before a session is fixated. All TAO discs contain 2 to 3 second gaps between tracks (run-in, run-out and link blocks) but some recorders have the ability to vary the size of the gaps.

SAO is much like DAO in that the Lead-In Area, Program Area and Lead-Out Area are consecutively written in a single uninterrupted operation. However, the first session is not finalized so additional sessions can be added. Typically, SAO is used to write

CD Extra (Enhanced Music CD) discs where the first session contains one or multiple audio tracks and the second session consists of multimedia computer data.

Packet writing records variable (CD-R) or fixed (CD-RW) sized chunks or “packets” of data to the disc for as many times as is needed to complete the writing of the user’s files. In the case of a CD-R disc (which is not erasable) data may be added incrementally until the disc becomes full. CD-RW discs, on the other hand, are completely rewritable and thus are a little different from their CD-R cousins in that files can be added and deleted as needed.

What is ISO 9660?
The ISO 9660 standard was introduced in 1988 and is the most widely used file format for data (CD-ROM) discs. ISO 9660 defines a common logical format for files and directories so discs written to ISO 9660 specifications can be read by a wide array of computer operating systems (MS-DOS, Windows, Mac OS, UNIX, etc.) as well as consumer electronics devices. Due to the vast differences which exist among native file systems ISO 9660 takes a lowest common denominator approach resulting in a variety of restrictions upon the nature and attributes of files and directories. Three levels of interchange define these restrictions with level one being the most constraining and level three is the least (at the cost of compatibility with some operating systems). Various protocols are available to extend ISO 9660 to accommodate file system features specific to individual operating systems (longer file names, deeper directory structures, more character types, etc.) while preserving ISO 9660 compatibility with other platforms. These protocols include Joliet (Windows 95 and higher), Apple Extensions (Mac OS) and Rock Ridge (UNIX).

Reading a CD-ROM

Digital data are carved into the CD-ROM as pits (low spots) and lands (high spots). As the laser shines into the moving pits and lands, a sensor detects a change in reflection when it encounters a transition from pit to land or land to pit. Each transition is a 1. The lack of transitions are 0s. There is only one laser in a drive. Two are used here to illustrate the difference in reflection.

What is The Universal Disc Format (UDF)?
The Universal Disc Format (UDF) specification was first released by OSTA in 1995 and is designed to be a common logical file system for all removable optical storage media. Over the years various updates to UDF have been introduced to add new capabilities. For example, UDF 1.02 is the standard file system used for prerecorded and recordable DVD discs while UDF 1.5 is commonly employed for packet writing CD-R and CD-RW media. Most recently, UDF 2.0 has added full support for Windows NT, enhanced data security and improved CD-R functions while defining backward read capabilities between discs created with the new UDF 2.0 format and discs created with earlier versions of UDF.

What is a hybrid disc?
The term “hybrid” is popularly used to describe several different types of discs. The first kind of hybrid disc is one that contains multiple file systems, such as ISO 9660 and HFS (Mac OS). A second type of hybrid is a CD that contains applications designed to interact with the Internet so static data resides on the disc and live information is downloaded as needed from the Web. These discs are sometimes called “connected CDs.” A third kind of hybrid is defined by Orange Book as a CD-R or CD-RW disc with a prerecorded (stamped) first session with the ability to potentially hold additional written sessions.

What is Running OPC?
Running Optimum Power Control (Running OPC) is a special technique used in many newer CD-R and CD-R/RW recorders that monitors and maintains the quality of the disc writing and ensures the accuracy of all the marks and lands lengths across the disc. The term Running OPC actually describes the general process that may be known by several trade names. Some differences in execution may be present to give some of these implementations competitive advantages over others.

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Understanding CD-R and CD-RW

AUDIO RECORDING

What is the Red Book?
Red Book is the set of specifications created by Philips and Sony to define the essential parameters for Compact Disc-Digital Audio (CD-DA). First released in 1980, Red Book has been adopted an international standard (IEC 60908:1999, Audio Recording — compact disc digital audio system) and forms the foundation for all other compact disc standards.

What types of audio CDs can CD-R and CD-R/RW recorders write?
CDs were originally designed for audio so it’s only natural that CD-R and CD-R/RW recorders write discs in the official Compact Disc-Digital Audio (CD-DA) Red Book format for use in any CD audio compatible player. Just like their mass produced prerecorded (pressed) cousins, CD-R and CD-RW discs can hold up to 80 minutes of CD quality audio (44.1 Khz, 16 bit) using as many as 99 separate tracks. In addition to Red Book discs, recorders also write compressed digital audio CDs which, instead of holding conventional tracks, contain MP3, WMA or other compressed audio files. Depending upon the scheme used, one compressed CD-R or CD-RW disc holds as much as ten to twenty ordinary audio CDs and can be played back in devices enhanced for compressed digital audio listening such as compatible computers, personal, home and car CD players as well as many DVD-Video players.

What types of material can be used as sources for audio CD recording?
Depending upon the capabilities of the recorders and software used, CD-R and CD-RW audio discs can be written from either digital or analog sources. Digital material such as existing MP3 files or CDs are conveniently read directly from the hard drive, recorder or from a separate CD or DVD-ROM drive. To record analog sources such as LP records, cassette tapes, microphone or radio tuner inputs connected to a home stereo, signals are first digitized through the computer’s sound card.

Digital
Digital audio material comes in many forms including compressed and uncompressed computer files such as MP3s, WMAs and WAVs, Compact Discs (CD), MiniDiscs (MD), Digital Audio Tapes (DAT), Digital Compact Cassettes (DCC) and Alesis ADAT. How they are handled by the computer for writing to CD varies depending upon the capabilities the individual recording system.

Digital Files
A popular way to create audio discs is to use uncompressed (WAV, PCM, etc.) and compressed (MP3, WMA, etc.) computer files as the recording sources. When producing a compressed digital audio CD these files are written to disc just as they come and, depending upon the recording software used, may be accompanied by MultiAudio or other navigational information. In the case of a Red Book audio CD, compressed files must first be uncompressed and translated into the correct format before recording. Historically, this had to be accomplished manually but most recording software now performs the conversion process automatically during the writing process. As with any audio recording it’s important to remember that the sound quality of a written disc will be no better than the source material used. Higher resolution digital audio files obviously will produce better results.

CD
Recording CD to CD is much simpler than recording from analog sources since most CD and DVD-ROM drives are capable of transferring audio directly (Digital Audio Extraction) without the necessity of converting from analog to digital. As a result, CDs can often be recorded disc to disc using a CD or DVD-ROM drive as the audio source. Where a suitable drive is not available the recorder itself can be used as the audio source. In this case, the audio is read using the recorder and stored temporarily on the computer’s hard drive until written out again.

DAT, MD, DCC, ADAT
Although the contents of DATs, MDs, DCCs and ADATs are already in digital form, most computers lack the proper connections for directly importing digital material. As a result the analog outputs from the source must be connected to the computer’s sound card and the audio re-digitized. Since there is always a loss of quality in the conversion process, some manufacturers offer special sound cards that connect to the digital outputs of the source deck to transfer the audio to the computer while keeping it in quality digital form.

Analog
Analog audio equipment such as LP record players, cassette tape recorders, microphones and radio tuners use continuous electrical signals of varying voltages to record and play sound. Computers, on the other hand operate, in the digital world where everything is represented in binary form. Thus, before the computer can manipulate or record analog audio sources to a hard drive or a CD-R/RW disc, the sounds must be converted into digital form through the computer’s sound card. Higher quality sound cards will produce better results but most cards are capable of recording at the 44.1 kHz frequency, 16 bit resolution used by audio CDs. Some recording software automates the conversion and writing processes into a few simple steps by performing time saving tasks such as detecting the silences between songs to automatically split the music into separate tracks.

What is MultiAudio?
The MultiAudio specification was created by OSTA in 2001 to provide a standardized structure for compressed digital audio files (MP3, WMA, etc.) written onto removable optical media, such as CD-R and CD-RW discs. This uniformity allows these discs to be played back in the same way on any compatible device including MultiAudio-compliant computer software media players and consumer electronics devices such as CD and DVD audio and video players. To accomplish this goal MultiAudio requires that, in addition to compressed digital audio files, an appropriately formatted disc also must contain a defined table of contents which the playing device will use for file navigation. In addition, the specification allows playlists to be created to organize material so it can be accessed by categories such as genre, album, artist or even in custom groupings created by the user. MultiAudio formatted discs are created by standard recording software packages and CD-R/RW recording-enabled audio jukebox applications which support the MultiAudio specification. Written discs can then be played back in MultiAudio compliant devices and even in compressed digital audio units not supporting the specification, albeit in a more limited fashion. Since MultiAudio is simply an organizing system it’s important to remember that the types of discs and specific compressed digital audio file formats supported depend upon the individual capabilities of the particular devices or software employed.

Can consumer compact disc audio recorders write to any CD-R or CD-RW media or are special discs required?
Even though general purpose CD-R and CD-RW discs and their consumer audio versions appear for all practical purposes identical, only blank media bearing the “Compact Disc Digital Audio Recordable” (CD-DA Recordable) and “Compact Disc Digital Audio Rewritable” (CD-DA Rewritable) logos can be written in consumer audio recorders. The reason for this restriction is to comply with international copyright agreements. A special Disc Application Code present in the ATIP information of a CD-DA Recordable/Rewritable disc’s pregroove wobble identifies it specifically for audio use. Consumer audio recorders are programmed to reject discs not containing the correct code. By adopting this safeguard various countries and other authorizing jurisdictions may selectively apply copyright levies to the price of blank discs intended for consumer audio use while exempting those destined for computer or professional applications.

Does using lower CD-R recording speeds and lower capacity media produce better sounding discs?
High speed CD-R writing often creates discs with low I3 and I11 signal amplitudes (optical signals generated from the smallest and largest marks) and 80 minute discs achieve their capacity by packing marks and lands more tightly together. These result in reduced recording and playing margins and sometimes lead to perceptible sound degradation, especially in older CD audio players which may not employ equalization (signal boosting). Consequently, many high speed recorder manufacturers recommend creating audio discs at reduced writing speeds while some recorders even limit their maximum speed to 24x when writing audio discs. In addition to slower recording speeds, some manufacturers also suggest using 74 minute instead of 80 minute discs. Several of the latest recorders even offer special writing modes which record audio discs with longer marks and lands than would normally be the case, albeit at the expense of some capacity. For example, an 80 minute disc written with longer marks and lands might only hold 74 minutes of audio and a 74 minute disc just 68 minutes of material.

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Differences Between CD-R/CD-RW Discs and Standard CD

The main physical difference between these two disc types and the standard prerecorded CD (audio or CD-ROM) is that the latter has no recording layer; the information is permanently stamped in the aluminium reflecting layer.

There is also a difference in terms of the data areas on the disc. Compared with standard CDs, the CD-R and CD-RW discs have an additional Cd-R/CD-RW area located in front of the lead-in area. This additional area is used to store data specific to the recording process, and is divided into two parts:

1.Program Memory Area (PMA), which contains the track numbers of the recorded titles and their respective start and stop points.

2.Program Calibration Area (PCA), which is used by the CDR 870 to calibrate the required laser energy by means of a brief trial recording (Optimum Power Calibration) each time a disc is loaded. This calibration is necessary to allow for production tolerances between individual discs, temperature variations etc. As well as this initial OPC, the required laser energy is constantly optimized during recording by running OPCs, which deal with dust, scratches and other possible variations across the disc surface.

See figures 1, 2 and 3 below.

The CD-R and CD-RW discs

Both CD-R and CD-RW discs have the same basic structure but with significant detail differences. The CD-R disc has a dye-based recording layer, with a reflectivity of 40 - 70 %, while the CD-RW disc has a phase-change recording layer with a reflectivity of 15 - 25 %. Both discs have an additional reflecting layer: golden for the CD-R, which accounts for that disc's distinctive appearance, and silver (aluminium) for the CD-RW.

Both disc types have a track spiral which is preformed during manufacture, onto which the audio data is written during the recording process. This track ensures that the recorder follows the same spiral pattern as a conventional CD, and has the same width of 0.6 mm and pitch of 1.6 mm as a conventional CD. In addition to the spiral pattern, the track has a slight superimposed sinusoidal excursion of ñ 0.3 mm at a frequency of 22.05 kHz. See figure 4.

The frequency of the sinusoidal excursion is used by the recorder to control the speed of rotation. The frequency read-out from the disc is constantly monitored, and the speed is adjusted as needed to maintain the frequency at exactly 22.05 kHz. An additional ñ 1 kHz frequency modulation is applied to provide the recorder with an absolute time reference. See figure 5.

The writing process: CD-R

Digital information is written to the disc by burning (forming) pits in the recording layer. The energy of the laser beam - in the range 4 to 11 mW - causes limited heating of the substrate and recording layer to approximately 250 C. At this temperature the recording layer melts, reducing its volume, while the substrate expands into the space that becomes available. By constant switching between writing and reading power, a pit pattern corresponding to that of a conventional CD is produced.

The write pulse initially has a higher power to produce the required heating of the dye. Subsequently, the power is reduced to a level that is sufficient to maintain the dye temperature at the desired level.

The writing process: CD-RW Recording

In the CD-RW disc, the recording layer is made of an alloy of silver, indium, antimony and tellurium. In its original state, this layer has a polycrystalline structure. During the recording process, the laser selectively heats tiny areas of the recording track to a temperature above the layer's melting point (500 - 700 C). For CD-RW writing, the laser power used is in the range 8 to 14 mW.

The pulsed energy delivered by the laser beam melts the crystals in the heate areas into a non-crystalline amorphous phase (`pits'), which has a much lower reflectance than the remaining crystalline areas (`lands'). This difference in reflectance allows the recorded data to be read-out, producing a signal similar to that obtained from a standard CD. The physical characteristics of the amorphous phase are `frozen-in' during cooling, making the recording just as permanent as any standard CD. See figure 7.

Erasing

Erasing of a CD-RW disc is performed by returning the material in the recording layer which has been changed to the amorphous state back to the crystalline state. This is done by an annealing process, consisting of heating the layer to a temperature of about 200 C (i.e. less than the melting point) and maintaining that temperature for an extended period (in practice, this takes some 37 minutes for a complete disc). The disc is then returned to its original, completely unrecorded state.

A much faster `on the fly' erasing facility is also available, allowing the last recorded track to be erased simply by erasing the subcode reference to that track while leaving the recorded data in place in the recording layer. See figure 8

Overwriting

A direct overwrite strategy is obtained by combining the write and erase techniques. In this case, new pits are written in the recording layer using the same pulsed laser beam energy as in the standard writing strategy. However, in the areas between the newly recorded pits, a lower-energy, non-pulsed laser beam is used to write new crystalline lands. The laser beam is repeatedly switched to the lower- energy erase level between the new pits, resulting in complete erasure of the audio data that was formerly contained in these areas.

As in the writing of a CD-R disc, a higher energy level is used initially to create the temperature increased required to melt the recording layer. Between the pits, the temperature is reduced to the annealing (erase) level. This provides a higher starting temperature, so less energy is subsequently needed each time the melting temperature has to be reached. See figure 9.

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Differences between CD-R, CD-RW, CD-DA, Music CD-R, Audio CD-R

The CD-R FAQ: Answers to 14 Common CD Recordable Questions

The variety of CD recordable discs in today's market is enough to confuse all but the most experienced user. Here is our "CD-R Frequently Asked Questions" or FAQ page for your information. It contains the latest information and advice we have available on -- CD recordable discs, labeling and printing issues, and packaging options.

How are CD-Rs different than store-bought CDs?

What do "disc write speeds" mean? (32X, 40X, 48X, 52X, etc.)

What is a "TruSilver Diamond CD-R"?

Why are some CD-R discs called "Improved"?

Why would I use a "Silver/Blue CD-R"?

Are gold CD-R discs better than silver?

What about 90-minute and longer CD-R discs?

How long do CD-R discs last?

What about making CD-Rs for cars and portables?

How should I label my CD-Rs?

What is a "printable CD-R"?

What is a "re-writable CD-RW"?

Which CD case or holder is best?

Will airport security scan X-Rays hurt my CD-R discs?

That's the list. Now here are the details...

(1) How are CD-Rs different than store-bought CDs?

A CD-R is a blank "compact disc - recordable". However, the music or software CD-ROM is a "compact disc - read only memory". The CD-ROMs you buy in stores are not recordable. They were never recorded. Instead they were mechanically stamped or pressed, like the old-fashioned vinyl LP albums.

Store-bought pre-recorded CD-ROMs use tiny pits or holes arranged in the tracks of the disc to encode the music, video or game software that you play. In a similar way, your CD-R burner uses laser-light bursts during your recording sessions to create tiny bubbles in the tracks around the CD-R. The burner's laser blinks rapidly on and off, heating tiny areas of the bottom of the disc which expand into bubbles that closely resemble the stamped pits of a CD-ROM. Later, when the CD-R is played back, the CD-R is now actually a CD-ROM. CD players read CD-R and CD-ROM discs equally well in almost all cases. (A few CD players may have difficulty reading CD-R discs, but playback problems are usually caused by scratches, poorly applied or too-heavy off-center CD labels, and discs that have been exposed to heat or UV light -- discussed below.)

You have probably heard of several types of CD-ROM discs, including those that contain music, software, video, photos, and games. On each of these types of CD-ROMs, the data is formatted differently. CD players are made to be able to read or decode each of these CD-ROM formats so you can easily use the disc, without knowing much about its contents. CD-R discs can be burned in the same formats as CD-ROMs, and played the same simple, easy way. CD creation software lets you select the final format of the disc you're creating. After you make a few optional decisions, the actual recording of a CD-R is usually quite simple. See the manual for your CD creation software for more details.

Once fully recorded or burned, a CD-R disc cannot be erased and used over. Therefore CD-Rs are sometimes called "write-once" discs. There are also erasable "re-writable CD-RW" discs. CD-RW discs are sometimes called "write-many-times" discs, and can be fully erased and re-written up to 1,000 times. Unlike CD-Rs, CD-RWs cannot be played by most CD players. They are for data storage and editing uses in computers. We discuss CD-RWs in detail under question #12 below.

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(2) What do disc "write speeds" mean? (32X, 40X, 48X, 52X, etc.)

CD-R discs are described by their recording capacity or runtime length. You can buy both 74-minute and 80-minute CD-R discs. Today most CD-Rs are sold in 80-minute lengths, but you will see some brands that offer both 74 and 80 minute sizes. The actual cost of making the discs is about the same. However, some of the very old CD burners do not recognize the 80-minute CD-Rs, so the short 74-minute discs are still offered by some makers. Both of the discs are the same physical dimensions or measurements - 120mm (12cm) in outside diameter, with a 21mm center hole.

CD-Rs are also described by their write-speed certification. A 2X speed means that the disc can be BURNED or recorded in 1/2 the length of the disc total runtime or 40 minutes for an 80-minute disc, an 8X disc at 1/8 the runtime, or 10-minutes -- on down to as little as 2 minutes or less at 48X speeds!

CD-Rs are tested and certified by their factories to be properly recordable at the rated speed. Today's fastest write-speeds are usually 48X, but 52X rated discs are also available. The most popular write speed purchased in today's market is the 48X rated CD-R (2004). Today's fastest rated discs can burn at up to 52x speeds on 52x capable writers.

In order to burn at a given speed, your CD burner, your computer and your software must be able to work at that speed, as a total CD recording system. CD burners come rated with a triple speed rating, often written like "52X/16X/60X". That statement would mean that the drive can WRITE CD-R discs at up to 52X, RE-WRITE CD-RW discs at up to 16X, and PLAY at up to 60X. (To read about the differences between a "re-writable CD" and a "write-once CD-R", see our question #12 below - What is a "re-writable CD-RW"?)

Whether or not you actually are able to achieve those speeds depend on many factors: The disc must be rated at that speed. Your computer needs to be able to handle data that fast through its connections, cables, motherboard and hard disc. Your CPU needs to be fast enough to do the work of translating the music or other signals you're recording into the encoding used to store the data onto the disc, and the CD creation software you're using needs to be able to handle the given speed. Each part of your system needs to be able to do its part of the job.

Today's 800mhz or faster CPUs, with fast hard drives and also with state-of-the-art internal motherboard hardware, are capable of easily handling any 32X or faster CD-R creation task. However, experienced users often choose to record their discs at a much slower speed. This gives their system an extra "cushion" to avoid many burning errors that sometimes occur at the faster speeds.

Since each different software, hardware and CD-R disc brand or type delivers a slightly different speed and recording-quality capability, a little experimentation will help you decide which speed to use. If you change your hardware, software, burner or other system components, or if you begin using a new type of CD-R disc, it's time to do a bit of experimentation again.

A TECH POSTSCRIPT: Bill O'Brien (who writes the Hard Edge column at Computer Shopper magazine) wants us to be sure to point out that the original X-rating applied to drive speed, and was related to 150KB/sec data transfer rates for each incremental "X" for drives, as opposed to the time it takes to burn a disc. So, a 2X drive could transfer data at 300KB/sec, and a 4X drive could achieve data transfers up to 600KB/sec, and so on. He feels that the connection between a disc's x-rating being expressed as a fraction of its runtime, and a drive's data transfer speed rating in KB/sec is a mere coincidence.

We want to publicly thank Bill for that technical reminder. Of course, he's absolutely correct about the 150KB/sec being the basis for the X-rating for drives. That was the speed needed to PLAY a music CD in "real time", so you could hear the music as fast as it was actually being read, decoded into sound, and processed through your sound system. That basic speed was the original design criteria for a CD-ROM player's data transfer and processing capability for music CDs. However, the fact that 1X drive speed related to a 1-to-1 runtime for the disc is certainly NOT a coincidence. So, when it comes to burning, if you burn a disc at 2X speed, it takes half the runtime of your recording to get it down onto a disc, and if you're doing it at 4X, then it takes one fourth the time, and so on. Basicly, faster X-ratings for discs mean that we can burn your discs at a proportional fraction of the disc's runtime. Remember, we're focusing here ONLY about burn time for discs, not about the basic data transfer rating of drives, or other theoretical considerations. However, whether experienced users and experts like Mr. O'Brien want to express the speed in KB/sec or in fractions of the full runtime -- either way you end up with the same facts, expressed different ways.

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(3) What is a "TruSilver Diamond CD-R"?

Advanced TruSilver Diamond CD-Rs are made to look as much like a store-bought pre-recorded music or software CD-ROM as possible. You may have noticed that most other blank CD-R discs have a colored bottom surface, usually a shade of light blue or green on the bottom. On the top, most CD-Rs usually have a blank shiny silver surface. Our TruSilver Diamond CD-Rs also have a silver top, but their bottoms are completely colorless - just like your music CD-ROMs. TruSilvers don't even have a slight hint of color on the bottom. They're completely colorless to the eye, so all you see from the bottom is the bright shiny silver top-reflector, just like a store-bought music or software CD.

The TruSilver Diamond's colorless bottom layer contains special plastic material that absorbs laser light almost as well as the older light green or light blue materials used on other discs. So, almost any CD-R burner can write to a TruSilver disc. And, once recorded by your burner, the disc will play in CD-ROM players just like your music or software CDs you bought in a music stores. Of course they also work fine for storing data or software.

PROs: They look much more attractive to most people and help you make a slick, professional impression on your customers, clients and friends. Close to 100% of CD-ROM players can read and play these CD-Rs perfectly, even at superfast 48X or 60X playback speeds. The colorless TruSilver bottoms are available with a wide range of top surfaces and colors, including inkjet printable surfaces and a wide variety of bright solid colored tops. See them at.

CONs: They cost a few cents more per disc. A small number of CD-R burners may not write or burn TruSilver CD-Rs. Even though new 40X write speed TruSilver CD-Rs are now entering the market, most TruSilvers generally burn at a slightly slower speed than the very fastest light green or blue bottomed discs.

(4) Why are some CD-R discs called "Improved"?

When CD-R discs were first invented about 20 years ago, they were made with expensive gold reflector layers over a dark blue bottom layer that was super sensitive to laser light. They needed this super sensitivity so that the slow computers, weakly powered lasers and unsophisticated logic circuitry in the drives and computers could produce a playable CD disc.

These dark-blue bottomed discs had a major flaw... if you accidently exposed your recorded disc to sunlight or heat, even a small amount from a window or bright office lighting... they became completely unreadable! You had to protect your discs in dark, cool storage all the time.

The thick coating of gold metal on top was used because it was known not to discolor when marked on or imprinted with logos, etc. Any discoloring of the metal reflector would make the disc unplayable.

The dark blue dye on the bottom recording side of the disc was formulated to absorb almost 100% of the laser light from the existing CD burners of that era. Against the yellow gold metal of the reflector, the dark blue dye appeared a dark shade of green to the eye. So, people called these discs "Gold/Green" CD-Rs.

However, as technology improved over the years, we began to see alloys of silver used for the top reflector layers. Advanced formulas included traces of other elements with the silver to make it resistant to degradation from inks and label adhesives. This reduced the price of CD-Rs, since silver costs less than 1/25th as much as gold. And, silver is actually about 5% more reflective to laser light than gold, so the total effect of using silver produced a better CD-R, at a much more affordable price than the old gold discs!

But, we were still stuck with that dreary old "blue" dye on the bottom of the disc. Now the CD-Rs looked "silver/blue". Some companies produced a lighter shade of blue which was less sensitive to heat and UV light than the old dark blue. These silver/light-blue discs soon became the most popular discs in the market. Even so, companies continued to look for a much more "stable" bottom dye formula -- one that would absorb the laser light and produce a clean, crisp recording -- but, one that would be much less sensitive to normal temperatures and office lighting. They wanted a disc that would last for 100 years or more in normal use and storage treatment.

Finally, the Mitsui company discovered a special very light-green dye that was almost a perfect combination of sensitivity to laser light and insensitivity to UV and "normal" temperature ranges. They called their new dye "phthalocyanine" and patented it. Soon other major companies were licensing and manufacturing CD-Rs using this new "improved" bottom dye.

Mitsui calculated that their new "improved" discs would last up to 200 years or more in cool, dark storage! And, users could expect that these discs would outlast any other kind of CD-R in normal use; in the office, the home, and even (if they were careful) in their cars!

Because the dye color of phthalocyanine was very light shade of green (just barely detectable in normal light), these new "improved" discs were often called "gold/gold" if they featured a gold reflector on top, or "silver/silver" if they used a silver reflector. However, after the recent development of so-called "TruSilver Diamond" discs with their absolutely colorless bottoms, few people still call these discs silver/silver. Nowadays, the Mitsui-type phthalocyanine discs are simply called "silver/green", "silver/light-green" or "Improved Silver".

Improved Silver CD-Rs are now the best-selling discs in the market. They are still considered the most stable, longest lived type of CD-R. This makes them an especially good disc for use with portable CD players, or for use in automobile CD changers and in-dash players.

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(5) Why would I use a "Silver/Blue CD-R"?

Because you may have to... There are a few of the older CD players and burners which will not work with the light green dyes used by the Improved Silver discs, nor with the colorless transparent dyes used by the TruSilver Diamond discs. These older drives' lasers were tuned specifically for the blue dyes being manufactured then. If you find that you own one of those machines, then you have no other option but to use silver/blue CD-R discs, or buy a newer model drive. Almost all new CD burners and players now being sold work perfectly with either the Improved or TruSilver discs. Also, today's CD burners can work at 32X or faster write-speeds. In addition to burning a longer-lived CD-R like the Improved Silvers, these machines will save you untold hours in production time! See our full list of new, versatile, fast CD-R burners at.

Silver/Blue CD-Rs are still an excellent product, and have been steadily improved over the last several years. Now made with a more stable silver alloy, and with better storage characteristics, the silver/blue types of CD-Rs remain a usable product.

(6) Are gold CD-R discs better than silver?

As explained above, the very first CD-Rs were made with genuine gold metal used as a top reflector layer. Gold was chosen because it did not tarnish when exposed to harsh inks and adhesives used to affix CD labels to the discs. However, because the gold metal itself added at least 25-cents to the cost of the disc, there was constant pressure to find a different metal alloy to use for the reflector layers.

Silver was especially attractive as an alternative to gold. Silver costs less than one cent per disc, and is actually more reflective by about 4% than is gold to laser light. The only disadvantage to silver was in its tendency to degrade or tarnish if the harsh inks and adhesive chemicals leached through the top plastic layers down into the metal.

Advances in CD research finally produced alloys of silver that had traces of other rare metals, producing a final reflector layer that was very resistant to tarnishing, yet still had the advantages of very low cost and high reflectivity.

Today, almost all CD-R discs are made with one of these new silver alloy reflectors, These discs can be treated almost exactly like the gold-covered discs of the past. Today's silver alloy CD-Rs should be able to survive 100 years or more of dark, cool storage, just like the much more expensive gold CD-Rs.

Further, because silver is more highly reflective than gold, today's silver discs can be burned (and played) at much faster speeds than gold CD-Rs.

Gold CD-R discs are still available in limited quantities. They are rated for slower 8X-16X write speeds, and their costs range from 200% to 400% higher than their faster write-certified 32X-40X silver cousins.

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(7) What about 90-minute and longer CD-R discs?

Decades ago, CD-Rs were originally designed in the 63-64 minute size, like the old "optical" discs. However, in a few years the 74-minute 650MB capacity became the standard, and soon after that 80-minute became the most common CD-R.

However, the data-length description built into each CD at the factory is 2 digits long. That means that theoretically the disc COULD be up to 99 minutes in runtime. Theory is one thing, but reality is another...

CD discs are read starting at the center and moving out toward the edge of the disc in a spiral, as the disc turns on the drive. The reading is done by a small laser and photo-electric sensor mounted on an arm that moves from the center outward as the disc is read. Of course there is a limit to this outward motion; it has to stop somewhere. Some of the older drives were made with an arm that would only reach out to a distance that corresponds to about 76 or 77 minutes of motion from the center. Those old drives could not accept the newer 80-minute discs (and, where they're still in use, still can't). Nowadays, in a similar way, most drives today won't read or write to a disc that is much more than 82-84 minutes in runtime. Their lasers' movements are limited to traveling just a bit more than their designers expected the 80-minute capacity of discs would require.

This arm movement limit is a physical barrier to how long you can record and then play a CD-R. Very early in the development of the CD-R industry, people began to "push the envelope". Some CD burner manufacturers made drives capable of burning up to 90-minute or even 99-minute CD-Rs. Of course, once they were recorded, many CD players could not playback these over-limit CDs. So, they had to be played on the machines that recorded them. At best "over-burned" CD-Rs playback situation is "iffy". Some web sites that discuss these extra-long discs can be found by going to.

Other than as a pastime for technological hobbyists, 90-minute and longer CD-Rs are not really very popular. If you want to experiment with over-burning, be sure you have software that is capable of handling 90-minute discs, and that your drive has the latest drivers and firmware installed. Like most companies in the industry, we can't help you much in this area. When you go beyond the "official" 80-minute capacity, you've entered the world of public support forums and hobbyist chat rooms.

We do sell 90-minute discs, and will be adding 99-minute discs soon, for those who are interested.

(8) How long do CD-R discs last?

Today's CD-R discs can last 100 years or more in cool, dark storage. Under normal use (avoiding hot conditions like automobile interiors and window ledges, other UV light sources and scratches, etc.) your CD-R recordings should last for many years -- probably longer than you'll own a player that can play them!

Our "improved" CD-Rs with light-green bottom layers will be slightly more resistant to UV light and heat than other discs, and are generally considered preferable for use in portable CD players and automobiles.

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(9) What about making CD-Rs for cars and portables?

Here's the scoop on how to create CD-R discs that will have a "fighting chance" to playback flawlessly in your portable and automobile CD players, as well as your home CD stereo system and computer drives...

First, you need to realize that store-bought music CD-ROMs and your home recorded CD-Rs are NOT the same kind of disc, even though they look very much alike, and are playable in the same players.

HERE IS WHY:
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Unlike store-bought music CD-ROM discs, your recordable CD-R discs have a special layer that contains a chemical that responds to the heat generated by a CD burner's laser. That's a very short (microsecond long) recording laser blast. It passes up through the bottom, then bounces down off the top silver reflector again almost instantly -- making the plastic even hotter in that area. This heats up the plastic around the laser beam, and creates a tiny bubble. When the disc is played back, the CD player shines a lower powered laser beam up into the discs and scans it. The player's logic chip decodes these little bubbles into beautiful music. This special bottom dye layer's material must be very sensitive to the laser heat in order to produce well defined bubbles for each and every tiny burst the laser makes.

By contrast, the CD-ROM discs you buy in music stores are MECHANICALLY stamped like old-fashioned vinyl LPs used to be. They do NOT contain the heat-sensitive layer like recordable CD-R discs do. Furthermore, since they do not need to be responsive to a heat-generating laser burst like CD-R discs, they use an inexpensive aluminum reflector on top, instead of the much more expensive silver or gold used by recordable CD-R discs.

When you leave your CD-R discs in a hot auto interior or portable CD player in the sun, the heat sensitive layer in the recordable disc responds to the heat microscopically, softening the edges of the bubbles that encode your music data. This process may continue over time, until the disc becomes no longer playable.

If you store CD-R discs in the sun, this process is unfortunately unavoidable. Any disc sensitive enough to a recording burners's laser to get properly "burned" or recorded will also be sensitive enough to an automobile's sun-heated interior to get ruined.

Due to the even MORE sensitive dyes used in high speed CD-Rs (those rated 24X and above), this problem can be even worse. And, most CD-Rs you buy these days are 24X or faster rated, meaning that they are more sensitive than ever to sitting in a sunlight automobile's "oven".

So, CD-ROM discs and CD-R discs are made differently. All CD-R discs will be at least somewhat sensitive to heat and strong UV light, especially if stored for long periods. The least sensitive disc we sell for heat exposure would be the "silver/lt-green" type discs, which use a special phthalocyanine recording layer dye, made to minimize environmental stability problems. However, no type of CD-R can withstand long exposures to extremely hot conditions such as the super-heated interiors of automobiles sitting in the sun.

RECOMMENDATIONS:
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* Order CD-R discs featuring the "Improved" light green dye on the bottom recording side. This is the phthalocyanine dye considered most stable and least sensitive to environmental heat and UV light exposure factors. See our Improved Silver CDRs at.

* Order the SLOWEST WRITE SPEED RATED CD-R discs that will meet your minimum requirements from the available offerings. Those discs have a tendency to be less heat sensitive. Remember that all discs will PLAY at any speed once they are properly recorded. Our 16X, 24X and 32X are preferred to minimize possible problems with heat and UV light.

* Be sure to use our "no-wobble" CD/DVD labels and apply them with the new Avery Label Tool to make sure they are bubble free and centered properly. This will minimize the possibility of playback errors when the discs are spun at high speeds to today's fast new CD players. See the "no-wobble" labels at.

* See Avery's "full face" type CD label applicator took kit at.

* Don't store CD-R discs in a closed up auto interior exposed to the sun, when possible.

* Also, when you have to leave them in the car at all, try to protect them inside a well padded and insulated CD case with a zipper closure, and NOT inside the in-dash or trunk-mounted CD player.

* Especially avoid leaving the CD-R discs in direct sunlight, such as on the dashboard or on the seats. Under the seats is better.

* If possible, roll down a window above a half-inch on each side of the car and use a windshield sun-shade to help lower the interior temperature.

That's our best advice for cars and portable CD-R burning... We hope this information helps you create CDs strong enough to have a fighting chance in today's popular in-dash and portable CD players, and that you will enjoy your CD-R discs for years to come!

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(10) How should I label my CD-Rs?

In a perfect world, you wouldn't. Even the best paper labels are susceptible to being ripped, torn, wrinkled, or slip-shod off-center applications, etc.

MARKING -- For many users, a good way to organize their discs is simply to mark on them lightly with a water based or alcohol based, soft tipped marker. We sell special pens for this purpose. To see them online, go to.

PRINTABLES -- Of course, that's not a very attractive option if you're selling your discs, or distributing them to clients or business associates. For professional purposes, the next best option is to print directly onto the top of the discs using special CD/DVD printers equipped with pass-through trays. We sell those printers at.

Printing onto CDs or DVDs requires that the top surface be specially designed to accept the ink, without smearing. Printable CD-Rs cost about 10-cents more per disc than the non-printable kind. They come in 2 varieties; for inkjet or for thermal printers. See the INKJET discs at.See the THERMAL discs at.

LABELS -- using labels is still the most popular way to organize and "index" the contents of a finished CD-R. Your choices vary from high-gloss to a smooth but non-glossy finish in white paper, or clear inkjet and laser labels, and our new light weight "no-wobble" frosted labels. There are even colored paper and metal foil labels for those special occasions! See our labels at.

APPLICATOR TOOLS -- if you're applying labels by hand, you're in for an interesting time of it... we strongly recommend using an inexpensive applicator tool to help you apply the labels smoothly and center them properly. A few bucks spent now can prevent lots of headaches later! Prices start as low as $12.99 each. .

(11) What is a "printable CD-R"?

Printable CD-R discs (and similar DVD-R discs) are discussed in the question above.

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(12) What is a "re-writable CD-RW"?

A regular CD-R is a write-once disc. That means that anything you burn onto the disc cannot be erased. Ever. By contrast, A CD-RW disc is "re-writable" or "write-many-times". It is fully eraseable, and can be erased and re-used or re-written up to 1,000 times. One warning: it is not a "random access" disc. You can't erase just parts of it like you can a hard drive. Once the disc is full, or whenever you want to re-write it, you need to completely erase everything on the disc and start over again. CD-RW discs are used primarily for data storage, backups, or for storing different versions of software, movies, audio tracks and so on. Unlike CD-Rs, they are not generally used for distribution.

CD-RW discs feature a special "phase-change" material in their recording layer, that changes from a crystalline to amorphous states when exposed to different levels of laser power bursts.

Whereas a CD-R disc uses an inexpensive organic dye layer to encode their data, a CD-RW disc uses an inorganic combination of several rare metals (antimony, tellurium, silver, and indium). This alloy layer is sandwiched between two dielectric layers to help produce the crystalline phase when exposed to the right laser power levels. You'll notice that the bottom color of a CD-RW disc is a medium-dark charcoal grey; very different from the bright silver, light blue or light green of CD-R discs.

Their complex structures helps make CD-RW discs much more expensive to manufacture than CD-Rs. Also, the difference between the phases of a CD-RW are relatively subtle,in terms of their reflectivity. So, it takes a more sophisticated read/write head to accurately detect and decode the data on CD-RWs. That sensitive capability is called a "MultiRead" feature. Normal CD players are not capable of reading CD-RW discs, although there are a few players with this feature now entering the market. Today most CD burners are capable of writing to either a CD-R or CD-RW. Due to their complex features and expensive materials, expect CD-RWs to cost 2-3 times as much as CD-R discs or more. See our CD-RW disc products at... click here

(13) Which CD case or holder is best?

Boy-oh-boy, what a question... but we do get this question from many users on a regular basis. Here are the things to consider in choosing a case for your CD-R discs:

DO YOU WANT TO MAIL IT? -- If you want your CD case to also act like a mailer, then the TrimPak CD Case is your obvious choice. See this case at.

WANT THE STORE-BOUGHT LOOK? -- Our "Standard Jewel Cases" are the ones for you if you want to imitate the way CDs look in a music or software display. They come with completely clear and clear/black designs, and can hold from 1 to 6 discs. These are the cases that use the little removable cards or booklets that slide under the front and under the tray in the back. They also come in lots of colors. See our standard jewel cases at.

See our jewel case insert cards (front and back) for standard jewel cases at.

WANT A RUGGED, UNBREAKABLE CASE? -- The problem with standard jewel cases is that they break easily. No way around that with the brittle clear hard plastic they're made from. Our non-breakable CD cases are made from a flexible, translucent polymer that resists breaking and cracking. See these cases at.

WANT A THIN CASE? -- We offer several designs in slender CD/DVD cases -- ranging from our TrimPak Mailer/Case to 5.2mm MaxiSlim and Double Slimline Cases. See these cases at... click here

(14) Will airport security scan X-Rays hurt my CD-R discs?

In today's crazy world, we're getting this question more and more often. The answer is, at the moment, a qualified "no". At least in theory, most x-rays merely zip right through a CD without being absorbed and "burning" the dye layer. Even though the silver layer does reflect many of the x-ray frequency photons, a CD-R disc's organic dye layer is designed to absorb a specific (and much lower) frequency of light from CD burning lasers. Of course, CD-R discs CAN be ruined due to exposure to UV ultra-violet light from the sun or other strong sources. This is because that light closely matches the laser burning light in color or frequency. Since scanning x-rays are much higher in frequency, they are not very likely to be absorbed by the organic dyes used in CD-Rs. Of course, who knows what technology may be coming ...

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