CD Burner

Here you will find background information on CD-Burners. From their origin to the importance they hold and to the vendors available.

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CD Burner - Overview
A CD recorder, CD writer or CD burner is a compact disc drive that can be used to produce discs readable in other CD-ROM drives and audio CD players. A DVD recorder produces DVD discs playable in stand-alone video players or DVD-ROM drives. They are generally used for small-scale archival or data exchange, being slower and more materially expensive than the molding process used to mass-manufacture pressed discs.

How it Works
A recorder encodes (or burns) data onto a recordable CD-R, DVD-R or DVD+R disc (called a blank) by selectively heating parts of an organic dye layer in the disc with a laser in its write head. This changes the reflectivity of the dye, thereby creating marks that can be read as with the "pits" and "lands" on pressed discs. The process is permanent and the media can be written to only once.

For rewriteable CD-RW, DVD-RW and DVD+RW media, the laser is used to melt a crystalline metal alloy in the recording layer of the disc. Depending on the amount of power applied, the substance may be allowed to melt back into crystalline form or left in an amorphous form, enabling marks of varying reflectivity to be created. Most rewriteable media is rated by manufacturers at up to 1000 write/erase cycles.

The competing DVD+R and DVD-R disc formats use very similar dye-based media, but differ mainly in the way timing hints for the write head are laid out on the disc surface. This is also the case with DVD+RW and DVD-RW.

Most internal CD recorders for personal computers, server systems and workstations are designed to fit in a standard 5.25" drive bay and connect to their host via an ATA, SATA or SCSI bus. External CD recorders usually have USB, FireWire or SCSI interfaces. Some portable versions for laptop use power themselves off batteries or off their interface bus.

SCSI recorders are less common and tend to be more expensive because of the cost of their interface chipsets and more complex SCSI connectors.

Compatibility
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Performance
There are mechanical limits on the maximum angular velocity at which discs can be spun: beyond a certain rate of rotation the tensile stress on the disc will cause 'creepage' of plastic as well as separation of the foil on top of the CD. In the more practical terms, this limits the maximum reading and writing speeds for CDs to about 52x at the outer edge of the disc. Modern 52x drives spin the disc at slightly over 10000 RPM. Higher reading speeds may be achieved by using multiple lens assemblies or by reading several consecutive tracks simultaneously, but those drives are expensive to manufacture and are uncommon.

History
Early-model recorders were CLV (constant linear velocity) drives. The recording speed on such drives was rated in multiples of 150 KiB/s; a 4X drive, for instance, would write steadily at around 600 KiB/s. The transfer rate was kept constant by having the spindle motor in the drive run about 2.5 times as fast when recording at the inner rim of the disc as on the outer rim.

To keep the rotational speed of the disc safely low, more recent high-speed recorders tend to use the Z-CLV (zoned constant linear velocity) scheme. This divides the disc into stepped zones, each of which has its own constant linear velocity. A Z-CLV recorder rated at "52X", for example, would write at 20X on the innermost zone and then progressively step up to 52X at the outer rim. Some drives also limit the maximum read speed to lower values such as 40x. The reasoning is that it is safe to assume that a blank CD fresh off the spindle will be clear of any structural damage, but the same assumption will not hold true for every disc inserted for reading.

In the late 1990s, buffer overruns became a very common problem as high-speed CD recorders began to appear in home and office computers, which—for a variety of reasons—often could not muster the I/O performance to produce a data stream to keep the recorder steadily fed. The recorder, should it run short, would be forced to halt the recording process, leaving a truncated track that often renders the disc useless.

In response, manufacturers of CD recorders began shipping drives with "buffer overrun protection" (under various trade names, such as Sanyo's "BURN-Proof", Ricoh's "JustLink" and Yamaha's "Lossless Link"); these can suspend and resume the recording process in such a way that the gap the stoppage produces can be dealt with by the error-correcting logic built into CD players and CD-ROM drives.

The DVD+R and DVD+RW disc formats were designed with discontinuous recording in mind because they were expected to be widely used in digital video recorders. Many such DVRs used variable-rate video compression schemes which required them to record in short bursts; some allowed simultaneous playback and recording by alternating quickly between recordings to the tail of the disc whilst reading from elsewhere.

Over-Burning
Over-Burning is the process of recording data past the normal size limit.

Many disc manufacturers extend a recordable disc to leave a small margin of extra groove at the outer edge. This lead-out was originally intended to provide tolerance for the read head of an audio CD player should it over seek, by providing a padding of up to 90 seconds of silent digital audio.

Recording onto the lead-out is possible with some combinations of CD recorder and authoring software. The actual amount of data that it will hold depends ultimately on the recordable media and varies somewhat between brands of disc, with some being up to 10% of the total disc capacity.

Almost all CD-ROM drives are capable of reading from the lead-out. For this reason, software publishers have on occasion shipped their software on similarly oversized compact discs to reduce packaging costs. Oversized discs have also been used as a form of copy protection because it is more difficult to record copies of them.

Copy Protection
Copy protection, also known as copy prevention, is any technical measure designed to prevent duplication of information. Copy protection is often emotionally debated, and is thought to sometimes infringe on some users' property rights: for example, the right to make a backup copy of a videotape they have purchased, to install and use computer software on multiple computers, or to upload their music into their digital audio player for easier access and listening.

The media industries have always referred to the technology as copy protection. Opponents believe the term encourages people to identify with publishers who benefit from it, rather than the users who are restricted by it. Copy prevention and Copy control are neutral terms that are sometimes used instead.

The term is also often related and/or confused to the concept of digital rights management. Digital rights management is a more general term because it includes all sort of management of works, including copy restrictions, but copy protection may include measures that are not digital. A more likely description to this is "technical protection measures" (TPM), which is often defined as the use of technological tools in order to restrict the use and/or access to a digital work. Using the scientific classification as an analogy, DRM is the genus, and TPM is the species.

What's Next?
The advent of CD burners marked a huge cultural shift. The technology made it feasible for the average person to gather songs and make their own CDs. Suddenly, music-mix makers everywhere had their hands on the means of production.

Today, writable CD drives (CD burners) are standard equipment in new PCs, and more and more audio enthusiasts are adding separate CD burners to their stereo systems. In less than five years, CDs have eclipsed cassette tapes as the mix medium of choice.

In this article, you'll find out how CD burners encode songs and other information onto blank discs. We'll also look at CD re-writable technology, see how the data files are put together and find out how you can make your own music mixes with a CD burner.

CD-RW discs have taken the idea of writable CDs a step further, building in an erase function so you can record over old data you don't need anymore. These discs are based on phase-change technology. In CD-RW discs, the phase-change element is a chemical compound of silver, antimony, tellurium and indium. As with any physical material, you can change this compound's form by heating it to certain temperatures. When the compound is heated above its melting temperature (around 600 degrees Celsius), it becomes a liquid; at its crystallization temperature (around 200 degrees Celsius), it turns into a solid.

What to Buy?
You'll have to consider a number of factors when you choose a burner. Of course, cash is king, and the amount you're willing to spend will largely dictate which drive you'll end up with. The price of DVD burners continues to plunge, and these do-it-all devices offer the best bang for the buck. Still, if you're not ready to spend at least $100 and you're primarily interested in burning CDs, you can pick up a CD-RW drive on the cheap. Or you can spend just a few dollars more for a combo drive--a CD-RW that can read, but not write, DVDs.


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