CD

CD, a disc designed for high-quality reproduction of texts or sound in DIGITAL recording. It is a plastic disc with a shiny layer of metal applied to it and a transparent protective plastic coating. The sound signal is made up of millions of tiny indentations pressed into one side of a metal layer. During playback, a narrow laser beam is reflected from the surface of the rotating disk. The sensor notes changes in the beam and generates an electrical signal in the form of a series of pulses. This signal is processed, decoded and turned into an ANALOG audio signal, which is amplified by loudspeakers. see alsoLASER DISC.

The CD player reads digital data from the disc (1) using a focused laser beam (2). Music or other information is recorded on the bottom side of the disc in the form of a spiral track with indentations (3) corresponding to a digital code of ones and zeros. When the disk rotates, the laser mounted on a movable bracket (4) moves along its surface. The laser beam passes through a silver-plated mirror (5) and is focused on the disk (6). When it hits a flat area, it is reflected through a mirror onto the sensor (7), and the information is sent to the integrated circuit. When the laser beam hits the recessed area, it is scattered.

Scientific and technical encyclopedic dictionary.

Synonyms:

See what "COMPACT DISC" is in other dictionaries:

Damn, disc, video disc, audio sidi, audio disc, video sidi, sidi rum disc, sidyukha, sidi rum, sidyushka, sidyuk, sidi, lasernik, compact, laser disc Dictionary of Russian synonyms. compact disc noun, number of synonyms: 15 audio disc (2) ... Synonym dictionary

CD- A device for storing large amounts of information. Data is recorded and read using laser technology. compact disc CD Optical disc of small diameter. Note: CDs are usually recorded... Technical Translator's Guide

Noun, m., used. infrequently Morphology: (no) what? CD, why? CD, (see) what? CD, what? CD, about what? about the CD; pl. What? CDs, (no) what? CDs, why? CDs, (I see) what?... ... Dmitriev's Explanatory Dictionary

COMPACT DISC, CD, male. An optical (laser) disk of small diameter with a signal recorded on it. Musical ensemble album on CD. CD with computer software package. Ozhegov's explanatory dictionary. S.I. Ozhegov... Ozhegov's Explanatory Dictionary

- [English] compact disc, abbr. CD compact disc] a small (20 cm in diameter) silver laser record with one-sided recording, containing a digital (DIGITAL) (digital) recording; miniature semiconductor LASER (in a special... ... Dictionary of foreign words of the Russian language

An optical disk of small diameter (usually 120 mm) with a permanent (non-erasable) signalgram. The most common are CDs with recordings of sound programs (digital optical records) reproduced using optical (laser) ... ... Big Encyclopedic Dictionary

CD- COMPACT DISC, audiodisc, audiosidi, videodisc, videosidi, sidi, sidi rum, sidi rum disc, decompressed. compact, colloquial laser, colloquial reduction CD, colloquial reduction sidyukha, colloquial reduction seat, colloquial reduction seat bench... Dictionary-thesaurus of synonyms of Russian speech

CD- COMPACT DISC, or optical disk, laser storage medium. In it, the recording is made by a laser beam in the form of microscopic grooves carrying a digital code. CD data is also read by a laser beam and converted from digital form to... ... Publishing dictionary-reference book

Modern encyclopedia

CD- COMPACT DISC, an optical disk of small diameter (usually 120 mm) with a permanent (indelible) recording of sound reproduced using optical (laser) players. The duration of the sound program on a CD is up to 1 hour. According to quality... ... Illustrated Encyclopedic Dictionary

QUESTIONS AND ANSWERS: What you need to know about burning CD-R and CD-RW discs.

1. What do you need to have to burn CDs?

You need a computer with a device installed in it called a CD-writer. This device connects to the computer in several possible ways. Most drives for recording discs have an IDE interface and are connected in the same way as regular CD-ROMs or hard drives and have an internal design. However, there are other versions, both external and internal - with a SCSI interface, connected to a parallel port or to the USB bus.
The second necessary part for burning discs is software. Its choice is very large - from the most popular commercial packages from Adaptec (Easy CD Creator, Easy CD Deluxe, Easy CD Pro) to shareware programs such as Nero or CDRWin.
And finally, you need a blank CD-R or CD-RW disc

2. What can you burn onto CD-R or CD-RW discs?

Traditionally, discs can store both sound and data. Data is stored on CDs in the same format as it is stored on a hard drive. It should also be noted that it is possible to create mixed discs, combining sound with data.

3. What is the difference between CD-R and CD-RW discs?

CD-R stands for CD-recordable, that is, “recordable.” This means that information recorded on such a disk cannot be deleted from there. The main difference between CD-RW (CD-rewritable) discs is that information from them can be deleted and recorded again. As a result, CD-RW discs, which are more flexible in use, are slightly more expensive than conventional write-once discs.

4. How much information can be recorded on a CD-R disc?

5. Why is the standard duration 74 minutes?

The general consensus is that this length was chosen because the CD developers wanted a format that would accommodate Beethoven's Ninth Symphony. They determined which diameter to use, and the length of some performances decided this issue.

Burned discs can be used on the following devices:

Home CD Player Given that home CD players predate CD-R burners, there is no guarantee that all recorded music CDs will play in audio players. However, for best results, it is recommended to use CD-R discs, since their specifications are much closer to traditional music discs than CD-RW discs. DVD-ROM drive or DVD player The vast majority of DVD players and all DVD-ROM drives (with the exception of the first examples of these devices) are able to read information from CD-R and CD-RW discs. CD-ROM drives

All modern CD-ROM drives read excellently, both write-once discs and CD-RW discs. Nuances exist only with old drives, which in some cases do not read CD-R discs, or read these discs, but do not read CD-RW discs. If your old drive is marked as having a Multiread function, then this means that you can use it to cope with this task. A good indication that a drive is capable of handling recordable discs is how fast the drive reads data. If the speed is 24x or higher, then, as a rule, such a drive is quite suitable for working with CD-R and CD-RW discs.

7. Why are the reflective sides of the discs different colors?

Different CD companies have patents on the various chemistries they use to produce the discs. Some companies produce disks themselves, others simply license their technology to them. As a result, the reflective side of CDs comes out different colors. CD-Rs are available in the following composition combinations: gold/gold, green/gold, silver/blue, and silver/silver, and their many shades. The visible color is determined by the color of the reflective layer (gold or silver) and the color of the dye (blue, dark blue or clear). For example, green/gold discs consist of a gold reflective layer and a blue dye, so the disc is gold on the label side and green on the recording side. Many have come to the conclusion that "silver" discs are made of silver and, based on this assumption, have tried to speculate about the reflectivity and durability of the media. Until a manufacturer's representative comes forward with a statement about the actual composition of the disc, it is unwise to assume anything specific. Some CDs have an additional coating (such as Kodak's "Infoguard") that makes the CD more scratch-resistant but does not affect the way the information is stored. The top (label) side of the disc is the most important area to worry about because this is where the data lives and is the area that is most easily damaged on a CD-R. You can protect the disc from scratches by sticking a round CD sticker over its entire area. CD-RW discs have a completely different structure. The data side (as opposed to the label side) is a silvery dark gray color that is hard to describe. You can also give a short list of which companies produce which discs:

Taiyo Yuden produced the first "green" CDs. They are now also made by TDK, Ricoh, Kodak, and probably a few other companies.

Mitsui Toatsu Chemicals (MTC) produced the first "golden" CDs. They are now also made by Kodak and possibly others.

Verbatim produced the first "silver/blue" CDs.

Many brands of CD-R (such as Yamaha and Sony) are OEM versions of one of the major manufacturers. By and large, it is difficult to determine who produces what, since new plants have been built and sellers may change suppliers.

8. What do the speed numbers (for example, 6x4x32) mean in the parameters of CD burners?

Conventional audio players play music CDs in 74 minutes. This speed is taken as the basis when measuring the speeds of playing and recording CDs and is called a single speed (1-x). Single speed corresponds to a transfer of 150 Kilobytes per second. A CD-ROM drive with two times the speed (2x) transfers data at a speed of 300 Kilobytes per second.

Three numbers in the parameters of CD-writers indicate the speed at which this device can write CD-R discs, CD-RW discs and, accordingly, read these discs.
For example, 6x4x32 means that this device writes CD-R discs at a speed of 6x (900 KB/sec), writes CD-RW discs at a speed of 4x (600KB/sec) and reads any type of CD at a speed of 32 (4800 KB/sec)

9. What formats exist when burning CD-R discs?

This is the most difficult question to answer, given that many different CD formats have emerged over the past few years, while there are still historical formats that have been around for a long time and are used in specialized applications. Below is an overview of the main formats:

Music discs (Audi o CD) or CD-DA or "Red Book"

To burn regular music CDs, you need the disc you burn to conform to the CD-DA standard. When recording, standard WAV files (or AIFF - Apple Audio Interchange File Format) are used as a source.

ISO9660 Data CD

This standard defines the form in which conventional data is written to CD-R discs. This standard has many restrictions, namely, the maximum number of subdirectories cannot exceed 8, file names cannot be longer than 8 characters, and 3 characters are allocated for the file name extension. However, this standard is compatible with a large number of computers and operating systems.

A format proposed by Microsoft simultaneously with the advent of the Windows operating system"95. The length of the file name is limited in this standard to 64 characters, and this format is now supported both in the Windows environment and in MacOS and Linux. Joliet is based on the ISO9660 standard and disks, written in this format can be read by almost any computer, however the file names will be truncated to an 8+3 format.

This format strictly applies to Macintosh computers. HFS CDs can only be read on this type of computer.

UDForPocket Writing

UDF (Universal Disk Format) is a radical extension of the ISO9660 standard, somewhat reminiscent of Joliet. Adaptec DirectCD software (included with Easy CD Creator Deluxe, or sold separately for the Mac platform) and, for example, CeQuadrat PacketCD software allow you to burn discs in this format. UDF differs from other formats in that you can treat a CD like a large floppy disk, copying files to it using standard Windows or MacOS tools. However, this format is not suitable for transferring discs to other people, because in order to read discs in this format, they will need to install special software for reading such discs.

ISO 9660 Rock Ridge

An extension of the ISO9660 standard, used exclusively in Linux and UNIX operating environments.

ISO Level 2

A slightly modernized ISO9660 format, simplified in terms of restrictions. For example, the file name length in it is limited to 31 characters. However, the low level of compatibility of this standard does not allow it to be used as widely as, for example, the Joliet format is used.

VideoCD or VCD or "White Book"

The VideoCD format was developed in the mid-90s and was intended for use in devices such as the Philips CD-I player. VideoCD discs contain video image and audio compressed using the MPEG1 standard. Despite the fact that the Philips CD-I player has not been produced for a long time, these discs can be used on the vast majority of DVD players if they support reading CD-R or CD-RW discs.

8. What format should I use if I want….

…. exchange data with friends who use an operating system similar to mine?

Everything is simple here. Windows operating system users should use the Joliet format, Mac users should use the HFS format.

…. share data with people who use different operating environments and platforms?

For maximum compatibility, it is recommended to use the ISO9660 format. However, if you need to store long file names on disk, then you should try using the Juliet format. Modern Macs and most operating systems now have the ability to read discs written in this format.

…. listen to music on a regular audio player?

Then you should burn the disc in CD-DA format, which will provide the highest level of compatibility with your audio player.

10. How to burn discs with mixed content?

There are two options for burning such discs:

Mode I- when using this format, data is recorded at the beginning of the disc (in any known format), then the recorded audio tracks follow. If you need to combine audio and data, then using this mode will provide the necessary level of compatibility with various devices and operating environments.
CD-XA (Mode II)- this mode differs from the previous one in that data and sound can be recorded in random order. However, this flexibility has a negative impact on the compatibility of the recorded discs.

11. What is a multisession CD?

This technology allows you to add data or sound to a disc that already has something written on it until the disc is closed. This was very relevant in the early 90s, when the cost of a blank CD-R disc reached $12, CD-RW discs did not exist, and hard drives had a small capacity.

Discs recorded using this technology have some compatibility issues, and therefore it is not recommended to use it without compelling reasons. The UDF format makes this technology unnecessary; With Direct CD and similar software, you can burn data without worrying about compatibility. If you need to give the disc to other people, then just burn it at once in Joliet format

12. What is "closing" a disk?

"Closing" a disc means that after this procedure is completed, nothing can be done on that CD-R disc. If you never use the "multisession" feature, then there is no point in thinking about it, because the disk will close automatically after the end of writing information to the disk. Many older CD-ROM drives and audio players have problems reading unsealed discs, so it makes sense to "seal" the disc for greater compatibility.

If you want to write something to a "closed" CD-RW disc, simply perform the "clear" function and you will be able to write data to that disc again. If you use the UDF format, then there is no concept of “closing” the disk in the traditional sense of the word - just copy and delete files from such a disk, as from a simple floppy disk.

And they merged with the thick mass of darkness that gravitated over them. The CD was dying...

(Based on: N.V. Gogol. The lantern was dying)

What is a CD

Wikipedia gives this definition:

“A compact disc is an optical storage medium in the form of a plastic disk with a hole in the center, the process of writing/reading information to/from which is carried out using a laser. Further development CD- steel discs DVD-disks. The compact disc was originally created to store audio recordings in digital form (known as CD-Audio), however, later it became widely used as a medium for storing any data (files) in binary form (the so-called. CD-ROM(English) Compact Disc Read Only Memory, read-only CD)...".

The CD is a polycarbonate substrate 1.2 mm thick and 120 mm in diameter, covered with a thin layer of metal (gold, silver, aluminum, etc.) and a protective layer of varnish, on which a label representing the contents of the disc was applied.

On the outer surface of the CD there is an annular protrusion 0.2 mm high, which allows the disc, placed on a flat surface, not to touch this surface.

There is a hole with a diameter of 15 mm in the center of the disk.

Disc weight – 15.7 g.

Data storage format on CD , known as Red Book("book"), was developed by the company Philips. In accordance with this format, audio can be recorded onto a CD in 2 channels with 16-bit pulse code modulation and a sampling rate of 44.1 kHz. Thanks to error correction using the Reed-Solomon code, light radial scratches do not affect the readability of the disc.

Information is written to the disk in the form of a spiral track consisting of pitov(English) pit– depression, “crater”, depression – non-reflective spot on the surface CD-ROM, representing the binary "0"), extruded into the polycarbonate base. Each pit is approximately 100 nm deep and 500 nm wide. Pit length varies from 850 nm to 3.5 µm. The spaces between pits are called Landom(English) land– contact pad, contact area – , reflective spot on the surface CD-ROM, representing binary "1"). The pitch of the tracks in the spiral is 1.6 microns.

Data from the CD is read using a beam with a wavelength of 780 nm. The principle of reading information with a laser is to register changes in the intensity of reflected light. the beam is focused on the information layer into a spot with a diameter of 1.2 microns. If the light is focused between the pits (on the landing), then the photodiode registers the maximum signal. If light hits the pit, the photodiode registers a lower light intensity.

Read/write speed CD 150 KB/s is indicated (that is, 153,600 bytes/s). For example, a 48-speed drive provides maximum read/write speed CD equal to 48 x 150 = 7200 KB/s (7.03 MB/s).

CDs originally held up to 650 MB information (or 74 minutes of audio recording). Since 2000, disks with a capacity of 700 have become increasingly widespread. MB, allowing you to record 80 minutes of audio.

CD-ROM-th legends

...There is a legend that the CD was not created Philips And Sony, and the American Russell, who worked in the company Optical Recording. Allegedly, already in 1971 he demonstrated his invention for storing data. He did this for “personal” purposes, wanting to prevent his vinyl records from being scratched by pickup needles. 8 years later, a similar device was “independently” invented by companies Philips And Sony.

...Vice President of the Corporation Sony Oga (English) Ohga), who adored classical music, believed that a CD should be able to contain Beethoven's 9th Symphony (the most popular piece of music in Japan in 1979, according to a special survey!). In this case, in his opinion, up to 95% of classical works can be distributed on disks. Further research showed that the 9th Symphony, performed by the Berlin Philharmonic Orchestra under the direction of von Karajan, had a duration of 66 minutes. And the longest performance was the symphony under the direction of Furtwängler, performed at the Bayreuth Festival - 74 minutes. Allegedly, this served as the decisive argument when deciding on the initial capacity of the disk - 650 MB information (or 74 minutes of audio recording).

…IN Philips And Sony until May 1980, there was no consensus on the outer diameter of the disc. From an engineering point of view Sony, a diameter of 100 mm was sufficient as it allows miniaturization of the portable player. From senior management Philips The idea was to make a disc no larger than the diagonal size of a standard audio cassette (115 mm), which had great success on the market. In May 1980, company executives compromised and approved the “final” disk diameter of 120 mm, a disk capacity of 74 minutes of audio recording and a sampling frequency of 44.1 kHz.

...Another legend says that the disc diameter of 12 cm was chosen because it corresponds to the size of a standard Dutch backing...

A story of rise and fall, or Requiem for a CD

CD Compact Disk, CD) was developed in 1979 by a Dutch company Royal Philips Electronics together with Japanese Sony. Philips developed a technological process for the production of compact discs and turntables. Sony has improved its recording method (signal encoding), previously used in professional digital tape recorders, which ensures error-free reading of data from the disk ( Pulse Code Modulation, PCM– pulse-code modulation of the signal).

“When we started, there was no alternative,” recalls Kramer ( Kramer), head of the optical development department of the laboratory Philips in the 70s XX century “The attempt to bring digital audio to the masses was very risky...”

In 1982, mass production of CDs began at a plant in Langenhagen near Hannover (Germany). Release of the first commercial music CD– it was a CD with a recording of the album "The Visitors" groups ABBA– was announced on June 20, 1982.

First sales CD-players began in the fall of 1982 in Germany, and they reached the US market only in the spring of next year.

Corporations made a significant contribution to the popularization of compact discs. Microsoft And Apple Computer. Sculley, then head Apple Computer, said in 1987 that compact discs would revolutionize the world. And he turned out to be right!..

The rise in popularity of CDs was greatly facilitated by the fact that they began to be used to record not only music, but also any (!) data. And then everything began to be equipped with a drive CD-ROM. In addition, discs intended for recording at home have become widespread: CD-R (Compact Disc Recordable; CD+R, CD-R) – for single and CD-RW (Compact Disc ReWritable; CD+RW, CD-RW) – for multiple recording.

The CD was a resounding success: by 2004, worldwide CD sales CD, CD-ROM, CD-R, CD-RW reached 30 billion pieces. By 2007, about 200 billion were sold worldwide. CD(for every inhabitant of the Earth, including babies and old people, at least 30 disks!).

But in 2007, the end of the CD era began - sales CD fell by 15%!..

For almost 30 years, the compact disc led the music media market. But time does not stand still! With the growth of information volumes, new media formats appear - DVD, , Blu-ray. Many people prefer to simply "" music (or videos) online and download to their hard drive rather than buy CDs.

There are many more reasons for the decline in the popularity of CDs: small volume CD, etc. and so on.

Honestly speaking, on CD They haven’t been paying attention for a long time, especially since they fell in price and their volume increased significantly. In addition, it allows you to quickly download large amounts of information.

Analysts Gartner think that CD has lost its commercial appeal - it has neither advantages nor prospects - so the recording industry must abandon CDs and seriously focus on distributing music via the Internet.

Save the format CD no innovations and tricks will be able to, including the one proposed in 2007 by the company Walt Disney format CDVU+ (CD View Plus), which in addition to music tracks may include other multimedia content.

The largest British company Linn Products was the first to abandon the release of home and professional CD- , after their sales fell by 40% in 2 years.

On April 1, 2009, the world's largest music store closed in New York City. Virgin Megastore. A few weeks before its closure, the iconic Times Square music venue announced a full sale. But, nevertheless, there was no influx of buyers, despite the fact that discounts on goods reached 60%, and the store itself is located in the center of Manhattan, where it is always very crowded.

The flagship of the American entertainment industry Virgin Entertainment Group announced that it will close 5 more record stores - in San Francisco, Denver, Orlando, Hollywood and lower Manhattan. The retail network of music and video products, once founded by the billionaire Sir Branson, known for his extraordinary projects, could not withstand competition with the Internet market. Sales fell from $230 million in 2002 to $76 million in 2008.

So, His Majesty the CD is dead, long live...

What is a CD-R disc (recordable compact disc).

Generally speaking in terms of definitions, recordable compact discs or CD-R are optical discs produced using technology that allows the user to independently create their own compact disc for printing on cd in one of the electronic formats.

In terms of its internal structure, a CD-R is a regular compact disc in which the reflective layer is made primarily of gold or silver film, and between it and the polycarbonate base there is a recording layer (dye layer) made of an organic material that changes the degree of reflection when heated. During the recording process, the laser beam heats selected points of the layer, which darken and stop transmitting light to the reflective layer, forming areas similar to pits. The production is based on write-once (WORM) disk manufacturing technology, standardized by Philips and Sony and described in the relevant documentation (Orange Book standard, Part II).

Or if we translate all this into a language that is more understandable to the user, we can say that - “A recordable CD-R disc is a disc produced using technology that allows the user to burn his own CD in one of the formats. After this, the disk can be used read-only."

History of recordable CDs for printing discs starts in 1985. Sony introduced the Discman portable CD player, leading to a boom in the CD market.

In connection with the development of this market, the largest disk manufacturers began to think about creating a disk on which the user could record any information himself.
At the first stages of creating the technology, the main problem was the selection of materials whose reflective ability would be sufficiently high.

In 1988, Tajio Yuden discovered the desired combination of coatings: gold and cyanine. The reflectivity was 70%.

The next problem was the method of applying the active organic layer to the surface, but this problem was also solved: the active layer is applied to the surface by rotating along a trajectory, the function of which is Know-how.

In June 1988, the world's first CD-R was released at Tajio Yuden's production facilities.

Tajio Yuden currently owns the following patents:
- optical structure of the disk
- technology of dividing the disc into tracks
- technology for obtaining the highest reflectivity of the layer

In 1989, Tajio Yuden began trial production of CD-Rs. That same year, the standard for the production of recordable compact discs, Orange Book Part II, was released.

The trendsetters in this market were Sony, Philips, and Tajio Yuden.

So, in the structure of a CD-R disc, four main layers can be distinguished (the fifth is the image applied to the surface of the disc), applied in stages.

Let's take the path of making a disk. Initially, the plastic base of the disc is made - polycarbonate (E), which makes up the main part of the CD-R and gives it the necessary strength and shape. Next, the active layer (D) /dye/ is applied to the finished plastic mold. It is this layer that allows you to write to the disk and determines its reliability and the quality of reading information in the future. Today, two types of active layer are widely used: cyanine and phthalocyanine.

Examples of cyanine CD-Rs

Examples of cyanine CD-Rs
Cyanine dye has a blue-green (aqua) or deep blue tint to the working surface; phthalocyanine, in most cases, is practically colorless, with a pale shade of light green or golden color, which is why discs based on a phthalocyanine active layer are often called " gold." It's hard to say which of these two types of layers is better. Cyanine dye is more tolerant of extreme read/write power combinations than gold phthalocyanine dye, so cyanine-based discs are often easier to read on some drives. Phthalocyanine is a slightly more modern development. Discs based on this active layer are less sensitive to sunlight and ultraviolet radiation, which increases the durability of recorded information and somewhat more reliable storage in adverse conditions.
Examples of phthalocyanine CD-Rs

There is an opinion that cyanine discs are better readable than phthalocyanine discs. Most likely, such assumptions could not arise out of nowhere; therefore, they are based either on one’s own observations or on non-scientific research, because from a technical point of view, the colorlessness of phthalocyanine is precisely what ensures the compatibility of disks based on it with a wider range of reading devices. The fact that the blank looks more transparent does not mean its poor optical characteristics. The recorded disc, whether cyanine or phthalocyanine based, is required to reflect light only at 780nm, not the entire visible spectrum.

After dye has been applied to the polycarbonate blank, the disc is covered with a special layer of reflective material (C). Conventional CD-ROMs use aluminum for this purpose, while CD-R discs use pure silver, which allows them to achieve a reflectivity of 65-80%.

The final stage of manufacturing a disc for CD replication is the application of a protective layer (B), on which images (A) can later be applied. The most common and easiest to manufacture protective layer is a special varnish. Disc varnishing does not provide a 100% guarantee of data safety when exposed to external mechanical or chemical influences. However, many Chinese “manufacturers” often skimp on varnish, or apply it in such a way that concentric waves in the form of waves form on the disc, which indicates either an incorrectly calculated application speed or an incorrect drying mode, which makes the discs practically defenseless against influence of external influences.

A higher degree of protection is provided by the application of additional coatings, which make CD replication more resistant to scratches and chemical influences (such as, for example, writing with various markers). One of these “advanced” coatings is the development of Kodak, which received the symbolic name “Infoguard” (“information guard”).

What, then, is the difference between a CD-R and a rewritable CD-RW disc? Rewritable discs use an intermediate layer of organic film, which changes its phase state from amorphous to crystalline under the influence of a beam, and vice versa - as a result of which the transparency of the layer changes. Changes in state are recorded due to the fact that the material of the recording layer, when heated above a critical temperature, changes into an amorphous state and remains there after cooling, and when heated to a temperature significantly below the critical temperature, it restores the crystalline state. CD-RW discs can withstand thousands to tens of thousands of rewrite cycles. However, their reflectivity is significantly lower than stamped and single-use CDs, which makes them difficult to read in conventional drives. To read CD-RWs, you formally need a drive with automatic gain control of the photodetector (Auto Gain Control), although some conventional CD-ROM drives and home players are capable of reading them on a par with regular discs.

Even though in the 21st century humanity has switched to using flash memory, the CD format still remains very popular and in demand among users. Compact discs, as the abbreviation CD (Compact Disk) stands for, unlike volatile media, have higher information reliability, low cost and 100% compatibility with all reading devices. The only difference that CDs have among themselves is information capacity. It remains to figure out which manufacturer’s product you need to buy, and what pitfalls can be encountered in the race for large containers.

World standard

Few people know that the world community owes the creation of the CD, whose information capacity according to the standard is 650 megabytes, to Sony Corporation. Back in 1982, the Japanese created a portable audio media that replaced vinyl discs. Beethoven's 9th Symphony, beloved by most Japanese, with a duration of 73 minutes, determined the size of the disc. When converting audio data into megabytes, it must be at least 640 MB.

Considering the recording of the pause and additional information for playback devices, approximately 10 megabytes were added. The physical size of the disk is 5.25 inches - the current ATX format for all personal computers.

Baseline

Even though the standard capacity of a CD is 650 megabytes, it will be difficult to find such a product in the store lately. But without much difficulty you can buy one with an information capacity of 700 and 800 megabytes. Such discs in the country's markets are nothing more than a marketing ploy by manufacturers trying to attract potential buyers. It’s clear: the greater the capacity, the more you can record. Only the manufacturer is silent that, with a constant physical size, such capacity is achieved due to high recording density, which not all recording devices can produce. Also, not every playback device is capable of correctly reading data from high-capacity media.

"Lottery" with high-density discs

Even though the manufacturer talks about 100% compatibility of its discs with all kinds of multimedia devices, the buyer should know that there is a possibility that the player or computer will not be able to play music correctly or open data files. And the larger the CD capacity, the higher this risk. Discs with a recording density of 700 megabytes are very popular in the domestic market. Users are attracted by their low cost. Such discs can be written and read by almost all devices without any problems.

But with CDs with a recording density of 800 megabytes, problems may arise. Not every writing device is capable of correctly recording information onto a medium. Judging by numerous reviews, the user often believes that the problem is in the burner drive and, scolding it, does not even suspect that in this case the manufacturer is to blame for producing a low-quality CD.

About the manufacturing plants

It's funny that the majority of buyers prefer expensive and well-known brands, whose names and logos are printed on the surface of the media, completely ignoring cheap, little-known CDs whose information capacity is suitable for the consumer. Often there is no difference between an expensive and a cheap disc, because they have the same manufacturer and the same batch number. It's all about advertising. One seller advertises his product and inflates the price, while the other sells discs at a low cost. An example would be discs from BASF and Intenso. The difference in price is colossal, and the CD is from the same batch. Before buying media, you should pay attention not to the sticker, but to reviews about the manufacturer. Recently, due to high competition, a lot of marketing research has been carried out, the results of which are picked up by computer magazines and Internet resources, so the buyer should not have problems finding information.

We will talk about CDs, the maximum information capacity of which is no more than 700 megabytes. Having studied the popular ones, we can conclude that there have been no significant changes in the optical media market over several decades.

Serious brands have only strengthened their positions, and manufacturing plants of low-quality products stay afloat only thanks to advertising. Regarding the types of disks by capacity, you can safely give your preference to the brands Mitsui, HP, Sony&Philips, 3M, Verbatim and FujiFilm. Professionals recommend refraining from purchasing CDs from brands such as Princo, Memorex, Arita, BASF, Dysan, MMore and JTEC. Not only do poor quality media have many errors during playback, but also the size of the CD is actually 5-20 megabytes smaller than what the seller stated on the packaging.

Active layer color

Often, when purchasing from a seller, you can hear that the quality of recording on a CD media directly depends on the color of the active layer - the darker it is, the better the safety of information, regardless of the type of disc capacity. Assuring the buyer that black music CDs with a protective vinyl layer, although they cost an order of magnitude more, will last for centuries, successfully complete the deal. In fact, the appearance of the disk, including the color of the active layer, is created according to the requirements that the customer sets to the manufacturing plant. Along with such indicators as capacity, there is a “design” column, in which the color of the active layer is indicated. But the column “active layer material” is responsible for the shelf life. For example, inexpensive cyanine can be destroyed under the influence of direct sunlight in ten years, but expensive phthalocyanine will allow you to read information from a disk without problems after a century.

Write speed

The size of a CD is always accompanied by an indication that can be set to the writing device when recording information onto optical media. Without going into technology, it is important for any user to know that the higher this figure, the less time will be spent on all types of disks in capacity have different time indicators, which differ slightly from each other. On average, at “1x” speed, recording will take about 40 minutes, and a disc with the “52x” parameter will be recorded in one minute.

In addition to the capabilities of the disc, you need to pay attention not only to the recording speed characteristics of the writing device, which are indicated on the front panel. You should also read the instructions for the device on which you plan to play the CD. For example, many car radios cannot play music from media recorded at speeds exceeding 24x.

Capabilities of the protective layer

A spontaneous purchase at the market or in a store forces you to produce a beautifully designed CD. A photo of your favorite character or the title of a movie instantly attracts attention, and the disc adds to your home collection. In any case, every person has ever come to the idea that in addition to recording information on a medium, it would be nice to design the appearance of a CD by applying your own drawing or photograph to its surface. There is no problem with this. It is enough to purchase a disk marked “Printable”. The surface of the protective layer is equipped with a special coating that can absorb ink from an inkjet printer, similar to matte photo paper. Naturally, to apply a picture you will need a printer whose functionality supports printing on CDs.

Business card disk

In big business, according to the rules of good manners between partners or contractors, the proposal should be in the form of a visual presentation, which many businessmen often prefer to familiarize themselves with in their free time. In a mailbox, a presentation can get lost among a large volume of email, and it’s unaffordable to give out flash drives to potential partners for free. In such cases, a business card disk will save you. Many printing companies provide this service. At the customer’s request, the manufacturer can add a logo or contact information to a CD disc cut to the size of a regular business card. For such a CD, information capacity is not critical. The 120-180 megabytes available for recording are quite enough to record several presentations. Such a business card, having non-standard dimensions, can be reproduced without problems on any optical disc reader.

About MiniDiscs

The mini-format of CDs is still quite popular among owners of video cameras and audio players with an 8 cm format factor. Among all existing standard types of disks, such a CD can hold no more than 210 megabytes per storage medium. But its price breaks records, exceeding several times the cost of the most expensive 5.25-inch CDs. It's all about the manufacturer. As practice and numerous tests show, the manufacturer, fulfilling the requirements stated by corporations producing audio and video equipment, produces a disc of the highest quality. Any user can verify this by simply comparing the characteristics of different disks by testing with specialized software.