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What types of optical discs are there? Types of optical media. UDF file system

DVD Directory

DVD

DVD is a family optical disks, the same size as compact discs (CDs), but with significantly greater storage capacity achieved by increasing recording density.

The advent of DVD. DVD forum

The idea behind the advent of DVD discs was to develop a storage medium that could be equally successfully used in audio and video equipment, in computer technology, game consoles. This would bring the different areas of electronics closer together.

The name DVD originally meant Digital Video Disc (Digital Video Disc). Later, in connection with the decision to expand the functions of DVD, the abbreviation began to be read differently - Digital Versatile Disk.

The development of the DVD format was officially announced in September 1995 by a group of 10 companies: Hitachi, JVC, Matsushita, Mitsubishi, Philips, Pioneer, Sony, Thomson, Time Warner and Toshiba. In May 1997, on the basis of this consortium, the DVD Forum was created - an organization open to membership, which today has more than 200 members.

The main tasks of this organization are the development and promotion of the DVD format, the development of agreed specifications, as well as licensing the activities of enterprises in the field of DVD technology. Within the framework of the forum there are special working groups on various aspects of DVD technology. International standards have been adopted for a number of specifications.

The most important advantages of DVD technology

Today DVD is already a widespread, time-tested and at the same time dynamic emerging technology with huge potential.

  • recording and playback of high-quality video and audio in real time, efficient work with computer multimedia information, as well as providing efficient random access to data stored in the form of many small files;
  • disk capacity up to 4.7 GB (about 2 hours MPEG-2) per side for single-layer recording and 8.5 GB per side for dual-layer recording;
  • the ability to record information in two layers on each side;
  • unified UDF file system;
  • possibility of recording and replaying DVD recording disks;
  • backward compatibility with existing CD disks - the geometric dimensions of DVD and CD disks are identical, all DVD equipment is capable of reading CD-Audio and CD-ROM disks (MultyRead specification).

First DVD formats

DVD technology initially relied on 3 main formats, the availability of which was determined by the specific requirements for various DVD applications:

  • DVD-ROM is used to record data, including multimedia, used in computer technology;
  • DVD-Video is used when recording video materials for later viewing on video equipment or using an attached computer DVD-ROM drive. The format provides protection against illegal copying of information;
  • DVD-Audio is used to record high-quality multi-channel audio. Additionally, the DVD Forum recommends additional support for video, graphics, and other information.
These formats described read-only disks. Information is placed on such disks once - during their production. With the development of DVD technology, disc specifications have emerged that allow disc users to record and rewrite information. However, the main forum participants were unable to agree on a single specification for such discs due to the desire to maintain independent control over their copyrights. technical developments. As a result, several competing specifications emerged (DVD-RAM, DVD-RW, DVD+RW formats). Let's look at the list of DVD disc formats being developed today.

Evolving DVD formats

Only for reading

  • DVD-ROM
  • DVD-Video
  • DVD-Audio
For multiple rewrites
  • DVD-RAM
  • DVD+RW (not supported by DVD forum)
  • DVD-RW
For one-time recording
  • DVD-R (G)
  • DVD-R(A)
For video recording
  • DVD-VR

Compatibility

The developers were unable to achieve a unified approach when developing the format of recordable discs. Competition has predetermined the lack of support for several recording formats by one device. Therefore, discs written in one of the formats, as a rule, are not readable on drives of other recordable formats. An attempt to overcome the disunity of recording formats was made by Panasonic, which in April 2001 introduced a device that works with DVD-RAM and DVD-R(G) formats.

Some devices may not understand that format DVDs, which was proposed after their release. Naturally, consumer electronics can be targeted at a very specific segment of the consumer market (DVD-Audio, DVD-Video, both formats), and does not necessarily have to be capable of reading computer discs, as defined by the DVD forum. At the same time, computer drives work equally well with video, audio, multimedia and other computer discs.

UDF file system

A major achievement in ensuring compatibility in DVD technology was the unified file system MicroUDF, adopted in 2000. File system MicroUDF is adapted for use in DVD version file system UDF (Universal Disk Format), which, in turn, is based on international standard ISO-13346. This file system is gradually replacing the outdated ISO9660, which was created at one time for use in CDs. For the transition period (until computer devices and disks operating in the ISO9660 format go out of circulation), the UDF Bridge file system will be used, which is some combination of MicroUDF and ISO9660. Only MicroUDF can be used to burn Audio/Video DVD discs.

The capabilities of the MicroUDF file system are as follows:

  • independence from the hardware and software platform used (in this sense, UDF is optimal choice in archival systems);
  • large capacity. The entire disk can be represented as a single volume;
  • optimal transfer speed. The speed of reading and writing data in UDF format can be faster than the performance of many "native" file systems when large files are served (for example, in multimedia systems)
  • maximum possible sizes file;
  • use of the UNICODE font format, which provides effective international support;
  • support for extended file attributes, which is used in some “native” operating systems;
  • support for long filenames with limit extensions operating system. The maximum file name length is 255 characters;
  • interchangeability of DVD discs consumer electronics and computer systems.
Using MicroUDF, you can simultaneously store videos, audio recordings, digitized photos, and computer files on a single DVD disc. This ensures cross-platform compatibility, i.e. the DVD becomes a single medium for Macintosh, DOS/Windows, OS/2, UNIX.

Perspectives DVD

The presence of different standards and specifications does not mean that DVD technology stands still. The efforts of various companies today are aimed at introducing “blue laser” technology - with a shorter wavelength. This will increase the recording density on disks with the resulting improvement in other characteristics.
Calimetrics Inc has proposed ML (multilevel) technology, which can triple the capacity of a standard DVD/CD. In this case, there is no need to make any modifications to the mechanism and optics of existing drives. To implement new technology, it is enough to use a chipset developed by this company. The essence of the technology is the ability to use information characteristics pit depth (up to 8 levels) when working with discs. Note that a similar technology, but for CD discs, is being developed by TDK in collaboration with other companies.

Read-only DVD formats

DVD-ROM(Digital Versatile Disc Read Only Memory)

DVD-ROM discs are intended for use in computer technology. Information is written to the disk only once - during its production.

The progress of DVD devices largely follows the path traveled by CDs, and is mainly aimed at improving speed characteristics and introducing a recording function. First-generation DVD-ROM devices used CLV mode and read from the disc at a speed of 1.38 MB/s (in traditional DVD notation this is 1x). Second-generation devices could read DVDs at twice the speed - 2x (2.8 MB/s). Modern DVD-ROMs - third-generation devices - use rotation control mode (CAV) with a maximum reading speed of 4x-6x (5.5 - 8.3 MB/s) or more. Modern DVD-ROM drives (disk drives) support reading almost all formats, including CDs.

DVD-Video

The DVD-Video format is designed for storing and playing video. Like DVD-ROM, this specification defines the ability to read-only information - playback of recordings using video players (video recorders). The specification is based on the DVD-ROM format, but provides a special way of placing data that prevents the possibility of bit-by-bit copying of discs. Video materials in encoded form are placed on the disk during the production process. Playing DVD-video is only possible on household video players (video recorders) or DVD drives connected to a computer. When using computer equipment, information decoding is carried out either in hardware or software. The modern specification ensures recording of high-quality video on disc (up to 2 hours in MPEG-2 compression format), as well as multi-channel sound accompaniment in 8 languages, selection of screen format, captions in 32 languages, interactive control via on-screen menu, up to 9 angular viewing directions, protection against illegal copying, delimitation of video viewing by region, control of children’s access to video materials.

DVD-Audio

A new generation of music format after CD. The format specification defines high-quality multi-channel audio, support for a wide range of sound quality (quantization 16, 20, 24 bits at frequencies from 44.1 to 192 kHz), playback of DVD players for CD discs, support additional information(including video, text, menus, screensavers, convenient navigation system), connection with websites providing information support, expanding capabilities when new technologies appear.

There are two versions of the DVD-Audio format: simply DVD-Audio - for audio content only, and DVD-AudioV - for audio with additional information.

Special measures have been developed to protect disks from pirated copying.

Rewritable DVD formats

Multiple write

All known specifications of rewritable DVD discs use multiple recording technology based on the physical principle of changing the phase state (crystalline/amorphous) of the information layer under the influence of a laser with a wavelength of 650 (635) nm (phase-change recording). Reading of information is carried out by determining optical characteristics information layer in its various phase states upon reflection of laser beams (the same as during recording).

Re-recordable material

The working material used is AVIST, created by TDK in 1995. The characteristics of this material almost perfectly meet the requirements of DVD rewriting technology:

  • high reflectivity - up to 25-35%, which is quite enough for compatibility of DVDs during playback;
  • ease of changing the phase state both at high and low low speeds recordings, which is especially important when working with various applications. Applications that work with rewritable CDs (such as CD-E) write at speeds less than 3 m/s. Working with data in the DVD-RAM format requires a higher recording speed from the working layer - from 3 to 6 m/s. When working with compressed video information, the recording speed must exceed 6 m/s;
  • excellent signal-to-noise ratio and phase change characteristics allowed TDK to achieve ultra-small marker sizes (less than 0.66 mm);
  • AVIST can withstand at least 1000 rewrite cycles even at speeds less than 3 m/s. With more high speeds recording, the number of rewrite cycles increases.
Each of the formats has its own advantages and disadvantages, which determined their areas of application. The most common format today is the DVD-RAM format due to the lower cost of drives and disks that work with it.

DVD-RAM(Digital Versatile Disc Random Access Memory)

Rewritable format developed by Panasonic, Hitachi, Toshiba.

The format was approved by the DVD forum in July 1997. Equipment and discs of this format were tested for 3 months in more than 20 computer manufacturing companies around the world. Over 160 forum participants voted to accept the specification. Today it is the most common DVD format in the computer industry.

DVD-RAM drives read DVD-ROMs. In turn, DVD-RAM discs can only be read by so-called third generation DVD-ROM drives produced since mid-1999.

The first generation of DVD-RAM discs held 2.6 GB per side. Modern - second - generation disks carry 4.7 GB on the side or 9.4 GB for a two-sided modification.

Two types of single-sided DVD-RAM discs are available: in a cartridge and without a cartridge. Disks in a cartridge are mainly intended for household video equipment, where it is necessary to exclude the influence of external factors during intensive manual use. Cartridges, in turn, can be of two types - openable and solid.

The most important advantages of DVD-RAM format discs are the ability to be rewritten up to 100,000 times and the presence of a recording error correction mechanism.

The largest number of rewrite cycles among all DVDs, an error correction mechanism and random access to the disk both when writing and reading predetermined the maximum efficiency of this format in secondary storage devices. The vast majority of mass storage devices - robotic DVD libraries - use this technology.

DVD-RAM discs can be used for recording and playback streaming video on equipment that supports the DVD-VR specification (see below).

DVD+RW(Digital Versatile Disc ReWritable)

The DVD+RW format is promoted only by its developers - Hewlett-Packard, Mitsubishi Chemical, Philips, Ricoh, Sony and Yamaha (not supported by the DVD forum).

DVD+RW discs can record streaming video or audio, as well as computer data. DVD+RW discs can be rewritten approximately 1000 times.

Based on DVD+RW, a streaming video recording format has been created - DVD+RW Video Format. Devices and discs operating in this format are positioned on the market as fully compatible with equipment operating in DVD-Video formats. This means that DVD+RW discs containing video content can be played on older consumer DVD equipment.

Philips announced the launch of its DVD video recorder in September 2001. DVD+RW discs recorded on this device can also be read by conventional DVD-Video players. This solution was proposed as a response to the DVD-VR specification adopted by the DVD forum (see below).

DVD-RW(Digital Versatile Disc ReRecordable)

There are other names for this format: DVD-R/W and less commonly DVD-ER.

DVD-RW is a rewritable format developed by Pioneer. DVD-RW format discs hold 4.7 GB per side, are available in single-sided and double-sided versions and can be used to store video, audio and other data.

DVD-RW discs can be rewritten up to 1000 times. Unlike DVD+RW and DVD-RAM formats DVD-RW discs can be read on first generation DVD-ROM drives.

TDK claims that its DVD-RW discs have a lifespan of approximately 100 years.

Write-once DVD formats

DVD-R(Digital Versatile Disc Recordable)
DVD-R is a write-once format developed by Pioneer. Devices based on this format were the first to record DVDs. The recording technology is similar to that used in CD-R and is based on an irreversible change under the influence of a laser of the spectral characteristics of the information layer coated with a special organic composition.

DVD-R discs can record computer data, multimedia programs, and video/audio information. Depending on the type of information recorded, discs can be read on other types of devices compatible with the recorded format, including DVD-Video video players and most DVD-ROM drives. Single-sided DVD-R discs hold 4.7 or 3.95 GB per side. Double-sided discs are only available in 9.4 GB total capacity (4.7 GB per side). Currently, the format does not support dual-layer recording technology.

The durability of DVD-R discs is estimated at over 100 years.

To protect against illegal copying, two specifications have been developed: DVD-R(A) and DVD-R(G). These two versions of the same specification use different laser wavelengths when recording information. Thus, discs can only be written on equipment that meets their specifications. Disc playback can be performed equally successfully on any equipment that supports the DVD-R format.

DVD-R(A) (DVD-R for Authoring) is used in professional applications. In particular, support for a special format (Cutting Master Format) allows you to use these discs to record the original replica of information (pre-mastering) instead of the usual use of DLT tapes for these purposes.

DVD-R(G) (DVD-R for General) is intended for wider use. Disks of this format are protected from the possibility of bit-by-bit copying of information onto them from other disks. The format is supported in mass storage devices (for example, in robotic DVD libraries offered by Pioneer itself).

The DVD-VR specification is based on DVD-RAM and is supported by the DVD Forum. The DVD-VR format allows you to record up to 2 hours of high-quality MPEG-2 video in real time on a single-sided 4.7 GB DVD-RAM disc and provides capabilities such as editing already recorded video footage and recording various types of still images. Electronics based on this format are produced, for example, by Panasonic, Toshiba, Samsung, Hitachi.

Lookup tables

Table 1. DVD disc capacities

Format Specification Number of sides Number of layers per side Capacity, GB*
DVD-Video and DVD-ROM DVD-5 1 1 4.7, or more than 2 hours of video
DVD-9 1 2 8.5, or more than 4 hours of video
DVD-10 2 1 9.4, or more than 4.5 hours of video
DVD-14 2 1+2 13.2, or more than 6.5 hours of video
DVD-18 2 2 17.1, or more than 8 hours of video
DVD-RAM (DVD-VR) DVD-RAM 1.0 1 1 2.6
2 1 5.2
DVD-RAM 2.0 1 1 4.7
2 1 9.4
DVD-R DVD-R 1.0 1 1 3.9
DVD-R 2.0 1 1 4.7
2 1 9.4
DVD-RW DVD-RW 2.0 1 1 4.7
2 1 9.4

* 1GB – 1 billion bytes

Table 2. Basic parameters of DVD discs of the latest modifications

Parameter Disk type
DVD-ROM DVD-RAM DVD-RW DVD+ RW DVD-R
One side capacity 4.7 GB 4.7 GB 4.7 GB 4.7 GB 4.7 GB
Laser wavelength 650 650 650 650 650 (G)
635(A)
Reflectivity 18-30% (two-layer) 15-25% (2,6) 18-30%
Recording method Impression from the matrix during production Phase change Phase change Phase change Changing dye color
Entry form Not applicable Wobbled Land& Groove Wobbled groove Wobbled groove Wobble pre-groove
Inter-track distance 0.74 µm 0.615 µm 0.74 µm 0.74 µm
Minimum pit length 0,40 0,28 0,40
Number of zones Not applicable 35 Not applicable Not applicable Not applicable
Rotation control method* CAV ZCLV
CAV within zone		 CLV CLV (for video) or CAV (for data) CLV
Data writing speed up to 8.31 MB/s (read) 2.77 MB/s 11-26 Mbit/s, 2.77 MB/s
File system Micro UDF and/or ISO9660 UDF/UDF Bridge UDF/UDF Bridge UDF/UDF Bridge Type1 UDF Bridge Type2 UDF
Cost of a single-sided disk (drive) $20-30($500) $10-15 ($1000)

* CLV - (Constant Linear Velocity) constant linear speed

CAV - (Constant Angular Velocity) constant angular velocity

ZCLV - (Zone Constant Linear Velocity) zone constant linear velocity

DVD formats Types of DVD drives
DVD-RAM DVD-RW DVD-R(G) DVD-R(A) DVD+ RW DVD-Video DVD-Audio DVD player (universal)
H Z H Z H Z H Z H Z H Z H Z H Z
DVD-ROM + − + − + − + − + − + − − − + −
DVD-R(G) + − + + + + + − + ? + − + − + −
DVD-R(A) + − + − + − + + + − − − + − + −
DVD-RAM + + − − − − − − − − − − + − + −
DVD-RW + − + + + + + − + − + − + − + −
DVD+RW − − + − + + + − + + + − + − + −
DVD-Video + − + − + − + − + − + − − − + −
DVD-Audio + − + − + − + − + − − − + − + −
DVD-AudioV + − + − + − + − + − + − − − + −

Note - in some cases, "+" means that reading or writing does not conflict with the DVD forum specifications, however such devices may not yet be on the market.
"-" means that there is no specific requirement for reading or writing, but there may be devices on the market that provide this capability

Optical storage

Optical drives are designed to read and usually write/rewrite from optical discs. Optical disks are round and flat plates made of dense material (usually consisting of polycarbonate) with applied layers that allow information to be stored in the form of tiny pits (pits, frompit - hole, deepening). The reading process is carried out by a laser beam, which, reflected from the surface of the disk, enters a photocell, where the light is converted into an electrical signal, the magnitude of which allows the recorded information to be decoded.

The most common optical disc formats for use in personal computers are CD, DVD, Blu-ray.

CD-ROM ( Compact Disc Read Only Memory, read-only CD) a type of CD,which appeared in 1982 as a result of research by two companies - Sony and Philips. The first discs used the "Red Book" format, in which the playing time of one cassette was 74 minutes 33 seconds, which corresponds to the playing time of Beethoven's 9th Symphony, which was very popular in Japan at that time. The audio sampling frequency is 44 kHz for stereo sound and the bit depth is 16 bits. They had a capacity of 650 MB and allowed storing 75 minutes of music (starting from 200, discs with thinner recording tracks appeared, which made it possible to increase the capacity to 700 MB with recording 80 minutes of music). CD-ROM drive and initially developed as an analogue of vinyl discs and were intended for recording and playback music information. They also have a single concentric track that runs from the outer edge to the inner, making many turns. The principle of reading information is optical, that is, the laser beam reads data that is recorded on an aluminum (or other type) substrate. In addition, the information is recorded on the disc, unlike a vinyl disc, in digital rather than analog form, and after reading it is decrypted and converted into sound. To protect the disc from damage, the aluminum substrate is covered with transparent plastic.

Creation technology CD-ROM drives next. First, a disk is made on which only those places where a unit of information is located are burned out and remain without changing the place with zero values. After this, a matrix is ​​made, with the help of which the blanks are stamped, a layer of metal (aluminum, silver, gold, etc.) is sprayed onto the information surface to increase the reflectivity of the laser beam, and they are coated with transparent plastic (varnish) to protect the data. When a disk is inserted into the drive, a laser beam slides along the concentric circle of the disk and by the reflected light it is determined whether it is recorded: a zero or a one.

Initially, CD-ROM discs were designed to store only music information. Due to the fact that disks use digital information rather than analog, they began to be used in computers.

Usually , storage device CD-ROM supports modes : Audio CD, Music Disc, Super Audio CD, CD-ROM (mode 1 & mode 2), CD-ROM/XA (mode 1, form 1 & form 2), Super Video CD, CD-Text, Video CD, CD -I/FMV, Photo-CD (Single & multisession), CD- i and others . The first drives could only handle certain formats, but eventually they could handle all formats. Therefore, the user does not need to know the format. As a rule, it is enough to know that there are audio, video discs and discs with programs (or text).

Next, the “Yellow Book” standard was developed, which contains a header that determines the type of disc: music or software. The music format was already well developed, and the software format was determined by each manufacturing company itself. Due to the rapid development of this technology, the discrepancy in the standard could not last long, so the High Sierra advisory standard arose, on the basis of which the ISO 9660 standard soon appeared. For this standard, there is a table of contents and a data area on the disk. The first track contains parameters for synchronizing the drive and disk with each other, followed by a table of contents in which the description of each file contains the direct address on the disk.

There are three types of such disks:

CD - ROM The disk is usually written in an industrial manner, and in the future it can only be read. It measures 120x1.2 mm and has a capacity of 650-879 MB. Service life 10-50 years. Such discs are often supplied with computer devices; they contain software, music discs, etc.

CD - R The disc has the same characteristics as a CD-ROM, but allows information to be written to them once.

CD - RW the disc has the same characteristics as a CD-ROM, but allows you not only to write information on them, but also to write more of it, also to erase previously recorded data and write new ones.

To work with them, CD drives were used, which have several types:

CD- ROMthe drive can only read CD disks. One of the most important characteristics of this device is reading speed information. Normal (single) speed corresponds to the speed of reading audio discs, which is 150 kb/sec. Then came CD-ROMs with 2, 4, 6, 8, 10, 12, 16, 24, 32, 36, 40, 52 times the speed. The data transfer rate is accordingly a multiple of 150 kb/sec. For example, for a 40x drive it will be equal to 40x150 = 6,000 Kb/sec, and here the maximum speed is indicated, which is equal to or lower for different types of drives, which depends on the manufacturer. The six-speed drive allows for video output at frame rates of 25 frames per second or higher, which is fast enough for on-screen viewing. Discs for use with this device are sometimes also called compact discs (this concept also includes CD-R discs, CD-RW) or CD-ROM discs (Compact Disk - CD; see figure below).

CD - R drive is a write-once optical drive. It allows you to read CD-ROM, CD-R, CD-RW discs, but also allows you to write CD-R discs once. This drive has the ability not only to read discs, but also to write them. For example, the read speed is 40 times, and the write speed is 6 times.

In such devices, a laser beam burns grooves on the surface of the disk, while the areas that reflect light are called “lands”, and the non-reflected areas are called “pits”. The combination of these sections makes it possible to encode information in a two-bit representation.

By virtue of various reasons In practice, when recording, it is impossible to achieve an ideal location of the burnt grooves, and during playback, sound defects and jitter appear, which is called “jitter.” IN to a certain extent The use of a special Audio Master mode allows you to get rid of such unwanted distortions, when the burnt grooves are forcibly increased in length. This mode is used in cases where you need to improve the quality of the recorded sound.

Typically recording is done at constant angular velocity (CAV). However, when the rotation speed changes several times (x2, x4, x8, etc.), the recording pauses and so-called “connection points” are formed, which deteriorates the quality of the recording. In such cases, a buffer underrun protection called SafeBurn is used. As a rule, it turns on only when the disk rotation speed changes, and the recording mode with constant angular velocity (CAV) is mainly used. This method of improving the quality of playback audio is called Zone Constant Line Velocity (Z-CLV) recording.

Very interesting is available on some devices for recording to discs. digital information the ability to burn text onto the surface of a laser disc, be it a list music files or your data. For this, the DiscT2 mode is used, in which any text is typed that is worthy of reproduction on the surface of a music or other type of disc created by oneself.

CD - RW (Compact Disc-ReWritable) storage device is a reusable optical storage device. It allows you to read CD-ROM, CD-R, CD-RW discs, write CD-R discs once, but also write and re-write, as well as rewrite previously recorded CD-RW discs. This drive has the ability not only to read discs, but also to write them. For example, the read speed is 40 times, and the write speed is 6 times. There could also be a speed of additional recording.

A CD-RW device works on a different principle, that is, when writing to them, the beam does not burn out, but transforms the substrate into an amorphous state, which allows you to establish a different reflective effect. Therefore, they can write data multiple times. However, discs dissipate information worse than standard CD-ROM discs, so they cannot always be read on standard media.

The more capabilities a device has, the more limitations it has. How easier wheels, the greater the reflective effect they have. CD-ROM discs have the best reflective effect, which can be read in CD-ROM, CD-R and CD-RW drives.

CD-RW format discs have even less reflectivity and may not be readable on all older CD-ROMs and CD-R drives (old drives). It is quite difficult to say definitely which drives will be readable and which will not, since it depends on the device model. Currently, CD-R compact discs are sold on which information can be recorded. If after recording there is still free space on the disk, then additional information can be written to the disk, and so on. CD-RW discs allow you not only to record information, but also to delete unnecessary data, that is, write data repeatedly and are somewhat more expensive than CD-R discs.

In 1996 they appeared DVD -discs(Digital Versatile Disc - digital universal disk, originally stood for Digital video Disc - digital video disk. Now it is not decrypted in any way), which had a capacity of 4.7 Gigabytes due to compaction of recording tracks, that is, 7 times more than the capacity of CD-ROM disks. This is the most common type of disc, which is single-layer and single-sided. However, there are discs that have two layers on one side and have a capacity of 8.5-8.7 Gigabytes (they may be called DVD 9, the number means rounded capacity), there are discs with one layer, but with recording on two sides, with a capacity of 9.4 Gigabytes (they may be called DVD 10), double-layer and double-sided with a capacity of 17.08 Gigabytes (they may be called DVD 18). Double-layer discs have two translucent layers with powerful beam focusing, allowing information to be read from either the first or second layer. More high density data is achieved by reducing the disk space per bit and applying compression techniques. But in practice, the most common are single-sided, single-layer ones.

After creation uniform standard DVDs to record movies on them, the whole world was divided into six zones so that movies recorded for one zone could not be read in others. Therefore, an old DVD drive may have a pictogram showing an image globe with numbers indicating which zones this drive works with or ALL (all) - to work with disks in all zones. Modern DVD drives do not have such a partition.

The information on the disks is located in sectors that contain data and 882 bytes for the error correction code, which makes it possible to increase the reliability of reading information, since in case of failures the values ​​​​are calculated using the correction code. If there are bad sectors, the reading speed slows down and repeated reading occurs, and so on up to a certain number of attempts. As a result, either the code will be read, or a message will appear on the screen stating that it is impossible to read information from of this disk, after which it switches back to maximum speed.

Unlike CDs, DVDs have their own file system, UDF, or ISO-9660 for data. Data is stored in 2048 byte sectors. Disks can be DVD-video, DVD-audio, DVD-Data and mixed types.

Discs DVD - ROM just like CD-ROMs are read-only. They have already been recorded somewhere and are sold with the recorded information.

The standard for recording on disk was developed in two ways, one standard called MMCD was developed by Philips and Sony, the second called Super Disc by Toshiba and several others. Therefore, two formats for recording data arose - DVD -R and DVD +R. These formats are close to each other, however, the plus format is better to use, since it takes less time to rewrite and the recorded data has fewer errors. Accordingly, there are two formats of rewritable discs DVD -RW and DVD +RW.

Write-once discs that have a double layer on one surface are designated by DL symbols, for example, DVD -R DL and DVD +R DL. They have a capacity of up to 8.5 gigabytes.

To work with DVDs, DVD drives are used, which have several types:

DVD - ROM The drive can only read both DVDs and CDs. One of the most important characteristics of this device is reading speed information. The multiplicity per unit is taken as 1.32 MB/sec, which is 9 times faster than CD speed. They have different reading speeds for CD and DVD discs, which are indicated in the device manual.

DVD - R drive is a write-once optical drive. It allows you to read CD-ROM, CD-R, CD-RW discs, all types of DVD discs, and also allows you to write CD-R discs and DVD +R and DVD-R discs once. This drive has the ability not only to read discs, but also to write them. For example, the reading speed is 40 times, and the writing speed is 6 times, and the speed is indicated separately for CDs and DVDs and, accordingly, separately for DVD -R and DVD +R disks.

DVD - RW storage device is a reusable optical storage device. It allows you to read and burn all types of CD and DVD discs. Reading and writing speeds are indicated separately for CDs, DVD -R, DVD +R, DVD +R DL, DVD -R DL, DVD +RW, DVD -RW, DVD +RW DL, DVD -RW DL, that is, those operations , which the drive can conduct. Here it is also better to use the plus format, since the minus format requires you to first erase the information and then write it, and the plus format allows you to rewrite data in real time.

Standard Blu - ray Disc (BD ) (blue ray- blue beam and disc- disk; writing blue instead of blue- intentional)was developed by the BDA consortium, released in 2006. U this standard there was a competitor - HD DVD from Toshiba, however, this company abandoned further support for HD discs in 2008 after the “format war”. The information reading speed (single speed) is 4.5 Mb/s. Increasing the volume of recorded information is achieved by using a laser beam in the blue-violet range with a shorter length of 405 nm, at the same time as CD and DVD drives They use red and infrared lasers with wavelengths of 650 nm and 780 nm.

A single-layer disk can store 25 gigabytes, a double-layer disk can store 50 gigabytes, a three-layer disk can store 100 gigabytes, and a four-layer disk can store 128 gigabytes. A disk can have more layers. So in 2008, 20-layer disks with a capacity of 500 gigabytes were demonstrated.

IN currently BD-ROM read-only, BD-R write-once, and BD-RE write-once discs are available. There are also double-layer disks with DL symbols in the name with a capacity of up to 50 gigabytes.

Drives for these disks are Blu - Ray Read-only discs that allow you to read and write all types of CDs and DVDs, as well as read-only BDs. Respectively Blu - Ray RE allow you not only to read, but also to write all types of CDs, DVDs and BD discs (single-layer, for multi-layer you need to read the instructions).

To insert a CD or DVD into the drive, first press the button on the front panel of the drive (picture below). At the same time, a tray is pulled out of the drive, into which you need to place the disk in a special recess for it with the working surface on which the data is located, down, or with the pattern facing up. Then press the button again, and the tray slides into the drive housing. Now you can work with the disk. The tray has a second recess for disks, approximately half the diameter and currently very rarely used (they are often shown in detective and science fiction films).


For normal operation, the drive must be in a horizontal position. There is a drive that can work in a vertical position. In this case, the disk is inserted into the slot by hand, after which a special mechanism holds it and inserts it into the drive.

The optical drive has an emergency eject hole for the tray if it does not eject. To do this, you need to insert a thin rod, for example, a straightened paper clip, and press on it. In addition, there may be a button to skip to the next song for audio CDs. A configuration switch can be installed at the back, it is advisable to install a Slave, and there is also a connector for testing the drive by the manufacturer. Some drives may come with microphones, headphones, or sound cards.

For boot disk need to:

Turn on the computer;

Press the tray open button and it will slide out;

Place the disc with the print side up on the tray;

Press the tray open button again. The tray slides in, after which you can start working.

Do not pull the tray out or in by hand. It is not advisable to keep the tray open for a long time when there is no work; you should not place foreign objects on the tray, for example, placing a cup of coffee; you should not put pressure on the tray when placing a disc.

When there is no operation, the drive goes into energy saving mode, and the drive noise stops. When a read command is received, the drive starts working automatically.

The production of a disk occurs as follows: first, a disk is made, which is called the “mother”, then a working copy is stamped - the “father”, then others are pressed on its basis.

Basic drive characteristics:

Type: interior or external. The internal drive is inserted into the system unit. The external one has a rectangular body, connects to a parallel port (in old computers), USB (in modern ones) and has a wire connected to the mains. There is also an external option for laptop computers, connected using a PCMCIA connector;

- baud rate(Data Transfer Rate, DTR), respectively indicated as two-speed, four-, thirty-two, etc.;

- buffer memory capacity(Buffer Memory). Cache memory is a RAM chip that is located on the drive board. They provide benefits, so the larger the volume, the better;

- average time between breakdowns(Mean Time Between Failure, MTBF). This characteristic available in many devices, but not described everywhere;

- interface type or bus to which it is connected;

- average access time(Access Time, AT). It is larger for CD-ROM drives than for hard drives, which is determined by fundamental differences in the design of the drive, and differs tens of times, and the greater the multiplicity, the shorter the access time. So, for a 4x drive it is approximately 150, and for a 32x it is 80 ms. This value can be found in the device passport;

- error rate(Error Time);

- list of supported formats.

There may also be other parameters, such as noise and vibration levels. In addition, when purchasing, you need to see whether the tray moves smoothly and whether it is firmly held open.

Latest BIOS versions allows you to boot your computer from CD and DVD disks. A CD-ROM disc at the beginning of the track has a service area, which contains information for synchronizing the drive and disk, then the volume table of contents (VTOC), which contains data about the organization of directories and files on the disk, then data and a label end of the volume. Thus, knowing the path and file name, you can use the table to find the file’s location on the disk and directly position the head to read data, which reduces search time and read operations.

Connects device using two cables: power and information. There are three types of drives: those connected to the SCSI bus, to the IDE bus or to the SATA connector. It is better to have a drive that connects to the IDE connector, if the motherboard supports it. Since there are usually few SATA connectors, and if you need to install several optical or hard drives, there may be a problem with the availability of a free connector.

The connection to just such a bus is described below. Optical drives can be connected together with hard drive. The data cable consists of 40 cores (shown in the figure above) and has three plugs. One is connected to the hard drive controller (on older boards) or directly to the motherboard (see also the description of the boards and hard drive). The second to the optical drive and the third to the hard drive. Do not forget that the edge of the cable, marked in red, when connecting the plug, should be located near the markings 1, 2, which indicate the first cores of the wire, the opposite end - near the numbers 33 and 34. The second power cable should be connected to the marking indicated on top of the plug, that is, red (5v), black, black and yellow.

If you have a sound card, to listen to sound from music discs, you must connect a third cord consisting of four wires. One end connects to sound card, the other - to the drive. They are marked with the symbols R and L. The wire coming from the sound card with the symbol R must match the R on the drive. The figure below shows the back of the drive, which has connectors for connecting wires.


The procedure for installing a new optical drive is the same as installing a floppy drive. If Windows 9x is installed, a corresponding message about finding a new device will appear on the screen. In Windows, the operating system itself recognizes new devices, including an optical drive.

When working with disks, you must do following rules:

Do not touch the work surface, otherwise greasy fingerprints may remain on it;

Take the disk by the outer edges, you can take it by the edges of the central hole;

Clean the disc from the center of the disc to the outer edge with a soft, dry cloth. Do not use strong solvents such as acetone, detergents, antistatic aerosols;

Store discs in a special box or disc sleeve;

Do not bend the disc;

Do not write on the working surface of the disc;

When storing the disc, avoid contact with sun rays, as well as strong heat, which can lead to warping of the disc.

Disks may have defects that prevent data from being read. If there is a displacement of the concentric tracks relative to the center of the disk, then such a disk will be difficult to read, and such a defect cannot be detected by eye. Reducing the disk rotation speed may help, for example, try doing this on a slower drive. If the disk is warped, sometimes noticeable to the eye, then reducing the rotation speed can also help to read such disks.

If there are specks on the disk, then, depending on their location and size, it is sometimes possible to use such a disk. Scratches that go from the edge to the center are often harmless, but scratches that run along the edge may prevent data from being read. Therefore, you need to wipe the disc from the center to the edge. To check the disk, special test programs. When installing, use an interrupt (IRQ) - 7 and higher, base addresses 300h to 340h, DMA1. CDs are quite reliable, however, if there are cracks on the CD, it is recommended to make a copy of the disc, as new cracks may appear in the future and the information on the disc will be unreadable.

Installing the drive. to install this device, need to:

Turn off computer;

Remove the protective cover of the system unit;

Insert the drive into the guides of the system unit. After installation, be sure to tighten the screws on the sides of the device. Sometimes, in order to reach with a screwdriver and tighten the screws, you may need to remove other devices. After this, connect the wires as described above, install the protective cover, turn on the computer and check the operation of the drive.

The technical installation of an optical drive is similar to installing hard disk.

If the tray does not extend, the reason may be that the drive is tightly secured with screws inside the system unit, which causes the drive to become skewed. The sound during CD overclocking is not a sign of malfunction. After installing the optical drive for testing, you can try copying some files from optical disk to your hard drive. You should not disassemble the drive yourself. The drive should not be exposed to rain or in a damp place.

In 1979, Philips and Sony created a completely new storage medium that replaced the gramophone record - an optical disc (Compact Disk - CD) for recording and playing back sound. In 1982, mass production of CDs began at a plant in Germany. Microsoft and Apple Computer made significant contributions to the popularization of the CD.

Compared to mechanical sound recording, it has a number of advantages - very high recording density and complete absence mechanical contact between the media and the reading device during recording and playback. Using a laser beam, the signals are digitally recorded on a rotating optical disk.

As a result of recording, a spiral track is formed on the disk, consisting of depressions and smooth areas. In playback mode, a laser beam focused on a track moves across the surface of a rotating optical disk and reads the recorded information. In this case, depressions are read as zeros, and areas that evenly reflect light are read as ones. The digital recording method ensures almost complete absence of interference and high sound quality. High recording density is achieved due to the ability to focus the laser beam into a spot smaller than 1 micron. This provides big time recording and playback.

Rice. 13. Optical CD

At the end of 1999, Sony announced the creation of a new media, Super Audio CD (SACD). In this case, the technology of the so-called “direct digital stream” DSD (Direct Stream Digital) is used. The 0 to 100 kHz frequency response and 2.8224 MHz sampling rate provide a significant improvement in sound quality compared to conventional CDs. Thanks to much more high frequency sampling, filters become unnecessary during recording and playback, since the human ear perceives this step signal like "smooth" analog. At the same time, compatibility with the existing CD format is ensured. New single-layer HD discs, dual-layer HD discs, and hybrid dual-layer HD discs and CDs are being released.



Keep sound recordings in digital form on optical discs is much better than in analog form on gramophone records or tape cassettes. First of all, the durability of recordings increases disproportionately. After all, optical discs are practically eternal - they are not afraid of small scratches, and a laser beam does not damage them when playing recordings. Thus, Sony provides a 50-year warranty on data storage on disks. In addition, CDs are not affected by the interference typical of mechanical and magnetic recording, so the sound quality of digital optical discs is incomparably better. Moreover, when digital recording opportunity arises computer processing sound, allowing, for example, to restore the original sound of old mono recordings, remove noise and distortion from them, and even turn them into stereo.

To play CDs, you can use players (the so-called CD players), stereo systems, and even laptop computers equipped with a special drive (the so-called CD-ROM drive) And sound speakers. To date, there are more than 600 million CD players and more than 10 billion CDs in the hands of users around the world! Portable portable CD players, like magnetic compact cassette players, are equipped with headphones (Fig. 14).


Rice. 14. CD player


Rice. 15. Radio tape recorder with CD player and digital tuner


Rice. 16. Music center

Music CDs are recorded at the factory. Like gramophone records, they can only be listened to. However, for last years Optical CDs have been developed for single (so-called CD-R) and multiple (so-called CD-RW) recording on a personal computer equipped with a special drive. This makes it possible to make recordings on them in amateur conditions. You can record on CD-R discs only once, but on CD-RW - many times: like on a tape recorder, you can erase the previous recording and make a new one in its place.

The digital recording method made it possible to combine text and graphics with sound and moving images on the personal computer. This technology is called "multimedia".

As information carriers in such multimedia computers Optical CDs are used: CD-ROM (Compact Disk Read Only Memory - i.e. read-only memory on a CD). Externally, they do not differ from audio CDs used in players and music centers. The information in them is also recorded in digital form.

Replaces existing CDs new standard storage media - DVD (Digital Versatil Disc or digital disc general purpose). They look no different from CDs. Their geometric dimensions are the same. The main difference between a DVD disc is its much higher recording density. It holds 7-26 times more information. This is achieved thanks to the shorter laser wavelength and smaller size focused beam spots, which made it possible to halve the distance between tracks. Additionally, DVDs may have one or two layers of information. These can be accessed by adjusting the position of the laser head. On a DVD, each layer of information is twice as thin as on a CD. Therefore, it is possible to connect two disks with a thickness of 0.6 mm into one with a standard thickness of 1.2 mm. In this case, the capacity doubles. In total, the DVD standard provides 4 modifications: single-sided, single-layer 4.7 GB (133 minutes), single-sided, double-layer 8.8 GB (241 minutes), double-sided, single-layer 9.4 GB (266 minutes) and double-sided, dual-layer 17 GB (482 minutes). The minutes indicated in brackets are the playing time of high-quality digital video programs with digital multilingual surround sound. The new DVD standard is defined in such a way that future reader models will be designed to be able to play all previous generations of CDs, i.e. in compliance with the principle of "backwards compatibility". The DVD standard allows for significantly longer playback times and improved quality of video movies compared to existing CD-ROMs and LD Video CDs.

The DVD-ROM and DVD-Video formats appeared in 1996, and later the DVD-audio format was developed to record high-quality audio.

DVD drives are slightly improved versions of CD-ROM drives.

CD and DVD optical discs became the first digital media and storage devices for recording and reproducing sound and images

History of Flash Memory

The history of the appearance of flash memory cards is connected with the history of mobile phones. digital devices, which can be carried with you in a bag, in the breast pocket of a jacket or shirt, or even as a keychain around your neck.

These are miniature MP3 players, digital voice recorders, photo and video cameras, smartphones and pocket personal computers - PDAs, modern models cell phones. Small in size, these devices needed to expand the built-in memory capacity to write and read information.

Such memory should be universal and used to record any type of information in digital form: sound, text, images - drawings, photographs, video information.

The first company to manufacture flash memory and put it on the market was Intel. In 1988, 256 kbit flash memory was demonstrated that was the size of a shoebox. It was built according to logical circuit NOR (in Russian transcription - NOT-OR).

NOR flash memory has relatively slow write and erase speeds, and the number of write cycles is relatively low (about 100,000). Such flash memory can be used when almost constant storage of data with very infrequent overwriting is needed, for example, to store an operating system digital cameras and mobile phones.

Optical disc

Optical disk

a data carrier in the form of a plastic disk intended for recording and reproducing sound (CD), images (video disc), alphanumeric information (CD-ROM, DVD), etc. using a laser beam. The first optical discs appeared in 1979. Philips created them for recording and playing back sound. An optical disc consists of a rigid, optically transparent base, on which a thin working layer and an additional protective layer are applied. Thanks to the optical reading method, optical discs are much more durable than gramophone records. The diameter of a standard CD is 120 mm (4.5 inches), thickness - 1.2 mm, center hole diameter - 15 mm. CDs are made from very durable transparent plastic - polycarbonate or polyvinyl chloride. A label is placed on one side of the disc, and the other side has a mirror surface that shimmers with rainbow colors. This is a recording zone, the spiral track of which consists of pits - recesses of various lengths. The distance between two adjacent spiral tracks is 1.6 microns, i.e. the recording density is 100 times greater compared to a conventional gramophone record. The width of the pits is 0.6–0.8 µm, and their length is variable. It reflects the length of the “1” sequences of the recorded digital signal and can vary from 0.9 to 3.3 µm. Information in the form of pits is protected from mechanical damage on one side with transparent disc material, and on the other with a layer of plastic and a label. Compared to mechanical sound recording, it has a number of advantages: a very high recording density and the complete absence of mechanical contact between the medium and the reading device during the recording and playback process. Music CDs are recorded at the factory. Like gramophone records, they can only be listened to. Using a laser beam, signals are recorded onto a rotating optical disk. digital code. As a result of recording, a spiral track is formed on the disc, consisting of miniature grooves and smooth areas. In playback mode, a laser beam focused on a track moves across the surface of a rotating optical disk and reads the recorded information. In this case, the depressions are read as ones, and the areas that evenly reflect light are read as zeros.

Contactless reading of information from a CD is carried out using an optical head or laser pickup. The optical head consists of a semiconductor laser, an optical system and a photodetector that converts light into electricity. The reading laser beam is focused on a spiral track with pits located deep in the disk. The head never comes into contact with the disk - it is always at a strictly defined distance from it, ensuring that the track of pits is in the focus of the optical system.

Multimedia technology allows you to combine text and graphics with sound and moving images on a personal computer. Optical CD-ROMs (Compact Disk Read Only Memory) are used as storage media in such multimedia computers. Outwardly, they do not differ from audio CDs used in players and music centers.

The capacity of one CD-ROM reaches 650 MB; in terms of capacity, it occupies an intermediate position between floppy disks and a hard magnetic disk (hard drive). A CD drive is used to read CDs. Information on a CD is written only once in an industrial environment, and on a personal computer it can only be read. A wide variety of games, encyclopedias, art albums, maps, atlases, dictionaries and reference books are published on CD-ROM. All of them are equipped with convenient search engines that allow you to quickly find required material. The memory capacity of two CD-ROMs is enough to accommodate an encyclopedia larger in volume than the Great Soviet Encyclopedia.

Information optical CDs are designed for single (so-called CD-R) and multiple (so-called CD-RW) recording of information on a personal computer equipped with a special drive. This makes it possible, like a tape recorder, to make recordings on them at home. On CD-R discs you can record only once, but on CD-RW you can write multiple times, just like on a magnetic disk or tape, you can erase the previous recording and make a new one in its place.

1 – CD; 2 – translucent coating that protects the information printed on the CD from damage; 3 – reflective coating (the recording medium itself); 4 – protective layer; 5 – focusing; 6 – laser beam; 7 – optical splitter; 8 – photodetector; 9 - ; 10 – electric motor rotating the disk

The existing CDs are being replaced by a new storage media standard - DVD (Digital Versatile Disc or general purpose digital disk). They look no different from CDs. Their geometric dimensions are the same. The main difference between a DVD disc is its tens of times higher recording density. This is achieved thanks to a shorter laser wavelength and a smaller spot size of the focused beam, which made it possible to halve the distance between tracks. The DVD standard is defined in such a way that future models of reading devices will be developed taking into account the ability to play all previous generations of compact discs, i.e., in compliance with the principle of “backwards compatibility”. In 1995, Philips developed CD replay technology. The DVD standard allows you to significantly increase the time and improve the quality of video playback compared to existing CD-ROMs. DVD drives are upgrades from CD-ROM drives.

Encyclopedia "Technology". - M.: Rosman. 2006 .


See what an “optical disk” is in other dictionaries:

    A data carrier in the form of a plastic or aluminum disk, intended for recording and/or playback of sound (CD), images (video), alphanumeric information, etc. using a laser beam. Recording density St. 108… … Big Encyclopedic Dictionary

    optical disk- A disc containing digital data that can be read using optical technology. [GOST 25868 91] Equipment topics. periphery processing systems information EN optical disk... Technical Translator's Guide

    OPTICAL DISC, in computer technology a compact storage device consisting of a disk on which information is written and read using a laser. The most common type is CD ROM. Audio CDs also represent... ... Scientific and technical encyclopedic dictionary

    Working with optical discs Optical disc An image of an optical disc, ISO image Optical drive emulator Software for working with optical disk file systems Recording technologies Recording modes Batch recording Types ... ... Wikipedia

    Data carrier in the form of a disk made of transparent material (glass, plastic, etc.) with metallization. layer, on which microscopy, recesses (pits) are formed using digital optical recording, collectively forming spiral or annular... ... Big Encyclopedic Polytechnic Dictionary

    A storage medium intended for recording and/or reproducing information using focused laser radiation. It consists of a rigid (usually optically transparent) base, on which a photosensitive or reflective layer is applied and... ... encyclopedic Dictionary

    optical disk- 147 optical disc: A disc containing digital data readable using optical technology

Optical media are 12 cm (4.72 in) CDs or 8 cm (3.15 in) MiniDiscs. Optical media consists of three layers:

1) polycarbonate base (outer side of the disk);

2) active (recording) layer of plastic with a changeable state phase;

3) the thinnest reflective layer ( inner side disk).

In the center of the CD is a round hole that fits onto the CD drive spindle.

Writing and reading information onto a CD is carried out by a head that can emit a laser beam. There is no physical contact between the head and the surface of the disc, which increases the life of the CD. The phase of the second plastic layer, crystalline or amorphous, changes depending on the cooling rate after the surface is heated by the laser beam during the recording process performed in the drive. When the plastic cools slowly, it turns into a crystalline state and the information is erased (a “0” is written); upon rapid cooling (if only a microscopic point is heated), the plastic element goes into an amorphous state (written “1”). Due to the difference in reflection coefficients from crystalline and amorphous microscopic points of the active layer during reading, the intensity of the reflected beam perceived by the reading head is modulated. The surface of the disk is divided into three areas. The Lead-In area is located in the center of the disk and is read first. It records the contents of the disk, a table of addresses of all records, the disk label and other service information. The middle area contains basic information and takes up most of the disk. The Lead-Out area contains the end-of-disk mark.

The information on a CD is encoded with great redundancy using a Reed-Solomon correction code, which ensures the restoration of the original information if it cannot be read from the disk.

A CD can withstand several hundred rewrite cycles. Information is read when the CD is rotated at a frequency of more than 10,000 rpm.

Depending on the read/write capabilities, all CDs can be divided into three types:

1) ROM (Read Only Memory) – read only; recording is not possible;

2) R (Recordable) – for writing once and reading multiple times; the disc can only be written to once; the recorded information cannot be changed and is read-only;

3) RW (ReWritable) – for repeated writing and reading; information on the disk can be overwritten many times.

These types of discs differ in the material from which the second plastic layer is made.

Let's look at the types of CDs (CD (Compact Disc), DVD (Digital Versatile Disc) and Blu-Ray, which have same size 4.72 inches.


CD capacity is 650 or 700 MB. Music discs are classified as CDs and are intended only for reading music from them. CD access time – 0.05-0.3 s.

The DVD format is a development of CDs; their volume is 4.7 GB due to denser recording. DVDs continue to improve. There are several competing DVD formats: DVD-, DVD+ and DVD-RAM.

Blu-ray format is a further development of DVD and allows you to record 25 GB of information on one layer.

The names of CD and DVD formats depending on read/write capabilities are presented in the table.