What discs came out after dvd discs. DVD is all about this round data medium. What do the letters in DVD stand for?

In recent years, CD-RW drives have become commonplace for all users. Almost any new PC comes with a CD-RW (or CD-RW + DVD-ROM combo) included. Moreover, many have completely abandoned the use of 3.5-inch floppy disks. Manufacturers of modern laptops no longer equip their products with floppy drives, magnetic storage devices are a thing of the past ...

At the same time, CD-RW drives have long reached their technological perfection. They decided not to increase the maximum write speed to 72x (except in rare models with several lasers) and put the final point at 52x. The peak rewriting speed is 32x and, apparently, will not increase. The volume of CDs, due to their technological features, cannot exceed 750-800 MB. And if a couple of years ago the main advantage of CDs was their capacity, now this is their main drawback. That is why DVDs are gaining more and more popularity in our open spaces.

What is DVD?

DVD is a disc recording format. Unlike CDs, it has a higher data density, double-layer recording capability and better protection of licensed discs from pirated copies. At the moment, the title of DVD is nothing more than a "sonorous" set of letters. However, in 1995, the acronym DVD was decrypted as Digital Video Disk. The fact is that DVD was originally developed to replace the outdated VHS format, and it was intended mainly for comfortable watching movies. After some time, it was decided to optimize DVD discs not only for multimedia use, but also for computers as a storage medium. Therefore, we decided to change the name of the format without changing the abbreviation. Thus, DVD from Digital Video Disk became Digital Versatile Disk. But the name did not "stick" and the abbreviation DVD became just a set of letters.

History of the DVD format

The first official information about the development of the DVD appeared in the spring of 1995. It was announced by 10 large companies (Pioneer, Matsushita, Mitsubishi, Philips, Sony, Hitachi, JVC, Time Warner, Thomson and Toshiba) that took part in the development of the format. To avoid the war of standards, these companies have merged into the so-called DVD Consortium. Its main tasks were: promotion of the format on the market, coordinated development of new specifications and licensing of enterprises that record information on DVD. Two years later, in 1997, a DVD forum was created. Its tasks were the same as those of the DVD consortium. There are currently about 200 official members of the DVD Forum. All of them are interested in the development of the format and are participating in the development of new, more advanced formats like Blue-ray, EVD or HD DVD.

DVD outside and inside

Outwardly, DVDs are almost indistinguishable from regular CDs. They have the same size and look very similar to each other. However, a DVD cannot be read on a regular CD drive. To do this, you need a drive with support for DVD-format, which, by the way, reads regular CDs without any problems.

All information on a DVD is stored in the MicroUDF (Micro Universal Disk Format) file system. It was officially approved in 2000. MicroUDB supports high-capacity media and large file sizes. File names are recorded in unicode format, which ensures DVD compatibility with all operating systems for PC, as well as with a variety of household appliances.

The essential difference between DVD and CD is the ability to write two-layer discs. One single-sided disk (there are also double-sided ones, with an information surface on each side) can store twice as much information. Both layers have a reflective surface, only one of them has a high transparency (up to 40%). When writing / reading, the beam simply changes focus, which makes it possible not to hit both layers at the same time.

Higher-capacity DVD-discs owe not only the ability to write two-layer discs, but also a higher density of information recording. Higher recording density was achieved by reducing the distance between information tracks on the spiral. This distance for CDs is 1.6 µm. DVDs have 0.74 microns. The capacity of DVD-discs, depending on their specific type, can be from 4.7 to 17 GB. Below is a list of all types of DVDs:

• DVD-5 - 4.7 GB single-sided, single-layer disc;
• DVD-9 - 8.5 GB single-sided, dual-layer disc;
• DVD-10 - 9.4 GB double-sided, single-layer disc;
• DVD-14 is a double-sided disc: one side has one layer, the other has two; capacity - 13.24 GB;
• DVD-18 is a 17GB double sided, dual layer disc.

The most common discs are DVD-5 and DVD-10. The rest are less popular due to the higher cost and less prevalence of the corresponding product lines. Today it is not difficult to find any type of disc on store shelves.

DVD protection

To protect DVDs from external damage and surface scratches, an additional transparent plastic layer has been provided. It is applied over the information reflective surface and does not interfere with the disc reading.

In different countries, the premieres of the same films take place at different times. And since film publishers are not interested in the appearance of a film where it has not yet been premiered, it was decided to introduce the so-called zoning.

The whole world was divided into 8 zones. If you have installed a disc from the "foreign" zone in the drive, it simply will not recognize it. Below is the list of DVD zones:

1. Canada and the United States;
2. Japan, Europe, South Africa, Middle East;
3. Southeast Asia, East Asia;
4. Australia, New Zealand, Pacific Islands, Caribbean, South and Central America;
5. The territory of the former USSR, the Indian Peninsula, the main part of Africa;
6. China;
7. Reserved area;
8. Extraterritorial zone: planes, liners, steamships ...;

In the fifth zone, as you can see, they placed Russia, Ukraine, Belarus and many other countries, ironically - with a high level of piracy.

The information on the DVD is encrypted for a specific region. The drives are also encrypted for the region in which they were brought. When reading a disc, the drive checks the coincidence of the regions on the drive and the disc and, depending on the result, continues or does not continue reading the disc further. There are also multi-zone drives and players that are not tied to a specific region. Now, however, they are rare, but it is still possible to find them. The so-called "locked" devices (configured to read disks of only one zone) can be changed to multi-zone if he is "able" to change the zone (as a rule, it is allowed to change it up to 5 times). Set it to a zero zone and your drive will become multi-zone. Sometimes there are new firmware for drives that disable zone dependence. But flashing such devices is much more dangerous than, for example, motherboards.

DVDs also use Content Scrambling System (CSS) digital copy protection. So that the disc cannot be copied to a PC, all information on it is encoded. Moreover, for decryption, you need a two-part key. One of them is on the disc, the second is programmed in the drive. When recording information on a PC, it will be simply impossible to view the movie, although the data will be copied without problems. You can bypass this protection using special software.

And finally, the last protection method is analog write protection. The principle of operation of APS (Analogue Protection System) is that during the playback of a movie, noise is deliberately created. And if you record the movie on another player, the image will be severely distorted. So much so that you won't be able to watch the movie.

DVD Video Features

As you know, DVD technology was conceived with the aim of improving the quality of watching movies. DVD-Video discs are found in every store. And many new films are released only on DVD. How do they differ from regular Video-CDs, except for a larger disc capacity? Externally, DVDs with films are distinguished by rectangular packaging made in the form of a booklet. Each side of the package has a high-quality, high-resolution image and text with information about the film. There may be one or two discs inside the box. Sometimes the second disc contains videos with fragments about the filming of the film, an interview with the director, the history of the film / film company, etc.

DVD-Video Movies have the following features:

• Each disc with a movie has its own unique menu in which settings for its viewing are made;
• The disc may contain several audio tracks with translations into different languages;
• Each sound track can be recorded in high quality formats with support for Dolby Surround for multichannel speaker systems;
• Multi-language subtitles;
• The official film length is limited to 135 minutes of high quality video. But in reality, it all depends on the type of disk, its capacity and compression algorithm settings. The larger the volume of the disc, the longer the movie will fit on it;
• The menu on the disc allows you to turn off / on subtitles, select the playback language and skip to the selected episode of the movie.

Within the framework of this material, we deliberately do not dwell on the specifications of the DVD Audio standard, since this conversation requires a serious separate article.

Matrix: overload
A lot of information has flowed under the bridge since those distant times when the full version of the newest 3D Action took only three floppy disks. I recall with nostalgia the kind uncles from the radio market, who at any time of the day could buy a couple of fresh toys "in their own container" (on their floppy disk, that is). But whatit was - that has passed, and now laser discos, laser swords and laser discs are in vogue.
The appearance of the first CDs looked like a revelation from above. One medium could hold up to 500-600 games, which was enough for months of continuous exciting gameplay. The first alarm bell sounded when the cult quest was released Myst- which one disk was already sorely lacking. Then these calls turned into an incessant trill: subsequent game products without hesitation took three or four disks. Another information revolution was brewing.
Now the speeds of CD-writers have reached the sprint pace - 700 MB of information is rolled onto a disc in just three to four minutes. The capacity rested its horn against the mark 800 It seems that MB simply cannot grow further. Meanwhile, eight million bytes are no longer enough for users. The soul asks for a holiday, bread and circuses. The industry is right there: helpfully holds out a tray with a new, multi-layered carrier of the human word ...
Born Hollywood
The history of the new recording standard epitomizes the catch phrase "Demand creates supply." If the CD standard became the answer of producers to the requests of the record companies, then the DVD was born with the light hand of Hollywood. In the immemorial 1994, the sharks of the movie businessformulated the requirements for a new carrier of video information:
• video stream resolution exceeding the then capabilities of MPEG-1 CDs;
• CD-quality soundtrack and support for Dolby Surround;
• at least 133 minutes of video on one side of the disc;
• the ability to choose between different dubbing languages ​​(5-6 languages);
• subtitles on different languages;
• support for widescreen image formats;
• protection of information from copying;
• backward compatibility with CDs;
• low price.
The call of the Hollywood lion has awakened the slumbering packs of developers. In pursuit of clients, all disagreements were forgotten. Gone into oblivion the stillborn standard Super Density Digital Video Disc developed by companies Toshiba and Time Warner, the unnamed recording standards from Sony and Philips... V 1995 year a consortium was formed to develop the latest recording and reproduction technologies. It included such monsters of the IT industry as Hitachi, Matsushita (Panasonic), Mitsubishi, Philips, Pioneer, Sony, Thomson, Time Warner, Toshiba and JVC... The stars lined up in the most correct way and presented to the consortium new standard video compression MPEG2 on a platter with a digital border. The saucer was called uncomplicated, but sonorous: DVD (Digital Video Disk- "digital video disc"). A little later, after a little watching the development of the newborn, the "dads" decided to "be shirsh" and christened the standard with a new name - Digital Versatile Disk("digital multifunction disc"). Presumably, from that moment on, it became clear to all hesitants that the prospects for DVD are considerable. And after just a few months, the camp of fans of the new standard increased to 240 companies. In particular, the consortium was honored with their presence by such grandees as IBM, Intel, NEC, Sharp, Lg Electronics and Samsung. Onions have layers, cannibals have layers
(c) Shrek
Externally, CD and DVD are two from the box, the same from the face. Discs of both standards look absolutely identical. The physical structure of DVDs and CDs is also similar. A kind of round sandwich with a diameter of twelve centimeters, consisting of a protective layer, a transparent polymer base and a reflective layer. The principle of recording also remained unchanged: there is a reflection of the ray - "1" , no reflection - "0" ... The main difference is in the size of the minimum sector for recording information (analogous to a magnetic cell in a floppy disk or hard disk). Its length has halved and is 440 nm. The information on the disc is still applied in a spiral, from the center to the edges. But the pitch of the spiral has also changedtwice - now it is only 740 nm versus 1500 at CD. To read the "compact" sectors, the size of the "gramophone needle" had to be reduced - the laser wavelength was reduced from 780 nm to 635 nm.
A significant difference is also that the "sandwich" DVD is equally useful on both sides - both the top and bottom surfaces of the disc can be used to write and read information. Even if the second side is not used for recording, it is present on all media.
The first generation DVD has a capacity of 4.7 GB and is officially named DVD-5... V 1996 year, the specifications were first presented to the suffering masses. And already at the end of the year drives and data carriers appeared on the open sale in the Land of the Rising Sun. It was from Japan that the new standard began its triumphant march around the world, transforming and acquiring new layers.
After a while, not wanting to stop there, the DVD consortium, already renamed to "DVD Forum", adopted a new recording standard - DVD-9... The idea behind the new technology is to use multilayer disks to increase the amount of stored information. The first layer is still mechanically pressed and the additional layer is spray applied. Moreover, the additional top layer is translucent and does not interfere with the reading of the "deep" brother. A DVD-9 disc can store up to 8,54 GB of data.
The only drawback of the "layered know-how" is that an expensive laser with a variable focal length is required to read the information. distance. Accordingly, the cost of end devices - "readers" increases significantly.
Further development of the DVD-5 and DVD-9 standards became double-sided DVD-10 (9,4 GB) and DVD-18 (17,08 GB). Modern DVD-ROMs read all disc formats described without any problems. Unfortunately, in our country, it is the one-sided single-layer discs (DVD-5) that have become more widespread, although in bourgeois Europe-America, both video and audio discs of the DVD-10 and DVD-18 standards have been on sale for a long time. Format compatibility table *

Disc format	DVD-ROM drive	DVD-R Drive (G)	DVD-R Drive (A)	DVD-RW drive	DVD-RAM drive	DVD + RW drive
DVD-ROM	+	+	+	+	+	+
DVD-R (G)	+**	+/+	+/-	+/+	+/-	+/-
DVD-R (A)	+**	+/-	+/+	+/-	+/-	+/-
DVD-RW	+**	+/-	+/-	+/+	+**/-	+**/-
DVD-RAM	-	-/-	-/-	-/-	+/+	-/-
DVD + RW	+**	+**/-	+**/-	+**/-	+**/-	+/+

* Reads / writes.
** Exceptions are possible, for example some DVD-R (G) cannot be read on the first versions of DVD-ROM drives. My number is 245, there is a stamp on the jacket
When developing Digital Versatile Disk, the interests of Hollywood tycoons, who are seriously concerned about the problem of information security, were also taken into account. To begin with, in the best traditions of Lieutenant Schmidt's children, the whole world was divided into six regional zones.
Each DVD-ROM contains in its firmware a hard-coded number of the region for which this player is intended. The same number is hardcoded into any licensed DVD. If the region codes do not match, it's a matter of seams. Keane will not be.
The ideological underpinning of this approach is that film distribution and sale starts in different regions at different times.Often, versions of the same films for America, Europe and omnivorous Russia are as different as heaven and earth. In addition, local censorship and legal restrictions play a role. The division of the world into regions made it possible to temporarily prevent the illegal distribution of Hollywood classics around the world. As it soon became clear, the protection was so effective that it was able to block the sale of even completely legal products. This has been fueled by the convoluted reseller channels of computer vendors and the slowness of the disk "localization" process. Excellent Japanese readers, brought from Siberia for the occasion, had a hard time taking excellent English-language films from the Canary Islands. As a result, many player manufacturers, at first illegally, and then with the tacit connivance of the fathers of the industry, began to release players with disabled regional protection. Nevertheless, you can still find a "geographically savvy" player on sale that is not on friendly terms with Gorbushka's pirate treasures.
Zonal protection is far from the only Cerberus that protects information from the plunderers of property caps. There are several other original technical solutions at the service of DVD, which seriously complicate illegal copying.
Protection standard Macrovision protects the video signal from recording on VCRs. The principle of operation is to create constant interference, which knocks down the automatic adjustment of VCRs to the incoming video signal and distorts the recording beyond recognition. Ways to combat this "evil" have already been found and consist in using the RGB output or in changing the player's firmware. Algorithm CGMS (Copy Generation Management System)protects the video stream from being captured by video editing cards and TV tuners. To do this, the signal NTSC a special protection line is added that distorts the picture and sound. Defense mechanism CSS (Content Scrambling System) encrypts all data on a DVD so that it can be decrypted on the fly during playback. V 1999 year this cunning algorithm could not withstand the pressure of pirate passions and fell victim to hackers, gifting the world with hundreds of illegal discs.
The audio part of the D disc was not ignored either.VD. Protection system CPPM (Content Protection for Prerecorded Media) reliably guards music hits by adding a special mark to the file being played that prevents copying of music in computer systems. And household systems give out a signal with a reduced bit rate to the linear output, reducing the result of all inventive attempts to absolute zero.Change dvd player to dvd player
What is a wedding without an accordion, and what is the standard storage of information without the possibility of self-burning discs? The DVD standard, having failed to establish itself reliably in the information storage market, faced serious competition from traditional CD-ROMs. The market was flooded with a stream of cheap recorders. Drive sales today CD-RW close to salestraditional CD-ROM drives. Prices for CD-RW drives have fallen almost below cost and have become enchantingly close to the wallet of almost any customer.
It goes without saying that the DVD Forum has to contend with this situation. At the front line of protection, the so-called "combo drives" stood up with a wide chest (CD / DVD-combo)... They successfully combine the ability to read DVD-ROM discs and write CD-R and CD-RW discs. The share of these devices on the market is relatively small - for large storage manufacturers, models of this line occupy 3-5 percent of the total product range. But they are the best choice for those people for whom the traditional CD-RW drive is no longer enough, and they are not interested in the ability to burn DVD discs yet.
Indeed, why pay more and buy two separate drives when combo drives completely replace them at a much lower price. Often this very reason is decisive when buying a CD-RW / DVD laser drive. For other advantages over competing devices, except for the price, combo drives do not have. Say what you like, but the CD-RW / DVD standard is a fly-by-night, designed to keep users entertained until the prices of DVD burners drop to reasonable levels.One time pleasure
The story of the birth of DVD recorders is a bit like a childhood fable about the swan, crayfish and pike. The monetary idea of ​​a device capable of cramming up to 4.7 GB of information onto one medium has brought contention to the previously monolithic ranks of the DVD forum. Having fed up with the fruits of collective creativity, the leading brands again scattered into groups of interested comrades.
Discs were the first to enter the market DVD-R from the patriarch of the digital industry - Pioneer. Media and devices of this format went on sale long ago. 1997 year. When creating the specification, the already debugged and proven idea of ​​the CD-R format was taken as a basis. In short, the difference between a DVD-R blank and a regular DVD-ROM disc is in a special pigment layer that is sensitive to the touch of a laser beam.
Wavelength laser 635 nm simply burns the necessary information onto the reflective layer. That is, in other words, there are no fundamental differences from the technology of recording CD-R discs. The only difference is the high density of information recording and a different file system. The first DVD-R disc contained "everything" 3,95 GB of information and cost an order 50 US dollars. The recorder itself was released to the market for an astronomically high price of $ 17 000 ... A little later, in 1999 year, the version appeared 1.9 DVD-R standard. The disc, made according to the new ideology, contains 4,9 GB of information.
Like CD / DVD discs, DVD-R comes in two form factors - diameter 80 and 120 mm. The thickness of the disc is 1,2 mm.
DVD-R version 1.9 has been officially certified by the DVD Forum. Now is the time to think about the notorious copyright protection. It was in thoughts of preserving copyright that the last standard to date was born DVD R 2.0, including protection against illegal copying. The solution is traditional: information is written into the service area of ​​a disc that prevents its contents from being overwritten.
With the spread of the concept of "copyright", DVD-R almost instantly split into two micro-standards - for recording studios and for ordinary users. Their main difference from each other is in the wavelength of the laser used. For professional format, use 635 nm, for "home" format - 650 nm. That is, you cannot record a studio disc on a household device, just as you cannot roll up a regular DVD-R disc on a studio device. Reading information from both types of disks occurs without problems.
Professional format DVD-R (A) (DVD-R For Authoring) retained backward compatibility with versions 1.0 and 1.9. The DVD-R (A) drive can burn old-style discs without any problems. The main highlight of the standard is the ability to record disc titles in the format Cutting Master Format (CMF)... This allows DVD-R (A) blanks to be used as master discs for subsequent serial production. Factory duplicators get everything they need to function from CMF headers. information.
Also note that the format did not initially include the ability to stream encrypt CSS data.
Standard DVD-R (G) (DVD-R For General) targeted at the mass consumer. The wavelength of the recording laser at 650 nm does not allow for the correct burning of discs of the old DVD-R 1.0 and 1.9 formats; they can only be read. To record information, discs of the General DVD-R standard are used. Both single-sided (4.7 GB) and double-sided (9.4 GB) drives are supported.
Another advantage of the format is the low cost of the burner drives - about one zero less than that of professional DVD-R (A) writers. It is the DVD-R (G) format that is now the generally accepted synonym for DVD-R and is supported by almost all DVD-ROM players.
The only drawback of the format is the inability to use DVD-R (G) as a master disc for subsequent duplication (there is no CMF support). It is believed that at home this opportunity is unlikely to be in demand.
Pioneer Notes
After the advent of write-once DVD-Rs, the next logical step was the release of rewritable discs.DVD-RW... Once again, Pioneer was the pioneer in this area. As a basis, the developers took the idea of ​​a rewritable CD-RW format, already proven by time.
The burner, like DVD-R devices, uses a laser with a wavelength of 635 nm. The only difference is in the material of the information layer. It can repeatedly change its optical characteristics under the influence of a laser beam of different power. Guaranteed until 1000 quality rewrite cycles. So far, there are only 4.7GB single-sided DVD-RW discs. Due to their structural relationship, DVD-RW drives can easily burn DVD-R (G) discs.
The first version of the standard was released in December 1999 of the year. It included a CSS protection system built into the burner to prevent it from burning copies of licensed discs. According to the specification in the title (lead-in) disk is squeezed out service information. It also prevents illegal copying of the contents of the disc. As a side effect of using CSS - many DVD-RW versions 1.0 having trouble reading in consumer players. As a result, a version of the standard was released 1.1 in which the lead-in was prescribed with a laser beam. This allowed us to solve the problem of incompatibility. It is the DVD-RW 1.1 discs that are the most frequent guests on our shelves.
A version of the standard was subsequently developed specifically for storing protected information. 1.1b... According to its specification, each disc has a unique 56 -bit identification number with which all the data it contains. As a result, even if the information can be rewritten, it will not be read due to the lack of a key.
The first blanks and drives of the new standard appeared on the market in 2001 year. Since then, the market share of DVD-RW discs has grown significantly. As a result, they are almost completely compatible with the entire existing fleet of DVD drives. The only exceptions are very old models of DVD-ROM and consumer players, the laser power of which is not enough to read information from the information substrate. After all, its reflectivity is seriously inferior to traditional DVD-ROM and DVD-R discs.Laser Winchester
But DVD-RW was not destined to become the "autocratic pioneer" of the DVD rewritable media market. The research department of the Matsushita corporation (in the world - Panasonic) has set its sights on a tidbit of the market. She developed her own, rewritable alternative format s media, dubbed DVD-RAM... In the process of technological upheaval, the standard has lost almost all of the inherent DVD features, including compatibility with DVD-ROM drives. The first DVD-RAM drives hit the market in 1998 year.
Drives and discs of the new standard have merged the main technologies of DVD and MO(magneto-optics). The laser heats up the surface of the disc, and it changes its reflective properties. The mainUnlike DVD-RW discs, sector labels are applied to the surface of the disc. This makes DVD-RAM technology similar to traditional hard drives and allows you to format DVD-RAM discs for any "traditional" file system including FAT32... The capacity of a single-sided disc is 4.7 GB, a double-sided one is 9.4 GB. Discs withstand up to 100 000 rewrite cycles.
The drives read all known DVD formats without any problems. Physically, a DVD-RAM media is a single or double-sided disc enclosed in a plastic cartridge with the dimensions 124.6x135.5x8.0 mm. It is because of this cartridge that the chances of reading a DVD-RAM disc in a regular DVD drive are close to zero. If the cartridge is not sealed tightly, you can remove the disc and try to read it in a "regular" drive that supports the DVD-RAM standard.
At the moment, the main application of recorders and disks of this standard is information backup. Both a high resource and a large storage capacity will be very useful here.Let's replace the minuses with pluses
The other members of the DVD forum also did not want to go hungry and developed their own standard for rewritable discs, contributing to the general confusion of titles andabbreviations. Philips, Sony, Hewlett-Packard, Dell, Ricoh and Yamaha, having united, replaced the "dash" in the abbreviation DVD-RW with "plus" and released their own standard DVD + RW... A workable version of the specification with support for video discs and media with a capacity of 4.7 GB appeared in 1999 year.
There are no fundamental technological differences between DVD-RW and DVD + RW. The difference is in the format of information presentation. DVD + RW, unlike DVD-RW, supports multisession recording (recording in several steps). Higher positioning accuracy of the laser beam allows for on-the-fly data correction, rewriting individual bad disk sectors in real time. Also, according to many experts, DVD + RW has a more advanced error correction algorithm.
In addition to supporting recording DVD + RW discs, the standard officially allows recording CD-R and CD-RW discs. For drives of other standards, this possibility is not officially declared. In terms of compatibility, DVD + RW discs are not inferior to their competitors DVD-RW - they are also readable by all new models of consumer and computer players.This is how we are non-standard
Without stopping at the achieved level of chaos, the members of the consortium of fans of the "pluses" released in 2002 year write-once media DVD + R. The principles of the new standard are completely similar to those of DVD + RW - the same "advanced error correction" and multisession recording of information.
DVD + R discs also use a special reflective layer with increased reflectivity. This eliminates disc compatibility issues due to insufficient laser power and low beam positioning accuracy in consumer players and older DVD-ROM drives.
The only critical drawback of the format is that no old DVD + RW drive is capable of burning DVD + R discs - their lasers do not support the required mode of operation. These backward compatibility issues have seriously slowed down the spread of the standard to the masses. Meanwhile, new recording technologies are just around the corner. The blue carriage runs, sways ...
Tired of the endless series of standards and titles that cost DVD technology a lot, the leading players in the market decided to join forces again. Companies Sony, Matsushita (Panasonic), Samsung, LG, Philips, Thomson, Hitachi, Sharp and Pioneer announced the development of a new media format. It was he who in due time will become the successor to DVD. The future hero was named Blu-ray("Blue Ray").
The media of the Blu-Ray standard has retained the dimensions of its predecessors - all the same 120 mm in diameter. Disk capacity has been increased by almost 7 once. Single-sided, single-layer Blu-ray disc capable of carrying up to 27 GB of information. The standard owes its name to the use of a blue laser with a wavelength 405 nm. For reference: CDs and DVDs used red lasers. The reduced wavelength made it possible to reduce the pitch of the spiral by half, to 320 nm.
The thickness of the protective coating of the disc has also changed - from 0,6 mm to0,1 mm. This will reduce errors that occur when reading and writing information. Various sizes of Blu-Ray discs are available. For example, Philips has released 30- mm disc with a capacity of 1 GB and a drive to it. Such discs are intended for mobile PCs and no less mobile phones.
27GB Blu-Ray discs have recently been standardized and given the name BD-27... The production also launched two-layer discs with a capacity 54 GB. This volume is enough to save a two-hour film in the increasingly popular standard. HDTV... These media are produced by companies Sony, JVC, TDK and Samsung... The drives are slated for mass market entry 2004 year. It is assumed that the main competitor of the new standard will be the same DVD... Analysts predict a massive drop in the prices of DVD drives and storage devices, which may shift from the middle-end systems to the mainstream market, completely replacing the CD-ROM format. Viva la Revolution!

Most Popular DVD Format Specifications

Parameter	DVD-ROM single layer	DVD-ROM double layer	DVD-R Authoring	DVD-R General	DVD-RW	DVD + RW
Capacity, GB	4,7	8,54	4,7 (3,95)	4,7	4,7	4,7
Wavelength, nm	650	650	635	650	650	650
Reflectivity,%	45-85	18-30	45-85	45-85	18-30	18-30
Modulation depth	>0,6	>0,6	>0,6	>0,6	>0,6	>0,6
Track width, μm	0,74	0,74	0,74	0,74	0,74	0,74
Minimum pit length, microns	0,4	0,44	0,4 (0,44)	0,4 (0,44)	0,4	0,4

There are currently four main types of DVD discs, which are classified according to the number of sides (single or double sided) and layers (single or double layer).

DVD-5 4.7GB single-sided, single-layer drive... Consists of two substrates connected to each other. One of them contains the recorded layer, which is called the zero layer, the second is completely empty. Single layer discs usually have an aluminum finish.

DVD-9 8.5GB single sided dual layer disc... Consists of two stamped substrates connected in such a way that both recorded layers are on the same side of the disc; on the other side there is an empty backing. The outer (zero) stamped layer is covered with a semitransparent gold film that reflects the laser beam focused on this layer and transmits the beam that is focused on the lower layer. A single variable focus laser is used to read both layers.

DVD-10 9.4 GB double-sided single-layer disc... Consists of two stamped substrates connected to each other by the back sides. The recorded layer (zero layer on each side) is usually aluminum coated. Please note that discs of this type are double-sided; the reading laser is located at the bottom of the drive, so the disc must be removed and flipped to read the second side.

DVD-18 17.1GB double-sided dual-layer disc... Combines two layers of recording on each side. The sides of the disc, each of which is formed by two stamped layers, are joined together with their backs to each other. The outer layers (layer 0 on each side of the disc) are covered with a translucent gold film, the inner layers (layer 1 on each side) are coated with aluminum. The reflectivity of single layer disc is 45-85%, double layer  18-30%. Various reflective properties are compensated for by an automatic gain control (AGC) circuit.

DVD disc construction different types shown in fig. 7.

Note that although Fig. 7 shows two lasers reading data from the bottom of double-layer discs, in fact only one is used. To read data located on different layers, only the focus of the laser is changed.

There are two ways to record the layers of dual-layer discs: opposite (OTP) or parallel (PTP) track direction. The OTP method allows you to minimize the time spent while reading a disk when moving from one layer to another. When the inner part of the disc is reached (the end of layer 0), the laser sensor remains in almost the same position and only moves slightly to focus on layer 1. The end area of ​​the disc when it is written in OTP mode is called middle zone.

Fig. 7. Types and construction of DVD discs

Writing (and reading) spiral tracks on PTP-recorded DVDs is different. When moving from layer 0 to layer 1, the laser sensor should move from the outside of the disk (i.e., from the end of the first layer) to its inside (to the beginning of the second layer). In addition, the focusing of the laser needs to be changed. To speed up the transition, almost all DVDs are burned in OTP mode.

The direction of the spiral tracks of the various layers recorded in the RTP mode also differs. This simplifies the process of reading tracks located one above the other. The spiral track of layer 0 is clockwise, and the track of layer 1, in turn, is counterclockwise. Therefore, to read the second layer, it is necessary to change the direction of rotation of the disc, but in OTP discs, the spiral reading occurs from the outside to the inside. Thus, the spiral track of layer 0 is directed from the inside to the outside, and the track of layer 1 is from the outside to the inside.

The differences between PTP and OTP DVDs are shown in Fig. eight.

The capacity of digital versatile disks depends on their type and reaches 17.1 GB. The capacity of double-layer discs is slightly less than that of two single-layer discs, even though the disc layers occupy approximately the same space (the lengths of the spiral tracks of different types of discs are the same). This was done to improve the readability of the disc layers in a dual layer configuration. The distance between the turns of the tracks was slightly increased, which entailed an increase in the length of the valleys and areas. To compensate for this, the drive speed increases when reading a dual-layer disc, so the data transfer rate remains constant. But since the spiral track is read faster, the overall capacity of the disc decreases slightly.

In addition to the listed types of standard capacity, double-sided discs can also be made with one layer on one side and two layers on the other. This type of disc is referred to as DVD-14 and has a capacity of 13.2 GB, or approximately 6 hours and 15 minutes of MPEG-2 video data. There are also 80mm discs that are smaller than standard 120mm discs of the same configuration.

Double-sided discs are more complex and expensive, and have to be removed from the drive and turned over to play both sides. All this led to the fact that the most widespread were DVD-5 (single-sided, single-layer) or DVD-9 (single-sided, double-layer) discs. The disc capacity of this type reaches 8.5 GB, which is 242 minutes of playback of MPEG-2 video data. Video discs DVD-5 with 133 minutes playback are suitable for more than 95% of films currently in existence.

Fig. eight. PTP and OTP recorded DVDs

Quite a few years have passed since the advent of DVD discs, but it still remains a mystery for many users which discs are better to use: DVD + R (W) or DVD-R (W)? This article is devoted to the main differences between the specified formats of DVD media and is designed to help the average user make a choice in favor of one format or another.

DVD-R (W)

The specifications for these discs were created by the DVD Forum, which includes about 200 different companies from Asia, Europe and America. This organization has developed specifications for DVD-ROM, DVD-RAM and DVD-R (W) discs.

DVD-Rs are write-once discs. They are of two types: general purpose disks and authoring disks. General purpose DVD-Rs, unlike authoring discs, contain built-in protection against illegal copying. General purpose discs can be recorded on a regular DVD burner. For recording authoring discs, special recorders are used. Discs recorded in this way do not contain protection against illegal copying and are used only for subsequent duplication in factories. General Purpose DVD-R 4.7 GB.

DVD-RW is a rewritable DVD disc format. One DVD-RW media can be erased and recorded up to 1,000 times. The capacity of this disc is also 4.7 GB.

DVD + R (W)

These discs are developed by the DVD + RW Alliance, which includes several well-known companies (for example, Sony, Philips and others). The specifications of these discs appeared in 2001 (RW) and 2002 (R), i.e. much later than their competitors. This allowed the developers of the plus format specifications to create technically more advanced media.

By analogy with the minus format, these discs are write-once (DVD + R) and rewritable (DVD + RW). One DVD + R (W) media also holds 4.7 GB of information. DVD + RW discs support up to 1000 rewrite cycles.

DIFFERENCES OF FORMATS

Note that DVD-R (W) and DVD + R (W) are not compatible. However, recorded discs can be read in most modern DVD players. The fact is that format differences affect mainly the recording of discs, and not their reading. The main differences between DVD-R (W) and DVD + R (W) discs from the technical point of view are discussed below.

Addressing and storage of service information

To burn a DVD, the drive typically receives three types of data from the disc:

1. Tracking data (track tracking) that allows the drive to record pits accurately onto a track.
2. Addressing data that allows the drive to write information to the allocated disk space.
3. Disk rotation speed data.

In DVD-R (W) discs, tracking and speed information is contained in the wobble of tracks, and addressing and other overhead information is contained in land pre-pits (LPP). The presence of LPP is determined by the jumps in the amplitude of a special jitter signal. These jumps occur when the head is near the pre-recorded pit. The wobble frequency for DVD-R (W) discs is 140.6 kHz.

DVD + R (W) discs use a higher jitter rate of 817.4 kHz, and the overhead is the jitter phase change, i.e. stored in the track itself. This method of recording service information is called ADress In Pre-groove (ADIP).

It is known from signal processing theory that the relative phase modulation method is more robust to noise than the amplitude modulation method. Therefore, in terms of resistance to external influences, DVD + R (W) discs are more reliable. Moreover, as the write speed increases, finding the LPP from the amplitude becomes more difficult than determining the phase change of the jitter.

From a disc creation standpoint, DVD-R (W) is harder to manufacture because it is required to produce two technological cycles instead of one, and it is also necessary to record LPP with very high accuracy.

DVD + R (W) discs transfer more information to the drive, which ultimately leads to better recording quality. V DVD discs the optimal power control (OPC) algorithm is used, which allows you to read the best parameters for a specific media recording and test them. These parameters, such as laser power versus wavelength, are contained in LPP blocks on DVD-R (W) or ADIP words on DVD + R (W). The number of adjustable parameters is the same for both disc formats, but with DVD + R (W) media, the parameters are more precise. In addition, in the plus format, you can set parameters for 4 different recording speeds, while in the competing format only for one (it is known that the recording parameters depend on the speed). In addition, the testing area for OPC on DVD + R (W) discs is larger than on DVD-R (W) (32768 vs. 7088 sectors).

Linking

When, for any reason, recording to a disc has been paused and needs to be resumed, it is necessary to pair the new data with the previously recorded. For DVD + R (W) discs, pairing is more accurate. In “minus” format media, the mating area is among the user data, so some of it is inevitably lost. In plus format media, the blending area does not affect user data.

Multi-session recording

In order for multi-session DVD-R (W) to be read by conventional DVD-ROM players, the user data area contains special border-in and border-out areas.

The sizes of border zones can vary from 32 to 96 Mb for the first zone, from 6 to 18 for subsequent zones. That. A DVD-R (W) disc with three recorded sessions will contain up to 132 MB (96 + 18 +18) overhead, which is more than 2% of its total volume.

Multi-session DVD + R (W) discs also contain special zones called Intro and Closure zones, but their size is always 2 MB. That. A DVD + R (W) disc with three recorded sessions will contain only 4 MB of additional service information (the first Intro zone is not recorded, Lead-In is used instead, the last Closure zone is not recorded, since Lead-Out is used) ...

MAIN CONCLUSIONS

Thus, the DVD plus format is more attractive in terms of technical characteristics. It makes it easier to write data to disk at a higher speed, due to the use of ADIP technology. Recording information on DVD + R (W) media occurs with more high quality, due to the drive receiving more accurate recording parameters from the disc itself. The amount of service information that appears during multi-session recording on DVD + R (W) discs is lower than on DVD-R (W). Finally, DVD + R (W) discs allow for more accurate data pairing when recording is paused.

In conclusion, it should be noted that, despite all the above differences, most modern recorders can record discs of both formats. Before deciding on any media, be sure to check the list of discs supported by your recorder.

Perhaps now it is impossible to meet a person who has never held a CD in his hands. Recently, these storage media have seriously lost ground due to the active introduction of more technologically advanced drives based on solid-state memory. However, for now, it is hardly advisable to completely abandon disks.

The capacity of a DVD is sufficient for storing most programs and multimedia files. Manufacturers indicate that 4.7 GB is available to the user. In reality, for the maximum information capacity is 4.38 GB, which is explained by the difference in the calculation method. Today we will talk about Digital Versatile Disc technology and deal with the nuances of calculating the volume of such media.

The problem with definitions

The term DVD, surprisingly, does not have an unambiguous decoding. This technology has been developed to replace conventional CDs, which are increasingly lacking capacity. Originally, the abbreviation DVD stands for Digital Video Disc. However, later it became clear that not only films, but also other files can be recorded on it.

This was the reason that some began to put a different meaning in the term, understanding DVD as a Digital Versatile Disc. In general, both transcripts are correct.

Increasing the available volume

It has already been stated that DVDs have replaced CDs, the capacity of which has become insufficient. In order to read the digital data recorded on the surface, it is necessary to use a thin laser beam. For this purpose, disk drives are equipped with a special unit consisting of an emitting element and a focusing system. The main difference between the light beam used to read and write information is that it is coherent, that is, it is very narrowly directed. This makes it possible to practically eliminate the effect of the phenomena of diffraction and interference of the light wave. During the development of the CD standard, the miniature semiconductor emitters available at that time were not able to create a sufficiently narrow beam, so the track width on the metal base of the disc was about 1.6 μm. Subsequently, more advanced light-emitting diodes were developed, the beam of which was so thin that the width of the track was reduced by half. Thus, it began to exceed the similar parameter CD by several times. In addition to the width of the track, we managed to change the distance between them, as well as the size of the pits.

"Pie" from discs

DVD capacity is not only determined by the above dimensions and laser beam configuration. Such ones were created that, in fact, combined several disks at once in one product while maintaining the standard dimensions.

These layered compacts can be compared to a sandwich. In production, not one, but two tracks are used at once, but located in such a way that the reading laser beam freely passes through the semitransparent upper surface. Their volume reached 8.54 GB. The maximum capacity of a DVD, which is not 12 but 8 cm in diameter, is 5.32 GB. Structurally, the drive can have two emitters, each of which focuses on its depth (surface). There are models with a single beam, the focus of which is controlled by the electronics. The storage capacity of a DVD could be even greater when so-called two-sided solutions were used. Outwardly, this is an ordinary compact, but writing / reading is possible from both sides, for which in most drives it was necessary to turn the media over. The capacity of a DVD disc of this modification ranges from 9.4 GB (double-sided single-layer) to 17.08 (four layers, recording from both sides). Nevertheless, such “cakes” have not become widespread due to the higher production cost and the need to handle them too carefully, since the slightest scratch could make it impossible to read data from deep layers.

Keeping information

RAM-disks are based on the technology of surface heating with a laser beam. Their feature is the ability to perform custom formatting and selectively delete files. Structurally, such disks are located in special cartridges, which increases their reliability. In theory, if you remove the DVD-RAM from the case, then you can work with it on a drive designated as Multi. These are fairly reliable solutions.

The storage capacity of this type of DVD ranges from 1.46 GB (single layer single sided, 8 cm) to 9.4 GB (double sided). The term RAM means that overwriting is physically possible. The acronym can be translated as Random Access Memory. In fact, this type of disk is intended for data backup and was an excellent solution before the appearance of alternative media. Especially when you consider the declared duration of data storage (about 30 years) and the number of rewriting cycles (over 100 thousand). The disadvantage is the relatively high cost and low distribution.

Video compacts

The next solutions are DVD-Video. Such discs are intended for recording a multimedia stream. Designated as "DVD-1 ... 18". The first four are modifications with a reduced diameter (8 cm versus the standard 12). DVD-5 is considered a classic, from which you can count 4.7 GB (single-layer, one-sided).

Accordingly, the maximum DVD capacity in this category is 17.08 GB (DVD-18, two sides, four layers). Since the simplest focusing units are used in mass video players, which makes it possible to reduce the cost of production, not all models are capable of reading large disks. The exception is single-layer double-sided ones, to work with which you just need to turn the disc in the drive. Their disadvantage is the lack of space for the label, so the name is indicated on the transparent part, next to the central hole.

Write once

The advent of drives capable of recording digital data to discs at home has revolutionized the backup and production of true movie libraries. DVD + -Rs are initially sold without recording. The owner of a special drive can save any information converted into digital form on such a disk.

The color is mirror-blue, with a shimmer in the violet region of the spectrum. Capacities of this type of DVD range from 4.7 GB (single layer on one side) to 17.08 GB. The volume depends, as usual, on the number of layers and sides. But still, because of the correct one, the simplest compacts of 4.7 GB are most widely used. Previously, recording could only be made using a computer drive, but now many video players that can save TV programs to discs have this feature. The problem of compatibility of "-" and "+" R has long been a thing of the past and is not considered in the article.

Multiple recording

The disadvantage of the previous type of discs is obvious - they cannot be rewritten by deleting the data. To resolve this issue, fundamentally different discs were proposed, called DVD + -RW. They can be used almost like a regular storage device. The term RW stands for Rewritable, i.e. rewritable. The capacity of DVDs of this class is exactly the same as that of "simple" R. However, double-layer ones are extremely rare due to the need to purchase a special drive capable of working with such discs.

In addition, rewritable solutions already require careful handling, and the complexity of their design means that dust particles have to be blown off such discs. And an accidental scratch on the surface may not allow reading information from the lower layers. Thus, the "classic" is a single-layer, single-sided disc. The surface color ranges from gray to almost black. The number of rewriting cycles is officially about several thousand, but in practice such a disc can be written no more than 50-100 times. And then over time, the reliability of data storage decreases. Thus, DVD-RW are suitable for short-term data storage and data transfer. Writing can be done in a block as usual. At the same time, using the Windows mechanism, it is also possible to work as with a regular drive (reading / writing arbitrary files). However, due to the fact that the standard of rewritable disks does not allow for high speeds, you usually have to be content with four times, which is 5.5 MB.

Recording feature

The standard DVD capacity may be slightly exceeded. This is achieved through the use of a lead-out zone. The Overburn feature must be supported by the device itself. It can be activated in popular program Nero by going to "Options - Expert properties". We do not recommend using this feature without, as you may face the impossibility of reading such a disc on a drive that does not know how to work with Overburn.

How the volume is calculated

Many computer owners have long noticed that it is impossible to burn the one specified by the manufacturer on a CD. In fact, there is no deception here. Simply, for marketing reasons, disk manufacturers believe that 1 KB is 1000 bytes, although in reality it is 1024 (we raise two to the tenth power). With the increase in volume, this number grows in progression. Consequently, no more than "fair" 4.38 GB can fit on a standard DVD.