Last year, devices equipped with optical drives based on a blue-violet laser finally appeared on sale outside of Japan. The confrontation between HD-DVD and Blu-ray Disc has entered the intramural phase. But China is seriously considering the issue of switching to its own format of optical drives - this step can significantly weaken the position of DVDs in the Asia-Pacific region and deprive holders of the rights to the corresponding patents of a considerable share of the profit received in the form of royalties. We will talk about these and other events in this review.
EVD is becoming a reality
Rumors that China is developing its own format of optical drives, similar in its parameters to DVD, but not compatible with it, began to circulate several years ago. In mid-2002, the Advanced Optical Storage Research Consortium (AOSRC), created in Taiwan with the support of government agencies, announced the development of its own standard for optical media Enhanced Versatile Disc (EVD), which is very similar to DVD. The main reason that prompted Chinese and Taiwanese manufacturers to take up this development was the dissatisfaction with the high license fees. The fact is that manufacturers of DVD-drives must transfer royalties to developers of the DVD standard, and in the case of DVD-players - also to MPEG LA and Dolby Laboratories. The total amount of contributions ranging from $ 15 to $ 20 for each DVD device, from the point of view of the Chinese government and AOSRC manufacturers, is unreasonably high. In addition, the transition to a proprietary optical media format is in full agreement with the Chinese government’s 1999 plan, which provides for the large-scale replacement of foreign technology with its own standards.
After the preparation of the basic EVD standard, it was decided to use the red range in laser drives (as in DVD). The capacity of single-layer EVD is 6 GB, double-layer - 11 GB. To record video on EVD, the American company On2 Technologies developed the new codecs VP5 and VP6. According to preliminary information, the retail price of EVD players will be from 75 to 150 dollars.
Household video player
EVD format
At first, many experts, as well as representatives of American and European companies, were very skeptical about the possibility of an Asian DVD clone. However, in November 2003, the official presentation of the EVD standard took place, and in February 2005 ITRI (Industrial Technology Research Institute - Taiwan Technology Research Institute) declared EVD the national Chinese standard for high-density optical drives.
At the end of November 2006, one of the leaders of AOSRC announced that 19 of the 21 consortium members would completely stop production of DVD players by the beginning of 2008. In this regard, it is appropriate to mention that in 2006 only one Chinese manufacturer of video players produced models with EVD support, supplying a total of about 700 thousand such devices. According to iSuppli, this represents less than 30% of the number of DVD players sold over the same period.
However, if the EVD format manages to prove its viability, it is likely to spread it outside of China - for example, in the markets of developing countries (primarily in India). In any case, Indian film studios have already given the green light to publishing their films on EVD.
HD-DVD and Blu-ray Disc: the long-awaited debut
In mid-2006, the first serial devices equipped with high-capacity optical drives based on a blue-violet laser, HD-DVD and Blu-ray Disc, finally appeared on sale in Europe and the USA. As one would expect, the prices of computer drives and household players of these formats turned out to be quite high: on average, from $ 600 to $ 1,000 and even higher. For example, in September, Sony’s European office began shipping BWU-100A (Blu-ray Disc) drives for PCs. The device allows you to play and write single and double layer media BD-R and BD-RE (2x), as well as read and write CD and DVD media. The price of the BWU-100A is 949 euros, despite the fact that its capabilities are quite limited. So far, owners of this ultra-expensive drive can use it only for writing and reading data, as well as for viewing video clips recorded directly on a PC. But watching movies distributed on Blu-ray Disc, in most cases, is impossible due to problems with the "raw" software and security systems (High-Bandwidth Digital Content Protection, HDCP) - for playing back videos that are replicated industrially, At least a video adapter equipped with a DVI or HDMI output and supporting HDCP is required.
Sony BWU-100A Recording Drive Supports
work with Blu-ray Disc, DVD and CD media
Optimistic experts promise an almost twofold (compared to the current level) reduction in the prices of Blu-ray Disc drives by the beginning of 2008, which should happen due to the entry of new players into this market. However, an optical drive and for 400 euros can hardly be classified as budgetary - especially despite the fact that not the worst recording DVD now costs only about $ 50. In addition, the average user has no serious incentives to switch to optical drives. generations: the volumes and speed characteristics of DVD-carriers are quite sufficient for the vast majority of everyday tasks, and the specific cost of storing data on them is still significantly lower than the corresponding indicator of HD-DVD or Blu-ray Disc.
Samsung BD-P1000 Home Video Player
appeared on sale in June 2006
at a price of about $ 1,000
Meanwhile, Japanese manufacturers already demonstrated second-generation Blu-ray recording drives at CEATEC 2006 in the fall. So, Pioneer introduced the BDR-202 model, equipped with a SATA interface and allowing you to record BD-R with a maximum speed of 4x, and BD-RE - 2x. In addition, DVD ± R (12x) and DVD ± R DL (4x) recordings are supported. The developers do not exclude the possibility of implementing in mass-produced devices also the functions of recording onto CD-R / RW and DVD-RAM media.
Cinema in HD
Along with the release of the first household video players and computer drives on the shelves, pilot runs of films recorded in high definition on new generation media began to appear.
Universal Studios and Warner Home Video, which have already released a total of more than 80 films on HD-DVD media, plan to present about 150 more films before the Christmas holidays. According to the alliance promoting the HD-DVD format, from April to October 2006, more than 110 films were released on carriers of this format, and the total number of discs sold exceeded 1.5 million. And this despite the fact that for the pleasure of joining the world of high-definition cinema, you have to lay out a fair amount: the average price of a film in HD format in the USA is about $ 40.
Naturally, at this stage, the novelty factor plays an important role. According to statistics, the films that are saturated with dynamic scenes and special effects are now in the greatest demand. For example, in October, Tokyo Fast Drift (“The Fast and the Furious: Tokyo Drift”) became the best-selling HD-DVD movie in the United States - almost 30% of the total print run was sold on the first day alone.
20th Century Fox became the first major publisher to decide to premiere new films for home viewing simultaneously on two types of media - DVD and Blu-ray Disc. So, on November 21, 2006, the film “Ice Age The Meltdown” on DVD and Blu-ray Disc went on sale. Following this, on December 12, a similar “double” premiere of the film “The Devil Wears Prada” took place.
In early October, the first commercial circulation of the film on a two-layer Blu-ray Disc media was released: Sony Pictures introduced a new “Click” picture in a new format.
Considering this topic, one can not help but mention that the largest Hollywood studios that produce trial copies of their products on HD-DVD are beginning to exert increasing pressure on members of the DVD Forum, insisting on the introduction of a regional coding system similar to the one used some time ago for DVD Video discs. This looks rather strange, especially since attempts to combat piracy and illegal import of films to DVD using the regional coding system have failed. In addition, the developers pay attention to the fact that as a result of the implementation of such protective measures, the interactive functions provided in household HD-DVD players may be affected.
Whether this idea will be implemented is not yet known. Nevertheless, this issue was already discussed at the beginning of October 2006 at a conference of members of the DVD Forum held in Japan. As a result of the discussion, it was decided to preliminary study this issue by the working commission, which will have to submit specific proposals for the introduction of regional coding in early 2007.
At the same conference, the possibility of recording HD-DVD Video / VR video format on conventional DVD media was considered. Soon, a similar function will appear both in household players and computer recording drives, and in DVD-camcorders.
Another important issue discussed at the conference was the standardization of TWIN DVD media. This hybrid ROM-drive, on which you can record data in the format of HD-DVD or ordinary DVD, experts at Memory-Tech and Toshiba began to develop back in 2004. According to the creators, this solution allows you to make the transition from one generation of optical drives to another painless for end users: the film purchased on a hybrid medium can now be played on any DVD player, and when switching to HD-format technology, you will not need to update the film library so that make full use of the potential of high-definition devices. In the existing version of the TWIN DVD specification, it is possible to create up to three layers: two HD DVDs (30 GB) and one DVD (4.7 GB) or one HD-DVD (15 GB) and two DVDs (8.5 GB). According to the decision, the standardization procedure for the DVD TWIN format will be completed in the first half of 2007, and the release of such media will begin in the summer.
“War of formats”: possible options
With the advent of the sale of devices and carriers of two competing standards (HD-DVD and Blu-ray Disc), a new round of discussion of the issue of their opposition began - now in-person. In mid-October 2006, Forrester Research analysts expressed the view that the victory will ultimately go to the Blu-ray Disc format, while clarifying that the victory will be pyrrhic and the stage of confrontation will be quite long. Ted Schadler, one of the leading employees of Forrester Research, said: “After a long and painful period of waiting, it’s now quite obvious that the Sony-led Blu-ray Disc format will win. However, after the HD-DVD group leaves the battlefield, it will take at least a couple more years before consumers finally make sure of the Blu-ray Disc victory and seriously think about purchasing a new format player. ” According to Mr. Shedler, the conservatism of the end users will also slow down this process: at present, the quality of DVD recording fully satisfies the needs of most of them.
Analysts note that one of the serious arguments in favor of Blu-ray Disc is its versatility - not only videos, but also games will be distributed on carriers of this format. Thus, Sony PlayStation 3 game consoles can play an important role in the “format war”.
While some are wondering about who will win the “format war” that has already become reality, others are convincing potential buyers of HD systems that this problem will be solved by itself with the advent of players that can play both Blu-ray Disc and HD-DVD discs. It is likely that multiformat devices will be available at the end of 2007. In any case, the companies NEC, Broadcom and STMicroelectronics, developing and producing specialized chipsets for optical drives, have already announced their readiness to begin supplying products on the basis of which it will be possible to create multi-format video players and computer drives. Shigeo Niitsu, vice president of NEC Electronics, is confident that the emergence of multi-format devices is only a matter of time. “Large PC makers such as HP are looking for solutions that are compatible with both formats. And technically, we are fully prepared for the production of such devices. ”
Nevertheless, the availability of ready-to-use technical solutions is not a sufficient condition for the emergence of multi-format devices - a lot depends on the position of leading manufacturers. For example, in the spring of 2006, Samsung Electronics and LG repeatedly announced the development of multi-format HD players (model names were even made public), but subsequently they abandoned these plans. According to some analysts, Korean electronic giants have decided to abandon the release of multi-format devices under pressure from the BDA (Blu-ray Disc Association), of which they are members. Around the same time, Pioneer representatives denied the earlier reports about the planned release of the BDR-103 optical drive, which supposedly supports both Blu-ray Disc and HD-DVD.
Schematic diagram of the optical drive reader VMD
It is possible that a solution to the compatibility problem will be found in a completely different plane: for example, by creating hybrid discs that allow you to store recordings of various formats on one physical medium.
In 2006, Warner engineers developed the principles of creating an optical medium that allows storing information in three different standards at once: DVD, HD-DVD and Blu-ray Disc. Such a disc is two-sided: a DVD-format layer is recorded on one side, and HD-DVD and Blu-Ray Disc on the other. The main secret is the manufacturing technology of the Blu-Ray Disc layer, which is closer to the surface of the disc (0.1 mm versus 0.6 mm for HD-DVDs). It was made translucent so that the laser beam reflected from it in the Blu-ray drive remained powerful enough for stable reading. In an HD-DVD device, a beam passes through a Blu-ray layer, is reflected from the surface of an HD-DVD layer, passes through a Blu-ray layer again, and returns to the optical receiver. The creators of the multi-standard disc have already received a patent for a new invention, and Warner plans to release a trial batch of one of the films on such media.
In September, a spokesman for New Medium Enterprises (NME), a UK-based company that developed the technology for industrial production of multi-layer multi-format discs for Warner, said solutions were found to significantly reduce the cost of such media. According to the data presented, the cost of manufacturing a “triple” disc will be only 1.5 times higher than the cost of a single-sided single-layer DVD-ROM. This news received a great public outcry, and some media outlets even appeared with headlines: ““ The format war ”can be killed in the bud.”
Considering that at this stage, the main interest in HD-DVDs and Blu-ray Disc is mainly related to the distribution of HD videos, a third one, namely HD VMD (High Definition Versatile Multilayer Disc), may well intervene in their struggle. In last year’s review, we already talked about the VMD format developed by the aforementioned NME. Let us briefly recall the features of this solution.
In essence, VMD technology is the logical development of the DVD9 format. Increasing the capacity of the optical medium is realized not by increasing the specific recording density (as in systems based on a blue-violet laser), but by increasing the number of information layers while maintaining the basic physical parameters of the basic DVD standard (in particular, track width and pit size, as well as wavelength of the light source used in the read drive).
To form information layers of VMD carriers, a special reflective material is used, the properties of which allow minimizing the interference of the laser beam and its reflections. The chemical composition and manufacturing technology of this material is NME's know-how. VMD media has the same physical dimensions (diameter and thickness) as DVD. The thickness of each layer formed on a plastic sub-substrate is only 20-30 microns. It should be noted that for the manufacture of layers of ROM media, injection molding technology is widely used in the industrial replication of CD-ROM and DVD-ROM media. This allows the use of existing DVD-ROM production lines for the production of VMD-ROM discs. With regard to the cost of VMD-ROM media, according to NME experts, it will be comparable to the cost of manufacturing a two-layer DVD.
Prototype Home Video Player
DVD / EVD / HD VMD
According to the creators of VMD, the technology developed by them allows (at least theoretically) to increase the number of information layers packed in one disk to 20. Each layer of a VMD disk contains a little more than 5 GB of data; thus, the maximum capacity of these media (when using systems based on a red laser) reaches 100 GB. Currently, prototypes of VMD ROM media with a capacity of 20, 40 and 50 GB have already been created.
Due to the minimal design differences from conventional DVD-ROMs, HD VMD drives can be produced on existing DVD device production lines. Thus, the production of HD VMD drives will cost only a little more expensive than DVD-ROM drives.
So, HD VMD format has enough capacity to record full-length films in HD format, but at the same time provides the ability to use much more affordable (compared to HD-DVD and Blu-Ray Disc) media and video players. Of course, at the current stage it is possible to create only HD VMD ROM media, which significantly limits the ability to use drives of this format in a PC. At the same time, in the eyes of representatives of the film industry, concerned about the problem of piracy, the inability to copy HD VMD media by end users seems more like a virtue. So in terms of the use of media for the replication of films HD VMD in the current environment looks more attractive compared to HD-DVD and Blu-Ray Disc.
Comparison of the main parameters of reading systems of optical drives of different formats
In November 2006, a representative of NME announced that it was planned to release an HD VMD player before the New Year. The device, with an estimated cost of about $ 175, will play DVD, EVD and HD VMD media. Last year, pilot editions of a number of Chinese and Indian films, as well as several American films adapted for the Chinese market, were released on HD VMD. But, despite the clear “Asian” orientation, the creators of HD VMD hope in the near future to begin the struggle for a place in the sun in the markets of Western Europe and the USA.
Promising developments
In the final part of the review, we will talk about several promising developments in the field of optical drives, information about which appeared in open sources over the past year.
SVOD
At autumn CEATEC 2006, Hitachi Maxell demonstrated a working prototype of the Stacked Volumetric Optical Disc (SVOD). True, unlike the development of NME mentioned above, in this case, not a monolithic multilayer medium is used, but many thin floppy disks enclosed in a protective cartridge, similar in size to those used in magneto-optical libraries. The use of nanostamping technology in the production of media has reduced the thickness of one disc to just 92 microns, which is 13 times less than a conventional DVD. The diameter of the disc remains the same - 120 mm. Despite the small thickness, such discs can be read using the standard optical system and electronic components used in conventional DVD drives.
The SVOD cartridge contains hundreds of these floppy disks
The presented SVOD prototype works with cartridges containing 100 ultra-thin DVDs - thus, the total capacity of one medium is 940 GB. Disks are removed from the cartridge automatically using a special mechanism that is installed inside the drive. In order to ensure the stability of the floppy disk during its rotation during reading or writing data, the SVOD drive uses a support disk made of glass. The thin disk removed from the cartridge is located on the supporting disk like a flexible record on the player. A magnetic clip is provided for fixing the floppy disk. The air flows arising during rotation reliably press the flexible disk against the supporting one.
Since it takes about 10 s to replace one floppy disk with another from the same cartridge, a capacious buffer memory module is provided in the drive, which allows for continuous reading and writing of data when working with large volumes of information.
Hitachi Maxell developers claim that the transition to using a system based on a blue-violet laser range will allow recording up to 50 GB on a single thin disk, which in the future will make it possible to increase the total capacity of SVOD media to 10 TB.
In the near field
As is known, it is possible to increase the specific recording density of optical carriers of a traditional design by reducing the size of the spot formed by the laser beam on the reflective layer of the carrier. This can be achieved both by reducing the wavelength of the laser used, and by increasing the numerical aperture of the optical system. CD drives use an infrared laser (wavelength - 780 nm) and optics with a numerical aperture of 0.45, DVD drives use a red laser (650 nm) and optics with a numerical aperture of 0.6, in Blu-ray Disc devices - blue-violet laser (405 nm) and optics with a numerical aperture of 0.85.
The Near-field optical recording technology developed by Philips Research specialists reduces the spot size by significantly reducing the distance between the optical head of the drive and the disk surface, which, in turn, makes it possible to use an optical system with a large numerical aperture.
In the experimental setup, built on the basis of a laser with a wavelength of 405 nm, scientists were able to reduce the distance between the optical head of the drive and the disk surface to 25 nm (which is quite comparable with the performance of commercially available hard disk drives). Thanks to this, it became possible to equip the drive reading unit with an optical system with a 1.45 numerical aperture. As a result, reducing the size of the spot allowed us to increase the capacity of a single-layer medium with a diameter of 120 mm to 75 GB, which is three times more than the same indicator of the Blu-Ray Disc format, which uses a laser with the same wavelength.
While there are a number of problems on the way to implementing this technology in mass-produced devices, however, according to the developers, methods for solving them have already been found.
A similar solution was applied by Sony developers who created Near Field Communication (NFC) technology. The prototype optical drive built using NFC technology was presented at the ODS 2006 international exhibition in Montreal (Canada). The gap between the optical drive head and the disk surface is only about 20 nm. The use of NFC made it possible to increase the capacity of a single-layer carrier with a diameter of 120 mm to 60 GB.
Nanorods instead of lenses
An interesting development was presented by a group of scientists at Harvard University led by Ken Crozier. According to the published information, the technology they created makes it possible to significantly increase the recording density of information on optical media. Scientists say about 3 terabytes per layer of a 120-millimeter disk when using a laser with a wavelength of 830 nm.
According to the developers, at present, the potential for increasing the recording density in optical drives of a traditional design is practically exhausted. The main problem is that optical systems equipped with conventional lenses do not even theoretically allow a clear spot, the diameter of which would be less than half the wavelength of the used light source - this is prevented by diffraction.
In order to solve this problem, scientists proposed to use not a lens, but a special nano-optical device to focus the beam. Its design is two gold-plated nanorods located at a distance of 30 nm from each other. This device allows you to concentrate the energy of the laser beam at a point whose diameter is equal to the distance between the ends of the rods. The distance between the nanorods and the “focal point” (that is, the plane on which the spot radius is minimal) is about 10 nm. Of course, it will not be so easy to provide such accuracy in removable storage drives. Nevertheless, as experiments using optical recording in the near field show, this problem is not insoluble.
1. Introduction
3.1. Technical features of competitors
4. Prospects for the development of an optical drive.
5. Comparative analysis of optical drives
5.1 ASUS DRW-1608P
5.2 NEC ND-3540A
6. Safety precautions when working with a PC
6.1 Organization of the workplace
6.2 Safety
Conclusion
List of references
1. Introduction
Over the past few years, optical drives have undergone significant changes. Today, an optical drive is an integral part of the PC - which determines the relevance of the chosen topic.
The optical drive has become an integral part of the PC, because a variety of software products (primarily games and databases) began to occupy a significant amount of space, and their delivery on floppy disks proved to be excessively expensive and unreliable. Therefore, they began to be delivered on optical disks (the same as regular music), and some games and programs work directly from the optical disk, without requiring copying to the hard disk.
Also, a modern computer is a powerful multimedia center that allows you to play music, watch movies.
The purpose of this thesis is the study of optical drives. In the process of studying the following questions will be studied:
¾ History of the optical drive
¾ History of the optical drive
¾ Prospects for the development of an optical drive
¾ Comparative analysis of optical drives
¾ PC safety
2. The history of the optical drive
Optical disks are almost the same age as personal computers. And they even have their parents - vinyl records. 1982 is considered the year of the arrival of optical discs in modern technology. It was then that the two largest companies Philips and Sony took up new developments. Sony's executive director Akio Morita, who also became famous for the authorship of the famous Walkman player, believed that such discs should be designed to listen to classical music. And the standard for the duration of the sound was the playing time of the 9th Beethoven Symphony, which is approximately 73 minutes. It was decided to make the standard playing time equal to 74 minutes 33 seconds. Thus was born the standard "Red Book" (Red book) which described the standard CD-DA (CD-Digital Audio). Moreover, the predecessor was the standard standard vinyl record lasting 45 minutes, which has the worst sound quality and incompatible media performance CDs. Along with Sony, Philips also participated in the development of the Red Book standard. Strict requirements were introduced for size, sound quality, data encoding method and the use of a single spiral track.
On CD-DA, data is presented as follows.
Structurally, the entire disk can be divided into three main parts: lead-in (the input zone that stores all the information about the structure and ownership of the disk), PMA (Program Memory Area - the data itself) and lead-out (the output zone, which consists practically of one " zeros "and is essentially an indicator of the end of the disk).
All information is recorded on CD-DA in the form of tracks separated by gaps (pre-gap) equal to 2 seconds. There can be 99 such tracks, and each of them can be divided into 99 fragments. The concept of tracks is somewhat secondary, but it is well suited for the simplest description of the structure of a disc.
In fact, the information on the disk is presented in the form of block segments that have a standard size (2352 bytes) and a standard read speed of 75 blocks per second. That is, if we are talking about a two-second gap, then we mean 150 "empty" block segments. The tracks themselves consist of blocks filled with information.
The block segment, in turn, consists of 98 micro frames, each of which has a size of 24 bytes (192 bits). 24 bytes may contain a description of the values \u200b\u200bof six discrete samples of the right and left channels. And the given value of 2352 bytes can be obtained by simply multiplying 98 by 24. So, speaking of this segment size, we are talking only about purely sound information.
3. The history of the development of the optical drive
The new specification for storing digital data on CD media developed by Philips and Sony has become known as the Yellow Book, and the media themselves are called CD-ROMs (Read Only Memory). A block segment of 2352 bytes was converted. That is, the standard provided for the types of Mode 1, designed to store digital computer data, and Mode 2 - compressed graphic, text and audio data. The block sector type Mode 1 stores the information on the correction and correction of errors EDC / ECC (Error Detection Code / Error Correction Code) and is the most common. 288 bytes are allocated for error correction and correction in each sector. As a result, 2064 bytes remain on the information, 12 of which are allocated for synchronization and 4 bytes for the sector header.
Thus, the main minimum unit in the CD-DA format is the track, and in the CD-ROM - the segment.
The device drives on a CD-ROM.
After the arrival of the two standards described by the Red and Yellow books, there was one significant problem: the carriers were strictly tied to the types of drives. That is, the combination of audio and digital data was not implemented at that time. Mixed-format discs have appeared that store both CD-ROM and CD-DA data. Moreover, the first data (CD-ROM) was recorded at the beginning of the disc. This is not very convenient, since audio storage devices try to read the first track, which can harm the audio equipment, and CD-ROM drives cannot simultaneously read the program and play audio.
In November 1985, representatives of leading CD-ROM manufacturers gathered to discuss compatibility and the general type of file system structuring for all media. That is, a standard was required for the file system, write and read structure, etc. A document was compiled, which was a specification (the name of the specification is HSG), which defines the logical and file formats of the CDs. The document was of a recommendatory nature, and although later it determined a lot for the technological industry as a whole, the color of the book was not found for it. The proposal of the HSG specification format was largely based on the presentation of the structure of a floppy disk containing a zero track or system track, which stores data on the type of medium and its file structure with directories, subdirectories and files. The CD is organized a little differently. That is, all data of this type is stored in the service and system areas. The first stores information necessary for synchronization between the carrier and the drive. The second is the file structure, and direct file addresses in subdirectories are indicated, which reduces the search time.
Three years later (1988), the international standard ISO-9660 was adopted, the main provisions of which were very similar to the HSG representation. This standard described the CD-ROM file system and had three levels. The first level looks something like this:
File names can contain up to 8 characters;
The file names use only uppercase characters, numbers and the symbol "_";
Special characters are not allowed in file names - "-, ~, \u003d, +";
Directory names cannot have extensions;
Files cannot be fragmented.
The second and third levels of ISO-9660 only facilitate and expand the capabilities of the first. In particular, on the second level, restrictions on the names of files and directories are removed (for example, it is already allowed to create names 32 characters long), on the third, it is already allowed to fragment files. It should be noted that the first level ISO-9660 standardizes mainly the formats of the MS-DOS and HFS file systems (Apple Macintosh). The second level in these systems is no longer readable.
For Apple Macintosh, there is a separate standard for the HFS (Hierarchical File System) file system format. This computer platform has its own special hierarchy of the file system, which is why this standard is in demand. You can write several file system formats to one disk at a time.
The specification, developed in 1991, was released in the form of Orange Books. There are two of them. The first standardizes magneto-optical drives that can erase, overwrite information. The second book is about write-once drives that can only be rewritten. That is, the second book deals with CD-R (Recordable). Gradually, modern technology began to allow overwriting discs. We are talking about CD-RW (Rewritable) or CD-E (Erasable), which, in essence, is one and the same. These media and drives are likely to fall under the first of the Orange Books.
In 1993, the White Book was released, in which a new product was standardized - a Video CD, jointly developed by JVC, Matsushita, Sony and Philips. The basis of this standard was the Karaoke video system developed by JVC. The new format allows you to store 72 minutes of video with stereo sound. The compression format is familiar to many - MPEG (Motion Picture Experts Group). The first track is recorded in CD-ROM / XA format, then there is a data block containing compressed video. Based on acquisitions made using the White Paper standard, experts subsequently made significant changes to the Green Book.
At the end of the last century, CD-R drives, which had reached 8X / 24X write / read speeds by that time, were replaced by more universal CD-RW drives, which allowed recording not only write-once discs, but also rewritable ones.
In contrast to the organic dyes used to form the active layer in CD-R disks, the active layer in CD-RW is a special polycrystalline alloy (silver-indium-antimony-tellurium), which becomes liquid when it is strong (500-700 ° С ) laser heating. With subsequent rapid cooling of the liquid sections, they remain in an amorphous state, therefore, their reflectivity differs from polycrystalline sections. The amorphous regions are returned to the crystalline state by weaker heating below the melting point, but above the crystallization point (approximately 200 ° C). Above and below the active layer are two layers of a dielectric (usually silicon dioxide) that remove excess heat from the active layer during recording; from above, all this is covered with a reflective layer, and the entire “sandwich” is applied on a polycarbonate base, in which spiral recesses are pressed out, which are necessary for precise head positioning and that carry address and time information.
Optical media are 12 cm (4.72 inches) compact discs or 8 cm (3.15 inch) mini discs. Optical media consists of three layers:
1) polycarbonate base (outer side of the disk);
2) an active (recording) plastic layer with a variable state phase;
3) the thinnest reflective layer (the inner side of the disk).
In the center of the CD is a circular hole that fits over the spindle of the CD drive.
Writing and reading information to a CD is carried out by the head, which 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, varies depending on the cooling rate after heating the surface with a laser beam during the recording process performed in the drive. When cooling slowly, the plastic goes into a crystalline state and the information is erased (“0” is written); when cooling rapidly (if only a microscopic point is warmed up), the plastic element goes into an amorphous state (“1” is written). Due to the difference in reflection coefficients from crystalline and amorphous microscopic points of the active layer, a modulation of the intensity of the reflected beam perceived by the reading head occurs during reading. The surface of the disk is divided into three areas. The start area (Lead-In) is located in the center of the disc and is read first. It contains the contents of the disc, a table of addresses of all the records, the label of the disk and other overhead information. The middle area contains basic information and occupies most of the disk. End Area (Lead-Out) contains the label of the end of the disk.
Information on the CD is encoded with great redundancy by the Reed-Solomon correction code, which provides restoration of the original information when it is impossible to read it from the disk.
The CD can withstand several hundred rewriting cycles. Information is read when the CD is rotated at a speed of more than 10,000 rpm.
Depending on the ability to read / write, all CDs can be divided into three types:
1) ROM (Read Only Memory) - read-only; recording is not possible;
2) R (Recordable) - for one-time recording and multiple reading; a disc can be burned once; the recorded information cannot be changed and is read-only;
3) RW (ReWritable) - for repeated writing and reading; disc information can be overwritten many times.
These types of discs are distinguished by the material of which the second plastic layer is made.
Consider the types of compact discs CD (Compact Disc), DVD (Digital Versatile Disc - digital universal (multilateral) disc) and Blu-Ray, having the same size of 4.72 inches.
The volume of the CD is 650 or 700 MB. Music discs belong to the CD and are intended only for reading music from them. CD access time - 0.05-0.3 s.
DVD format is a development of CD, their volume is 4.7 GB due to more dense recording. DVDs continue to improve. There are several competing DVD formats: DVD-, DVD +, and DVD-RAM.
The Blu-ray format is a further development of the DVD and allows you to record 25 GB of information on one layer.
The names of the CD and DVD formats, depending on the read / write ability, are presented in the table.
Optical drives
Optical drives are designed for reading and, as a rule, recording / dubbing from optical discs. Optical discs are round and flat in shape plates made of dense material (usually consisting of polycarbonate) with layers deposited, allowing you to store information in the form of tiny holes (pit, frompit - fossa, deepening) The reading process is carried out by a laser beam, which is reflected from the surface of the disk into the photocell, where the light is converted into an electrical signal, the value of which allows you to decode the recorded information.
The most common optical disc formats for use in personal computers areCD, DVD, Blu - ray.
CD-ROM ( Compact Disc Read Only Memory, read-only CD) a variety of CDs, which appeared in 1982 as a result of a study of 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 sampling frequency of the sound of the signal is 44 KHz for stereo sound and the resolution is 16 bits. They had a capacity of 650 MB and allowed to store 75 minutes of music (starting from the 200s, disks with thinner tracks for recording appeared, which allowed to increase the capacity to 700 MB with recording 80 minutes of music). CD-ROM discs initially developed as an analogue of vinyl discs and were intended for recording and playing music information. They also have one concentric track that runs from the outer edge to the inside, making many revolutions. 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 a disc, unlike a vinyl disc, in digital rather than analog form, and after reading it is decrypted and translated into sound. To protect the disc from damage, the aluminum substrate is covered with transparent plastic.
The technology for creating CD-ROM discs is as follows. First, a disk is made on which only those places where the unit of information is burnt are burned out and the place with zero values \u200b\u200bremains unchanged. After that, a matrix is \u200b\u200bproduced, with the help of which the blanks are stamped, sprayed onto the information surface of a metal layer (aluminum, silver, gold, etc.) to increase the reflectivity of the laser beam, coated with transparent plastic (varnish) to protect data. When a disk is inserted into the drive, a laser beam glides along the concentric circle of the disk and it is determined from the reflected light that it is recorded: zero or one.
Originally, CD-ROMs were designed to store only music information. Due to the fact that digital information is used on the disks, 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 work only with certain formats, but over time with 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).
Further, the standard of the "Yellow Book" was developed, in which there is a title, with which the type of disc is determined: musical or software. The music format was already well developed, and each producer company determined the software format itself. Due to the rapid development of this technology, the disagreement in the standard could not continue for a long time, so the High Sierra recommendation standard arose, on the basis of which the ISO 9660 standard soon appeared. According to this standard, there is a table of contents and data area on the disk. The first track contains the parameters for synchronizing the drive and the drive with each other, followed by a table of contents in which the description of each file contains a direct address on the drive.
There are three types of such disks:
CD - ROM the disc is usually recorded in an industrial way, and in the future it can only be read. It has dimensions 120x1.2 mm, has a capacity of 650-879 MB. Service life 10-50 years. Such disks often come with devices for the computer, they have software on them, there are music disks, etc.
CD - R a disk has the same characteristics as a CD-ROM, but it allows you to record information on them once.
CD
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Rw a disk has the same characteristics as a CD-ROM, but it allows you to not only record information on them, but also to overwrite it, also erase previously recorded data and record new ones.
To work with them, CD-drives were used, which have several types:
CD- ROM the drive can only be readCD wheels. One of the most important characteristics of this device is read speed information. Normal (single) speed corresponds to the reading speed of audio discs, which is 150 kb / s. Then came the CD-ROM with 2, 4, 6, 8, 10, 12, 16, 24, 32, 36, 40, 52 times the speed. The data rate, respectively, is a multiple of 150 kb / s. For example, for a 40-fold drive, it will be 40x150 \u003d 6,000 Kb / s, and here the maximum speed that is equal to or lower for different types of drives, which depends on the manufacturer, is indicated here. The six-speed drive allows video output at a frame rate of 25 frames per second and higher, which is enough for viewing on the screen. Disks for working with this device are sometimes also called compact disks (this concept also includes CD-R, CD-RW) or CD-ROM disks (Compact Disk - CD; see the figure below).
CD - R The 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 characteristic not only of reading disks, but also for recording. For example, the read speed is 40 times, and the write speed is 6 times.
In such devices, the laser beam burns out on the surface of the disc grooves, while the light-reflecting areas are called “lands”, and the non-reflecting areas are called “pits”. The combination of these sections allows you to encode information in a two-bit representation.
For various reasons, in practice, when recording, it is impossible to achieve the ideal location of the burnt grooves and during playback, defects in sound appear, its trembling, which is called “jitter” (jitter). To a certain extent, the use of a special Audio Master mode allows you to get rid of such unwanted distortions when the burned grooves are forced to increase in length. This mode is used in cases where it is necessary to achieve improved quality of the recorded sound.
Typically, recording is performed at a constant angular velocity (CAV). However, when the rotation speed changes at times (x2, x4, x8, etc.), the recording is paused and so-called “connection points” are formed, which degrades the recording quality. In such cases, buffer underrun protection called SafeBurn is used. As a rule, it is turned on only at the moment of changing the disk rotation speed, and the recording mode with constant angular velocity (CAV) is mainly used. This method of improving the quality of reproduced sound is called constant-speed linear recording (Z-CLV).
The possibility of burning text on the surface of a laser disc available on some devices for recording digital information discs is very interesting, whether it is a list of music files or your own data. For this, the DiscT2 mode is used, in which any text worthy of reproduction is typed on the surface of a music-created or other kind of disc created by oneself.
CD - Rw (Compact Disc-ReWritable) the drive is a multi-record optical drive. It allows you to read CD-ROM, CD-R, CD-RW discs, burn CD-R discs once, but also record and re-record, as well as overwrite previously recorded CD-RW discs. This drive has the characteristic not only of reading disks, but also for recording. For example, the read speed is 40 times, and the write speed is 6 times. There could also be a recording rate.
The CD-RW device works in a different way, that is, when recording on them, the beam does not burn out, but puts the substrate in an amorphous state, which allows you to set a different reflective effect. Therefore, they can record data multiple times. However, discs scatter information worse than standard CD-ROM discs, so they cannot always be read on standard media.
The more features the device has, the more limitations it has. The simpler the disks, the greater the reflective effect they have. CD-ROM discs that can be read in CD-ROM, CD-R and CD-RW drives have the best reflective effect.
CD-RW format discs have even lower reflectivity and may not be readable on all old CD-ROMs and CD-R drives (on older drives). It’s quite difficult to say which drives will be read and which ones will not, since it depends on the device model. Currently, CD -R CDs are sold on which information can be recorded. If there is free space after recording on a disc, then you can add information to the disc and so on. CD-RW discs allow you to not only record information, but also delete unnecessary data, that is, record data many times and are slightly more expensive than CD-R discs.
In 1996 appeared DVD drives(Digital Versatile Disc - a digital universal disc, originally decoded as Digital video Disc - a digital video disc. Now it is not decrypted in any way), which had a capacity of 4.7 Gigabytes due to the compression of the recorded tracks, that is, 7 times the capacity of a CD-ROM disc. This is the most common type of disc that is single-layer and single-sided. However, there are discs that have two layers on one side and they have a capacity of 8.5-8.7 Gigabytes (they can 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 can be called DVD 10), double-layer and double-sided with a capacity of 17.08 gigabytes (they can be called DVD 18). Two-layer disks have two translucent layers with powerful beam focusing, allowing you to read information from either the first or second layer. A higher data density is achieved by reducing the area on the disk for one bit and applying compression methods. But in practice, the most common are unilateral, single-layer.
After creating a single DVD standard for recording videos 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 icon can be applied to an old DVD drive, which shows an image of the globe with numbers indicating which zones the drive is working with or ALL (all) for working with disks in all zones. In modern DVD-drives such a partition is not available.
Information on the disks is located in sectors that contain data and 882 bytes for the error correction code, which allows to increase the reliability of reading information, since in case of failures, values \u200b\u200bare calculated by the correction code. In the presence of bad sectors, the read speed slows down and re-read, 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 this disk, after which it switches back to the maximum speed.
Unlike CDs, DVDs have their own UDF file system or for ISO -9660 data. Data is stored in sectors of 2048 bytes in size. There may be DVD-Video, DVD-Audio, DVD-Data and mixed-type discs.
Disks DVD - ROM as well as CD-ROMs are read-only. They have already been recorded somewhere and are being sold with recorded information.
The standard for writing to a disc was developed in two ways, one standard called MMCD was developed by Philips and Sony, the second under the name Super Disc - Toshiba and several others. Therefore, there were two formats for recording data - 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 having a double layer on one surface are denoted 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 DVD, DVD-drives are used, which have several types:
DVD - ROM the drive can only read both DVD and CD-ROM drive. One of the most important characteristics of this device is read speed information. Multiplicity per unit is taken as 1.32 MB / s, which is 9 times faster than CD speed. They have different speeds for reading CDs and DVDs, which is indicated in the manual for the device.
DVD - R The 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 once CD-R discs and DVD + R and DVD-R discs. This drive has the characteristic not only of reading disks, but also for recording. For example, the read speed is 40 times, and the write speed is 6 times, and the speed is indicated separately for CDs and DVDs and, accordingly, separately for DVD-R and DVD + R.
DVD
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Rw The drive is a multi-record optical drive. It allows you to read all types of CDs and DVDs and burn them. Read and write speeds are specified 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 that can drive. It’s 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 overwrite the data in real time.
Standard Blu
-
ray
Disc
(Bd
)
(blue ray - blue ray and disc - disk; spelling blu instead blue - intentional)was developed by the BDA consortium, released in 2006. This standard had a competitor - Toshiba’s HD DVD, however, this company refused to further support HD discs in 2008 after the “format war”. The speed of reading information (single speed) is 4.5 Mb / s. The increase in the amount of recorded information is carried out by using a laser beam in the blue-violet range with a shorter length of 405 nm, while CD and DVD drives use red and infrared lasers with a wavelength of 650 nm and 780 nm.
A single-layer drive can store 25 gigabytes, a double-layer drive - 50 gigabytes, a three-layer drive - 100 gigabytes, a four-layer drive - 128. A disk may have more layers. So in 2008, 20-layer drives with a capacity of 500 gigabytes were demonstrated.
BD-ROM discs for reading, BD -R write once and BD -RE write once are currently available. There are also double-layer discs with DL characters in the name with a capacity of up to 50 gigabytes.
There are drives for these drives Blu - Ray read-only discs that allow you to read and write all types of CDs and DVDs, as well as only read BDs. Respectively Blu - Ray RE allow not only reading, but also writing all kinds of CDs, DVDs and BDs (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 of the drive (see figure below). At the same time, the tray extends from the drive into which the disk must be placed in a special recess for it with the working surface on which the data is located, down, or with the pattern up. Then press the button again, while the tray slides into the drive housing. Now you can work with the disk. The tray has a second recess for the disks, approximately half the diameter and is currently very rarely used (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 an upright position. In this case, the disk is inserted into the slot with your hands, after which a special mechanism holds it and inserts it into the drive.
The optical drive has a hole for emergency extension of the tray, if it does not extend. To do this, insert a thin rod, for example, a straightened paper clip, and press on it. In addition, there may be a button to go to the next song for audio discs. 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, sound cards.
For disk boot need to:
Turn on the computer;
Press the button to open the tray, while it extends;
Put the disc label up on the tray;
Press the tray open button again. The tray slides in, after which you can begin work.
Do not manually slide in and out the tray. It is undesirable to keep the tray open for a long time in the absence of work, do not put foreign objects on the tray, for example, put a cup of coffee, do not put pressure on the tray when the disc is stacked.
If there is no operation, the drive enters the energy conservation mode, while the drive noise stops. When a read command is received, the drive starts working automatically.
The manufacture of the disc is as follows: first, the disc is made, which is called "mother", then a working copy is stamped - "father", then others are pressed on its basis.
The main drive characteristics:
Type of: interior or external. The internal drive is inserted into the system unit. The external one has a rectangular case, is connected to a parallel port (in old computers), USB (in modern computers) and has a wire that connects to the mains. There is also an external option for laptop computers, connected using the PCMCIA connector;
- data rate(Data Transfer Rate, DTR), respectively, is indicated as two-speed, four-, thirty two-, etc .;
- buffer memory(Buffer Memory). The cache memory is a RAM chip, which is located on the drive board. They provide benefits, so the larger the volume, the better;
- average time between failures (Mean Time Between Failure, MTBF). This feature is available for many devices, but is not always described;
- interface typeor the bus to which it connects;
- average access time (Access Time, AT). It has more CD-ROM drives than hard drives, which is determined by fundamental differences in the design of the drive, and differs dozens of times, and the greater the multiplicity, the shorter the access time. So, for a 4-fold drive it is approximately 150, and for 32 - 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 level, vibration. In addition, when buying, you need to see if the tray moves gently and firmly holds it open.
The latest BIOS allows you to boot your computer from CD and DVD discs. The CD-ROM disk at the beginning of the track has a service area in which there is information for synchronizing the drive and the disk, then a table of contents of the volume (Volume Table of Contents or VTOC), which contains information about the organization of directories and files on the disk, then data and label end of volume. Thus, knowing the path and file name, you can find the file location on the disk from the table and directly position the head to read data, which reduces the search time and read operations.
Connects device using two cables: power and data. There are three types of drives: connected to the SCSI bus, to the IDE bus or SATA connector. It is better to have a drive connected to the IDE connector if the motherboard supports it. Since usually SATA connectors are few and if you need to install several optical or hard disk drives, you may have a problem with the availability of a free connector.
The connection to such a bus is described below. Optical drives can be connected with a hard drive. The information 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 near the marking 1, 2, which indicate the first cores of the wire, the opposite end should be near the numbers 33 and 34. The second power cable should be connected to the marking indicated at the top of the plug, i.e. 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 the 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 correspond to R on the drive. The figure below shows the back of the drive, on which there are connectors for connecting wires.
The installation sequence for the new optical drive is similar to installing a floppy drive. If Windows 9x is installed, an appropriate 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 perform following rules:
Do not touch the work surface, otherwise fatty finger marks may remain on it;
Take the disk by the outer edges, you can take the edges of the central hole;
The disc is cleaned 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 envelope for discs;
Do not bend the disc;
Do not write on the working surface of the disc;
When storing the disc, avoid direct sunlight and strong heat, which can cause 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 poorly read, and by eye such a defect is not detected. Reducing the speed of the disk may help, for example, try to do this on a slower drive. If the disk is deformed, it is sometimes noticeable to the eyes, then a decrease in 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 edge to center are often not dangerous, but scratches along the edge may not allow data to be read. Therefore, wipe the disc from the center to the edge. To test the disk, special test programs are used. When installing, they use interrupt (IRQ) - 7 and higher, base addresses 300h to 340h, DMA1. Compact discs 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 not be readable.
Drive Installation. To install this device, you need:
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 get a screwdriver and tighten the screws, you may need to remove other devices. After that, connect the wires, as described above, and 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 a hard drive.
If the tray does not extend, the cause may be a hard drive mounting with screws inside the system unit, at which the drive skewed. Sound during the acceleration of the CD is not a malfunction. After installing the optical drive for the test, you can try to copy some of the files from the optical drive to the hard drive. Do not disassemble the drive yourself. The drive must not be exposed to rain or in a humid place.
It's no secret that the story began with phonograph records. It is problematic to save information at home, and only sound was stored on it. The principle of operation is not a secret, so vinyl disc has been popular for over a hundred years, and collectors and DJs still use and store them. It was fun to watch how the needle, while scrolling the disk, walked with a shaker, as it were, on a perfectly even spiral. On this was built the principle of obtaining sound. When the depth and width of the groove changed, the sound wave changed and was further amplified by a pipe (gramophones, gramophones). With the development of electronics, the principle of removing information was made on a piezoelectric needle and received a modern, until recently, record player.
So the 70s came up. And there was a jump in the storage media (we will skip magnetic tapes). They invented a disc made of polycarbonate, which had transparency, with aluminum coating. Polycarbonate served as the basis and protected the spraying from external influences, and depressions were burned out in a spiral spiral pattern. The principle of recording and recording information on this is based, as you see, not far gone from the record. A thin beam was reflected from the surface of the deposition and came to the light detector, which in turn determined the changes and units and zeros were created with respect to the received information. And then on the principle of alphabet Morse code information is converted to music, movies, photos, files, etc.
Now we will understand the notation on CDs:
But with DVD disks, everything turned out much more complicated. This disk was created to store information in a large volume and a large number of companies were engaged in development (DVD-R and DVD-RW). Different spraying had various characteristics and household players, of various companies, began to conflict with discs, hence the versatility was lost. Therefore, having united, they invented a new type of disk, called DVD + R and DVD + RW, they cost, oddly enough, cheaper. Now it doesn’t matter which disk to use, as household players have adapted. There is only difference in rewriting discs, DVD-RW need to be completely washed before recording, and DVD + R just erase the "cap" and overwrite the entry on top.
As they say, how much we don’t give and everything is not enough for us. Therefore, progress did not stop there, bilateral and bilayer and two in one drives. Well with bilateral, everything is simple, spraying was applied from two sides, and as an audio cassette you need to turn the disc over. Double layer - This is one of the layers adjacent to the laser, made translucent, and you do not need to get up from the couch to turn the disc over. Well, with the last option, take two bilayer and glue together.
So we have reached the peak of the development of the modern world of the optical disc, this is - HD-DVD and Blu-ray.
HD DVD - this is a disc that was made on the basis of our hard workers described above, but using a blue laser.
Blu ray - A completely different development, using a blue laser.
If we recall the spectrum (rainbow), it will be seen that with a blue ray, you can get a much thinner ray, so these disks have turned out much more voluminous. But more on that in the next topic.
It seems that today, that's all. There is only a little left to tell about storage and use of the disk. A disk is not tasty, it is not necessary to bite it, well, if only someone has a lack of plastic in the body. And it’s also not a tool for playing on the nerves, so you don’t need to drive it with its claws. It is advisable not to bend, although it breaks hard, but fragments can get where you should not, and this will affect your body. Also, a constant bend violates the inside of the spraying, it cracks and the zeros of a unit will no longer coincide with you. Do not fry it in the sun, it’s an element D not needed at all, but to turn into a sousy product and you won’t shove it anywhere. Do not insert a disk with a crack into the drive, otherwise it will have to be spent either on repairs or on the purchase of a new one.
I hope YOU literate and you don’t need to list all the points, you need to treat things with care and they YOU they will thank for this.
