DVD drive device building. Free download of the book: "Modern DVD players. Device and repair". The most interesting videos on Youtube

What is a DVD?. 3

DVD Device Basics 3

Plenty of DVD Surfaces 5

Transfer rate and access time. 6

Burning to DVD 7

Video on DVD 8

DVD in action. eight

Sound on DVD 9

The official DVD successor has been announced - Blue-ray Disk. eleven

What is DVD? After a long period of time spent in planning and development, the new format that everyone has been waiting for has been released. The appearance of the DVD format marked a transition to a new, more advanced level in the field of storage and use of data, sound and video. Initially, the abbreviation DVD stood for digital video disc, these are high-capacity optical discs. These discs are used to store computer programs and applications, as well as feature-length movies and high-quality sound. Therefore, the decoding of the abbreviation DVD, which appeared a little later, as a digital versatile disc, i.e. universal digital disk - more logical.

From the outside, DVD discs look like normal CD-ROM discs. However, DVDs have much more possibilities. DVD discs can store 26 times more data than a conventional CD-ROM. With the physical size and appearance of a regular CD or CD-ROM, DVD discs represent a huge leap in storage capacity from their 650MB ancestor. A standard single-layer, single-sided DVD disc can store 4.7GB of data. But this is not the limit - DVDs can be produced according to the two-layer standard, which allows you to increase the capacity of data stored on one side up to 8.5GB. In addition, DVD discs can be double-sided, which increases the capacity of one disc up to 17GB. Unfortunately, you will have to buy a new device to read a DVD, but this new hardware will read your old CD-ROMs and audio CDs just as well. What does all this mean for us with the new drives' high capacity? This means that we have truly unlimited opportunities for learning and entertainment, for watching movies with amazing digital picture and sound quality. DVD provides sharper and higher quality images than laser disc (LD) and richer sound than CD. What's more, the DVD gives you a choice. You can choose from which angle to view a movie scene, due to the fact that the same scene is filmed from different camera angles. Thanks to this, one and the same film can be watched, for example, with scenes of violence or without them, and the plot of the same film can change in a bizarre way. And almost all of it is already on sale! Next, we'll take a closer look at the technology that offers us so many possibilities.

DVD Device Basics Like CD-ROMs, DVDs store data by scoring along spiral tracks on a reflective, plastic-coated metal surface. The laser used in DVD readers slides along the tracks along the notches, and the reflected beam is interpreted by the receiving device as ones or zeros. The main requirement in the development of the DVD was simple: to increase the capacity of the stored data by placing as many notches as possible along the tracks on the disc, while the production technology must be cheap. The result of the research was the development of a higher frequency semiconductor laser with a shorter wavelength, as a result of which it became possible to use smaller notches. While the laser in a conventional CD-ROM device is 780 nanometers (nm), DVD devices use a 650-nm or 635-nm laser, which allows the beam to cover twice as many notches on a single track, and twice as many tracks located on one recorded surface. Other innovations are a new sector format, a more robust error correction code, and improved channel modulation. Together, these improvements further increase data density by a factor of 1.5. Strict production requirements and a marginally large recording surface were the last obstacle in the development of the DVD, due to which the data capacity placed on the disc is limited to 4.7Gb. But it turned out that this is not the limit. To record video and sound on DVD, a very complex data compression technology called MPEG-2 is used. MPEG-2 is the next generation standard for compressing video and audio data, providing the ability to fit large amounts of information into a smaller space. The MPEG compression standard was developed by the Moving Picture Experts Group (MPEG). MPEG is a standard for compressing audio and video files into a more convenient format for downloading or sending, for example, over the Internet, a format. MPEG-1 streams video and audio data at 150 kilobytes per second -- the same speed as a single-speed CD-ROM player -- and is controlled by sampling key video frames and filling in only the areas that change between frames. Unfortunately, MPEG-1 provides lower video quality than TV-standard video.

MPEG-2 compression changes things dramatically. More than 97% of the digital data representing the video signal is duplicated, i.e. are redundant and can be compressed without compromising image quality. The MPEG-2 algorithm analyzes the video image in search of repetitions, called redundancy. As a result of the redundancy removal process, excellent MPEG-2 video is provided at a lower bit rate. For this reason, modern video software delivery systems such as digital satellite systems and DVD use the MPEG-2 standard.

Plenty of DVD surfaces

Most DVD discs have a capacity of 4.7GB. The use of density doubling schemes and their combination makes it possible to have larger capacity disks: from 8.5Gb and 9.4Gb to 17Gb.

The following DVD structure types exist:

Single Side/Single Layer: This is the simplest structure of a DVD disc. On such a disk, you can store up to 4.7 GB of data. By the way, this capacity is 7 times larger than the capacity of a conventional audio CD and CD-ROM disc.

Single Side/Dual Layer: This disc type has two data layers, one of which is translucent. Both layers are read from the same side and 8.5 GB of data can be placed on such a disk, i.e. 3.5 GB more than a single layer/single sided disc.

Double Side/Single Layer (double-sided/single layer): 9.4 GB of data is placed on such a disc (4.7 GB on each side). It is easy to see that the capacity of such a disc is twice that of a single-sided/single-layer DVD disc. Meanwhile, due to the fact that the data is located on both sides, you will have to turn the disc over or use a device that can read the data on both sides of the disc by itself. Double Side/Double Layer (double-sided/double-layer): the structure of this disc allows you to store up to 17 GB of data on it (8.5 GB on each side). Note that all figures given correspond to the capacity given in millions of bytes; if you round using a different method, taking as a basis that 1Kb = 1024 bytes, and not 1000 bytes, then you get other numbers: 4.38GB, 7.95GB, 8.75GB, and 15.9GB, respectively. It is easy to see that the simplest way to double the capacity is to use double-sided discs. Manufacturers can produce DVD discs with a thickness of 0.6mm, which is half the thickness of a standard CD disc. This makes it possible to connect two disks with the reverse sides and get a capacity of 9.4Gb. According to another technology, a second layer is created to accommodate data, this allows you to increase the capacity of one side of the disk. The first layer is made translucent, so the laser beam can pass through it and reflect off the second layer. According to this scheme, 8.5GB of data can be placed on each side of the disk.

Being complex electronic-optical-mechanical devices, CD/DVD drives are among the most unreliable computer components. The causes of breakdowns can be very diverse. Most often, the laser dies or loses its emission, the chipset crashes even more often, especially if both drive motors and laser focusing coils are hung on a single microcircuit. I'm not even talking about mechanical breakdowns and contamination of optical surfaces. Is it possible to repair a failed drive at home, or is it easier not to suffer, but to buy a new one?

Introduction

Not every drive failure is fatal. Often, the drive can be repaired at home, without any special equipment or preliminary training that goes beyond the competence of an ordinary craftsman electronics engineer. Don't be afraid to experiment with a broken drive! It will not be worse for him anyway (of course, provided that the drive is not under warranty). You can, of course, take it to a service center, but ... it's long, expensive, and not interesting.

You will need spare parts for repairs. And where to get them? Go to the market, shock your friends - and you will surely find a lot of "scrap metal" that will be given to you for next to nothing. First of all, pay attention to drives built on the same element base as yours (this primarily concerns the laser head and chipset, the marking of which is determined by the inscriptions on their case). Let's say your electronics board flew out, and a friend's gears crumbled. Then the entire non-working board can be replaced entirely, without even understanding what the problem is. All other models are also useful. From there, in particular, you can pull out some specific spare part - for example, a fuse.

Troubleshooting methodology is not provided here, as this is too broad a topic. Our task is much faster - to give the reader a first push, orienting him in which direction to dig, listing the main categories of breakdowns and methods with them, sorted in descending order of their relevance. Well, the rest, as they say, is a matter of technology ...

Picture 1.

Laser

Laser emitters used in reading (and especially writing!) drives are rather short-lived devices that massively fail after several years of operation. Why is this happening? Well, firstly, the natural loss of emitter emission affects, and secondly, the unfavorable mode of operation. Self-respecting manufacturers adjust the parameters of each laser strictly individually, either by setting the required modes with trimmers (in cheap models), or by entering them directly into the firmware itself (in more expensive models). Noname set all parameters to the average level, which is too low for some head instances, and too high for others. By the way, when unlocking DVD drives and replacing the firmware with its "hacked" version, the previous settings are not saved, and if the hacker does not attempt to save them first, the laser will quickly fail or become unstable.

Decreasing the brightness of the laser light increases the number of read/positioning errors (some of the disks are no longer recognized at all), and starting from a certain moment, the drive refuses to recognize the disks at all, often without even trying to spin them up (usually the drive motor spins up only when the sensor detects the reflected signal , and if there is no signal, it is considered that the disk is not inserted and do not spin it).

After carefully disassembling the drive, connect it to the computer and see if the laser flashes when the tray is closed. With normal emission, you will see the beam even in daylight, and a “sunk down” laser is only distinguishable in a darkened room. If there are no traces of the presence of the beam even in complete darkness, look for the cause of the failure in the electronics (just remember that the laser is not visible from any angle). Actually, this is a rather risky operation, because. if the beam hits the eye, you can go blind, but this risk is not so great ...

Services for replacing a laser head on average cost half the cost of a new drive, and given that scientific and technological progress does not stand still and new drives are much better than old ones, there is little point in such repairs. Alternatively, you can try to bring the laser back to life simply by increasing the supply voltage. Follow the conductors connected to the laser emitter - in their path they should rest against a resistor, in parallel to which you have to solder another one, choosing its resistance so that the drive confidently recognizes all the disks. A more honest option - after finding out the brand of the chipset that controls the laser (usually the largest chip), surf the Internet in search of its technical specifications. There, among other useful information, the mechanism for adjusting the power of the laser beam should be described. As a rule, one or more resistors connected to the chipset (not to the laser head!) are responsible for this. Some models allow you to configure the laser via the SCSI/ATAPI interface (via special commands described in the technical documentation for the drive) or via the process connector.

In principle, the laser head can be disassembled by directly replacing the emitting element itself, which can be torn out of another drive, but few managed to assemble the head correctly. Just in case, below are explanatory photographs showing its device, the principle of operation and the disassembly procedure.

Figure 2.

Figure 3

Figure 4

Figure 5

Chipset

The chipset is the heart of the drive. It not only provides information processing, but also controls the position / rotation motors, laser head and focus coils. Thrifty manufacturers integrate the entire chipset into a single chip, often not caring about its cooling. As a result, the chipset quickly fails, literally burning through, and the drive completely or partially fails to work.

The behavior of a broken chipset can be very diverse - from complete unwillingness to recognize the drive at all to a decrease in reading speed. The minimally operable chipset recognizes the drive and, when power is applied, moves the optical head to the beginning of the disk, after which it starts to bounce the focusing lens. If this does not happen, the chipset is unusable or the electrical components serving it are faulty (but they fail quite rarely).

Replacing a burned-out chipset at home is unrealistic, because. firstly, there is no place to buy it, secondly, its price is comparable to the cost of a drive, and thirdly, without special equipment, this jewelry operation can only be performed by Left-handers and extreme sportsmen.

But it is quite possible to prevent the failure of the chipset. Glue at least a tiny heat sink to the largest drive chip using double-sided tape or special glue. Scotch tape can be bought at the stationery store, and glue - at the radio market (glue is better, and scotch tape is more affordable). Also equip the drive with a fan by attaching it to the back of the case, having previously drilled several holes there. Well, or at least do not place the drive above the hard drive, because. hard drives (especially high-speed ones) get very hot and overheat the drive.

Cache memory is not formally included in the chipset, but it is very closely connected with it. Often she gives oak and fails. If a defect affects one or more cells, then in the vast majority of cases this does not affect the operation of the drive (after all, it has corrective codes), but with large damage (and even more so with a complete failure), the drive either stops reading discs altogether, either reads them extremely slowly and with many errors. Since the drives use the same memory as DIMMs, it can be replaced (at least in theory, but in practice it all comes down to the art of high-quality soldering).

Figure 6 The largest chip is the chipset, the smaller chip is the memory.

Figure 7

Mechanical damage

CD/DVD drives are great dust collectors, especially if they have a fan underneath them to keep the hard drives cool. Dust passes through the slots of the housing and settles on the moving mechanical parts, increasing their wear, which smoothly flows into chronic jamming. The drive either refuses to close the tray at all, or immediately spits out the disc after closing, or cannot turn the disc (rotates the disc with a strange sound). The same applies to the positioning mechanism.

Disassemble the drive, remove all dirt, lubricate the rubbing elements (just not so that it drips from the tail and remembering that plastic gears do not require lubrication), if necessary, adjust the play so that everything rotates effortlessly, but does not hang out. Make sure that the gears / worms do not have excessive wear, chipped teeth and nothing else gets into them (this primarily applies to fragments of discs torn by the drive, as well as wires that get underfoot).

Figure 8 Assembled drive mechanism. This plastic will not last long and may fail at any time, then the broken parts will either have to be machined on their own or pulled out of other drives.

Figure 9 Dust buildup on moving mechanical parts can cause jamming.

Other electronics failures

First of all, check all mechanical contacts (connectors, trimmers, buttons and switches, tray closing sensors, etc.), as well as the integrity of the supply wires. When the power connector (interface cable) is carelessly pulled out, thin tracks can break, and this break is often not noticeable to either the eye or the ohmmeter, but at high frequencies (the normal operating condition of the drive) it makes itself felt.

Carefully inspect all rubbing cables - often they are rubbed to holes, causing either a short circuit to the case or a break in the conductor. Or both at the same time (especially New Vasyuki, fie New-TEAC "and drives sold under the TEAC trademark, but assembled by third-rate companies - at present TEAC has left the CD drive market, having sold its label noname- manufacturers).

Don't forget the fuses too. If the drive is connected incorrectly or power surges, they could well burn out, saving the drive from inevitable death. A modern fuse is such a small piece of crap, completely unlike the glass tube we are used to with a thin wire inside, and it is not so easy to notice it with a cursory examination of the board. By the way, there are usually many more than one fuse, so check everything you find.

Pay attention to the state of other elements. Swollen varnish, traces of burning, deformation or physical defects (such as chips or breaks) quite eloquently indicate the source of the malfunction. Unfortunately, the vast majority of electronics failures go without visual manifestations.

To check the health of the motors, connect them to a 5 volt source (the black wire is a minus), of course, after disconnecting them from the drive. Since engines tend to be more or less standard, finding a replacement for them will not be difficult. Well, in general, check everything that can be checked: the electrolytes have not dried / broken, the resistors have not broken, the diodes, stabilizers, key transistors are intact and everything, everything, everything ...

Small logic almost never fails, but for power elements this is in the order of things.

Figure 10.

Optics

If you do not abuse smoking and do not exhale a jet of smoke aimed at the drive, you do not need to clean the optics. One of my drives has already worked for 10 years and has never been cleaned.

Forget about cleaning kits - they can easily damage an optical lens (by the way, usually made of organic glass) without the slightest hope of restoring it. It is strongly not recommended to wipe optical surfaces. Try to blow off dust particles with a rubber enema (lieutenants, not a word about perversions!), after making sure that there is no talc inside it, and in no case do it with your mouth (droplets of saliva are deadly for optics). If the resinous substances of tobacco smoke have formed a characteristic oily film, do not try to scrub it off. It is better to apply a drop of a thick solution of laundry soap on the lens and, after letting the chemistry work for fifteen to twenty minutes, remove it with a napkin, gently bringing it to the drop, but without touching the surface of the lens. Then, with a few drops of distilled water, rinse the lens of soap.

Figure 11.

Summary table of the main symptoms

Conclusion

Every day the drives are getting cheaper and cheaper, making their repairs meaningless. Meanwhile, their quality is steadily declining. The crisis of overproduction forces manufacturers to save on everything they can, and above all on reliability and durability. It often turns out to be much cheaper to occasionally repair good old drives than to join the race for new models. However, everyone is free to choose the upgrade policy on their own ...

optical drive or a CD drive is an opto-mechanical device designed to read information from, presented in the form of CDs with sizes of 8 and 12 cm. Modern CD drives are universal, in addition to reading, they can also write various kinds of information to discs of various formats : Disposable and reusable CDs (CD-R and CD-RW), disposable and reusable DVDs (DVD-R and DVD-RW).

How an optical drive works

The main element of the drive is an optical system that forms a laser beam that reads information from a rotating medium. Information on a CD is recorded as a spiral track, on which microscopic depressions are burned by a laser beam. In the mass production of data discs, information is entered on them by stamping from a special matrix.

If you look at the surface of the disk through a microscope, you can see alternating bumps and pits, from which the laser beam is reflected with different intensity - more from the tubercle, less from the pit. And given that the computer processes information in binary terms (encoded as a sequence of zeros and ones), then in the alternation of pits and tubercles, data can be written in a certain way. Here the tubercle acts as a unit, and the depression represents a binary zero.

CD drive device

The most common CD drives today are devices for installation in the internal bay, the so-called optical drives in the 5.25-inch form factor. Here 5.25 inches is the size of a large compartment in the computer case for installing devices.

Inside the iron case there is an electronic board, motors for rotating the disk and the optical system, the optical system itself for reading and writing to a CD. On the back side of the drive there are connectors for connecting to the motherboard and power supply. The front panel includes a slide-out CD tray, a tray eject/close button, and a read/write indicator.

Your computer will most likely have at least one optical disc drive that accepts a DVD or CD disc.

Alternative to optical drives

Recently, the popularity of CDs for a computer has fallen sharply due to the massive distribution of other types of storage media, primarily flash memory or, in other words, “flash drives”. The popularity of flash drives is due to their low cost, sufficient memory and read / write speed. In addition, external hard drives connected to

Universal digital disc (digital versatile disc - DVD) - a type of drive, which, unlike the CD from the moment it entered the market, was designed for widespread use.

DVD formats

There are five physical formats (or books) of DVD that are not much different from the various "shades" of CD:

• DVD ROM - high-capacity, read-only storage medium;
• DVD video is a digital storage medium for motion pictures;
• DVD audio - audio storage only; a format similar to an audio CD;
• DVD R - write once, read multiple times; format related to CD-R;
• DVD RAM is a rewritable (erasable) version of DVD, which first appeared on the market and subsequently found DVD RW and DVD + RW formats as competitors.

Having the same size as a standard CD (diameter 120mm, thickness 1.2mm), DVD discs provide up to 17GB of storage with faster transfer rates than CD-ROM, CD-ROM-like access times, and come in four versions:

• DVD 5 - single-sided single-layer disc with a capacity of 4.7 GB;
• DVD 9 - 8.5 GB single-sided double-layer disc;
• DVD 10 - double-sided single-layer disc 9.4 GB;
• DVD 18 - capacity up to 17 GB on a double-sided double-layer disc.

In addition, there is a draft DVD 14 format - two layers on one side, one on the other, which, being easier to manufacture, will replace DVD 18 until the need for the latter is fully manifested.

It is important to recognize that in addition to the five physical formats, DVD also has many application formats such as DVD video and DVD audio.

DVD technology

At first glance, a DVD disc is no different from a CD: a plastic disc 120 millimeters in diameter and 1.2 millimeters thick, both using lasers to read the data written in the pits on the spiral track. However, DVD's sevenfold increase in data capacity over CD was largely achieved by tightening all the tolerances of the predecessor system.

First, the tracks are placed more tightly, the DVD track pitch (the distance between them) is reduced to 0.74 µm, more than 2 times compared to 1.6 µm for CD. The pits (pits) are also much smaller: the minimum length of the pit of a single DVD layer is 0.4 µm compared to 0.834 µm for CD. Overall, this gives DVD ROMs four times the capacity of CDs. Dense data packing is only part of the solution, DVD's main technological achievement is due to its laser. Smaller dimples mean that the laser has to illuminate a smaller area, and in DVD technology this is achieved by cutting the laser wavelength from 780nm (infrared light for a standard CD) to 635 or 650nm (red light).

Characteristics of the recording environment for CD (a) and DVD (b)

Secondly, the DVD specification allows reading information from more than one layer by changing the focus of the reading laser beam. It only takes a moment to move from track to track from different layers in order to refocus the lens from one level reflective layer to another. Instead of an opaque reflective layer, a transparent layer is used here with an opaque reflective layer behind it. Although the second layer may not be as dense as a single layer, it still allows 8.5 GB of data to be written to a single disk.

• a - one-sided single-layer (4.7 GB);
• b - one-sided two-layer.

Thirdly, DVD allows you to use double-sided discs. To make it easier to focus the laser beam onto the smaller, dimpled tracks, manufacturers used a thinner plastic substrate for the disc than for CD-ROM. This reduction has resulted in discs that are 0.6 millimeters thick - half the size of a CD-ROM. However, since these discs are too thin to remain flat when processed, the manufacturers glued two discs together, resulting in discs that are 1.2 millimeters thick. This effectively doubles the potential storage capacity of the disk.

• a - one-sided, single-layer (4.7 GB);
• b - one-sided, two-layer (8.5 GB);
• c - double-sided, single-layer (9.4 GB);
• d - double-sided, two-layer (17 GB).

Finally, the DVD uses a more efficient data structure. When CDs were developed in the late 1970s, they used relatively simple and crude error correction systems. More efficient error-correcting code for DVDs leaves more memory for real data.

Compatibility Issues

The DVD format has been plagued with compatibility issues from the beginning. Some of these are now allowed, but others, especially rewritable and video disc compatibility, remain and look set to grow into the Beta vs. VHS format war that has been going on for several years between VCR manufacturers.

Incompatibility with some CD-R and CD-RW drives has been a longstanding problem. The blanks used in some of these devices cannot properly reflect the laser beam used in DVD ROM readers, making them "unreadable". For CD-RW media, this problem has been easily solved by the MultiRead standard and by equipping the DVD ROM drive with two different wavelength lasers. However, getting DVD ROM drives to reliably read all CD-R media is a much bigger problem. The DVD reader's laser has difficulty reading CD-Rs due to reduced surface reflectance at 650nm, while at 780nm it is almost the same as for CD-ROM.

By the fall of 1998, DVD ROM drives were still unable to read rewritable DVDs. This incompatibility was finally eliminated in the so-called "third generation" drives, which began to appear in mid-1999. They use a modified LSI designed to recognize the different physical layout of DVD RAM data or handle additional headers in the DVD+RW data stream.

Speed ​​was another issue for early DVD ROM drives. By mid-1997, the best CD-ROMs were using Constant Angle Velosity (CAV) to achieve higher transfer rates and lower vibration. However, early DVD ROM devices used constant linear velocities (CLV). This was not a problem with DVDs, as their high density allows for slower spin speeds. However, since constant line speed was also used to read CD-ROMs, it turned out that the effective reading speed of CLV DVD ROMs could not be greater than 8x.

The table contains cumulative read/write compatibility information for various formats. "Yes" means that some of the devices of this type can handle the corresponding disk format, it does not guarantee that all such devices will be able to do so. "No" means that the corresponding type of drive can only rarely or never process the format.

Table of Compatibility Parameters of Various DVD Optical Media

Recordable DVD

DVD-R (or recordable DVD) is conceptually similar to CD-R in many ways - it is a write-once media that can contain any type of information normally stored on a mass-produced DVD - video, audio, pictures, data files, multimedia programs, and so on. Depending on the type of information being recorded, DVD-R discs can be used on virtually any compatible DVD playback device, including DVD ROM drives and DVD video players. The very first DVD R played a significant role in the development of the DVD ROM market, as software developers needed an easy and relatively cheap way to create test discs before going into mass production.

Originally introduced in the fall of 1997, DVD-R discs had a capacity of 3.95 GB, which then increased to 4.7 GB for a single-layer, single-sided DVD R disc. be written to DVD at 1x speed (11.08 Mbps, which is approximately equivalent to 9x CD-ROM speed). Once burned, DVD-R discs can be read at the same speeds as mass-produced discs, depending on the x-factor (multiple of the speed) of the DVD ROM drive being used.

The table illustrates the differences between some of the main parameters of both formats.

Table of formats CD-R, DVD-R

DVD-R, like CD-R, uses constant line rate (CLV) to maximize recording density on the disc surface. This requires a variable number of revolutions per minute (rpm) as the track diameter changes as one moves from one edge of the disc to the other. The recording starts on the inside and ends on the outside. At 1x, the rotation speed varies from 1623 to 632 rpm for a 3.95 GB disc and from 1475 to 575 rpm for a 4.7 GB one, depending on the position of the record-playback head on the surface. For a 3.95 GB disc, the track spacing (pitch), or the distance from the center of one turn of a spiral track to the adjacent part of the track, is 0.8 µm (micron), or half that of CD-R. On a 4.7 GB disk, an even smaller track feed is used - 0.74 microns.

DVD-R discs are recorded using a layer of substance that is converted (colored) by a highly focused red laser beam. The layer is applied to a transparent base, which is made of polycarbonate by injection molding, and has a microscopic spiral groove (track) formed on its surface. This recess is used by the DVD-R drive to guide the recording laser beam and also contains the recorded information after the process is completed. In addition, firstly, the spiral groove has a wavy profile (a pre-recorded sinusoidal signal), which is designed to synchronize the disc spindle motor during recording, and secondly, “surface marks” (“Land Pre- Pits", or LPP) used for positioning (addressing) purposes. Next, a thin layer of metal is sputtered onto the recording layer so that the reading laser beam can be reflected from the disc during playback. A protective layer is then applied to the metal surface, along which the two sides of the disc can be glued.

These operations are performed for each side of the disc that will be used for recording. If both sides are used for recording, the two sides to be recorded can be connected together as shown in the figure. In this case, each side must be read directly by turning the disc over. If a single-sided disc is being created, then the opposite side may contain a label or some other visible information.

Recording is carried out by instantaneous irradiation of the recording layer with a highly focused laser beam of high power (approximately 8-10 mW). When the ink layer is heated, it changes so that microscopic marks are formed in the spiral groove. These marks have a variable length depending on how long the writing laser has been on or off, which corresponds to the information stored on the disk. The recording layer is only sensitive to light of the appropriate wavelength, so that exposure to ambient light or the reproduction laser beam cannot degrade the recording.

Reproduction is carried out by focusing on the surface of the disk a laser beam of lower power and approximately the same wavelength (635 or 650 nm). The surface areas between the recorded marks are highly reflective and most of the rays of light are returned to the player's optical head, and vice versa, the marks themselves reflect little light. Thus, a modulated signal is formed, which is then decoded into the original user data by the playback device.

By the end of 1999, distribution of DVD R remained slow and drives were prohibitively expensive - about 10 times the cost of DVD ROM drives. Later, in mid-1999, DVD ROM drives capable of reading DVD RAM discs appeared. Such media qualities as high capacity and durability (a typical "lifespan" of more than 100 years) make these technologies a good choice for long-term archival storage of any information that can be presented in digital form. Because the physical dimensions of DVDs are identical to the CD family, they can be placed on existing mass-produced CD drives ("jukeboxes"). This allows for automated searches of data recorded on DVD-R volumes in networked environments, while increasing storage capacity by 6-7 times compared to CD-R technology.

The appearance in May 2000 of Version 2 of the DVD Forum Specification and the subsequent increase in capacity to 4.7 GB led to an increase in the role of DVD R as a tool for creating master discs (matrices) before mass release of software tools, multimedia production and as a medium for to make copies of films. At the same time, it became clear that a different type of DVD R media was needed for the consumer market, so the format was eventually split into "DVD R for Authoring" (authorized) and "DVD R for General" (regular).

The DVD R(A) format is still aimed at the professional user and other format differences are related to their relative market positioning. The use of the Cutting Master Format (CMF) in DVD R(A) is fundamental. This allows the 4.7 GB DVD R(A) media to be used as a direct replacement for DLT master tapes used in disc duplication.

A key characteristic of the DVD R(G) format (and quite possibly a major factor in the DVD Forum's decision to split the DVD R format), first, is that it uses content protection measures that make it physically impossible to make bit-by-bit copies of encrypted discs. by a special method. Secondly, DVD R(G) uses the descending address built into labels (LPP) system, built-in control area, and allows you to create double-sided discs.

Until mid-2001, DVD-Rs were primarily used in professional applications such as video duplication and image storage. However, the prospects for wider adoption of the DVD R (G) format have been greatly improved with the introduction of the Pioneer DVR-A03 recorder, which is designed to record DVD R (G), DVD RW, CD-R and CD-RW formats at a price of about $ 1,000

In the fall of 2003, around the same time that DVD+ proponent Philips released dual-layer DVD+R media, pioneer announced that a version of the dual-layer DVD R format had been developed and was intended to be offered to the DVD Forum as a new disc standard after further improvement.

Using the color-changing layer recording method, the new dual layer DVD R technology exhibits almost the same performance as dual layer DVD ROM discs, sensing 9.34 percent wobble on the first recording layer (L0) of a disc with a reflectance of 17.3% and wobble 8.08 percent on the second layer (L1) with a reflectance of 19.5%. This means that it will be possible to play dual-layer DVD-R discs on most existing DVD players, and that it will be easy to develop DVD burners using this technology.

RVD-RAM

The rewritable DVD ROM or DVD RAM uses a phase change technology, which is not a pure optical technology of CD and DVD, but mixed with some features of magneto-optical methods, and is derived from PD (Panasonic technology) optical disc systems. The applied format "surface-recess" (land groove) allows you to record signals both on the recesses formed on the disk, and in the gaps between the recesses. Recesses and sector headers are formed on the surface of the disc during its casting. The first generation of 2.6 GB reusable DVD RAM products on both sides of the disc appeared in mid-1998. However, these early devices are not compatible with higher capacity standards that use a contrast expansion layer and a thermal buffer layer to achieve higher recording densities. The specification for version 2.0 of DVD RAM with a capacity of 4.7 GB per side was released in October 1999. Hitachi achieved a capacity of 4.7 GB by reducing the laser mark size from 0.41-0.43 µm to 0.28-0.30 µm and the track feed from 0.74 to 0.59 µm.

The main difference between DVD RAM and ROM is compatibility. Single-sided DVD RAM discs are available with or without cartridges. There are two types of cartridges: type 1 - sealed, type 2 - allows you to remove the disc. The dimensions of the cartridge are 124.6 x 135.5 x 8.0 millimeters. Discs can only be written while in a cartridge. Double-sided DVD RAM discs come in sealed cartridges and cannot be read by older DVD ROM drives. The first DVD ROM drive capable of reading DVD RAM media, sometimes referred to informally as a "third generation drive", hit the market in 1999

DVD-RW

Formerly known as DVD R/W or DVD ER, DVD RW media comes from Pioneer's evolutionary development of existing CD-RW/DVD R technologies, which became available in late 1999. One of the goals was to produce a format that would be compatible with existing DVD environment. In particular, DVD-RW discs do not require protective cartridges, allowing them to be used with the disc-loading mechanisms found in all existing players and drives.

DVD RW discs use phase change technology to read, write and erase information. A 650 nm laser beam heats the sensitive alloy layer to either crystalline (reflective) or amorphous (dark, non-reflective) depending on the temperature level and subsequent cooling rate. The resulting difference between the recorded dark marks and the erased reflective marks is recognized by the player or drive and allows the stored information to be reproduced.

DVD-RW media uses the same physical addressing scheme as DVD-R media. During recording, the drive's laser follows a microscopic depression, writing data in a spiral track. The walls of the microscopic recess are modulated in a sinusoidal fashion, forming a signal that is read by the disk drive and compared with the signal generator to ensure accurate rotation of the disk. This modulated pattern is called a “modulated (oscillating) recess” (wobble groove), because the walls of the recess seem to oscillate from side to side. This signal is only used during recording and does not affect playback in any way. Among the DVD format family, only recordable media uses modulated tracks.

A preformatted addressing scheme is created on the disk using surface marks (LPP) to identify the physical address of the data blocks being written. This scheme uses a series of microscopic protrusions that stand out in the surface area between the depressions.

The first DVD RW home video recorder released in Japan in late 1999 used the new DVD VR (Video Recording) format. Consequently, the discs recorded on it could not be used in existing DVD players as they were compatible at the "physical level" but not at the "application level". The subsequent adoption of the DVD Video format resolved this particular problem, and Pioneer's DVR-A03, released in 2001, provided the most complete coverage of the DVD R, DVD RW, CD-R, and CD-RW recordable formats.

However, despite the success of the project, many obstacles remained to DVD RW being fully compatible with existing players. For example, some drives and players mistake a DVD-RW for a dual-layer disc due to the low reflectivity of the media and unsuccessfully try to locate a non-existent second layer. Therefore, some DVD ROM players are unable to play DVD RW discs.

One of the main advantages of the third rewritable DVD format, DVD+RW, is that it provides better compatibility than any of its competitors.

DVD+RW

The DVD RAM specification was a compromise between two different offerings from major competitors - the Hitachi grouping, Matsushita Electric and Toshiba on the one hand, and the Sony/Philips alliance on the other. However, there has been a constant tug-of-war since the beginning of DVD development, and in the summer of 1997, Sony and Philips, together with Hewlett Packard, abandoned the agreed-upon format in order to develop a phase-shifting method known as DVD+RW. The format is based on CD-RW technology, but is not compatible with the DVD RAM standard, which was only agreed upon three months earlier. Because they weren't going to leave the DVD Forum entirely, the DVD+RW camp submitted a modified form of the original specification to the European Computer Manufacturers Association (ECMA) for approval as a standard. The format, however, was not supported by the DVD Forum.

Since DVD RAM media usually used casings or cartridges (resembling a size 5 floppy disk), this was especially criticized by DVD+RW proponents, who argued that this approach forces future DVD ROM media to be placed in similar casings (cartridges). A single-sided DVD RAM disc can be removed from the casing to be used in any DVD ROM drive, but disc manufacturers believe that the DVD RAM disc will not be able to write reliably afterwards. Proponents of DVD+RW have further argued that placing DVD RAM in a cartridge requires a large drive mechanism, limiting the technology's use in laptops or small computer cases. Companies in solidarity with the DVD Forum (Matsushita, Hitachi, and Toshiba), on the other hand, have argued that DVD RAM cartridges improve reliability, especially for double-sided media, and that the cost and difficulty of making DVD ROM discs that are physically compatible with RAM-DVD are exaggerated. .

DVD+RW shares many similarities with competing DVD RW technology in that it uses phase change media and assumes the user experience of CD-RW discs. Users can either burn a blank disc or use a protective sleeve or cartridge. This is the main difference from DVD RAM devices, which require cartridge-based media. DVD+RW discs can be recorded in either constant linear velocity (CLV) for sequential video recording or constant angular velocity (CAV) for direct access. "Linking loss" is the result of pausing and then resuming a recording using constant bit rate (CBR), resulting in a disc that is incompatible with readers like DVD players or DVD ROM drives. "Lossless linking" is a technique developed specifically for DVD+RW that, when using Variable Bit Rate (VBR), allows video applications to pause and resume recording without lossy consequences. To do this, it is necessary to write an arbitrary block of data to a certain place on the disk with high accuracy (within 1 micron). For this purpose, the tracks on the disc are printed at a higher wobble frequency, which provides conditions under which the recording of information can be started and stopped at precisely defined positions. Together with the "no defect control" option, this feature allows DVD+RW discs to be written in a way that maximizes compatibility with existing DVD players and drives.

Initially, the phase-variable recording layer of a DVD+RW disc is in a polycrystalline state. During the recording process, a focused laser beam heats selected areas of the material above the melting point (500-700 °C), so that the substance quickly becomes liquid. Then, upon sufficiently rapid cooling, the liquid state stabilizes in the so-called "amorphous state". If the recording layer is heated below the melting temperature but above the crystallization temperature (200°C) for a sufficient time (longer than the minimum crystallization time), the atoms return to an ordered state, i.e. polycrystalline.

The amorphous and crystalline states have different refractive indices (indices) and therefore are optically different.

In DVD+RW, the amorphous state has a lower reflectivity than the crystalline state, and during the reading process, this results in a signal identical to that produced by dual-layer DVD ROM discs, allowing DVD+RW discs to be read on DVD ROM drives as well as DVD video players.

The carrier consists of an etched floor and a carbonate base, on which four layers are usually deposited. The base is molded with a spiral recess (track) for controlling the servomotor, address information and other data. The phase-changing layer is placed between dielectric layers, which remove excess heat from the recording layer. An alloy of silver, indium, serbium, tellurium (Ag-In-Sb-Te) is usually used as a phase-changing layer. The chemical composition of the phase-changing layer determines the minimum crystallization time. The structure of the disk (the thickness of the layers, their heat capacity and thermal conductivity) determines the rate of temperature decrease during the recording. Precise specification of the composition of the recording layer is important to obtain the required recording qualities. In general, low write beam power can be used if thin layers are present.

Perhaps the main advantage of DVD+RW over DVD W lies in the area of ​​compatibility. Its proponents claim that it is the only rewritable DVD technology that offers seamless media exchange between consumer electronics and computers, and that the format is compatible with most of the more than 35 million DVD video players and DVD ROM drives installed by the end of 1999. A recording made by a DVD VCR to a DVD+RW disc (4 hours of recording-playback per side of the disc) can be played on a DVD video player in the same way as on a personal computer with a DVD ROM drive and an MPEG-2 video decoder. In addition, DVD+RW allows you to combine digital video and digital data in a single file system, as required for recording multimedia applications.

All drives on the market in early 2002 used both constant linear speed (CLV) to achieve a maximum write speed of 2.4x for DVD+RW media (corresponding to 3.32 MB/s) and constant angular speed to allow CD-ROM reading. at a speed of 32x. Using these "x-factors", which are not very convenient in this "multi-format era", especially since there is a 9:1 ratio of actual transfer rates between DVD and CD, we can say that the characteristics of the devices were: read speed - 8x (DVD ROM , DVD+RW), recording - 12x (CD) and dubbing - 10x (CD).

Which of the competing formats dominates remains unclear in the long run. The addition of DVD R capabilities allows DVD RAM devices to write mutually compatible discs. However, the use of cartridge-based rewritable media makes this format more useful for storing archival data than as an everyday device.

By early 2002, the DVD RW format seemed to have the upper hand. However, despite its proponents' claims of excellent format compatibility, the fact that DVD+RW discs are less reflective than DVD R and therefore less compatible with some DVD players and DVD ROM drives is a potential barrier. The uncertainty of which of the competing formats would have won the final victory is reflected - Sony releases a drive that supports both formats - DVD RW and DVD + RW.

DVD+R

Early DVD+RW drives did not have the ability to write to DVD write-once media. However, in early 2002, Mitsubisi Kagaku Media (better known by the brand name Verbatim) became the first manufacturer of media designed for DVD + RW technologies in both formats: rewritable (Rewritable) and write-once (Write-once). Like previously released DVD+RW media, the new DVD+Recordable discs have been certified for 2.4x write speed (equivalent to 3.32 MB/s or CD-R performance at 22x speed).

In the spring of 2002, the second generation of DVD+RW drives began to appear, capable of handling both types of media. Philips was the first to demonstrate the ability to convert drives to new formats by patching firmware.

In October 2003, Philips and Verbatim showed at Ceatec (Japan, 2003) a new dual-layer DVD burning technology that effectively doubles the capacity of recordable DVD+R discs from 4.7 to 8.5 GB while maintaining compatibility with existing DVD players and DVD ROM drives.

The dual layer DVD+R system uses two thin organic films of the material to be dyed separated by a spacer (filler). Heating with a concentrated laser beam irreversibly changes the physical and chemical structure of each layer so that the changed areas acquire optical properties that are different from the unaltered medium. This causes the reflectivity to fluctuate as the disc rotates, resulting in a read signal similar to that found in stamped DVD ROM discs.

Started in 2001, the main objective of this technology's development is to ensure compatibility with the DVD ROM standard to ensure that the new dual layer discs will be readable on commercially available DVD players. This was achieved by using a silver-containing alloy as the reflective material for the top layer of the thin film, which provides a reflectivity of at least 18 percent (which is in line with the dual layer DVD ROM standards). In addition, the degree of transparency of the upper layer of the record is above 50 percent, which allows reading and writing at the lower layer. This level has a higher light sensitivity, since the top level absorbs and reflects some of the incident light, and a much higher reflectance (over 50 percent), which, after passing through all layers, provides an effective reflectivity (on the surface of the disk), at least , at 18 percent. These high values ​​of transparency and reflectivity are achieved by optimizing the thickness and placement of the layers, the size of the tracks, and so on. Other parameters - amplitude and signal flow - have also been optimized to ensure compatibility with current DVD standards.

CD-ROM drive device.

CD-ROM drive is a complex electronic-optical-mechanical device for reading information from laser discs. A typical drive consists of an electronics board (sometimes two or even three boards - a spindle control circuit and an opto-receiver amplifier separately), a spindle assembly, an optical read head with a drive for its movement, and disk loading mechanics.

On the electronics board are placed:

• circuit for amplifying and correcting the signal from the optical head;
• signal PLL circuit and ACS spindle;
• Reed-Solomon code processing processor;
• ACS circuits for beam focusing and dynamic track tracking;
• optical head movement control circuit;
• control processor (logic);
• buffer memory;
• interface with controller (IDE/SCSI/other);
• connectors for interface and audio signal output;
• block of mode switches (jumpers/jumpers).

A typical drive consists of an electronics board, a spindle motor, an optical readhead system, and a disc loading system. The electronics board contains all the control circuits of the drive, the interface with the computer controller, the interface connectors and the sound signal output. Most drives use a single electronics board, however, in some models, separate circuits are placed on auxiliary small boards.

Systems for writing, reading and post-processing information determine the overall functional diagram of the CD-ROM, presented in the functional diagram. In addition to the systems discussed above, it includes a clock generator that provides clock signals to all nodes of the CD-ROM, and an EFM demodulator that converts 14-bit code packets from the disk into an 8-bit serial code. Further, the information enters the digital data processor, which, together with the system control processor, is the heart of the entire device. This is where data deinterleaving and error correction takes place. The task of data interleaving when recording information is to "stretch" each byte of information into several recording frames. In this case, if even a few frames of information are lost as a result of mechanical damage to the disk surface, the result of data deinterleaving will be the presence of small errors in individual bytes. Such errors are corrected by an error correction circuit.