DVD is the latest generation optical media format. DVDs are significantly larger and faster than regular CDs. They may contain cinema-quality video footage, music files, digital photographs and computer data. The purpose of DVD is to combine multimedia, computer and business information into one universal format. DVD has already practically replaced laser discs, video cassettes and game cartridges and, perhaps, in the near future will also replace CDs. The DVD format has wide support among major electronics and computer manufacturers, as well as among sound recording and film studios. For this reason, DVD has gained such enormous popularity among consumers and has become the most common format in just three years. By 2003, within six years of its existence, there were already more than 250 million DVD devices in the world - DVD players, recorders, computer DVD drives and game consoles - making DVD the leading standard in the video industry.

It's important to recognize the difference between physical formats (such as DVD-ROM and DVD-R) and application formats (such as DVD-Video and DVD-Audio). DVD-ROM – the disk itself on which information is stored; DVD-Video (or simply DVD) determines how information is stored on a disc and how it is played on a DVD player. Exactly the same difference between CD-ROM and Audio CD.

DVD-ROM, in addition to standard ones, also includes recordable formats: DVD-R/RW, DVD-RAM and DVD+R/RW. Application formats: DVD-Video, DVD-Video Recording (DVD-VR), DVD+RW Video Recording (DVD+VR), DVD-Audio Recording (DVD-AR), DVD Stream Recording (DVD-SR), DVD-Audio (DVD-A) and Super Audio CD (SACD). There are also several special application formats for game consoles (such as Sony PlayStation 2 and Microsoft Xbox).

What does the abbreviation DVD stand for?

There is no generally accepted definition of the abbreviation “DVD”. The name originally came from the first letters of the phrase “digital video disc”. Some DVD Forum members believe that this interpretation arose from a corruption of the phrase "digital versatile disc" (digital versatile disc), but this point of view was never officially accepted. In 1999, the DVD Forum ruled that DVD, as an international standard, is just three letters with no meaning.

DVD-Video capabilities

• More than 2 hours of high-quality digital video (double-sided, dual-layer discs can hold approximately 30 hours of VHS-quality video, or approximately 8 hours at best quality)
• Supports both widescreen (16:9) and standard (4:3) aspect ratios
• Up to 8 digital audio streams (for different languages, commentary, etc.), each with support for 8-channel audio
• Up to 32 files with subtitles/karaoke texts
• Up to 9 camera angles (different camera positions can be selected directly during viewing)
• On-screen display and convenient interactive options (for games, quiz shows, etc.)
• Supports multilingual text in file titles, album titles, song titles, artist list, etc.
• Instant rewind/forward
• Quickly search for a file, section, music track and address code
• Durability (does not depend on playback intensity, only on physical damage)
• Immunity to magnetic fields; resistance to temperature fluctuations
• Small size (DVDs are easy to transport and store; some manufacturers produce portable DVD players)

Note: Most drives do not have all the features (multilingual file names, child lock, etc.), as each of them must be specially preinstalled. Some discs may not support "search" and "skip".

Most players support a standard set of functions:

• Language selection (for automatic selection of video clips, audio stream, subtitles and menus)*
• Special playback effects: freeze frame, skip, slow down, speed up and search
• Child lock (prohibits playback of discs containing explicit scenes).*
• Possibility of programming (playing selected fragments in the required order)
• Play a random file and play it again
• Digital audio (PCM stereo and Dolby Digital)
• Supports DTS Digital Surround audio files
• Playing music CDs

Some players support additional options:

• Component video output (YUV or RGB) for higher picture quality
• Component video output supporting progressive scan (YUV or RGB) for best analogue image quality
• Digital video output (SDI, 1394 or DVI/HDMI) for digital image playback
• Six-channel analog output from built-in decoder (Dolby Digital, DTS or MLP)
• Playing Video or Super Video CDs
• Playing MP3 CDs
• Playing MP3 DVDs
• Plays DivX and MPEG-4 video files
• Playing CDs containing drawings and digital photographs
• Laserdisc and CDV playback
• Rewind (reverse) frame-by-frame rewind
• Reverse (reverse) playback (at normal speed)
• Radio (RF) output (for TVs without video input)
• Multilingual OSD Menu
• Multi-disc DVD changer
• Digital zoom (2x or 4x zoom in image fragment); This is a function of the player, not the DVD.

DVD-Video quality

DVD can reproduce studio-quality video and audio material that is incomparably better than video cassettes and laser discs. However, in reality, everything depends on many production factors. With the advancement of technology, DVD quality has improved significantly; but due to the widespread use of the format and the decline in prices for such discs, more and more “counterfeits” are appearing. Sometimes, when recording low-budget DVDs, MPEG-1 (comparable in quality to VHS) is used instead of the generally accepted MPEG-2 encoding.

DVD video is usually encoded from professional digital recordings into the MPEG-2 format. This uses a compression algorithm that “cuts off” unnecessary information (for example, static image fragments) or frames that are not perceived by the human eye. As a result, when playing back a fragment with many moving objects, image errors sometimes appear, the number of which depends on the quality of processing and the level of compression. At average bitrates of 3.5 to 6 Mbps (millions of bits per second), compression artifacts become noticeable. The higher it is, the better the quality. At a bitrate of more than 6 Mbit/s, the encoded signal is practically no different from the original. As MPEG compression technology improves, it becomes possible to achieve better quality at lower bitrates.

DVD images sometimes contain visible artifacts such as color segmentation, blur, blocking, noise, elements falling out, and even foreground sliding relative to the background. Note that the concept of “artifact” includes any element that should not be in the image. Of course, errors are sometimes caused by poor-quality MPEG encoding, but most often the cause is inaccurate TV settings, bad cables, electrical interference, poor noise reduction, inaccurate analog-to-digital transfer, source film grain, disc reading errors and much more. In most cases, artifacts can be avoided by properly configuring your system.

Many TVs have their SHARPNESS setting too high, which reduces the clarity and brightness of DVD content. This unnecessarily enhances high-frequency video and causes distortion. To improve image quality, the SHARPNESS level should be set to almost a minimum, while BRIGHTNESS should also not be too high. Some DVD players have the default black level set to 0 IRE (Japanese standard) rather than 7.5 IRE (US standard), which may cause streaking to appear during dark scenes if not properly adjusted. don't tune the TV. The player may have a black level adjustment menu.

The DVD video format has improved color accuracy. Therefore, if the image becomes dim and faded when playing DVDs, then the problem most likely lies in the TV settings, and not in the player.

Disadvantages of DVD

• Uncertainty in technical specifications and insufficient testing of players and discs often lead to incompatibility - some DVDs are not supported by some players.
• DVD recorders are more expensive than VCRs
• DVD has built-in protection against unauthorized copying and region blocking
• When recording DVDs, digital compression technology is used. Poor-quality data compression leads to the appearance of image artifacts: blocky structure, noise, increased sharpness, etc.
• DVD does not always support HDTV standard
• Some DVD players do not support CD-R
• Some DVD players do not support DVD-R/RW
• Most DVD players do not support DVD-RAM discs
• Only a few players support reverse playback at normal speed
• Formats such as DVD-Audio, DVD-VR and DTS are not supported by all players

Music on DVD: DVD-Audio and SACD

Note: Do not confuse DVD-Audio and DVD-Music formats

When the first DVDs appeared in 1996, the DVD-Audio format did not yet exist, although the audio capabilities were already significantly superior to their CD counterparts. To ultimately define the DVD format, Forum sought support from the music industry. The first draft of the format was created by specialists from the DVD Forum's Working Group 4 (WG4) in January 1998, and version 0.9 was released in July. The final specification (version 1.0, without copy protection) was approved in February 1999, but the release The product was postponed to a later date due to the need to develop detailed protection against unauthorized copying (such as encryption and watermarks). In 2010, Pioneer released the first DVD-Audio player in Japan (without copy protection support).

In July 2000, Matsushita released the first universal DVD-Audio/DVD-Video players under the Panasonic and Technics brands, priced from $700 to $1,200. Pioneer, JVC, Yamaha and other manufacturers created their DVD-Audio players in late 2000 - early 2001. Thus, by the end of 2000, about 50 models were presented on the market, and a year later - more than 200.

DVD-Audio quality is excellent. Digital audio supports pulse code modulation, with wider frequency sampling and amplitude than CDs. Audio tracks for many films are stored as separate, multi-channel audio, using Dolby Digital or DTS compression (much the same as digital audio in movie theaters). As with video, audio quality is directly related to how accurate the encoding was. But even despite compression, the quality of Digital and DTS formats is much better than the quality of CD formats.

DVD-Audio is a format independent from DVD-Video. DVD-Audio discs are usually not supported by conventional DVD-Video players, since their specification includes new standards and options, and the information is stored in a separate area of ​​the disk - in the AUDIO_TS directory - which DVD-Video players do not play. To play a disc in this format, you need a DVD-Audio or a "universal" player (also known as a VCAP) that plays both DVD-Video and DVD-Audio discs.

DVD-Audio and "universal" players work with almost all existing receivers. They reproduce sound in PCM and Dolby Digital formats, and some also in DTS and DSD formats. However, most modern receivers are not capable of decoding high-resolution multi-channel PCM signals; but even if such a standard is supported, a special digital connection is required. DVD-Audio players with high-quality digital-to-analog converters (DACs) can only be connected to receivers with 2- or 6-channel audio inputs, but if the receiver converts the signal back from analog to digital, there will be some loss in quality. To avoid such losses, you should use new receivers equipped with an IEEE 1394 (FireWire) digital interface.

DVD-Audio discs are protected against unauthorized copying: digital watermarks. For protection, a special signal processing technology is used, which, through a digital signature and additional encryption, creates inaudible noise during playback. Thus, the player recognizes the illegal copy and does not play it.

In August 1999, Aris and Solana formed the Verance alliance. Together they developed Galaxy copy protection technology, which was later used when recording DVD-Audio discs. In November 1999, Galaxy protection was also adopted for the SDMI standard. Based on tests, specialists from the production union Verance and 4C stated that the noise from the protection is not perceived by the human ear, however, some users claim the opposite.

Sony and Philips jointly developed a competing Super Audio CD (SACD) format that uses DVDs. Sony released a trial SACD version (0.9) in April 1998, and the final version (1.0) appeared in April 1999. At the moment, a significant part of music is recorded on SACD not in multichannel, but in stereo format. SACDs were originally intended to be "licensed" dual-layer discs; one layer was intended for playback in conventional CD players, and the second, with a high data density, was intended for DVD-Audio players. Due to technical difficulties, the release of the dual-format disc was postponed until the end of 2000. Pioner's first DVD-Audio player, which appeared in Japan at the end of 1999, supported the SACD format. If other manufacturers follow Pioneer's example, then the struggle between SACD and DVD-Audio formats may well come to naught, since all DVD-Audio players will support both types of discs.

In May 1999, Sony released its first SACD player in Japan at the exorbitant price of $5,000. The player appeared in the USA at the end of 1999 in limited quantities. In mid-2000, Philips released a player for $7,500, and Sony - only $750. Thus, by the end of 2000, more than 40 models of SACD players were presented on the market, and by the end of 2001 - more than 500.

The biggest drawback of DVD-Audio and SACD players is that most receivers with a six-channel analog input do not control the bass. Receivers with Dolby Digital and DTS decoders handle the low frequencies, but incoming six-channel analog signals are usually routed directly to the amplifier. Therefore, without bass management, any audio system (that does not contain 5 full-range speakers for each channel) will not be able to reproduce bass frequencies properly.

If you want to get the best quality from your DVD-Audio or SACD player, you need a receiver with a six-channel analog audio input. If your receiver cannot handle the low frequencies of an analog signal and you do not have a special external set-top box (such as from Outlaw Audio), you will also need 5 full-range speakers (each capable of reproducing low frequencies) and a subwoofer. Difference between DVD-Audio and DVD-Music.

DVD-Music is not an official DVD format; This is often the name given to DVD-Video discs that mainly contain music files. DVD-Music disc can be played by any standard DVD player. At the same time, the video sequence accompanying the music is displayed on the TV screen. DVD-Audio discs, on the other hand, contain exclusively high-fidelity audio tracks that can only be played by DVD-Audio players.

Ability to record from TV, VCR, etc.

Recording is only possible if you have a DVD recorder. When the DVD format was introduced in 1997, only players were on the market. Even now, as DVD recorders become more and more popular, most DVD devices still only “play” discs. DVD recorders first appeared in Japan at the end of 1999, and in Europe in 2000. The first devices were quite expensive: from $2,500 to $4,000. Of course, even today DVD recorders are not very cheap (on average from $500 to $2000), but, most likely, they will eventually be equal in price to VCRs.

A DVD recorder works in much the same way as a VCR - it has a built-in tuner and audio/video inputs, and can also be programmed to record a particular program. The main difference is that to play the desired fragment, you do not need to fast forward/rewind - you can instantly access any recording from the on-screen menu. Most DVD recorders have an electronic program menu (EPG) that contains a list of video recordings available for playback (no need to enter date, time, channel, etc.). Note that DVD recorders cannot copy write-protected discs. Also, unfortunately, there are several recordable DVD formats, and they are not always compatible.

One type of recorder is computer DVD drives. These recorders can record data, but to create a full-fledged DVD-Video, additional software is required - for video encoding (MPEG) and audio (Dolby Digital, MPEG or PCM), creating a navigation system and data control, etc.

Consequences of scratches on a disk

Scratches may cause minor data errors that can be easily corrected. With the help of error correction technology used in DVDs, information can be recovered even from deep scratches without any loss. The most common misconception is that many users believe that, due to their higher storage density, scratches cause more damage to DVDs than to CDs. DVD recording density is four times higher than CD, and scratches actually cause more damage to DVDs. But the error correction technology of DVD technology is tens of times more powerful than that of CD; therefore, the resulting damage is significantly less. It is also important to understand that MPEG-2 and Dolby Digital compression is based in part on removing or correcting subtle image details. Therefore, during decompression, the amount of information obtained is less than theoretical. Severe damage to the surface of a DVD disc can cause input/output errors on the computer or brief jumps in the image. The paradoxical fact is that even the smallest damage can cause serious errors (depending on the direction and refraction of the scratches). There are currently many projects to eliminate such errors, which may find their application in future models.

Advantages of DVD over VHS

The main advantages of DVD are the following: high video quality, surround sound support and other features mentioned above. Moreover, DVD quality does not degrade over time or with repeated use, as does video tape. This makes the DVD format better suited for film collecting. Plus, the better your TV, the greater the difference in picture quality between VHS and DVD.

Dual Layer Disc Compatibility

Dual-layer discs contain two layers of information. Because the outer layer is made of translucent material, the laser beam can pass through it and read information from the inner layer. Since both layers are on the same side, a dual-layer disc can hold twice as much information as a single-layer disc (typically up to 4 hours of video). Most discs are produced using two-layer technology. Initially, only a few factories produced such discs; but now this technology is supported by almost all manufacturers. The inner layer can use either the PTP standard, in which the tracks are arranged in parallel (for recording independent information or special effects), or OTP, in which the tracks are arranged in a reverse spiral. The laser beam, reading information from the outer layer, first moves from the center of the disk to its edge, and then, when processing the inner layer, changes direction. The OTP standard is designed for recording long-term video material on both layers. Their change can occur on any video fragment, regardless of the location of the chapters. There is no guarantee that the transition will go unnoticed. On most players, changing the layer really goes unnoticed, but on some it can cause playback to stop (up to 4 seconds). It all depends on how carefully the disc is prepared and how well the player is made. The OTP standard is also known as RSDL (Reverse Spiral Dual Layer). The main advantage of dual-layering is that a long film can be recorded with better quality.

Here are a few features that can help you distinguish a double-layer disc from a single-layer disc:

1) gold color,
2) menu for selecting widescreen or full-screen format,
3) two serial numbers on one side.

The technical specification for producing DVD players includes support for dual-layer discs. Therefore, only some players have problems playing double-layer discs. The reason for this is a manufacturing defect, and the player must be repaired free of charge by the manufacturer under warranty. Some discs are created using “invisible layer change” technology, which is acceptable from the point of view of modern specifications. True, such discs do not always work correctly with older models of players.

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

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

Problem with definitions

The term DVD, surprisingly, does not have an unambiguous definition. This technology was developed to replace conventional compact discs (CDs), which were increasingly becoming insufficient in capacity. Originally, the abbreviation DVD stood for Digital Video Disc. However, it later became clear that it was possible to record not only movies, but also other files.

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

Increasing available volume

It was previously indicated that DVDs have replaced CDs, the capacity of which has become insufficient. In order to read the digital data recorded on the surface, it is necessary to use a thin laser beam. For this purpose, disk drive devices implement a special unit consisting of a emitting element and a focusing system. The main difference between the beam of light used to read and write information is that it is coherent, that is, it is very narrowly focused. This makes it possible to practically eliminate the effects of diffraction and interference of light waves. When the CD standard was developed, the miniature semiconductor emitters available at that time were unable to create a sufficiently narrow beam, so the width of the track on the metal base of the disc was about 1.6 microns. Subsequently, more advanced light-emitting diodes were developed, the beam of which was so thin that the width of the track could be halved. Thus, it became several times higher than the same parameter CD. In addition to the width of the track, it was possible to change the distance between them, as well as the size of the pits.

"Pie" from disks

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

Such multilayer compacts can be compared to a sandwich. During production, not one, but two tracks are used at once, but located in such a way that the reading laser beam passes freely through the translucent upper surface. Their volume reached 8.54 GB. The maximum capacity of a DVD disc whose diameter is not 12, but 8 cm is 5.32 GB. Structurally, the drive can have two emitters, each of which focuses on its own depth (surface). There are models with a single beam, the focusing of which is controlled electronically. The information capacity of DVDs could be even greater when so-called double-sided solutions were used. Outwardly, it is an ordinary compact, but writing/reading is possible on both sides, which in most drives required turning the media over. The capacity of a DVD disc of this modification ranges from 9.4 GB (double-sided single-layer) to 17.08 GB (four layers, recording on both sides). However, such “pies” were not widely used due to the higher cost of production and the need to handle them too carefully, since the slightest scratch could lead to the inability to read data from deep layers.

Saving information

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

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

Video compacts

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

Accordingly, the maximum DVD capacity in this category is 17.08 GB (DVD-18, two sides, four layers). Since mass-produced video players use the simplest focusing units, which reduces the cost of production, not all models are capable of reading large-capacity discs. The exception is single-layer double-sided ones, to work with which you just need to turn the disk over in the drive. Their disadvantage is that there is no space for a label, so the name is indicated on the transparent part, next to the central hole.

Write once

The advent of disk drives capable of recording digital data on discs at home has made a real revolution in the field of backup and the creation of real film libraries. DVD+-Rs are initially sold without recording. The owner of a special drive can save any information converted into digital form on such a disk.

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

Multiple write

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

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

Recording feature

Standard DVD capacity may be slightly exceeded. This is achieved through the use of the lead-out zone. The Overburn function must be supported by the device itself. It can be activated in the popular Nero program by going to “Options - Expert Properties”. We do not recommend using this feature without it, as you may be unable to read such a disc on a drive that cannot work with Overburn.

How is volume calculated?

Many computer owners have long noticed that it is impossible to burn onto a CD what is specified by the manufacturer. In fact, there is no deception here. It’s just that disk manufacturers, for marketing reasons, believe that there are 1000 bytes in 1 KB, although in reality there are 1024 (raising two to the tenth power). With increasing volume, this number grows progressively. Consequently, no more than an “honest” 4.38 GB fits on a standard DVD.

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

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

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

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

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

The design of various types of DVD discs is shown in Fig. 7.

Please note that although in Fig. Figure 7 shows two lasers reading data from the bottom of dual-layer disks; in fact, only one is used. To read data located on different layers, only the laser focus changes.

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

Res. 7. Types and design of DVD discs

Writing (and reading) to spiral tracks of DVDs recorded in PTP mode works differently. When moving from layer 0 to layer 1, the laser sensor must move from the outside of the disk (ie, the end of the first layer) to the inside (the beginning of the second layer). In addition, the laser focus must be changed. To speed up the transition, almost all DVDs are written in OTP mode.

The direction of the spiral tracks of different layers recorded in the PTP mode also differs. This simplifies the process of reading tracks located one above the other. The spiral track of layer 0 is directed clockwise, and the track of layer 1, in turn, is counterclockwise. Therefore, to read the second layer, you need to change the direction of rotation of the disk, but in OTP disks, the reading of the spiral occurs from the outside to the inside. Thus, the spiral track of layer 0 is directed from the inside to the outside, and the track of layer 1 is directed from the outside to the inside.

The differences between DVDs recorded in PTP and OTP modes are shown in Fig. 8.

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

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

Double-sided discs are more complex and costly, and require that the disc be removed from the drive and turned over to play both sides. All this has led to the fact that DVD-5 (single-sided, single-layer) or DVD-9 (single-sided, double-layer) discs are most widely used. The capacity of this type of disc reaches 8.5 GB, which is 242 minutes of playback of MPEG-2 video data. With 133 minutes of playback, DVD-5 video discs are suitable for more than 95% of currently available movies.

Res. 8. DVD discs recorded in PTP and OTP modes

Optical discs are a popular storage medium. Most users are only familiar with CDs and DVDs; in fact, there are many more types of discs. The Land of Soviets will tell you what there are types of disks, and will help you understand their diversity.

Types of CDs

CDs or compact discs, were originally intended for recording and playing music, but are now used to store almost any computer information. Writing and reading disk information is carried out using a laser. CD thickness - 1.2 mm, diameter - 120 mm, capacity - 650 or 700 MB (corresponding to 74 or 80 minutes of sound). Exist mini CD with a diameter of 80 mm, but their capacity is smaller - 190-200 MB (21 minutes of sound). Mini CD can be read on any media except car radio. There are curly cds of various shapes, they are produced mainly for commercial purposes. Such disks are not recommended for use in computer drives, because they can burst at high rotation speeds.

CD discs can be divided into CD-ROM, CD-R and CD-RW. This division is determined by the ability to write information to the disk and the purpose of the disk. Information on disk CD-ROM recorded by the manufacturer, it cannot be changed or deleted, you can only read the data. To disks CD-R(they are sometimes also called “blanks”) you can record your information, but it will be impossible to erase or change it. If there is free space left on the disk, and you enabled the option to add information when recording, you can add files to the disk. Discs CD-RW support deleting and rewriting information, but such discs will not be readable by all drives.

Types of DVDs

DVDs allow you to store more information than CDs due to the use of a laser with a shorter wavelength. The capacity of a standard size DVD (120 mm) can range from 4.7 GB to 17 GB, and the capacity of a mini DVD (80 mm) is 1.6 GB.

Depending on the capacity of DVD, the following types of discs are distinguished:

• DVD-5— single-layer, single-sided disk, capacity — 4.7 GB
• DVD-9— double-layer single-sided disk, capacity — 8.5 GB
• DVD-10— single-layer double-sided disk, capacity — 9.4 GB
• DVD-14- double-sided disc, double-layer on one side and single-layer on the other, capacity - 13.24 GB
• DVD-18- double-layer, double-sided disc, capacity - 17.1 GB

Dual-layer discs contain two layers of information on one side and are marked with the abbreviation DL. A double-sided disk is actually two disks glued together with non-working surfaces. Naturally, the thickness of such a disc is controlled to match the thickness of a conventional single-layer DVD.

Based on the possibility of recording, rewriting and deleting information, DVD discs, like CDs, are divided into ROM, R and RW. But additionally, the following types of disks are distinguished:

• DVD-R for general, DVD-R(G)- a recordable disc intended for home use.
• DVD-R for authoring, DVD-R(A)— a one-time recordable disc for professional purposes.
• DVD-RW- rewritable disc. You can overwrite or erase information up to 1000 times. But you cannot erase part of the information, you can only erase the disk completely and completely rewrite it.
• DVD-RAM use phase change technology. They can be rewritten up to 100,000 times and have a theoretical service life of up to 30 years. But they are expensive, are produced mainly in special cartridges and are not supported by most drives and players.
• DVD+RW are based on CD-RW technology and support rewriting information up to 1000 times. This format appeared later than DVD-RW.
• DVD+R- A recordable disc similar to DVD-R.

It is clear that no single drive or player fully supports all DVD formats. Most modern drives support both the DVD-R(W) and DVD+R(W) formats. But older drives and home players released before the advent of the DVD+R(W) format will only read DVD-R(W) discs. There are "super multi" drives that support all types of discs, including DVD-RAM.

Other types of disks

Standing apart are the so-called Dual Discs. These discs combine CD and DVD formats. On one surface of such a disk music is recorded in CD format, and on the other - five-channel sound, video, menus, subtitles, images, etc. in DVD format.

HD DVDs (High Density DVDs) can have a capacity of up to 15 GB, and double-layer ones - up to 30 GB. Their main competitor is BD, Blu-ray Disc holds from 23 to 66 GB depending on the number of layers. A prototype of a four-layer disk with a capacity of 100 GB has been announced, and it is also planned to release ten-layer disks with a capacity of up to 320 GB.

The confrontation between BD and HD DVD is called the “fight of formats.” But leading film studios abandoned the use of HD DVD in favor of BD discs, so the release and support of the HD DVD format was officially discontinued.

So, there are many types of optical discs. You should choose a disk for recording information based on its capacity, the ability to rewrite information and the model of your drive or home player. Knowing the main types of disks, you will never get confused in their rich assortment.

DVD (di-vide-di) is a disc-shaped storage medium that is similar in appearance to a compact disc, but has the ability to store a larger amount of information due to the use of a laser with a shorter wavelength than for conventional compact discs.
The first discs and DVD players appeared in November 1996 in Japan and March 1997 in the USA.
Initially, “DVD” stood for “Digital Video Disc”. Later, many began to decrypt DVDs as Digital Versatile Disc (digital multifunction disc). Toshiba, which runs the official DVD Forum website, uses "Digital Versatile Disc". But a consensus has not yet been reached, so today “DVD” is not officially decrypted at all.

Basic characteristics of DVD. Advantages of DVD

DVD can exist in several modifications. The simplest of them differs from a conventional disk only in that the reflective layer is not located on an almost full-thickness (1.2 mm) layer of polycarbonate, but on a layer of half thickness (0.6 mm). The second half is the flat top layer. The capacity of such a disc reaches 4.7 GB and provides more than two hours of television-quality video. If both layers carry information, then the total capacity is 8.5 GB. And if you use a double-sided, two-layer disc. In this case, its capacity will be 17 GB! This characteristic alone is enough to imagine the impact that such a disc could have on the film/video industry. It is not for nothing that a significant part of the disputes and delays in the production of DVD devices is caused by the coordination of divergent methods of copyright protection.
The DVD read/write speed is indicated as a multiple of 1350 Kb/s, that is, a 16-speed drive provides reading (or writing) of discs at 16 × 1350 = 21600 Kb/s (21.09 MB/s).
To play DVDs with video, you need a DVD drive and an MPEG-2 decoder (that is, either a household DVD player or a computer DVD drive and software player). DVD movies are compressed using the MPEG-2 algorithm for video and various (often multi-channel) formats for audio. Compressed video bitrate varies from 2000 to 9800 Kbps, often dynamic. (VBR Variable bitrate)
The audio data in a DVD movie can be in PCM, DTS, MPEG, or Dolby Digital (AC-3) format. In countries that use the NTSC standard, all DVD movies must contain a PCM or AC-3 soundtrack, and all NTSC players must support these formats. Thus, any standard disc can be played on any standard hardware.
In countries using the PAL standard (most of Europe), at first they wanted to introduce PCM and MPEG-2 formats as the audio standard for DVD, but under the influence of public pressure and, contrary to the wishes of Philips, DVD-Forum included Dolby AC-3 in a list of optional sound formats on discs and required formats in players.

Difference between DVD and CD

First of all, DVD discs have a smaller diameter of the recesses, they are located on the track with a smaller “step” and there are much more tracks on the disc. The use of smaller notches is made possible by using a laser with a shorter wavelength, sending a more “dense” beam. While the laser in a typical CD-ROM device has a wavelength of 780 nanometers, DVD devices use a laser with a wavelength of 650 or 635 nm, which allows the beam to cover twice as many notches per track and twice as many tracks. In addition, the disk surface available for storing data is slightly larger than that of a CD-ROM; DVD also provides a different sector format and a more robust error correction code. All these innovations have allowed DVDs to achieve approximately seven times the storage capacity of traditional CDs.
But a sevenfold increase in disk capacity is far from the limit. Perhaps the most interesting thing about DVD specifications is the ability to create double-sided and dual-layer discs. A double-sided disc is easy to make: since a DVD disc can be only 0.6 mm thick (half the thickness of a regular CD-ROM), it is possible to connect two discs back to back to create a double-sided DVD. True, you'll have to manually flip it over, but as DVD technology advances, there will be drives that can read both sides without user intervention.
Unlike CDs, where the structure of an audio disc is fundamentally different from a data disc, DVDs always use the UDF file system.
In addition, there are restrictions for DVDs - DVD regional locking.

Single-layer and double-layer discs, single-sided and double-sided recording.

A DVD may have one or two working sides and one or two working layers on each side. The capacity of the disk depends on their number:

• single-layer, single-sided (DVD-5) hold 4.7 gigabytes of information,
• double-layer single-sided (DVD-9) hold 8.7 gigabytes of information,
• single-layer double-sided (DVD-10) holds 9.4 gigabytes of information,
• double-layer, double-sided (DVD-18) holds 17.4 gigabytes of information.

It's worth noting that the capacity of dual-layer DVDs is not twice that of single-layer ones, as you might expect, but rather slightly less. To minimize interference when the laser beam passes through the outer layer, the minimum size of the track recesses has been increased from 0.4 mm to 0.44 mm. By the way, as a result, the speed of reading information from such disks has increased slightly.
Capacity can be determined by eye - you need to look at how many working (reflective) sides the disk has and pay attention to their color: double layer sides usually have a golden color and single-layer- silver, like a CD.

Different DVD formats

There are three types of DVDs based on their data structure:

• DVD-Video - contain films (video and sound);
• DVD-Audio - contains high quality audio data (much more

higher than on audio CDs);

DVD-Data - contain any data.

There are four types of DVD media:

• DVD-ROM - factory-pressed discs;
• DVD+R/RW - single-use (R - Recordable) and multiple-use discs

(RW - ReWritable) records;

DVD-R/RW - single-use (R - Recordable) and multiple-use discs

(RW - ReWritable) records;

DVD-RAM - rewritable random access discs

(RAM - Random Access Memory).

Burn to DVD

For recording, there are DVD-R and DVD-RAM devices that allow you to store data on special recordable or rewritable DVD discs.
DVD-RAM devices will allow you to rewrite DVD-RAM discs many times.
DVD-R devices can only be written once
There are not many parameters to consider when choosing DVD drives:
1) Speed;
2) The number of standards it supports.

Problems with writing various DVDs on DVD burners

There is a whole list of drive “failures” to write this or that disc. In simple terms, this is explained by the difference between discs and in order to write a disk, the drive must “know” it. When a drive is released, the manufacturer cannot pass on the "knowledge" of all future drive types, so all such problems are solved by updating the drive's firmware.
If the drive continues to refuse to write to a specific disk model, this does not mean that the drive is faulty. Perhaps this is a defective disk or simple incompatibility. In such cases, this cannot be the basis for warranty service.
Let's look at recording to DVD using the example of one of the programs - Paragon Easy CD/DVD Recorder 6.0

DVD Applications

• DVD Video: Digital Cinema and Sound
• DVD Audio: Digital Audio
• DVD ROM: High-capacity CD-ROM storage media for computer applications and game consoles

The main application of DVD, according to the creators of the format, was to be films on CDs. Indeed, of all the areas of DVD application, video has become the most widespread. The DVD format provides excellent audio and video quality for playback on a large screen with surround sound. The number of films produced on DVD is increasing every year.
The music DVD appeared in 2000 in the USA.
The great promise of DVD in areas such as education, entertainment, interactive applications and demo kiosks is not clear enough. And so far DVD is perceived only as a home theater. Will DVD remain just a film carrier or will it become something more? Or will a completely new technology be created? Time will tell.

Here's another answer

1. DVD (Digital Versatile Disc/ Digital Video Disc)- a storage medium made in the form of a disk, similar in appearance to a CD, but with the ability to store a larger amount of information due to the use of a laser with a shorter wavelength than for conventional CDs. Read/write speed? 21 Mb/s. The storage capacity of a single-sided DVD is up to 4.7 GB. A double-sided DVD disc, in terms of its information capacity, is equivalent to four “simple” DVDs or a whole bunch of regular CDs. Like CD, DVD has several formats (DVD-Video, DVD-VR, DVD-Audio, Data DVD) and types (DVD-ROM, DVD-RAM, DVD-R, DVD-RW, DVD+R, DVD+RW ).

2. Blu-rayAndHD DVD.

Blu-Ray BD is an optical media format that is used for recording and storing digital data, such as high-definition video with increased density. The Blu-ray standard was developed and maintained by a group of companies under the auspices of the Japanese Sony. BDA (Blu-ray Disc Association) members also include Dell, Hitachi, HP, LG, Mitsubishi, Panasonic, Pioneer, Philips, Samsung, Sharp, TDK and Thomson. Blu-ray (literally “blue ray”) got its name because a short-wavelength (405nm) “blue” (blue-violet) laser is used for recording and reading. The commercial launch of the Blu-ray disc format took place in the spring of 2006. From 2006 (when this format appeared) until the beginning of 2008, Blu-Ray had a rather serious competitor - the alternative HD DVD format.