DVD

January,27 2024

**DVD** (Digital Versatile Disc or Digital Versatile Disc, **DVD**) is a type of Second-generation optical disc that is a recording medium for digital data.

## Positioning of DVD

The shape of the medium and the recording / reading method are almost the same as those of a CD ( compact disc ), but the recording capacity is much larger than that of a CD, which is about 6 times that of a normal 12 cm, so a long time that was not possible with a CD. The feature is that it can record images. In the development, it was decided to aim for "recording time of 133 minutes or more on one side per sheet with high image quality and high sound quality exceeding the current media"  at the request of the Hollywood movie industry, and the recording capacity per sheet. Was developed as a 4.7GB (single-sided, single-layer) disc capable of recording 133 minutes with the same image quality as the VHS videotape system , in consideration of the technical level at that time.

Like conventional video tapes (VHS, etc.), it is positioned as the main medium for video recording , and various video software such as movies , documentaries , and dramas are commercially available. In addition, with the spread of consumer camcorders and non-linear editing compatible personal computers , it has become possible to save self-edited images on DVD.

## Overview

According to the description  on the DVD Forum ,  polycarbonate disks with a thickness of 0.6 mm and a diameter of 12 cm are laminated together. It is the same size as a CD ( compact disc ) and is used not only as a DVD-Video but also as a data storage (storage medium) for computers.

The read, 650 nm of a red laser beam using. Players and drives are generally those that can also be used for playing CD-DAs and CD-ROMs .

Sales of home DVD players began in 1996. The PlayStation 2 , a game console released by SONY on March 4, 2000, also had a function to watch DVDs. In 2004, domestic shipments of DVD players exceeded VTRs . It can be said that the center of optical media has shifted from CDs to DVDs in the personal computer field as well. In the audio field, it remained for some enthusiasts and did not spread ( see DVD-Audio ).

The manufacturing cost of media is about 120 yen per VHS, while the cost of DVD is about 20 yen per sheet, which is extremely low. It's easy to handle, so it's easy for publishers to make money. For this reason, more and more companies in the video industry are using cell DVDs as their primary source of revenue (rather than secondary), changing the industry.

DVD standards differ depending on the physical structure of the disc and the format (logical format) of how the data is written. In addition, there are differences depending on the application format for video applications, and there are many more types for each combination.

### Recording method

It can be recorded by making a dent called a **pit** along the track . When reading, a laser beam is applied and the difference in reflection depending on the presence or absence of a dent is used.

The track shape of a DVD is not a concentric circle, but a spiral shape similar to that of a CD.

### Recordable DVD

DVD-R (writable only once), DVD-RW , and DVD-RAM (writable multiple times) have been established by the DVD Forum as recordable DVD standards . To counter this, there are DVD + R and DVD + RW developed by the DVD + RW Alliance . Each disc will be described in detail by DVD type .

Regarding recordable DVDs, some overseas manufacturers may have serious quality problems  . Poor quality discs are likely to cause block noise when playing videos, stop playing, erase saved data, and shorten the life of drives and recorders.

However, there is no guarantee that it will be okay to use domestic media because the writing quality may deteriorate depending on the performance and compatibility of the drive (even domestic brands may use overseas media). In order to use it with peace of mind, it is desirable to buy one piece of media to be used from now on and perform a writing test to confirm that there are no problems before using it. In addition, the durability of writing media, which was said to last for about 100 years when it was first released, is only an acceleration test of good quality media (not actually tested for 100 years, but instead changing the irradiation intensity of ultraviolet rays, etc. It is a result of the environment equivalent to 100 years), and in reality, there are some poor quality discs whose data disappears in a few years (conversely, there are media that can be used even after 100 years). To do). In order to make it last longer, it is important to avoid places exposed to ultraviolet rays and places with high temperature and humidity. Also, compared to VHS, there is no concern that the tape will get entangled and break down, but if the disc is damaged, it may become unreadable.

## DVD name

The DVD Forum says that DVD means **Digital Versatile Disc**  , but **the official name of** the **disc is "DVD"** .

In contrast to CD, which is the first-generation optical disc, DVD was planned as the second-generation optical disc " Digital Video Disc "  that can record movies . Initially, the demand for replacement of VHS was mainly assumed, but when it was pointed out that "the use is not limited to video", the name has been questioned. Therefore, there is a history of changing to " Digital Versatile Disc " by using versatile , which means "multipurpose", instead of video .

For the above reasons, it is wrong to abbreviate DVD as " Digital Video Disc "  but the official name was changed to "DVD " and it can be said to be "V" from the video tape that was the video storage medium. For example, because it is associated with " video " and how it was developed,  " Digital Video Disc " is also used as a limited name.

## Background to the appearance of DVD

### Development of 2nd generation optical discs and format war

In the early 1990s, before the advent of DVD, as a standard for second-generation optical disc media with higher density than CDs, we initially developed optical discs using a blue SHG laser, but we hope that they will be commercialized as soon as possible in the Hollywood movie industry. at the request that, to the end of 1994 is Toshiba , time Warner , Matsushita Electric Industrial Co. (now Panasonic ), Hitachi , Pioneer , Thomson , Victor Company of Japan (now JVC Kenwood using a red laser according to the Union of) *Super Density Disc* (SD ) Was being developed. On the other hand, Philips , Sony by camp *MultiMedia Compact Disc* (MMCD) have also been developed at the same time, the 1980s of VHS vs. BetaThere was concern about the return of the war .

So, IBM of Lou Gerstner enter the (Lou Gerstner) is an intermediary, Philips and Sony in exchange for giving up the adoption of MMCD standard, the SD standard servo tracking is to admit the modification of two items on the mechanism, Philips and Sony The two camps have reached an agreement on the SD standard led by Toshiba.

The first item was the adoption of pit geometry to enable Philips Sony's patented "push-pull tracking" technology. The second was the adoption of Philips EFM Plus , designed by Kees Schouhamer Imink . This was 6% less efficient than Toshiba's SD code, so the capacity of the SD standard itself was 5GB, but the result was 4.7GB. EFMPlus was highly resistant to scratches and fingerprints on the disc surface. As a result, **DVD specification Version 1.0** was announced in 1995 and completed in September 1996. The name has changed to DVD, but the SD logo is inherited by the SD memory card logo.

It was once thought that this integration would avoid a rush of standards, but after that, many orders were placed from home appliance makers and movie companies (random access, 2-hour recording, Dolby Digital recording, etc.), and the later "DVD Many derivative standards such as "-", "DVD +", "DVD-RW", and "DVD-RAM" were born.

### Commercialization of DVD-Video media player

The first commercialization of DVD-Video media and players took place in Japan in November 1996, in the United States in March 1997, in Europe in March 1998, and in Australia in February 1999. The world's first commercially available DVD-Video software is " Castrato ", which was released on October 1, 1996.

By the way, " Twister " is the first 2.1ch surround sound, and " Independence Day " is the first 5.1ch surround sound .

## Standard

### Capacity

 Double layer on one side
 Double-sided layer
 Double-sided double layer

* The capacity per sector is 2,048 bytes, which is 2064 bytes by adding 16 bytes of the header. CSS etc. also use this header, but basically this 16 bytes cannot be ripped at the time of ripping.
* There is also a single-sided 12 cm DVD with a capacity of 4.9 GB .
* Double-sided discs have twice the capacity of one side, while double-layer discs do not have twice the capacity of one layer (more on this later).
* 1 GiB = 1024 3 bytes (bytes) = 2 30 bytes = 1.073741824 x 10 9 bytes = 1.073741824 GB . Although capacity in the commodity of the DVD is displayed in GB, OS and application is file size a GiB when you display in the unit (and at that time most "hundred GiB " hundred, not in such a form as " GB It is confusing because it is displayed as "), but it should be noted that there is a difference of 7% or more in terms of numbers. Since the area used for file management is secured on media such as DVD-R, the capacity that can be used for user files is the amount obtained by subtracting it. If you can't write a file larger than 4.25 GiB to a 4.7 GB DVD, for example , it's not a "misrepresentation" of capacity, and there's a good reason for this.[1]DVD

### Dual-Layer = DL

A DVD is a disc aimed at recording a large capacity, and a CD has a standard for double-sided recording so that it can be recorded on the surface corresponding to the label surface. However, it is troublesome to turn it over when the reading of one side is completed like a laser disc . Therefore, if a two-layer structure is provided on one side, more capacity can be secured than the one-layer structure, and there is no need to turn it over. User-recorded DVD + R DLs appeared on the market in June 2004, and DVD-R DLs in May 2005. Depending on the optical drive , it may not be possible to read due to compatibility and specifications. Also, if you do not handle the label side more carefully than the single layer method, you will have troubles such as damage to the recording layer like a CD.

In the case of a two-layer structure, if two layers that perform total reflection are provided, the layer in the back cannot be read. Therefore, the first layer ("Layer 0", or "L0" for short) of a single-sided (double-sided) dual-layer disc is made of a thin metal film, and the second layer ("Layer 1" or "Layer 1" or " (Called L1) has a structure that totally reflects. Since layer 0 is a thin film, the detection rate of reflected light for reading is worse than that of layer 1, but the reading performance is ensured by lowering the recording density . Therefore, the capacity of a dual-layer disc is less than twice that of a single-layer disc.

Layer 0 is a method of recording / reading from the inner circumference side to the outer circumference side (same as a CD), but there are the following two recording methods of layer 1.

Parallel method
Similar to layer 0 (1st layer), this method goes from the inner circumference side to the outer circumference side.
Opposite method
The opposite of layer 0, the method goes from the outer circumference side to the inside.
This information is recorded on the innermost side of layer 0 as DVD management information. By the way, DVD + R DL has only opposite method. When playing a DVD on a dual-layer disc, it's time to switch layers to read in the middle. When playing a DVD-Video, some players may take a long time to switch layers and the video playback may stop for a moment. (There is an advantage that the opposite movement requires less movement of the reading pickup when the layers are switched during continuous playback than the parallel method.)

Double-layer DVDs are often abbreviated as "DL", but the official name is Dual Layer for DVD-DL and Double Layer for DVD + DL , which are different.

### Transfer speed

The data transfer rate is 11.08 Mbps (= 1385 kiB / s) at 1x speed . This is equivalent to about 9x speed, assuming that the CD transfer speed is 1x speed (150 kiB / s). The maximum transfer speed specified in the standard is 16x (in the case of DVD-R), which is equivalent to 177.28Mbps (= 22.16 MiB / s).

### Logical format

There are two main logical formats used for DVDs.

* ISO 9660
* Universal Disk Format (UDF 1.02, 1.50, 2.00, 2.01)

In addition to ISO 9660, which has been used since the CD era, it supports more expandable UDF. UDF 1.02 is used for DVD-Video for video applications, and UDF 2.00 is used for DVD-VR used for recording digital broadcasts.

Data DVDs for PCs can be used in any of the above formats, but cannot be read unless the PC's DVD drive and OS support it. Since ISO 9660 is an old standard and lacks extensibility, it has excellent compatibility, so a UDF Bridge that supports both ISO 9660 and UDF 1.02 is also used.

### License

DVD format and logo licenses are managed by DVD Format / Logo License Corporation  (DVD FLLC).

## Usage

### Digital Video Recording

The DVD itself was developed primarily as a medium that exceeds the storage capacity of a CD for recording digital video footage. In reality, various other digital data can also be recorded. Digital video has become so widespread that it is recognized as a DVD, but to be precise, it is just one of several types of digital video. DVDs on which digital video images are recorded are often collectively referred to as "DVD videos", but apart from that, "DVD-Video" is one of the methods for recording digital video image data on DVDs. Yes, the two are not synonymous but completely different.

" DVD-Video " is limited to DVD-Video format ("DVD-VF") recording of digital video video data on a DVD.

On the other hand, the generic term "DVD-Video" refers to all recorded digital video video data on DVD (DVD-Video, DVD-VR , AVCHD , AVCREC, etc., recorded in a video-only application format, without using a video-only format. to MPEG files and AVI , such as those that records the file directly) becomes the target. What is recorded as a shooting recording medium of a video camera is also generally included here.

## References

This is a list of references for **DVD**. These citations are used to identify the reliable sources on which this article is based. These references appear inside articles in the form of superscript numbers, which look like this: [1]

1. ↑ Japanese Wikipedia DVD