DVD (di-vi-di, Eng. Digital Versatile Disc - a digital versatile disk, also English. Digital Video Disc - DVD) - the media, in the shape of a disk that has the same size as a CD, but more dense structure of the working surface, which allows you to store and retrieve more information through the use of a laser with a shorter wavelength and a lens with higher numerical aperture.

DVD-ROM drive - the device reading (and writing).

Content

1 History
2 Technical Information
2.1 Format of DVD-R and DVD + R
3 DVD-Video

History

The first discs and DVD players have appeared in November 1996 in Japan, and in March 1997 in the United States and the CIS.

In the early 1990s developed two standards for optical information carriers of high density. One of them was called the Multimedia Compact Disc (MMCD) and was developed by Philips and Sony, second - Super Disc - supports 8 major corporations, among which were Toshiba and Time Warner. Later efforts of developers of standards have been combined under the IBM, which did not want to repeat format war, as the standards of VHS tapes and Betamax in the 1970s. Officially, the DVD was announced in September 1995, at the same time published the first version of specifications DVD. Changes and additions to the specification makes organizing DVD Forum (formerly the DVD Consortium), whose membership includes 10 founding companies and over 220 individuals. DVD is the fastest growing category of consumer electronics in the history of mankind.

The first drive that supports recording DVD-R, Pioneer released in October 1997. The cost of this drive that supports DVD-R specification, version 1.0, was $ 17 000 Blank size 3.95 GB worth of U.S. $ 50.


Comparative sizes: 12 cm DVD-RW next to 19-cm pencil
Originally «DVD» stood for «Digital Video Disc» (DVD), since this format was originally designed as a replacement for videotape. Later, when it became clear that the carrier is suitable for storing any information, many people began to decode DVD as the Digital Versatile Disc (digital versatile disc). Toshiba, head of the official site of the DVD Forum'a uses «Digital Versatile Disc». By consensus is not reached yet, so today «DVD» officially not in any way stands.

Technical information

To read and write DVD uses a red laser with a wavelength of 650 nm.

DVD format for the data structure can be of four types:

DVD-Video - contain movies (video and sound);
DVD-Audio - audio contain high quality (much higher than audio CD-ROM);
DVD-Data - contain any data;
mixed content.
Unlike CDs, audio CD, in which the structure is fundamentally different from the data disks, the DVD is always [source not specified 274 days] file system is UDF (data can be used by ISO 9660). DVD-Video, for which there is a requirement "to be lost on the domestic players," use the same file system UDF [Source Unknown 274 days], but with some restrictions (document ECMA-167) - for example, are not allowed to file fragmentation. Thus, any type of DVD media can be any of the four data structures (see above).

Physically, the DVD may have one or two working parties, and one or two working layers on each side. Their number depends on the disk capacity (which is why an 8-cm discs were called DVD-1, -2, -3, -4, and 12-cm discs - DVD-5, -9, -10, -14, - 18, on the principle of rounding off the disk space in GB to the nearest whole number above):

Capacity and range of DVD
Designation of number of sides of coats Diameter Capacity
(Cm) (GB) (GiB)
DVD-R SS SL (1.0) 1 1 12 3.95 3.68
DVD-R (W) SS SL (2.0) 1 1 12 4.70 4.38
DVD-R SS DL 1 2 12 8.54 7.95
DVD-R (W) DS SL 2 2 12 9.40 8.76
DVD-R DS DL 2 4 12 17.08 15.90
DVD-R (W) SS SL 1 1 8 1.46 1.36
DVD-R SS DL 1 2 8 2.66 2.47
DVD-R (W) DS SL 2 2 8 2.92 2.72
DVD-R DS DL 2 4 8 5.32 4.95
DVD-RAM SS SL (1.0) 1 1 12 2.58 2.40
DVD-RAM SS SL (2.0) 1 1 12 4.70 4.37
DVD-RAM DS SL (1.0) 2 2 12 5.16 4.80
DVD-RAM DS SL (2.0) 2 2 12 9.40 8.75
DVD-RAM SS SL 1 1 8 1.46 1.36
DVD-RAM DS SL 2 2 8 2.65 2.47

These figures - are approximate. The DVD data is written to sectors, one sector contains 2048 bytes. Therefore, the exact value of the capacitance can be determined by multiplying the DVD in 2048 the number of sectors on the disk, which varies slightly among different types of DVD media:

Disc type (12 cm) Number of sectors capacity in bytes KB MB GB CIB MiB GiB
1-layer DVD-RAM 2.295.072 4.700.307.456 4.700.307,456 4.700,307 4,700 4.590.144 4.482,562 4,377
1-layer DVD-R (W) 2.298.496 4.707.319.808 4.707.319,808 4.707,320 4,707 4.596.992 4.489,250 4,384
1-layer DVD + R (W) 2.295.104 4.700.372.992 4.700.372,992 4.700,373 4,700 4.590.208 4.482,625 4,378
2-layer DVD-R 4.171.712 8.543.666.176 8.543.666,176 8.543,666 8,544 8.343.424 8.147,875 7,957
2-layer DVD + R 4.173.824 8.547.991.552 8.547.991,552 8.547,992 8,548 8.347.648 8.152,000 7,961

Note: The format for DVD-R (W) does not specify the exact number of sectors, but only requires that the tank does not fall below 4.7 billion bytes. However, most manufacturers adhere to the number of 2,298,496 sectors, as indicated in the table.

The unit of speed (1x) read / write DVD is 1.385 million bytes / sec (ie about 1352 KB / s = 1.32 MB / s), which roughly corresponds to the 9th speed (9x) read / write CD, which is equal to 9 × 150 = 1350 Kbytes / sec. Thus, 16-speed drive provides a speed reading (or writing) DVD is 16 × 1,32 = 21,12 MB / sec.

Formats DVD-R and DVD + R

Standard for recording DVD-R (W) was developed in 1997 by a Japanese company Pioneer, a group of companies joined to it and included in the DVD Forum, the official specification is written (later, and rewritable) discs.

Created based on DVD-R discs DVD-RW, initially had trouble relating to the incompatibility of the old drive with the new drives (the problem was in contrast to the optical layer is responsible for "remembering" information, which had a smaller (compared to a write-once media and pressed disks) reflectivity). In the future this problem has been almost completely solved, although earlier it was because of that old DVD-drives could not normally play new rewritable discs.

Since the development of standards DVD-R and DVD-RW is not taken into account the development of firms Sony, Philips and some others (as well as the price of licenses for the technology was too high), these manufacturers are recording drives and media to record together in the DVD + RW Alliance (English), which was developed in the mid-2002, standard DVD + R (W), the cost of a license for which was lower.

Created an alternative format, called DVD + R and DVD + RW, the other stuff was a reflective layer and a special layout that facilitates the positioning of the head (LPP, Land pre-pits - pits predzapisannye between tracks containing the data address and other proprietary information, these data suggest DVD drive to record information in the desired location on the disk) - the main difference between such "plus" discs of "freezing". With this DVD + RW discs are capable of several methods of recording (over existing), as in a regular VCR, except the tedious pre-erase the entire contents (for DVD-RW, you must first erase the entire existing record).

In addition, when using rewritable "plus" discs of errors decreases, and the correctness of entries increases, resulting in a bad sector can be easily overwritten and not wash and do not write the entire disk again. Therefore, if you intend to use the function and overwrite recording, it is better to choose the recorder that supports "plus" format (which is now capable of most of the models).

DVD-Video


Typical content file structure of DVD-Video.
To play a video DVD requires DVD-optical drive and MPEG-2 decoder (ie, household or DVD-player with a hardware decoder or a computer DVD-ROM drive and software player with a decoder installed). DVD movies are compressed using the algorithm of MPEG-2 video and the various (often multi-channel) audio formats. Bitrate of compressed video will vary from 2000 to 9800 kbit / s, it is often variable (VBR). The size of the video frame for the PAL standard is 720 × 576 pixels, and for the standard NTSC - 720 × 480 pixels.

The audio data into DVD-movie may be in the format PCM, DTS, MPEG or Dolby Digital (AC-3). In countries using the standard NTSC, all the films on DVD should contain the audio in PCM or AC-3, and all players have NTSC-support these formats. Thus, any standard CD can be played on any standard hardware.

In countries using the standard PAL (most of Europe), first sought to introduce as a standard audio format for DVD PCM and MPEG-2, but under public pressure and against the wishes of the Philips DVD-Forum has included Dolby AC-3 in the list of optional audio formats on disk, and mandatory formats in players.