DVD Overview
From Rejon.org Wiki
This is a general overview of DVD (digital video disc also called digital versatile disc). The point of this presentation is to see just how versatile this this disc is, where it comes from, and how we can manipulate it as a medium.
DVD (also known as "Digital Versatile Disc" or "Digital Video Disc") is an optical disc storage media format that can be used for data storage, including movies with high video and sound quality. DVDs resemble compact discs as their physical dimensions are the same (12 cm (4.72 inches) or occasionally 8 cm (3.15 inches) in diameter) but they are encoded in a different format and at a much higher density. The official DVD specification is maintained by the DVD Forum. [1]
Contents |
DVD History
- Two standards MMCD and SDCD which combined into DVD
- First DVD was Twister in 1996
- 1999, price dropped below $300 so Walmart started to carry
- DVD rentals first topped those of VHS during the week of June 15, 2003 (27.7 M rentals DVD vs. 27.3 M rentals VHS)
- DVD players now cheaper than VHS players
- DVD works with xbox and ps2 (cementing place in gaming)
DVD Specs
- 3 recordable formats
- -R/RW (minus)
- +R/RW (plus)
- -RAM (ram).
- Dual-Layer Discs
- Double the data, 8.5 gb
- severe problems with compatibility with players
DVDs are made from a 0.6 mm thick disc of polycarbonate plastic coated with a much thinner reflective layer of aluminium or gold. Two such discs are glued together to form a 1.2 mm disc that can be designed to be read from one side (single sided) or both sides (double sided). The substrates are half as thick as a CD to make it possible to use a lens with a higher numerical aperture and therefore use smaller pits and narrower tracks. Discs commonly come in 8 cm or 12 cm diameters. [2]
A single-layer DVD can store 4.7 GB (4.38 GiB, or 4,707,000,000 Bytes), which is around seven times as much as a standard CD-ROM. By employing a red laser at 650 nm wavelength (compared to 780 nm for CD) and a numerical aperture of 0.6 (compared to 0.45 for CD), the read-out resolution is increased by a factor 1.65. This holds for two dimensions, so that the actual physical data density increases by a factor of 3.5. DVD uses a more efficient coding method in the physical layer. CD's error correction, CIRC, is replaced by a powerful Reed-Solomon product code, RS-PC; Eight-to-Fourteen Modulation (EFM) is replaced by a more efficient version, EFMPlus, which uses eight-to-sixteen modulation. There is no subcode as in CD. As a result, the DVD format is 47% more efficient with respect to CD-ROM, which uses a "third" error correction layer. [3]
Formats
- DVD-5: single sided, single layer, 4.7 gigabytes (GB), or 4.38 gibibytes (GiB) - Supported by
- DVD-9: single sided, double layer, 8.5 GB (7.92 GiB) - Supported by DVD±R
- DVD-10: double sided, single layer on both sides, 9.4 GB (8.75 GiB) - Supported by DVD±R/RW
- DVD-14: double sided, double layer on one side, single layer on other, 13.3 GB (12.3 GiB) - Not commonly found
- DVD-18: double sided, double layer on both sides, 17.1 GB (15.9 GiB) - Supported by DVD+R
Competing Formats from the Beginning
DVDs are a study in bad standardization with multiple consortiums and competing formats.
"The "+" (plus) and "-" (minus, dash) are similar technical standards and are partially compatible. As of 2005, both formats are equally popular, with about half of the industry supporting "+", and the other half "-". Around 90% of DVD readers (drives and player) can read the recordable formats, with DVD-R having the best overall compatibility in independent tests. Almost all DVD writers can write both formats and carry both the +RW and DVD-R/RW logos."
Speed of DVD
The reference data rate of DVD is 11.08 Mbit/s (million bits per second). The data transfer rate of a DVD drive is often given in multiples of 1352 kB/s, which means that a drive with 16x speed designation allows a data transfer rate of 16 × 1352 = 21640 kB/s (21.13 MB/s). As CD drive speeds are given in multiples of 150 kB/s, one DVD "speed" equals nine CD "speeds," so an 8x DVD drive should have a data transfer rate similar to that of a 72x CD drive. In physical rotation terms (spins per second), one DVD "speed" equals three CD "speeds," so an 8x DVD drive has the same rotational speed as 24x CD drive.
DVD-Video
This is the standard we are using for our projects and is the most common.
- Instant rewind and fast forward (no "be kind, rewind" stickers and threats on rental discs)
- Instant search to title, chapter, music track, and timecode.
- Durable (no wear from playing, only from physical damage).
- Not susceptible to magnetic fields. Resistant to heat.
- Compact size (easy to handle, store, and ship; players can be portable; replication is cheaper than tapes or laserdiscs).
VIDEO
- The video resolution on NTSC discs is 720 × 480 and on PAL discs is 720 × 576.
- MPEG-2 compression
- Over 2 hours of high-quality digital video (a double-sided, dual-layer disc can hold about 8 hours of high-quality video, or 30 hours of VHS quality video).
- Support for widescreen movies on standard or widescreen TVs (4:3 and 16:9 aspect ratios).
Audio
- The audio data on a DVD movie can be of the format PCM, DTS, MP2, or Dolby Digital (AC-3).
- Up to 8 tracks of digital audio (for multiple languages, commentaries, etc.), each with as many as 8 channels.
Subtitles
- DVD Video may also include one or more subtitle tracks in various languages, including those made especially for the deaf and hearing impaired. They are stored as bitmap images with transparent background which are overlaid over the video during playback. The subtitle track is contained within the VOB file of the DVD. Subtitles are restricted to four colors (including transparency) and thus tend to look cruder than permanent subtitles on film.
- Up to 32 subtitle/karaoke tracks.
Interactivity
- DVD Video may contain Chapters for easy navigation (and continuation of a partially watched film). If space permits, it is also possible to include several versions (called "angles") of certain scenes, though today this feature is mostly used—if at all—not to show different angles of the action, but as part of internationalization to e.g. show different language versions of images containing written text, if subtitles will not do (for instance, credits). Multiple angles have found a niche in pornography though.
- Automatic seamless branching of video (for multiple story lines or ratings on one disc).
- Up to 9 camera angles (different viewpoints can be selected during playback).
- On-screen menus and simple interactive features (for games, quizzes, etc.).
- Multilingual identifying text for title name, album name, song name, cast, crew, etc.
- Overview
- There are 24 system registers for information such as language code, audio and subpicture settings, and parental level. There are 16 general registers for command use. A countdown timer is also provided. Commands can branch or jump to other commands. Commands can also control player settings, jump to different parts of the disc, and control presentation of audio, video, subpicture, camera angles, and so on. The command set enables relatively sophisticated discs, such as games or interactive educational programs.
Overall
A major selling point of DVD Video is that its storage capacity allows for a wide variety of extra features in addition to the feature film itself. This can include audio commentary that is timed to the film sequence, documentary features, unused footage, trivia text commentary, simple games and film shorts.
Restrictions
Macrovision
Content Scrambling System (CSS)
- Try to scramble content if out of region.
region codes
- Region of player must match region of disc (to limit piracy)
- 8 regions
- computers go around easily and so do many consumer decks
disabled user operations (UOPs)
- Control where a users is in the menu (disable functions)
- Many players ignore (especially open source players)
Overview
- None of these work 100% and have all been hacked.
Disadvantages of DVD
- Vagueness of the DVD specification and inadequate testing of players and discs has resulted in incompatibilities. Some movie discs don't function fully (or don't play at all) on some players.
- bad support for interactivity
- DVD recorders are more expensive than VCRs.
- DVD has built-in copy protection and regional lockout.
- DVD uses digital compression. Poorly compressed audio or video may be blocky, fuzzy, harsh, or vague.
- The audio downmix process for stereo/Dolby Surround may reduce dynamic range.
- DVD doesn't fully support HDTV.
- Some DVD players and drives can't read CD-Rs.
- Some DVD players and drives can't read recordable DVDs.
- Most DVD players and drives can't read DVD-RAM discs.
- Very few players can play in reverse at normal speed.
- Variations and options such as DVD-Audio, DVD-VR, and DTS audio tracks are not supported by all players.
Developing DVDs
Production of a DVD is broken down into Development and Publishing.
Development (Authoring)
- Encoding (converting content into usable assets)
- authoring (design, layout and testing)
- premastering (formatting the disc image)
Publishing
- Replication
- duplication of final master disc
- Packaging
- Printing of final disc and any printed matter
- Manufacturing
- combinging all printed matter, boxes, etc together
- Release
- Distribution
PLEASE READ: Most of this is from [5].
Great Workflow Overview
Future Discs
http://upload.wikimedia.org/wikipedia/commons/d/d2/CD_DVD_BD_HDDVD.gif
HD-DVD
- MPEG-4
- 15gb per layer, upt to 3 layers and double sided, so max, 90gb
- easy for manufacturers
- backwards compatible with DVD and CD
Blueray Disc
- same video/audio standards as HD-DVD and previous DVD
- max is 200gb
- is leading
- expensive for manufacture (usually most expensive loses, see VHS wars)
Holographic Versatile Disc
- starts at 300gb
- made by maxell
