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DVD Technology Page

    General information on DVD system

    In terms of entertainment quality, DVD players have had more impact on the home entertainment market than any consumer electronics component since the television, allowing individuals to enjoy extremely high video quality combined with the potential for surround sound in their homes at a relatively low cost. DVD (Digital Versatile Disc) is a modern multimedia format that holds video, audio and computer data.DVD discs are designed to play in either set-top boxes connected to yourtelevision, or in DVD-ROM drives built into personal computers. In one sense, DVD is the natural evolution of the CD.In fact, DVD discs look just like CDs. However, the capacity of DVD discs is much higher than that of CD. DVD discs can hold up to 17 GB of data,thereby allowing hours of extremely high-quality video and audioon a single disc.What makes DVD superior to its CD counterpart is the manufacturingprocess and internal design. The basic manufacturing process for DVDis similar to the current process for CD-ROM, with some exceptions. For a normal viewer of DVD disks this format has following benefits compared to many other optios:

    • No degradation through normal viewing: You can watch your DVD as many times as you want and it will look the same every time, unless you physically damage the disk by improper handling (cause lots of scratches etc.)
    • Near-instant access: You can fast forward or rewind to almost any point in the feature with the flick of a finger.
    • Very good audio: DVD support CD quality stereo digital audio and several high quality multichannel sound formats (5.1 channel DD and DTS being most used ones)

    DVD is comprised of several models, each positioned to meet the needs of specific industries. DVD-Video and DVD-ROM, which were the first DVDs to hit the consumer market, are read-only versions that are ideal for full length feature films and computer games. This is what people generally refer to when they talk about DVD.

    But there are more DVD options available. DVD-Audio is a DVD format targeted to store audio signals. DVD-Audio disk can store entire compilations of musicians with even bettersound quality than CD disks.DVD-R (write once, read many) and DVD-RAM (rewritable) discs are designed to meet the ever increasing storage capacity demands of the computer industry. DVD-RAM drive can store up to 5.2 GB (2.6GB on each side) on one DVD-RAM disk.

    A DVD disc with video signal in it is recorded with Component Video signal in digital format. The video signal is stored in digital format. The digital format is based on MPEG2 video coding. The data rate on DVD video can vary on different DVD disks and even the same video can use different data rate on different parts of the program. The maximum allowed data rate is 9.8 Mbit/s. Component Video is the natural format to display a DVD on a TV. This format is common in US and Japan. Most European/Asian/Australian DVD players converts and output the signal into RGB, without any noticable effects on video quality..

    There are 2 kinds of DVDs: Some have an interlaced format and some are transferred from film to DVD directly, thus have 25 progressive frames encoded. There are also DVDs designed for PAL and NTSC video systems playback in mind. Those selections are purely a decision of the DVD company.

    The history of DVD system has few steps in it. During the later months of 1994 and the early months of 1995, four companies began production of the standards that eventually led to the design of the digital video disk (DVD). Initially led by Phillips and Sony, a singled sided, dual layered high-density disk was developed. Then Time-Warner and Toshiba followed suit, creating a double-sided disk. It took around four years for all those companies to agree on the standards of the DVD.In the DVD market there was also a special model called Divx. Divx was a limited-use consumer DVD format for rental markets developed by Circuit City and Digital Video Express. Consumers buy a disc for few dollars. Once the disc is played for the first time, the clock starts ticking: Divx discs are only usable for 48 hours after the first playback. Customers can then either pay more to "unlock" more rental time, or actually purchase the disc.The Dixv format was only in some use in USA and it is nowadays not inpractical use. (Nowdays if you see name DIVX, it generally refers to sspecial compressed video format not related to DVD itself).

    The status of DVD system development is that for DVD-Video there isone single widely available format (All major studios are now supporing the open DVD-Video format). For DVD-Audio (audio onbly discs) there is on efficial standard, but very few products (both discs and players) on the market and still possibility for format fights (2 competing formats with one available worldwide).

    For DVD-R (recordable) there are 3 competing formats (1 widely available). For DVD-RAM (many times recordable) there are 4 competing formats (1 widely available today).

    DVD players can also play normal audio CDs, so they can be used as a normal CD player also. First generation DVD players cannot play CD-Rs at all - they came out beforeCD-Rs were 'routine', and do not have the correct wavelength laser. Later DVD players have dual lasers - one for DVD and the other for CD, and usually specify this as a feature.

    The DVD disc manufacturing itself is a small percentage of the cost of a DVD you buy at shop. A high percentage of the cost of a DVD is the content, bonus content, profit, and packaging. DVD is well establishes technology that will stay with us for quite a bit of time because of various reasons. The Video industry believes they have found a sweet spot with DVD's at sell through price. The image quality available from DVD is very good (better than many other video formats). There are very movies that many people want to "own", so they an put into a player to watch it again and again and again. Very many people have made investment in DVD based home entertainment systems already and they're not going to throw those away anytime soon. For those reasons DVDs won't disappear in any very short timeline, even though there is always new technologies coming. The lifeline of DVD is not forever. No doubt DVD will go the way of the VHS in 20 years or so but there will always be a need for physical media out there that can hold high quality audio and video. Besides, Hollywood will alway want to sell the consumer movies and I as a consumer will always want to have physical media so I can watch a movie I really like any time.

    DVD's will continue to evolve, in the next couple years you'll have High Definition DVDs. High definition DVD is expected to be the next big thing for movie industry. At least in USA market, where HDTV display devices has catched some market together with HDTV broadcasts. There are two competing options how HDTV resolution will come to DVD. The competing systems are Blue Rays and HD-DVD.

    Sony wants to sell blue laser based Blue-ray players and the Blue-ray disks to go with it. The at the moment cost of the equipment to press blue laser type DVD's is VERY expensive. Blue-ray disks have very much more data storing capacity than traditional DVD disks. The video program is stored to the disk using MPEG2 video format, the same format as used in DVD. Only the resolution and data rate have been increased so that they can bring you very good quality high definition picture. Blu-ray Disc supports 25GB for one layer, 50GB for two and 100GB for four layers. Blu-ray is now called "future-proof" by the consortium because it has the capability to play back both Blu-ray discs and standard definition DVDs within one player. It was even shown that a DVD-9 layer can be laid down onto a Blu-ray disc to make a true hybrid disc. On the upper layer, DVD-9 content (DVD-9 layer is the standard definition version of the movie or video) is stored, and on the lower level Blu-ray content is available. There is enough storage capability on one side of the disc to hold a Blu-ray version, a standard definition movie, a completely interactive menu and a navigation system. Blu-ray has Sony-owned Columbia Tri-Star behind them, plus Sony just bought MGM. Twentieth Century Fox and Disney have also committed themselves to Blu-ray.

    A competing format is called HD-DVD format introduced by Toshiba. It has HDTV resolution encoded using a new video coding system on a pretty much standard manufactured DVD's. HD DVD has a single layer capacity of 15 GB and a dual-layer capacity of 30 GB. Toshiba has announced a triple-layer disc is in development, which would offer 45GB of storage. The HD resolution content is pushed to almost the same size as original DVD data by using more advanced video compression technologies. A HD-DVD can be encoded with several different advanced video formats. Advanced video formats don't necessarily improve picture quality, they just allow you to get higher resolution picture to almost the same file sizes as normal definition video took in DVD disk (MPEG2 video format). MPEG-4 AVC A later video standard finalized by the MPEG group. Also known as H.264 or Advanced Video Coding. VC-1 The version of Microsoft's Windows Media 9 video codec submitted to industry standards bodies for use on DVDs and elsewhere. Was temporarily known as VC-9. HD-DVD is much cheaper and faster to produce than Blue-ray (no special manufacturing techniques needed). There is marketing benefit that ordinary people know what DVD is about, and they can easily understand that HD-DVD has the benefits of DVD, but with HD content. HD DVD has proposed for a hybrid disc, which makes the end user flip the disc over to play a standard definition or high definition version of the same movie. HD-DVD is backed by Time Warner (Warner Bros., HBO and New Line), Universal (DreamWorks), and Paramount. Microsoft and Intel Back Toshiba's HD DVD. In November 2003, HD DVD was selected by the DVD Forum as the successor to the DVD standard. Commercialized HD DVD's will integrate highly secure protection technology that is expected to be developed by AACS LA (Advanced Access Content System License Administrator). Audio Watermark Protection is also being created for use on HD DVD. All HD-DVD players will have a sensor that looks for inaudible watermarks in the soundtrack of movies, and will be included in the soundtracks of all major movies (will not play back movies copied with video camera and microphone).

    Both formats look strong and, sadly, it looks like a format war is unavoidable. But a war can be tough on the success of high-definition content on DVD and may create hesitation on the part of consumers eager to invest in it. It is expected that in year 2006, there will be special movie editions providing the high-res versions of movies and DVD Players that play the new format, at the same time. Maybe some day all new releases will be available in the HDTV format.

    Picture format

    The movie on DVD disk can be recorded a variety of picture formats.Th emost common formats are normal TV 4:3 and widescreen 16:9.

    Area / region codes

    Region codes are the most unwelcome feature that exist in both the DVD players and discs. A player was intended to play the discs with same region code that assigned to it by the main studios. The use of the area code protection is descided by the disc manufacturer. Some DVD disks are deigned to have Zone 0 are code in them, which means thatthey play in every country of the world.There is practically nothing you can do to alter the region code on the disc itself to match the regional setting of your player.But it is most likely possible to do it the other way round. It seems as though most manufacturers of DVD players are only half-heartedly embracing the inclusion of region codes on their machines.This means that in many DVD players the effect of area code restrictionscan be defetead with with some hardware modifications (some older models),with firmware upgrades (on some models) or directly with some "secret"keypresses on the remore control / device itself.

    • DVD Players Hack List - You can find links to DVD player hacks to remove are codes and Macrovision from many DVD players.    Rate this link
    • DVD regional codes - Region codes are the most unwelcome feature that exist in both the DVD players and discs. A player was intended to play the discs with same region code that assigned to it by the main studios. Divide and rule. Hollywood's regional coding standard can be a real pain to DVD consumers of this wired global village.    Rate this link
    • Multi-Region Hacks for Domestic DVD Players - There are many players available on the market which, and with a little help from some simple easy to follow methods, some of these can be altered without so much as opening the lid and invalidating the warranty, to become multi-region. For those who don't quite understand the jargon, this means you will be able to play discs purchased from not only your country but also a far wider selection at cheaper prices in the US.    Rate this link
    • Regional Coding Enhancement (RCE) - Regional Coding enhancement is a digital enhancement added to some Warner Bros, New Line, Columbia DVDs to stop region 1 (R1) DVDs from playing on Region-free DVD players.    Rate this link

    DVD content protection systems

    Most film studios include anti-copying technology on DVDs to prevent digital-to-digital recording, for example, to a computer hard drive. Most DVDs also include a separate encryption layer that interferes with recording to analog devices such as VCRs. Many studios have used technology from Macrovision and others for analog encryption on DVDs, which produce videotape recordings with blocky, unrecognizable images or a blue screen. CSS is a scrambling system used in the distribution for movies on DVD ( Digital Versatile Disc. Its main purpose is to prevent the unauthorized duplication of disc contents. This is achieved through encrypting the files, and storing keys in hardware. Many DVD disks also use a protection technology called Macrovision toprevent consumers to copy the DVD movie to a normal video tape.Macrovision is a kind of analogue copy-protection system to prevent commercial DVD/VHS contents being copied to VHS. However, Macrovision produces distortion patterns when you try to record content from DVD/VHS systems. It should not prevent normal playback for most DVD systems.Macrovision adds a special disturbance signal to a video outputsignals (composite video, S-video and component video) which disturbsa normal VCR so that it does not make a proper recording, but shouldnot cause problems with normal video viewing devices when viewing picturesthat come directly from DVD player.Macrovision, does occasionally, prevent proper genuine playback of DVDs on some video systems, because some video processing or display devicesdo not like Macrovision signal.Macrovision technology is incorporated in all DVD players to protect againstunauthorized recording of DVD programming.DVD Copy Protection Works in the following way:Rights owners seeking to copy protect their programs would instruct theirauthoring facility to set certain digital-analog copy protection triggerbits to "on." When the disc is played back in a consumer's home, thesetrigger bits activate a Macrovision-enabled digital-analog converter chipinside the player. The chip then applies copy protection to the analogoutput of the DVD player. This allows for transparent viewing of theoriginal program, but causes copies made on most VCRs to be substantiallydegraded.

    • Cryptanalysis of DVD Contents Scrambling System - CSS is a scrambling system used in the distribution for movies on DVD ( Digital Versatile Disc). This article describes the system, and shows that even if the keys can be securely stored in hardware, the data will not be protected from unauthorized copying.    Rate this link

    DVD player connections

    In terms of entertainment quality, DVD players have had more impact on the home entertainment market than any consumer electronics component since the television, allowing individuals to enjoy extremely high video quality combined with the potential for surround sound in their homes at a relatively low cost. DVD has brought a new level of readily-accessible video quality into the home environment, and along with it, several unfamiliar ways of connecting up to your video display device to access this additional quality.

      Normal DVD video connectors

      The picture format from your DVD player can come out in composite video,S-video, component video (also referred to as a YPbPr or YCbCr) and/orRGB video formats. A typical DVD player support usually two or moreof those video formats. Sometimes it can be a fustrating task to figureout what are the best common formats which the DVD player gives outand the display device you use (TV or video projector typically)can take in. Here is list of the most commonly used DVD player connectorsfrom the best to worst in picture quality.

      • RGB
      • Component (YPbPr or YCbCr)
      • S-video (Y/C)
      • Composite video
      Notes: The picture quality on the particular devices can vary somewhat, because in some devices some of the available interface formats may work better than other. There are different views on if RGB or component is really better than the other (different views can vary because those interfaces are very similar in performance, but the quality they are implemented in different devices varies).The DVD players in USA have typically composite video, S-video and component video outputs. The DVD players sold in Europe have typically a SCART interface, which give out composite video and RGB signals. In addition there is usually separate S-video connectoravailable.Nowdays with introduction to DVDs with progressive video output there has been few DVD players with VGA output. This kind of progressive output DVD player with VGA output can be easily interfaced to any video projector that is designed originally to be connected to a PC to give a very good picture quality. VGA interface carries a high resolution non-interlaced RGB signal, so technically it give a very good picture quality.Please note that what is actually available in specific DVD player models can vary though, so before bying a device is worth to check the technical specifications that it has the interfaces you want to have or need.The following links are here to give you guidance on this topic.

      Progressive video output

      Nowadays there is also some new DVD playwers which have "progressive" or "non-interlaced" output. Those DVD players can output the picture without interlacing. This picture format is viewable with displays that can accept this kind of signals (most often video projector or HDTV capable TV). A progressive video DVD player reads the same information off a standard DVD but interpolate the information differently from the way an interlaced DVD player would. DVDs are based on MPEG-2 encoding, which allows for either progressive or interlaced sequences. While films are originally progressive material on the original film marerial, they are seldom stored progressive, because most of the DVD players are specifically designed for interlaced output. There arevery few discs use progressive sequences. If the sequence is progressive, then all sorts of rules kick into place which ensure that the material stays progressive from start to finish. Whereas if the sequence is interlaced, then there are fewer rules and no requirement to use progressive frames. The encoder can mix and match interlaced fields and progressive frames as long as each second of MPEG-2 data contains 60 fields, no more, no less (or 50 fields per second for PAL discs). The progressive frames, when they are used, are purely for compression efficiency, but the video is still interlaced as far as the MPEG decoder is concerned. The input to a DVD encoder (the instrumentation that is used to author a DVD) is almost always an interlaced digital master tape, even if the original material was shot on film. The video transfer is typically done at a different facility, and the output of the transfer is interlaced. In short, the content on a DVD is interlaced conceptually, and is stored in interlaced sequences. Frames can be marked "progressive" to help compression, but are not always marked that way, even when it would be correct to do so. In interlaced sequences, the encoder can either keep the fields separate, or combine them together into one frame, whichever is best for compression purposes.

      Properly implemented "progressive" or "non-interlaced" output gives better picture quality than normal interlaced TV picture (more stable picture without resolution loss and flickering caused by interlacing). 480p (progressive) is the resolution of a progressive-scan DVD player. It is twice that of a standard DVD player's 480i.It is generally not considered to be true high-definition, but is already much better than normal TV.The "progressive" outputs on the DVD players is most often available only in "high-end" DVD players. The most often used electrical interface for "progressive" signal is component video (YPbPr or YCbCr). "progressive" video signal cannot be viewed with a "normal TV"."progressive" video signal can be interfaced to a normal computer VGA monitor with a suitable converter.

      To display a perfect progressive image from a film-sourced DVD, the player needs to figure out which fields in the MPEG stream go together to make each film frame. In theory, the progressive_frame flag should tell the player that the frames on the disc were originally from a film, and will go together, but this information is not always properly coded to the disk. The best DVD players with non-interlaced output use a standard MPEG-2 decoder to generate digital interlaced video and then feed that video to a deinterlacing chip. The chip makes decisions constantly about whether the video was originally from film by looking for repeated fields. In the standard 3-2 cadence, the 1st and 3rd fields are identical. If the deinterlacing chip sees a constant stream of 5-field sequences in which the 1st and 3rd fields are identical, it switches to film-mode deinterlacing. Once it?s in film mode, the deinterlacer just combines fields 1 and 2 to make one progressive image, outputs that for 3 progressive frames, then combines fields 4 and 5 to make another progressive image, and outputs that for two frames. Then it repeats the process with the next 5 fields. The player is still outputting frames in a 3-2 pattern, but it?s creating 60 full progressive frames per second instead of 60 fields per second. In film mode deinterlacing can be objectively perfect. Documentaries, concerts, and made-for-TV material often is shot on video cameras, and then there is no good way to create perfect progressive frames, because video cameras capture 60 separate fields, each with one field has half the scanning lines of the display. To get properly de-interlaced output from this material algorithms get much tougher, and perfect results are just not possible, only different sorts of compromises that look subjectively better or worse.

      Just about every DVD player manufacturer claims, in one way or another, that their player is the only ?true? progressive player on the market, and claims that other solutions use some kind of primitive line doubler. With the possible exception of some very low-cost progressive players, all progressive players are capable of outputting the entire film frame, without compromise. They are all ?true? progressive players. Whether the player reads the progressive frame directly off the disc, or recreates it with a deinterlacer in the digital domain, the end result is the same. What varies between the players is their video performance, and the ability to handle material that wasn?t encoded the ?standard? way. Most progressive players contain the same deinterlacing chips used in external deinterlacers like the Faroudja Native Rate, the Focus Enhancements CS-1, and the Silicon Image iScan. The major advantage the progressive player has over the external deinterlacer is that in the player, the deinterlacing can be done to the video in the digital domain, using the digital video directly out of the MPEG decoder, without any intervening analog conversions. If you have a good quality external deinterlacer/scaler with a digital vidoe interface combined with a DVD player that has a compatible digital output, they provide no-compromise deinterlacing and scaling completely equivalent to a good progressive DVD player with the same chipset.

      DVD audio connectors

      Typical DVD player has typically stereo audio output connectors in a form of pair of RCA connectors. This is the connector type which you can use to connect your DVD player audio to a TV set, normal stereo amplifier or old Dolby Surround home theater amplifier.If you have a more modern home theater amplifier to get the best sound quality with a modern home theater amplifier, the digital audio interface is the preferred connection method. With digital connection you can enjoy the benefits of advanced digital sound formats like Dolby Digital (DD) and DTS. The digital interface come in to flavours: electrical (RCA connector) and optical (optical fiber connector). Those both interface work exactly in the same way in the practice (they transfer the exactly same digital audio data). Just check that your amplifier and DVD player has the same connector type and get a suitable cable for the connection. A 75 ohm video cable with RCA connectors is the right cable type for electrical interface (you do not need any expensive"digital" cable). If you use optical interface, you need to buy suitable fiber cable for this. If the conector types in your amplifier and DVD player do not match each other, you need to buy a digial audio interface connecvertor for doing the conversion between electrical and optical interface.Some DVD players have also analogue 5.1 channel connectors (usually in the form of six RCA connectors). Those connectors are deisgned to be wired to home theater amplifiers that have 5.1 channel analogue inputs, but no suitable digital interface. All DVD players have analog 2 channel outs which you would be suitable to use with any normal stereo system or Dolby Pro Logic surround system. What that output provides depends on what theproducer of the DVD wants to do. For many, if not most movies thathave DD 5.1 tracks, the analog outs will provide a 2 channel signalwith Dolby Surround encoded information down mixed from the 5.1 trackor from a separate DD 2 channel track. Your Dolby Pro Logic decoder would then produce surround sound (not as good as originalk 5.1 channel sound, but better than normal stereo). The bottom line is you shouldn't really 'lose' any of the channelswith your Dolby Pro Logic system and a DVD player. But it won't be the sameeffect as a full Dolby Digital system would provide, and it probably won't sound quite as good. Some music DVDs have PCM stereo tracks and/or DD 2 channel and 5.1channel tracks. Those different tracks could be in some cases mixed differently (2 channle version for stereo playback and 5.1 channel version for surround use).The general preferred order of the connections selection for DVD to amplifier connection (from best to worst):

      • Digital connection (electrical or optical)
      • Analogue 5.1 channel connection
      • Analogue stereo audio connection
      Select the best audio connection that is supported by your system.

    HD-DVD

    Current DVD-Video does not directly support HDTV. The reason for this is that no digital HDTV standards were finalized when DVD was developed. In order to be compatible with existing televisions, DVD's MPEG-2 video resolutions and frame rates are closely tied to NTSC and PAL/SECAM video formats. DVD does use the same 16:9 aspect ratio of HDTV and the Dolby Digital audio format of U.S. DTV. The current DVD-Video spec covers the standard definition TV modes 640x480 and 704x480 at 24p, 30p and 60i.DVD-Video does not currently support HDTV video content. DVD players will soon have digital outputs, since the DVD Forum finalized specifications for supporting 1394 and HDMI in 2002. When the DVD stream recording (SR) format is finalized, DVD-SR players may be usable as "transports" that output any kind of A/V data (even formats developed after the player was built) to different sorts of external displays or converters.It seems that there is coming a new DVD format for HDTV resolution video. As of September 5th, 2002, there are no less than FOUR candidate specifications that have been proposed to the DVD Forum for high-definition DVD (HD-DVD). It is expected that there will be quite long time until HD-DVD will be on the shops. HD-DVD "technology demonstrations" being made by various companies do not mean that HD-DVD is around the corner.


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