The proportion of width to height of a video transfer. The most commonly found aspect ratio on DVD is 1.85:1 and represents an image that is 1.85 units wide and 1 unit high. The aspect ratio of a standard television is 1.33:1 and is often expressed as 4:3.
16x9 Enhanced (also Anamorphic, 16:9 Transfer)
The image on VHS tapes (and television) has traditionally been stored as a 4x3 shape even when in the widescreen format commonly found on VHS Special Editions known as Letterbox. To capture the entire scope of a film, movies are originally recorded in widescreen and present cinema audiences with an enhanced viewing experience. The advent of DVD introduces this concept to Home Cinema. 16x9 Enhancement simply means that the video transfer or image of the DVD is recorded as an image that is 16 units wide by 9 units high (hence 16x9 or 16:9) rather than the traditional 4x3.
When viewing an Anamorphic DVD on a standard TV, 2 things can occur depending on the hardware configuration. Firstly, and most likely the preferred option, is for the DVD player to convert the Anamorphic transfer into Letterbox by shrinking it to fit in the screen and placing black bars on the top and bottom of the image. The alternative is to retain the height of the transfer, but shrink the width to fit the television, resulting in an undesirable 'squished' appearance.
The process of taking the original source materials such as video, audio, and text, to produce high definition transfers that are then compressed onto DVDs ready for playback.
Blu-ray discs are the successors to DVD featuring a significant increase in storage capacity allowing for high definition video and audio. Blu-ray derives its name from the blue-violet laser used to read and write to the disc.
Blu-ray supports 720p, 1080i and 1080p HD video and introduces 7.1 audio mastering, plus lossless DTS HD and Dolby TrueHD audio formats. A Blu-ray Disc (BD) can hold up to 50GB worth of data and offers the most advanced copy protection, backward compatibility with the current DVD format, superior connectivity and advanced interactivity. A Blu-ray Disc player (such as the PlayStation 3) is required to play discs of this format.
Blu-ray competed with rival format HD DVD to become the leading carrier for high-definition content. However, in February 2008, Toshiba abandoned the HD format, announcing it would no longer develop or manufacture HD DVD players.
Also known as 'scenes', a DVD movie can be broken up into sections much like the chapters of a book, that can be accessed quickly and easily via the DVD menu or remote control.
DVD discs can come in a variety of storage capacities:
- DVD-5: Single Sided, Single Layer DVD - can store roughly 133 mins of video
(4.7GB, 7 times more than a regular CD)
- DVD-9: Single Sided, Dual Layer DVD - can store roughly 4 hours of video
(8.5GB storage capacity )
- DVD-10: Double Sided, Single Layer DVD - 133 minutes
(9.4GB) 4.7GB of storage on either side so 9.4GB storage in total.
- DVD-18: Dual Sided, Dual Layer DVD - roughly 8 hours of video spread on two sides
(17GB of storage)
Dolby Digital (Also Known As AC-3)
Dolby Digital is the standard DVD sound format and is capable of containing up to 6 sound channels comprising of 5 normal speakers (left, centre, right, left surround and right surround) plus a subwoofer, hence the common term "5.1". A Dolby Digital audio track doesn't necessarily feature the maximum 6 available audio channels - a track can range from mono (one speaker), stereo and many other multi-channel variations up to 5.1. A Dolby Digital decoder is required to take advantage of a multi-channel Dolby Digital audio track.
Dolby Digital EX 5.1
This is an extended version of Dolby Digital 5.1 that utilises a 6.1 speaker setup. However, it is not a true 6.1 system like DTS ES as the audio channel for the centre rear speaker is matrix encoded within the left and right surround channels and therefore cannot accurately be described as a true 6.1 format. An expensive Dolby Digital EX decoder is required in order to take advantage of this audio format.
Dolby TrueHD is an advanced lossless multi-channel audio codec intended primarily for high-definition home-entertainment equipment such as HD DVD and Blu-ray Disc. Dolby TrueHD uses Meridian Lossless Packing (MLP) as its mathematical basis for compressing audio samples. MLP was used on the earlier DVD-Audio format, but details of TrueHD and DVD-Audio differ substantially. A Dolby TrueHD bitstream can carry up to 14 discrete sound channels. Sample-depths up to 24 bits/sample and audio sample-rates up to 192 kHz are supported.
One of the rival sound formats to Dolby Digital is called DTS (Digital Theatre Systems). DTS is another six channel (5.1) format that requires much more storage space on a disc than Dolby Digital and is able to operate at a higher bitrate. Most consider the audio quality superior to Dolby Digital and DVD enthusiasts favour DVDs featuring a DTS audio track. Once again a DTS capable decoder and DVD player are required to utilise this audio format.
An acronym for Digital Versatile Disc, which is an optical-disc technology developed by the DVD Consortium, a collection of 10 companies who contributed to the DVD standard and specification. There are five specified DVD disc varieties: DVD-ROM, DVD-Video, DVD-Audio, DVD±R (recordable/write once), DVD±RAM (re-writable).
DVD discs can also be played on DVD-Video equipped personal computers. DVD-ROM are computer-specific features that are added to DVD-Video discs that can only be played through DVD-ROM drives. These features can be screenplays, links to web sites (often called "web links"), advanced interactive games and text based information. These features are not accessible via DVD-Video players; one must have a DVD-ROM drive or DVD device with DVD-ROM capability.
Listed below are some of the most commonly found DVD cases:
- Amaray Case (aka Keep Case) - The most common type of plastic storage case for DVDs and is capable of holding up to 2 discs with the addition of a 'flippable' insert.
- Jewel Case - Another less popular means for DVD storage that consists of a hard slimline plastic case, used mostly for CD and DVD-Audio titles.
- Snapper Case - A cheaper cardboard DVD case that has mostly been phased out of production due to it being highly unpopular among consumers. Its name is derived from the way a plastic latch is 'snapped' shut to close the case.
Some production runs of dual-layered DVDs result in a manufacturing defect where the adhesive used to bond the two layers is either sub-standard or improperly applied. When the disc is new, the 'DVD Rot' is not visible and the error correction capabilities of DVD players compensate for the defect. Over time, however, the layers separate and the 'DVD Rot' increases in severity to the point where the disc becomes unplayable and may also become visible under certain lighting conditions. Even if one such defective disc were to be stored under the most ideal conditions, and never touched, it would still become unplayable over time.
Dual Layer / RSDL
Reverse Spiral Dual Layer (RSDL) allows longer movies to fit onto one side of a DVD, allowing continuous play for longer programs and no need to "disc flip". There is usually a noticable pause during the layer change as the player's laser adjusts to read the second layer. The length of the pause varies from disc to disc and player to player. Dual-layer discs are easy to spot because it is gold in colour, versus the silver shimmer of a single layered disc.
Hidden features on a DVD that can be discovered and accessed by navigating the menu system of the disc.
Before the advent of dual layer discs, movies that could not fit on a single layer were often split over both sides of the disc. This became an unpopular means of DVD authoring as the consumer was required to turn the disc over in the middle of watching the film, hence the term 'flipper'. This method of DVD production has mostly been phased out.
HD DVD, or High-Definition Digital Versatile Disc, is a high-density optical disc format designed for the storage of data and high-definition video. HD DVD was designed principally by Toshiba, and was envisaged to be the successor to the standard DVD format.
HD DVD could support 720p, 1080i and 1080p HD video and introduce 7.1 audio mastering, plus lossless DTS HD and Dolby TrueHD audio formats. It has a data capacity of up to 30GB and was backwards compatible with DVD. A HD DVD player was required to play discs of this format.
The HD DVD format competed with rival Blu-ray to become the leading carrier for high-definition content. However, in February 2008, Toshiba abandoned the format, announcing it would no longer develop or manufacture HD DVD players.
An interactive menu is a series of screens or pages (very similar to a web site) that allows the viewer to navigate and select different features on a DVD disc. The menus are used for scene selections, video and audio setup and accessing special features. As DVD progresses the menu systems become increasingly more elaborate, especially for high profile titles, with striking graphics, music and animation.
Before widescreen TV's and Anamorphic DVDs became available, Letterboxing was used in order to fit a widescreen movie into a standard 4:3 screen. This method of authoring involves shrinking the widescreen video transfer to fit into a 4x3 area and adding black panels above and below the image. This process is still used today on VHS and also on DVD where the original transfer is unavailable or because smaller distributor's lack the resources to create an anamorphic transfer.
Macrovision is a copy-protection technique intended to keep you from making copies of DVDs with your VCR. It works by continuously adjusting the video signal level that results in a recording where the brightness of the picture continuously fluctuates between light and dark, and the colour levels fluctuate between oversaturated and washed out. Macrovision "encoded" DVDs contain a bit of data that tells the DVD player to activate its internal macrovision circuitry in order to prevent copying.
Multiple Audio Tracks
A DVD disc can contain up to eight audio tracks. You can select which of the eight language tracks through the DVD menu or via the remote control. The value of such tracks is that they can be accessed instantly, and provide additional synched audio material in addition to the main soundtrack. Common uses are for foreign languages, alternate soundtracks, isolated musical scores or audio commentaries by the director, cast & crew or others associated with the material.
Multiple Video Tracks
Another of DVD capabilities is its ability to show different angles or versions of a scene. These multiple video streams can be accessed instantly via a player's Angle function and DVD discs can contain up to 8 separate video streams. This feature has been relatively under-utilised to date however as Hollywood continues to embrace the format - there are very few DVDs that utilise this feature to date.
National Television Systems Committee. The colour TV broadcast system used in the US, Canada and Japan. An NTSC picture is made up of 525 horizontal lines and has inferior picture quality in comparison to the PAL system.
Please note: All DVD players sold in PAL countries (Australia) play both NTSC & PAL discs, but your TV monitor must be NTSC compatible in order to view in full colour. Please refer to your user manual or manufacturer to determine compatibility.
A slim outer cardboard case with openings in the top & bottom for the removal of the DVD case within.
Phase Alternating Line. The colour TV broadcast system used in Australia, UK & Europe. A PAL picture delivers a better quality picture than NTSC due to its 625 horizontal lines (sharper picture and better colours).
Please note: DVD players sold in NTSC countries (United States, Canada and Japan) may not be compatible with the PAL system, preventing playback. Your TV set will also need to be PAL compatible in order to view these DVDs in colour. Please refer to your user manual or manufacturer to determine compatibility.
Pan & Scan
One method of converting a widescreen movie to fit in a standard 4:3 television is known as letterboxing (described above) and the other commonly found process is Pan and Scan (also known as Panning and Scanning). To retain a fullscreen 4x3 image, the most important part of each scene is chosen and the left and right edges of the scene are cropped. Obviously, this process results in a loss of some data and does not fully represent the film as it was intended to be portrayed by the director. As such, DVD enthusiasts are not overly fond of DVDs authored via this method.
PCM sound is an uncompressed two-channel stereo or mono soundtrack that requires more disc space due to its uncompressed nature.
Regional Coding - DVD
A security system introduced to DVD at the request of Hollywood's major studios to ensure that DVDs released and sold in one region will not play on DVD machines in other regions. Movie distributors therefore maintain control over release dates of their films, as well as enabling discs to be produced that conform to different censorship laws, language and subtitle requirements. When a DVD disc is manufactured, a region code is applied at the authoring stage such that the final disc will play only on those players distributed in the designated world region.
There are 8 region codes in use throughout the world:
- Region 1 - Canada, United States, U.S. territories, Bermuda
- Region 2 - Europe, Western Asia, Egypt, Japan, Lesotho, South Africa, Swaziland, British overseas territories, French overseas territories, Greenland
- Region 3 - Southeast Asia, South Korea, Hong Kong, Macau, Taiwan
- Region 4 - Australia, New Zealand, Oceania, Central and South America, Caribbean, Mexico
- Region 5 - Africa, Central and South Asia, Belarus, Mongolia, North Korea, Russia, Ukraine
- Region 6 - Mainland China
- Region 7 - Reserved for future use (found in use on protected screener copies of MPAA-related DVDs and "media copies" of pre-releases in Asia)
- Region 8 - International venues such as aircraft, cruise ships, etc.
Additionally, DVDs may be encoded as Region 0, or Region All, which means that they are compatible throughout regions 1-6. Similarly, some DVDs region encoding may be listed as 1,2,3,4,5,6 which also indicates compatibility in all regions.
Regional Coding - Blu-ray
Blu-ray discs are region coded, similar in principle to the DVD region codes, although the used geographical regions differ.
- Region A - Americas, East and Southeast Asia, U.S. territories, Bermuda
- Region B - Africa, Europe, Australia, New Zealand, Oceania, Middle East, Netherlands, British overseas territories, French territories, Greenland
- Region C - Central and South Asia, Mongolia, Russia, China
Some Blu-ray discs may also be multi-region, ie A, B and C, which means they are compatible in all regions.
Regional Coding - HD DVD
There is no region coding in the HD DVD specification, which means that titles from any country can be played in players in any other country.
Regional Coding Enhancement (RCE)
RCE 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.
SDDS (Sony Dynamic Digital Sound)
A multi channel audio format containing up to 8 discrete sound channels and capable of a high data rate in excess of 1280 kbps. SDDS is available only in cinemas and Sony currently has no plans to make it available for home use.
A slim outer cardboard case with an opening in the right-hand-side for the removal of the DVD case within.
A DVD can feature up to 32 subtitle tracks that can be turned on or off and selected via the DVD menu or remote control.
Taking Care Of Your Discs
Because a DVD consists of two sides glued together (each a mere 0.6 mm thick), it can be susceptible to damage from bending and/or twisting. Also, though DVD error-correction encoding is nearly ten times better than those of audio CDs, because of DVD's much higher compression ratio, shorter pit length and narrower tracks, severe scratches can create occasional problems in playback.
A good rule of thumb is to handle a DVD more carefully than a CD: Make contact only with the center hole and the outside edge of the disc. When removing a DVD from its case, press the button on the center hub and push downward. Using your other hand, gently remove the disc by its outer edge. Never remove a DVD from its package simply by prying up the outer edge of the disc.
Single-sided discs should be inserted into the player with titles/artwork facing up. Make sure the disc is seated properly inside the player before closing the tray.
Clean disc only with a damp, non-abrasive, lint-free cloth. Do not use any harsh or abrasive chemicals or cleaning agents. Wipe the disc carefully in a straight line from the inside hole to the outer edge. Never use a circular motion when cleaning a disc.
Do not stack your DVD discs. Always store the disc inside its protective case when not in use. And, of course, keep your DVD's away from extreme heat, such as the back window of a car or the trunk area -- and keep them out of direct sunlight.
THX is not another sound format, but a set of quality control standards set by Lucas films. The full effect of a THX mastered disc is delivered using equipment that has been marked with the THX seal of approval. Even without THX equipment, a THX DVD is generally thought to be of better quality to sound and video, due to the strict THX codes of production and replication.» back to top