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 Video
  DVD Glossary

ASPECT RATIO | BITSTREAM | DTS | DOLBY DIGITAL | LETTERBOX |


16:9
See aspect ratio.

3-2 pulldown processing
A process which improves the look of film-based video when it is converted to progressive-scan. The frame rate for film is 24 frames per second (24 fps), and that's the way movies are stored on DVD. The frame rate for broadcast video in the U.S. is 30 frames per second (or more precisely, 60 fields per second).

So, one of the primary tasks of the MPEG decoder inside every DVD player is to take the 24 fps data stored on the DVD and convert it to 60-fields-per-second video for TV viewing. Since 24 doesn't divide evenly into 60, a process called "3-2 pulldown" is employed, where 3 video fields are created from the first film frame, then 2 fields from the next frame, then 3, then 2, 3-2-3-2-3-2, etc. The result is 60-fields-per-second interlaced-scan video, and that's the end of the story for non-progressive-scan DVD players.

Progressive-scan DVD players add an important additional step to create a better-looking picture — they generate a progressive-scan video signal through a process called de-interlacing (sometimes called "line-doubling"). The de-interlacer's first task is to look at the interlaced video signal as it leaves the MPEG decoder and determine whether its original source was 24-frame-per-second film or 30-frame-per-second video. The original frame rate determines the type of processing necessary to create an optimized progressive-scan signal.

Advanced de-interlacers detect 3-2 pulldown on film-based sources and apply 3-2 pulldown processing to create a 60-frame-per-second progressive-scan signal that maintains the original frame integrity, with no mixing of non-matching fields. This processing eliminates jagged edges on still objects and moving angled lines, producing video with the naturally smooth look of film.



4:3
See aspect ratio.

Anamorphic
A type of widescreen display format commonly found on DVD movies. It is optimized for playback on a TV with 16:9 aspect ratio (or TVs with a "vertical squeeze" viewing mode like Sony's 16:9 Enhanced). On a standard TV, anamorphic material looks horizontally squeezed. Anamorphic DVDs are often labeled on their cases "enhanced for 16x9 televisions," "enhanced for widescreen televisions," "16x9 anamorphic," or "anamorphic widescreen."

An anamorphic widescreen DVD has significantly higher resolution than a letterboxed widescreen DVD. For example, for a film shot in the commonly-used 1.85:1 aspect ratio, a letterboxed DVD presentation uses only 345 vertical scan lines (the remaining scan lines are taken up by the horizontal black bars above and below the image). That same film in anamorphic widescreen will use anywhere from 460 to the full 480 scan lines. See aspect ratio for more information.

Aspect ratio
The shape of an image or display screen expressed as a width-to-height ratio. The NTSC analog television standard is the rather square-like 4:3 (1.33:1), while anamorphic DVDs and High-definition TV broadcasts are in the wider 16:9 (1.78:1) shape. Most movies are made for the wide screen of a theater, and are originally displayed at the wider ratios of 1.85:1 or 2.35:1.

DVD's data storage capacity makes it possible to include multiple versions of a movie on a single disc. It's not unusual for a DVD disc to feature a Standard (4:3) version on one side and a Widescreen (16:9) version on the other.


For TVs with standard 4:3 screens, movies  must be re-formatted to either "letterbox" or "pan-and-scan." If you usually rent or buy VHS movies, you're probably used to pan-and-scan versions, which are preceded by this message: "This film has been modified from its original version. It has been formatted to fit your screen."

Pan-and-scan provides an image with full height, but shows a central "window" that is only 75% of the original widescreen width. What this window shows is determined by the preferences of the person(s) performing the film-to-disc transfer.

Widescreen DVDs will be either letterboxed or anamorphic. For letterboxed DVDs, the player uses a "letterbox filter" that adds horizontal black bars to the top and bottom of the picture. What you see is a short, rectangular image that maintains the movie's full original width.

Anamorphic DVDs deliver a higher-resolution widescreen presentation. For an explanation of anamorphic widescreen, see anamorphic.

Bitstream
A signal that contains digital data in its undecoded state. An example is the signal that's fed through a DVD player's digital output(s) coax or optical, which carries Dolby Digital, DTS, or PCM signals.

Chrominance
The color information portion of a video signal that describes an image's color shade and vividness.

Component video
A video signal in which the brightness (luminance) and color (chrominance) portions of the signal are processed separately. Component video signals provide greater color accuracy than S-video or composite signals.

Nearly all new DVD players and many new TVs include 3-jack component video connections (green, blue, red).

Why is component video superior to S-video? Where S-video separates the luminance and chrominance portions of the signal, component video goes a step further and splits the chrominance portion into two components. The benefits — improved color accuracy and less color bleeding — are especially noticeable on larger-screen TVs.

Composite video
A video signal in which the brightness and color portions of the signal are combined. Examples of composite video include standard VHS, laserdisc, and NTSC broadcast TV. A DVD player's standard RCA-type video jack (yellow) provides a composite video signal.

Copy protection
A system for preventing the unauthorized reproduction of copyrighted media like movies or music. The DVD format includes both digital and analog forms of copy protection. You will probably not be able to copy DVDs with your VCR. (In fact, because the copy protection system is triggered by a circuit found in most VCRs, simply playing a DVD and running the signal through your VCR will often result in a distorted picture. You should bypass the VCR altogether and connect your DVD player directly to your TV.)

De-interlacing
The process of converting an interlaced-scan video signal (where each frame is split into two sequential fields) to a progressive-scan signal (where each frame remains whole). De-interlacers are found in progressive-scan DVD players and digital TVs. More advanced de-interlacers include a feature called 3-2 pulldown processing. With TVs, de-interlacing is sometimes referred to as "line-doubling" or "upconversion."

Digital output
All DVD players include at least one digital audio output for sending the Dolby Digital or DTS bitstream to a compatible decoder (which is usually built into an A/V receiver). Digital data transfer offers extremely wide bandwidth, immunity to RF interference, and an easy one-cable connection.

The two most common types of digital output are digital coaxial (round orange or black) and optical (square black). Although a coaxial digital jack looks like a standard RCA-type audio jack, both coaxial and optical jacks require special cables to connect to the digital input of your Dolby Digital/DTS-equipped receiver. Note: Most DVD players do not include digital audio cables.

Digital-to-analog converter (DAC)
An electronic circuit that converts a series of digital "words" into a continuous analog signal. DVD players include separate DACs for audio and video.

Dolby® Digital
A discrete multichannel digital audio standard offering enhanced sonic realism. Dolby Digital is normally associated with 5.1-channel surround sound. Though this channel configuration is common, it is only one of several possible variations — a "Dolby Digital" soundtrack can mean anything from 1 to 5.1 channels.

If you are looking for titles with a 5.1 soundtrack, you should carefully read each DVD disc's packaging. Relatively few older movies with stereo or mono soundtracks will be remastered with 5.1-channel surround for DVD.

Dolby Digital 5.1 soundtracks will in most cases provide the most satisfying sound quality for a home theater system. It is referred to as a 5.1-channel system because it offers five full-bandwidth channels (including true stereo surrounds), plus a "low frequency effects" subwoofer channel.

Unless your DVD player has its own built-in Dolby Digital decoder, you'll need to connect your player to a A/V receiver or processor that can take the digital bitstream from the disc and convert it into 6 channels of audio. Dolby Digital uses a data compression technique called "perceptual coding" to reduce the original amount of audio data by a factor of about 10:1.

Downmixed audio
If you don't have a Dolby Digital system, you can still enjoy excellent Pro Logic® or stereo sound. All DVD players have the ability to take a 5.1-channel Dolby Digital soundtrack and "downmix" it to two channels, which can then be sent to a stereo TV, a stereo receiver, or to an A/V receiver with Dolby Pro Logic decoding.

DTS® (Digital Theater Systems)
DTS is a multichannel audio format. Like Dolby Digital, DTS is primarily a 5.1-channel format. The compression scheme used in DTS is far less "lossy" than Dolby Digital, so theoretically it should sound better, but few people can tell the difference.

Nearly all new DVD players are DTS-compatible; some DVD players and most new A/V receivers include DTS decoding. 

DVD-Audio (DVD-A)
A music-oriented DVD format that can carry up to 6 channels of 96kHz/24-bit audio (music for 5.1-channel home theater systems), or 2 channels of ultra high-resolution 192kHz/24-bit audio. Most DVD-Audio discs also carry lower-resolution Dolby Digital or stereo soundtracks for playback on DVD players that lack DVD-Audio decoders. A DVD-Audio disc usually also contains lyrics, menus, and related still images that display on your television.

DVD-R/RW, DVD-RAM, DVD+R/RW
See recordable DVD.

Field
In interlaced-scan video, each complete frame is split into 2 sequential fields, each of which contains half the scanning lines of the frame. One field contains the odd scanning lines, and the other field the even lines.

Frame
A complete, individual picture in a movie film. In a video signal, a frame contains all of the picture's scanning lines.

Frame rate
The rate at which frames are displayed. The frame rate for movies is 24 frames per second (24 fps). In regular NTSC video, the frame rate is 30 fps.

HDCD® (High Definition Compatible Digital)
An enhanced method of audio recording for CDs developed by Pacific Microsonics. HDCD claims to be able to capture 20-bit resolution. Although the HDCD-enhanced information can only be heard using a DVD or CD player with built-in HDCD decoding, HDCD discs are still playable on regular DVD and CD players.

Interlaced scan
An interlaced-scan video signal splits each complete picture frame into 2 sequential fields, one containing the frame's odd scanning lines, and the other containing the even lines. Interlaced scan has been an effective way to maximize our 60-year-old NTSC video system, but it is prone to problems like motion artifacts, which become more noticeable on TV screens larger than 27". These artifacts are generally reduced or eliminated by progressive-scanning.

Letterboxing
The scaling of a widescreen image to fit a standard 4:3 aspect ratio TV screen by shrinking the image so that the width fits exactly. The horizontal black bars that appear above and below the image are actually recorded with the picture, so some of the picture's vertical resolution is lost when you view it. Letterboxing is much more common on DVD movies than VHS videos.

Luminance
The brightness component of a color video signal. Determines the level of picture detail.

Meridian Lossless Packing or MLP is the data-reduction technique selected for DVD-Audio. MLP sounds better because it is a lossless data algorithm. It is not like MP3 for instance. You get back exactly what you put in, so it does not distort or change any of the audio information. MLP on average reduces the size of the file by about 50%. So, with MLP you can put 6 channels of 24/96 on the disc, and still not hit the 9.6 Mbs data limitation. MLP can also be used to simply get longer recording times onto the disc.

MPEG2
The digital video signal compression standard used for DVD. This adaptive, variable bit-rate process is able to allocate more bits for complex scenes involving a lot of motion, while minimizing the bits in static scenes. The average data rate for DVD is 3.5 Mbps (million bits/second).

MPEG stands for Moving Picture Experts Group.

Multi-language capability
DVD is designed to make it easier for movies to be distributed in multiple languages. A single DVD disc can contain soundtracks in up to 8 different languages.

In addition to multilingual dialog, a DVD also has space for subtitles in up to 32 languages. Note: the number of soundtracks and subtitles will vary from disc to disc depending on the length of the movie and whether or not other playback features are included.

Pan-and-scan
A technique for making a widescreen movie fit a standard TV's 4:3 aspect ratio by showing only selected portions of the original image. This is the standard practice on VHS videos ("formatted to fit your screen"), but is less common on DVDs.

Parental lockout
A small percentage of DVD movies include variable ratings capability. According to the movie rating level you select, the player will skip over certain scenes, playing the version that you choose from those available on the disc.

PCM (Pulse Code Modulation)
The digital audio signal format used for Compact Discs (CD). Digital outputs on DVD players are often labeled "Bitstream/PCM" because they can send the Dolby Digital or DTS bitstream from a DVD, or the PCM bitstream from a CD.

Perceptual coding
A type of data compression used in recent digital audio and video formats. Audio examples include Dolby Digital and MP3. The best example of video compression is MPEG2, which is used for DVD and digital satellite TV. These forms of data compression are based on research into how humans perceive sounds and images.

Perceptual coding omits "imperceptible" sound and image data which is redundant or which is judged to be masked by similar information. In the case of DVD, by discarding a lot of redundant and unnecessary information, it's possible to fit multiple versions of a movie on a 4.8 inch disc.

Progressive scan
Instead of splitting each video frame into two sequential fields like interlaced scan, progressive scan displays the entire frame in a single sweep. So, where a standard DVD player's 480i output displays 30 frames (60 fields) per second, a progressive-scan player's 480p output displays 60 full frames per second. Progressive-scan picture quality is more like film, with more fine detail and less flicker. Progressive-scan viewing requires a compatible digital TV.

Recordable DVD
DVD recorders function like a VCR only using recordable DVDs instead of videotape.
There are three recordable-DVD types. These three types are DVD-R/RW, DVD-RAM, and DVD+R/RW. Some of these formats use discs that can only be recorded once; others use discs that can be erased and re-recorded.
  • Write-once: DVD-R, DVD+R
  • Rewriteable: DVD-RW, DVD+RW, DVD-RAM
For more details on recordable DVD, DVD Recorders.

Region codes
The DVD standard includes codes which limit playback to a specified geographical region of the world. 

DVD players have a built-in region code lockout feature, while the DVD discs may or may not contain a code. A player will be unable to play a disc that has a different region code. Discs may contain codes for more than one region, or may not have any code, which allows them to be played on any player in any country. 

Regional Coding: The DVD regions are defined as follows:

Region 1 - United States of America, Canada
Region 2 - Europe, including France, Greece, Turkey, Egypt, Arabia and South Africa

Region 3 - Korea, Thailand, Vietnam, Borneo and Indonesia
Region 4 - Australia and New Zealand, Mexico, the Caribbean, and South America

Region 5 - India, Africa, Russia and former USSR countries
Region 6 - Peoples Republic of China

Resolution
In DVD, resolution is the number of pixels in the height and width of the picture frame. DVD resolution is 720X480.

RF Output
Used on a laserdisc player to carry the Dolby Digital signal over a coaxial cable.

RSDL
Reverse Spiral Dual Layer. A type of DVD that allows twice (8.5 GB) the ordinary amount of DVD data per side.

S-Video
A cable that carries the luminance ("Y") and chrominance ("C") on separate channels. Same as Y/C.

Sampling 
Process of creating a digital representation of an analog signal. Standard CD PCM is sampled at a rate of 44.1 kHz (44,100 "samples" of the sound are taken per second).

Signal-to-Noise ratio (video)
This ratio is a measure of the content (desirable) portion of the video signal in relation to the noise (undesirable) in the signal. As with audio, video signal-to-noise is measured in decibels (dB). The way the decibel scale works, if component A has a signal-to-noise (S/N) ratio of 20 dB and component B has a S/N ratio of 30 dB, component B will have ten times less noise in the signal than component A.

A S/N ratio describes how "clean" a video signal is. A standard VHS VCR may have a S/N ratio of 40 dB; a laserdisc player, 50 dB. DVD is rated to deliver a video S/N ratio of 65 dB.

SPDIF
Sony/Philips Digital Interface. The standard for transmitting digital data (like Dolby Digital) on consumer-grade components. Uses either a 75-ohm coaxial or TOSLINK optical cable.

Substrate
The clear material (polycarbonate) that surrounds and protects the stamped information on a DVD. The substrate is thin and helps the DVD ensure greater accuracy in the laser pick-up, because the laser is less likely to refract.

Super Audio CD (SACD)
A digital audio format developed by Sony and Philips. Instead of using PCM audio encoding like CDs, SACDs use Direct Stream Digital™ (DSD) encoding. DSD is a 1-bit technology that samples music at the rate of 2.82 million times per second, compared to standard CD's rate of 44,100 times per second. All SACDs contain a high-resolution stereo mix; many also contain a high-resolution surround mix, with up to 6 independent channels.

THX
A specification developed by Lucasfilm Ltd, designed to indicate that a product meets the minimum specifications for achieving high performance, to ensure a high-quality playback of a film or video.

Timbre Matching
Making sure that loudspeakers in a surround sound setup have equivalent tonal characteristics. This helps to ensure that sound is uniform as sound moves between speakers.

Toslink
A plastic fiber optic cable used for SPDIF (e.g. DVD optical output).

Variable Bit Rate
The flow of data being processed on a DVD can be variable, depending on the complexity of the information being processed. Fast moving, dynamic scenes require a high data rate, while a static (non-moving) image requires a lower data rate.

Widescreen
An image with an aspect ratio greater than 1.33:1. Can include aspect ratios: 1.66:1, 1.85:1, and 2.35:1.

   


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