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DVD Glossary

A type of widescreen display format optimized for playback on a TV with 16:9 aspect ratio.

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

Component video signals:
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.

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 regular broadcast TV. A DVD player's standard RCA-type video jack 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, you should probably bypass the VCR altogether and connect your DVD player directly to your TV.

Digital output:
All DVD players include at least one digital audio output for sending the Dolby Digital bitstream to a Dolby Digital decoder (either a stand-alone decoder or one built into an A/V receiver). Digital data transfer offers extremely wide bandwidth and immunity to RF interference.

The two most common types of digital output are coaxial and optical. Both types require a special cable to connect to the digital input of your Dolby Digital receiver or decoder. Note: most DVD players do not include digital cables.

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're specifically looking for titles with a 5.1 soundtrack, you should carefully read each 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 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 amount of audio data by a factor of about 10:1.

DTS (Digital Theater Systems):
DTS is an established multichannel audio format in movie theaters, but a relative newcomer to home theater. Like Dolby Digital, DTS is a 5.1-channel format. The compression scheme used in DTS "throws away" significantly less audio data than Dolby Digital, so it should sound better, but so far A-B tests have been inconclusive.

Although DTS-compatible DVD players and receivers are becoming more common, the number and availability of DVD titles with DTS soundtracks is still limited.

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

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).

Some DVD players can display an on-screen "bit rate meter" — a visual measure of data flow in the form of a bar graph. MPEG stands for Moving Picture Experts Group.

PCM (Pulse Code Modulation):
The digital audio signal format used for Compact Discs. Digital outputs on DVD players are often labeled "AC-3/PCM" because they can send either the AC-3 (Dolby Digital) 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 MiniDisc's ATRAC; video examples include digital satellite TV and DVD. This approach is based on sophisticated research into how we perceive sounds and images.

Perceptual coding omits "imperceptible" sound and picture data which is redundant or which is judged to be masked by similar information. In the case of DVD, by "throwing away" a lot of redundant and unnecessary information, it's possible to fit multiple versions of a movie on a single 5-inch disc.

Region codes:
The movie industry insisted that the DVD standard include codes which would limit playback to a specified geographical region. This was done because theater and home video releases of movies do not occur simultaneously worldwide. For example, a movie may be released on video in the U.S. just as it's first appearing in theaters in Europe.

DVD players have a built-in region code lockout feature, while the DVD discs may or may not contain a code (region codes are optional on DVD software). 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. The region code for USA/Canada is "1".

Signal-to-Noise ratio (video):
This ratio is a measure of the content portion of the video signal in relation to the noise 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.

Basically, a S/N ratio tells you how "clean" a video signal is. Because of the way they process signals, digital video formats like DVD and digital satellite TV are extremely clean. A standard VHS VCR may have a S/N spec in the low 40s; a laserdisc player, the low 50s. DVD is rated to deliver a S/N ratio of 65 dB.

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