Car Video Glossary
The features and terms to know about in-car video
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Active Matrix Display
A type of flat-panel display in which the screen is refreshed frequently for superior resolution. The most common type of active matrix display is based on technology known as TFT (thin film transistor). TFT technology provides the best resolution of all flat-panel display techniques. The two terms are often used interchangeably.
The ratio between the width and height of an image or display screen. The NTSC television standard is 4:3 (1.33:1). However, 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 huge 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 version on the other.
For monitors with standard 4:3 screens, movies (whether on disc or tape) must be re-formatted to either "letterbox" or "pan-and-scan."
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 displayed. Letterboxing is much more common on DVD movies than VHS videos.
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.
Composite Video Output
A video signal in which the brightness and color portions of the signal are combined. A standard RCA-type video jack provides a composite video signal.
Most DVD players and some DVD receivers include at least one digital audio output for sending the Dolby Digital or DTS bitstream to a compatible decoder. Digital data transfer offers extremely wide bandwidth, immunity to radio frequency (RF) interference, and an easy one-cable connection. 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 a Dolby Digital/DTS-equipped surround processor.
A discrete, multichannel digital audio standard offering enhanced sonic realism. Dolby Digital is normally associated with 5.1-channel surround sound. A 5.1-channel system offers five full-bandwidth channels (including true stereo surrounds), plus a "low frequency effects" subwoofer channel.
Dolby Digital 5.1 soundtracks will in most cases provide the most satisfying sound quality for a mobile theater system, though it is only one of several possible variations. A "Dolby Digital" soundtrack can mean anything from 1 to 5.1 channels.
Unless your DVD player or receiver has its own built-in Dolby Digital decoder, you'll need to connect your player to asurround processor that can take the digital bitstream from the disc and convert it into 6 channels of audio.
If you're looking specifically 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.
If you don't have a Dolby Digital system, you can still enjoy excellent Pro Logic® or stereo sound. All DVD receivers and 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 surround processor or an in-dash receiver with Dolby Pro Logic decoding. The decoder converts the matrixed 2-channel signal back into three channels of full-range sound (left front, center, right front), and a fourth mono channel of limited bandwidth that is shared by two surround speakers.
Digital Theater Systems (DTS®)
DTS is an established multichannel audio format in movie theaters. Like Dolby Digital, DTS is primarily 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, side-by-side comparisons have been inconclusive.
Nearly all new DVD players are DTS-compatible; many in-dash receivers and most surround processors include DTS decoding. Still, the number and availability of DVD titles with DTS soundtracks remains somewhat limited.
A music-oriented DVD format that can carry up to 6 channels of 96kHz/24-bit audio (music for 5.1-channel mobile theater systems), or 2 channels of ultra high-resolution 192kHz/24-bit audio. Most DVD-Audio discs also carry Dolby Digital or stereo soundtracks for playback on DVD players that lack DVD-Audio decoders. A DVD-Audio disc may also contain liner notes, lyrics, menus, and still pictures that can display on your video monitor. DVD-Audio never caught on commercially, and DVD-Audio discs are relatively rare.
The DVD/CD player plays DVD movies (and may play DVD audio discs), but does not include a built-in AM/FM tuner. Some models send the video signal to an outboard backseat monitor for on-the-go viewing, while other models include a built-in screen for stationary viewing. Its audio signal is sent to an in-dash receiver or to external amplifiers.
Versatile DVD receivers have built-in AM/FM tuners, and can play DVD video and CD audio discs. Most will play MP3, WMA, or AAC files that have been burned onto CDs or DVDs and feature flash memory inputs, like SD card slots and USB inputs. Alomost all models include a built-in screen for viewing while parked and can send the video signal to an outboard, backseat monitor for on-the-go viewing.
A screen that translates a video signal into a picture. In car systems, a monitor can be mounted in a seatback or headrest, floor console, or the ceiling of the cabin. A TV is a monitor with a built-in VHF/UHF tuner.
Special four-pin connectors that carry the chrominance (color) and luminance (brightness) portions of the video signal separately, for improved color accuracy and reduced distortion
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). Here's how 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 are extremely clean. A standard VHS VCR may have a S/N spec in the low 40s, while DVD is rated to deliver a S/N ratio of 65 dB!
A device which can decode (or simulate the effect of) multi-channel soundtracks found on DVDs and videocassettes. These processors usually send separate audio information to right front, center, left front, right rear, and left rear speakers, with a separate signal for a subwoofer. In a car's confined listening environment, the effect of a fully-realized multi-channel audio/video system can be stunning.
A type of LCD screen that uses thin film transistor (TFT) technology. Each pixel is controlled from 1 to 4 transistors, giving TFT screens the best resolution of all flat-panel displays.
A Toslink connector is a specialized plug found on many optical cables. Optical cables permit distortion-free connections from a digital source to a digital recorder or digital receiver/processor. Since the signal is carried optically rather than electronically, an optical cable is virtually impervious to magnetic or electrical interference.
A conventional TV tuner receives UHF and VHF television broadcasts (from channels 2 to 69), providing local programming for a mobile video system. Products offering television programming from satellite services are also available.
Video Cassette Player (VCP)
A video cassette player (VCP) is designed strictly for playback — it does not have the ability to record.
Virtual Surround Sound (VSS)
This feature makes a two speaker system sound as though it includes rear speakers; the "virtual" rear speakers allow you to enjoy a surround-like effect. It is for use with Dolby Digital DVDs only.