STEVE'S HOME THEATER GLOSSARY

Anamorphic DVD	Some DVD movies are produced in a way that results in a higher resolution image when viewed with a widescreen television (typically an HDTV). Also referred to as "enhanced for 16x9 televisions," it works by squeezing a wide screen movie into the same frame that is displayed closer to "square" on normal televisions. In the setup menu of DVD players you tell it what type of TV you have, 4x3 or 16x9. If you choose 4x3, the DVD player will reduce the height of anamorphic DVD's so that everyone doesn't look skinny! For more information, click here.
Aspect Ratio	The ratio of the width to the height of a television picture or movie. Normal NTSC televisions have an aspect ratio of 1.33 (or "4 x 3"), while HDTV's have an aspect ratio of 1.78 (or "16 x 9"). Motion pictures usually have an aspect ratio of 1.85 (Standard) or 2.35 (Panavision). To make a movie watchable on a regular television means that either the movie has to be scaled down so that its entire width fits on the screen (letterboxed), or simply chop the sides off (pan & scan).
Dolby Digital	A multi-channel digital sound format used in film, laserdisc, and DVD. It will probably also be the standard (eventually) for HDTV. Material encoded in Dolby Digital usually specifies how many channels of audio are present. The most common flavor is Dolby Digital 5.1, which refers to five normal channels of audio (left front, right front, center, left rear, and right rear) and one subwoofer channel. While Dolby Digital 2.0 only provides two channels of audio, it is typically still encoded in Dolby Pro Logic, so a form of surround sound can still be achieved.
Dolby Pro Logic	A non-digital precursor to Dolby Digital. Most prerecorded VHS tapes are encoded with this type of surround sound. From the two channel output of a hi-fi VCR or stereo TV, a center and rear channel are decoded, though the way the extra channels are derived means the center and rear channels aren't always very "discrete," depending on the equipment. Typically the single rear channel signal is fed to two rear speakers.
dts	Digital Theater Sound. First used on Jurrasic Park in the theaters, Digital Theater Sound is available on certain laserdiscs and DVDs. In order to get dts sound from a dts-encoded DVD, you must have a DVD player capable of outputting dts as well as a receiver that can decode dts. It is generally considered superior to Dolby Digital, but the difference can be subtle. Also, there is no standard "bit rate" for either dts or DD, so that can make comparisons difficult as well.
DVD	Depending on who you ask, DVD either stands for Digital Versatile Disc, Digital Video Disc, or nothing at all. In any case, all DVD's are the size of CD's and can contain movies, computer data, or soon, audio. In the context of home theater, a "DVD" refers to a movie or other video content.
DVD-18	Refers to a dual-layer, double-sided DVD. They are called DVD-18's since they hold up to 18 gigabytes of data. DVD-18's can contain up to 8 hours of video, so, for instance, an entire mini-series could fit on a single disc.
HDTV	High Definition Television. The digital television standard that replaces the current NTSC standard. Unfortunately there are 18 formats that are all considered HDTV, so calling it a "standard" is a bit of a stretch. HDTV normally has an aspect ratio of 16x9, has up to 1080 lines of resolution, and is transmitted at a rate of up to 19 million bits per second. The various HDTV formats are identified by the number of lines, followed by whether the signal is interlaced or progressive scan. So, 1080i means 1,080 interlaced lines and 720p means 720 progressive scanned lines. While the FCC had mandated that the network affiliates in the top 30 markets "must" be broadcasting some HDTV by November of 1999, many stations simply ignored them. Since HDTV sets are still very expensive and there's very little programming available, it may be quite a while before HDTV becomes commonplace.
Interlaced video	The way a normal television draws each frame of video is called interlacing. Every 1/60th of a second, half the scan lines are drawn on the screen. First, the odd-numbered lines are drawn, then the even-numbered lines are drawn, and so on. When this type of video is projected at home theater sizes (above 40 inch screens or so), the lines are not only visible, they appear to flicker. Progressive scan DVD, line doublers, and HDTV all attempt to solve this by either drawing the lines consecutively or just drawing more of them.
Letterboxed	When movies are converted to home formats such as broadcast TV, VHS, laserdisc, and DVD, there are a few options available to fit a wide screen movie onto a normal television. A letterboxed movie is shrunk down so that its entire width fits on the screen. The advantage is that you get to see the entire picture as it was seen in the theater. The disadvantage is that it can make the picture quite small. Also, some people find the black bars at the top and bottom of the screen objectionable. Movie purists always prefer letterboxed over pan & scan.
Line Doubler	A device (either inside or outside of a television) which takes an NTSC video signal and attempts to eliminate the flicker that results from interlaced video.
NTSC Video	The National Television Standards Committee came up with the U.S. standard for how television is broadcast and received. This is the TV format that has been the authorized FCC standard since 1954 and will someday (hopefully) be replaced by HDTV. Other countries use formats such as PAL. (stands for Phase Alternate Lines if you were wondering)
Pan & Scan	The process of chopping the sides off of a widescreen movie in order for it to "fill the screen" of a regular television. The advantage is that things on the screen aren't as tiny, which can be an issue on a small TV. The disadvantage is that almost half of the original picture can be missing. While the "pan" in Pan & Scan refers to the fact that when the video is produced, someone tries to fit the main action or character on the screen, many times other characters or events end up simply gone.
Progressive Scan DVD Player	A few DVD players can output a type of signal known as "progressive scan." Basically this means that if you have the right kind of TV (typically also capable of HDTV), you can watch movies on DVD without the annoying flickering lines that you get with normal NTSC television. There are other ways to help eliminate scan lines, such as line doublers. While HDTV's typically come with internal line doublers, though, many are not as adept at converting 24 frame per second movies into a progressive scan format. Note that "progressive scan", "line doubled", and "non-interlaced" all refer to the fact that scan lines are drawn consecutively instead of "odd lines, then even lines."