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This Glossary is a concise collection of some of the terminology that you may confront; it is not intended to be a complete compendium of technical terms.


G

Gain

Measures the light-reflecting ability of a projection screen. The higher the number, the greater the amount of light reflected back to the viewer.

Geometric Distortion

Unnatural bowing of straight lines or other distortion of shapes, especially at the sides and corners in a TV picture.

Geometric Linearity

Ability of a television to reproduce lines, shapes, and sizes accurately.

Ghosting

1) A visual phenomenon in LCDs and other digital displays where an image moves faster than the display can redraw it, thereby leaving a trail of former versions of the image in the wake of the redrawn image Ghosting might also be called trailing or streaking. As LCDs evolve, faster pixel-response times are reducing the ghosting problem.

2) In television and in flat-panel displays such as LCDs, a shadowy ghost of a displayed image that may appear due to signal interference. DTV broadcasts can suffer from ghosting, which is sometimes called multipath.

3) CRTs that display the same image for a long period of time will eventually develop a permanent shadow burned onto the screen, called a ghost. The advent of screensavers has helped reduce the occurrence of ghosting.

Grayscale

Range of gray at different intensities from completely black to completely white. Since color information is overlaid atop black-and-white information in a composite, S-Video, and component-video signal, the ideal is to set the entire range of the grayscale as close to the standard of 6,500K as possible to preserve color fidelity.

Grayscale Variation

The average variation above or below 6,500K, measured on the grayscale from 20 to 100 IRE in 10-IRE increments.

H

Hanging Dots

An artifact of composite video signals that appears as a stationary, zipper-like, horizontal border between colors.

HDCP

High-bandwidth Digital Content Protection. Copy-protection scheme developed by Intel to be used in conjunction with DVI and HDMI connections.

HDMI

The newest and currently the best type of cable connection for your HDTV is HDMI (High-Definition Multimedia Interface). An all-digital interface, HDMI carries both high-resolution video and uncompressed multichannel audio through a single cable. Use it to connect any digital audio/video source (set-top box, DVD player, PC, video game system, or AV receiver) with a compatible digital audio and/or video monitor (HDTV). It is an alternative to component video, separate video, DVI, coaxial, and other forms of connector interfaces, and is primarily used for transmitting video in high definition. Incorporates HDCP digital copy protection.

HDMI 1.3

HDMI 1.3 is a new technology standard that roughly doubles the data-carrying bandwidth of HDMI cable from 5 Gbps to 10 Gbps. In order for this to happen, your HDMI input/outputs and HDMI cable must all be of the 1.3 standard. The extra data capacity enables even better picture (a wider range of colors can be displayed) and sound (more audio formats).

If you already have a home entertainment system, HDMI 1.3 is backwards compatible with HDMI 1.1, which is the current standard for most HDTVs, receivers, high and standard definition players.

HD DVD

High-definition digital video disc. Several formats have been proposed for these high-capacity DVDs, including Blu-ray.

HD-ILA

High-definition Direct-drive Image Light Amplifier.

HDTV

High-Definition Television, A TV signal that offers a much higher resolution and a wider aspect ratio than traditional NTSC (regular broadcast) signals. It can also refer to the actual television sets that pick up these signals.

High Definition Television. Not the same as DTV, it's actually a subset of DTV. The HDTV standard requires a screen resolution of 720p or better.

* 720p - The picture is 1280x720 pixels, sent at 60 complete frames per second.

* 1080i - The picture is 1920x1080 pixels, sent at 60 interlaced frames per second (30 complete frames per second).

* 1080p - The picture is 1920x1080 pixels, sent at 60 complete frames per second.

HDTV Blur

It is a common term used to describe a number of different artifacts on consumer modern high definition television sets.

The following factors are generally the primary or secondary causes of HDTV blur; in some cases more than one of these factors may be in play at the studio or receiver end of the transmission chain.

- Pixel response time on LCD displays (blur in the color response of the active pixel)

- Slower camera shutter speeds common in Hollywood production films (blur in the HDV content of the film)

- Blur from eye tracking fast moving objects on sample-and-hold LCD, Plasma, or Microdisplay.

- Resolution resampling (blur due to resizing image to fit the native resolution of the HDTV)

- Blur due to 3:2 pulldown and/or motion-speed irregularities in framerate conversions from film to video

- Computer generated motion blur introduced by video games.


HDTV-Ready

Used to describe any TV that can display high-definition formats when connected to a separate HDTV tuner or source. These TVs generally have built-in tuners for receiving regular NTSC broadcasts, but not ATSC digital broadcasts. The CEA's official term for an HDTV-ready TV is HDTV monitor.

HDTV Monitor

Official CEA term for HDTV-ready.

High Gain Screen

Material that reflects more light than a reference material. Increases a projector's light output at the expense of uniformity.

High Pass

A filter that passes high frequencies, and attenuates low frequencies.

Hz - Hertz

Also called cycles per second and in video displays is the rate at which an image is refreshed.

I

ICT

The Image Constraint Token (ICT) is a digital flag within the AACS (Advanced Access Content System) that determines how Blu-ray and HD DVD players output high defintion video signals through the player's component outputs.

The Advanced Access Content System (AACS) is the digital rights management (DRM) standard which will be used by Blu-ray and HD DVD to protect movies from unauthorized duplication.

If the ICT token is set on a Blu-ray or HD DVD disc, then the player will down-convert the video resolution through analog outputs from 1920 by 1080 pixels to 960 by 540. The purpose of ICT is to prevent pirates from creating high resolution copies of HD DVD and Blu-ray discs via the unsecured analog outputs.

The video output through HDMI is unaffected by ICT since the HDMI output is copy protected by High-Bandwidth Digital Content Protection (HDCP).

The Image Constraint Token is set by the movie studio when a disc is mastered therefore whether the player down converts the video signal will be determined by the studio on a title by title basis. It is expected that most major movie studios will set the Image Constraint Token on all titles.

If the ICT is set, then your HDTV must have an HDMI input in order to watch high definition from a Blu-ray or HD DVD movie.

IEEE 1394 (FireWire)

A digital interface developed by the IEEE 1394 working group. Transports data at 100, 200, or 400 Mbps. Can be used to connect digital television devices together. IEEE 1394 data transfer can be – “asynchronous” - or “isochronous.” Asynchronous transport is the traditional computer memory-mapped, load and store interface. Isochronous data channels provide guaranteed data transport at a pre-determined rate. This is especially important for time-critical multimedia data where just-in-time delivery eliminates the need for costly buffering.

IRE (UNIT)

An IRE is a unit used in the measurement of composite video signals. Its name is derived from the initials of the Institute of Radio Engineers.

Integrated HDTV Tuner

The terrestrial ATSC high-definition tuner built into an HDTV, it allows the set to receive over-the-air HDTV broadcasts without having to attach a set-top box.

Interlaced Display

A cathode-ray tube (CRT) display in which the electron guns skip every other line on their first pass, then fill in those lines on a second pass. This allows for a lower refresh rate at higher resolutions (such as 1,024x768) without producing flicker, but the scheme doesn't work well when displaying animated graphics. Most monitors aren't interlaced, but lower-quality display adapters pushed into high resolutions and high color sometimes do interlace. Opt for a noninterlaced monitor.

Interlaced Scanning

Scan method used by the majority of televisions and the 1080i HDTV format. As opposed to progressive scanning in which the CRT's electron beam scans or "paints" all lines at once, interlaced scanning TVs paint odd-numbered lines in succession, then go back and fill in the remaining even-numbered lines. This method is more prone to artifacts and less stable than progressive.


I/O: Input/output

Typically refers to sending information or data signals to and from devices. Often used in referring to video/audio component connections.

J

Judder

A visual artifact that often occurs when film is transferred to video. The result is what appears to be jerky or stuttering camera movement, where it should be a smooth pan.

K

Kelvin (K)

A temperature measurement scale where 0° Kelvin (0°K) is equal to absolute zero, the temperature at which all molecular movement ceases. One degree of Kelvin is equal to 1 degree of Celsius. The color temperature of large image devices is measured in Kelvin. The higher the temperature, the bluer the light.

Keystone

Keystoning occurs when the projector is not perpendicular to the screen, thereby creating an image that is not rectangular.

Keystone Correction

Keystone correction makes a projected image rectangular. This can be accomplished by positioning the projector to be perpendicular to the screen. Since this is not always possible, most projectors are equipped with keystone correction that allows the image to be keystone corrected (made rectangular) by adjusting optics, making mechanical adjustments, or applying digital scaling to the image. Keystone correction can be one or two dimensional and manual or automatic depending on the projector and the manufacturer. Be aware that digital scaling will introduce some artifacts that are more evident when viewing small text and less evident in presentation type material or video.

L

Latency

The time between a device being requested to do something and the start of the device actually doing it. It’s a measurement usually used for LCDs where the shorter the latency the better. NSTC requires a latency of no more than 16ms in order to update the screen in time without leaving a ghost of the previous image.

LCD TV

Liquid-Crystal Display, A television that employs a liquid-crystal display screen rather than a CRT; used in small, personal TVs, portable video equipment, front projectors, and larger flat-panel displays. An LCD projector uses a lamp to shine light through liquid-crystal panels, then through mirrors and lenses to the screen.

LCoS

Liquid Crystal on Silicon. Whereas LCDs uses liquid crystals sandwiched between two glass plates, this newer hybrid projection TV technology employs liquid crystals coated on a silicon chip, which results in easier, lower-cost manufacturing and higher-resolution images.

LED

Light-Emitting Diode,A semiconductor device that emits light when electrical current is applied to it. LEDs require very little power and can last for decades. They are used as indicator lights on electronic devices, for digital and alphanumeric readouts on equipment, in fiber optic data transmission, and in remote-control devices.

Lens Shift

The Lens Shift feature of a projector allows the optical lens to be physically shifted up and down (vertical) and/or left and right (horizontal). Some lens shift mechanisms are motorized with vertical lens shift being the most popular. Lens shift can avoid or minimize the need for keystone correction. It is also used to geometrically align images when stacking projectors.

Letterbox

A wide-screen movie on DVD,laserdisc, or videotape presented in its original theatrical wide-screen width on a standard square 4:3 TV. The film is shown with black bars above and below the picture area to create the wider, theatrical image. Often used to indicate a nonanamorphic DVD.

LFE 0.1 channel

This channel reproduces low­frequency signals. The frequency range of this channel is from 20 Hz to 120 Hz. This channel is counted as 0.1 because it only enforces a low­frequency range compared to the full­range reproduced by the other 5/6 channels in Dolby Digital or DTS 5.1/6.1­channel systems.

Light Valve Projector

A projector that uses an imaging system that either blocks or reflects light such as LCD, LCoS or DLP.


Line-Doubler/Tripler/Multiplier

Technology used in televisions to create a higher-quality picture by increasing the number of lines of resolution displayed; it can be a separate device or a feature built-in TVs, primarily DTVs. A poor-quality line-doubler can actually degrade the image from lower-resolution analog or digital signals.

Line-Level

A low-voltage pre-amplified signal usually between .3 and 5 volts.


Linearity

A display’s ability to show an image’s geometric characteristics accurately. Also called geometric linearity.


LNB: Low-Noise Block converter

The LNB sits at the end of a pole facing the dish of a satellite dish assembly. It converts the incoming signal to a lower set of frequencies to make them easier to send over a wire without distortion. The lower the rated degrees of an LNB, the cleaner the picture will be.


Long Throw Lens

A long throw lens allows greater distance between the projector and the screen while being able to maintain the image size and brightness of a shorter throw lens for any given projector. Depending on the room, a long throw lens may be required due to mounting constraints nearer the projected image.

Lossless

Lossless: Refers to audio that has been reproduced from the original source (Blu-ray disc, CD, eg.) without having lost any information. Lost information results in a ‘less-than-perfect’ reproduction of the audio track. Uncompressed PCM, Dolby True HD, and DTS-HD MA are examples of lossless audio feeds. All Blu-ray players are capable of transmitting uncompressed PCM data to a receiver using an HDMI cable. Not all players are capable of decoding/transmitting every type of compressed data. See your player’s user manual for details. See Compression. For comparison, See Lossy.

Lossy

Lossy: Refers to audio that is not an exact reproduction of the original. During the recording/compression process, information has been lost, and may result in the perception of less quality/depth/richness of sound. Not all players are capable of decoding/transmitting every type of compressed data. See your player’s user manual for details. Examples of Lossy sound compression methods include DTS, Dolby Digital, and DTS-HD HR. See Compression. For comparison, See Lossless.

Low Pass

A filter that only passes frequencies under a specified Hertz.

Lumens

The unit of measure for the light output of a projector. Different manufacturers may rate their projectors' light output differently, and these numbers are usually inflated. "Peak lumens" is measured by illuminating an area of about 10 percent of the screen size in the center of the display. This measurement ignores the reduction in brightness at the sides and corners of the screen.

Luminance

Portion of a television transmission that controls brightness of the red, green, and blue proportions in a television picture. The standard luminance setting in a picture is 30 percent red, 60 percent green, and 10 percent blue. These numbers are adjusted to produce varying colors, grays, whites, and blacks.

M

Macro Blocking

MPEG 2 encoding is a lossy compression based on Discrete Cosine Transformation (DCT). It breaks the image into small rectangular areas called macroblocks. Within these blocks the grid of picture elements (pixels) are encoded to represent their horizontal and vertical video frequencies. It does this so that when it has to throw out some information, it starts with the higher frequencies (finer detail) and works its way down.

Motion vectors is another compression technique that MPEG 2 uses to take advantage of redundant frame-to-frame information. The use of motion vectors allows the amount of DCT compression to be decreased. If there is so much motion that the encoder cannot keep up, it can no longer effectively use the motion vectors, and the amount of compression is increased. Fine detail is eliminated in each of the blocks, and what's left is more of an average. Since each block probably has a different average, it makes a mosaic looking set of squares on the screen. When things slow down, and the encoder can decrease the amount of compression the detail will return.

Moiré Pattern

An image artifact which is an interference pattern caused by two patterns overlaying each other. Looks like cross-hatching, herringbone or other patterns.

Mosquito Noise

An artifact of MPEG compression which looks like a mosquito buzzing around. Usually found around sharp edges and most easily seen on solid color areas. It is a time dependent video compression impairment in which the high frequency spatial detail in video images having crisp edges is aliased intermittently.

MPAA

Motion Picture Association of America, Industry association for producers of motion pictures.

MPEG

A set of standards (pronounced "EM-peg") for compressing multimedia files. MPEG-1 is used in CD-ROMs. MPEG-2 is used for a broad range of formats, including DVD, high-definition TV, and surround sound. MPEG-4 is a standard for low-bandwidth video telephony and multimedia on the World Wide Web. (MPEG-3 was merged into MPEG-2.) The acronym MPEG stands for Moving Picture Experts Group, a working group of the International Standards Organization.

MPEG-2

Moving Picture Experts Group-2. Video-compression scheme used to condense digital video content for broadcast over thin TV bandwidths or via the Internet, and to squeeze full-length digital films onto a DVD.

MPEG-4

Advanced compression scheme finalized October 1998, designed to enable transmission and reception of high-quality audio and video over the Internet and next-generation mobile telephones; potentially enables mobile video phones, video e-mail, and cordless video cameras. Two major versions are MPEG-4 Simple Profile for low-resolution digital video content, usually for distribution over the Internet, and MPEG-4 AVC (Advanced Video Coding), which offers faster and higher-quality compression than MPEG-2 for HDTV content.