HD Glossary

What do SD, HD, Ultra HD, and 4k mean? What about SDR and HDR? Here are some basic terms you should be aware of when purchasing home entertainment equipment, viewing high definition movies and shows, and building your home theater. Note: This page has been migrated to our Home Theater Glossary to encompass more related terminology.

HD (High Definition) Glossary of Terms


4k refers to 2160p video resolution in media or screens that display 4 times the amount of pixels as its predecessor the “Full HD” 1080p format. The 3840 x 2160 lines of resolution in 4k Ultra HD TVs are twice the amount of both vertical and horizontal lines of the 1920 x 1080p format. Therefore, Ultra HD provides 8.3 megapixels compared to the 2.1 megapixels of 1080p. 4k is also referred to as Ultra HD or UHD.


8K UHD resolution is commonly defined as 7680 × 4320 resolution at 16×9 aspect ratio (although there are other 8k formats). 8k is double the resolution of 4K (2160p) and four times the resolution of Full HD (1080p) in both height and width dimensions, effectively delivering approximately 33.18 megapixels.

1080i (1080/60i)

Refers to a standardized High Definition production format (SMPT 274M and ITU 709) having a digital sampling structure of 1920 (horizontal) x 1080 (vertical) and operating interlaced scan mode at 60 fields per second. This format differs from 1080p in that it uses fields instead of frames.

1080p (1080/24p)

Refers to an internationally recognized High Definition production format (ITU BT 709) having a digital sampling structure of 1920 (horizontal) x 1080 (vertical) and operating at 24-frames per second progressively scanned.


The term for 24 full frames per second of digital video progressively captured.

720p (720/60p)

Refers to a standardized High Definition production format (SMTE 296M) having a digital sampling structure of 1280 (horizontal) x 720 (vertical) and operating at 60-frames per second progressively scanned.

Active Speaker

A speaker which includes an active crossover and built-in amplifier.


A component to your audio/video system which increases the gain or levels of an audio signal.

Analog TV

Analog television encodes television picture and sound information and transmits it as an analog signal (one in which the message conveyed by the broadcast signal is a function of deliberate variations in the amplitude and/or frequency of the signal). All systems preceding DTV (e.g. NTSC) are analog television systems.

Analog Channel

A communications path that carries voice or video in analog form — as a varying range of electrical frequencies (See Analog Signal).

Analog Pass-Through

Digital converter box capability, which allows analog broadcast signals to pass through the converter box to be tuned by your analog TV.

Analog Signal

A type of signal that encodes voice, video, or data transmitted over wire or over-the-air that is commonly represented as an oscillating wave. An analog signal may vary in frequency in response to changes in physical phenomena, such as sound, light, heat, position, or pressure.

Analog Spectrum

A traditional range of frequencies used for radio and television transmission. This is a less-efficient and lower-quality system that uses Radio Frequency (RF) waves to transmit and display pictures and sound.

Analog Transition Date

In the US, this refers to June 12, 2009, which is the DTV Transition deadline mandated by Congress for the turnoff of analog broadcasting by full-power TV stations. Stations are permitted to cease analog transmissions before this date, and some started doing so after February 17, 2009, which was the original analog transition date.


Device designed to receive the radio waves broadcast by television stations.

Aspect Ratio

The ratio of an image from width to height. Traditional television screens have an aspect ratio of 4:3. Most widescreen televisions and HDTVs have an aspect ratio of 16:9.


Advanced Television Systems Committee. This is the name of the DTV system used by broadcasters in the U.S.

ATSC Tuner

Often called an ATSC receiver or HDTV tuner, allows reception of DTV signals broadcast over-the-air by TV stations. May be integrated into a television set, VCR, DVR, or set-top box.


Bass is defined as low frequency signals below 200Hz.


See Blu-ray Disc

Beta (Betamax)

Developed by Sony and introduced to homes in 1975, the Betamax format eventually was shadowed y VHS in the early 1980s.

Blu-ray Disc

This HD format developed by Sony that is in direct competition with HD DVD. Blu-ray technology uses a blue laser instead of red (used by HD DVD and EVD) which allows it focus more sharply allowing more capacity per disc.

Center Channel Speaker

The speaker that usually sits dead center within a surround sound system and may contain most of the dialogue of the movie or program.


In audio/video terminology a singular path of audio. In a 5.1 channel system the audio is split into 5 different channels and the .1 represents a single channel for a subwoofer.


The color of an image – represented as (U) on most cables.

Component Video

Video signal in which luminance (brightness) and chrominance (color) are separated to allow for better picture quality. A better quality than composite which does not separate.

Composite Video

Video signal in which luminance (brightness) and chrominance (color) are combined. This is a lesser quality than Component (found in NTSC and PAL) which keeps the signals separated.

CRT (Cathode Ray Tube)

Traditional television technology where the image is created by an internal gun firing electrons.

Direct-Stream Digital

A format for encoding high-resolution audio signals.


The spreading of audio signal over a wide area.

DLP (Digital Light Processing)

Video processing system that was developed by Texas Instruments which uses a light source to reflect off an array of microscopic mirrors.

Dolby Atmos

An object-based audio format that adds discreet channels for speakers that can be placed overhead for a more immersive sound. Atmos presents audio in a three-dimensional space and is an extension of Dolby TrueHD. In audio descriptions, height speakers may be represented by the number after the second period. So, for example in 7.1.2 the “2” describes two overhead channels. Some home audio systems will support up to four overhead channels. If an audio system does not support Atmos it is backward compatible with other formats starting with Dolby TrueHD. Many Blu-ray Discs, 4k Ultra HD Blu-ray Discs, and Digital HD/UHD movies and TV shows feature Dolby Atmos.

Dolby Digital

Audio encoding system that compresses up to 5.1 discreet audio channels (left, right, center, left surround, and right surround). If a subwoofer is integrated, the .1 carries that single stream.

DTS (Digital Theatre Systems)

Compression of 5.1 discreet channels of audio (left, right, center, left surround and right surround) into a single bitstream. The .1 channel is usually used for a subwoofer. Dolby Digital is other competitor in this technology.


An object-based immersive audio format improving upon DTS-HD Master Audio that allows for overhead speakers for a more life-like sound experience. Some Blu-ray Discs and 4k Ultra HD Blu-ray Discs feature DTS:X audio.

DTV (Direct Television)

The television broadcast system that replaced the analog NTSC system in the United States. The scheduled turnover to DTV in the US was set to February 2009 (the actual switch was June 12, 2009 for full-power stations) when analog channels were turned off or possibly switched for use by government programs. The FCC promoted and gave away digital-to-analog converters to analog television owners so they could receive digital broadcasts. DTV scan rates in the U.S. include 480i, 480p, 720p and 1080i.

DVD (Digital Video Disc)

DVDs (using a single layer, and being single sided) can hold up to 4.5 – 17Gb storage capacity. DVDs are currently the most popular way to view movies and other content.


Digital Versatile Disc-Audio can hold up to six channels of high-resolution audio.


Allows for recording of media only one time.


Recordable format that is capable of being erased more than 100,000 times.


Allows for recording of media multiple times.


A VHS recorder that records digital signals onto magnetic tape and has a greater storage capacity than standard VHS.


Enhanced TV Binary Interchange Format

EDTV (Extended Definition Television)

Describes televisions capable of displaying digital content (DTV) of resolutions 480p or higher


Process of altering a frequency to change its acoustical output.


Also known as 1EEE 1394. A high-speed connection between electronics that can send large data signals.

Full-Range Speaker

Speaker designed to replicate a full audio range from 20Hz to 20kHz.


HDR stands for “High Dynamic Range” — a format that produces a greater range of luminosity than possible with standard digital photography, digital cinema, and digital video. In home media applications, HDR can expand the color range of traditional media from 8-bits to 10-bits, therefore offering wider color range, contrast ratio, and deeper color depth. The three current standards include Dolby Vision, HDR10/HDR10+, and HLG. Also read: What is HDR.

HD (High Definition)

A term used for high-definition video and audio. In terms of video in home media applications, HD represents resolutions of 1080i, 720p, and 1080p (Full HD). High Definition can also be used as a generic term for high quality, and not tied into a specific format. Also see (HDTV)

HD Capable

Term for HD hardware that needs an additional receiver or converter to allow HD signals. This is the opposite of HD Ready.

HD DVD (High-Definition DVD)

Developed by Toshiba, the HD DVD format is the successor to the DVD format. HD DVD is a high-definition format that can store 3-4 times more than the traditional DVD. Toshiba conceded its HD DVD format to high-definition disc competitor Blu-ray Disc in Feb. 2008.


Single cable that supports any TV or PC video format as well as multi-channel digital audio. Enables one to use only one cable, compared to 5 cables needed for component video (high definition quality) and stereo audio. Video is improved as the signal is purely digital and therefore no analog interference. Audio is also improved allowing 8-channel uncompressed digital audio at a 192 kHz sample rate with 24 bits/sample. Supports compressed streams such as Dolby Digital, or DTS.

HD Ready

Term for HD equipment that is readily capable of receiving HD signals, as opposed to HD capable which needs additional equipment to convert the signal.

HD Receiver

Set-top box that receives and transmits HD signals to the HDTV.

HDTV (High-Definition Television)

A television that is capable of accepting and displaying high-resolution digital images. HD TVs are widescreen format (usually 16:9). HDTV has a level of clarity is at least 5 times greater than traditional sets. HD TVs produce resolutions of 1080i, 720p, and 1080p. The most common types of HDTVs are CRT, DLP, LCD and Plasma.

Home Theater

A home theater attempts to recreate the movie theater experience within the comfort of your home.


Interactive Television Application

Integrated Amplifier

A combination preamp and amplifier.


Imaging technology that uses alternating scan lines to produce an image. In contrast to Progressive, Interlaced imaging captures a moment in time in alternating lines, (odd and even), which combined make a frame. Interlaced is represented with a lower case “i” next to the number representing resolution. For example 1080i.


Short form of kilohertz (equal to 1000 Hz)

LCD (Liquid Crystal Display)

Television that uses liquid crystals between two transparent displays. A light source transmits the image through the crystals.


Method in which the original widescreen format of a movie (used in theaters) is presented on a non-widescreen television with black bars across the top and bottom. This prevents excessive distortion and renders the image closer to the originally intended aspect ratio.


The brightness of an image – represented in (Y) on most cables.


Short form of Megahertz (1 million Hz)


One channel audio

Mounting Brackets

Brackets used to affix a flat-panel television to a wall.

Passive Speaker

A speaker that does not have an internal or built-in amplifier.


In electronic imaging, video or still, a pixel represents data that when combined with hundreds, thousands, or millions of other pixels forms an image.


Flat panel television technology that ignites tiny pockets of gas to light up phosphors.


Unit that controls and switches audio. May also contain equalization functions.


Imaging technology that scans a moment in time all at once into a frame. In contrast to Interlace, which scans a moment in alternating lines. Progressive is represented by a lower case “p”, as in 720p or 1080p.

Projection System

A system in which mirrors reflect an image which is then projected onto a screen or wall.

Quantum HD 

Refers to TV screens, projectors, or media with the capability of displaying 7680 × 4320 resolution. See (8k)

Rear-Projection Television (RPTV)

A television system that uses a mirror to reflect an image in reverse on the back of a screen material. When viewed from the front the image appears correct.


An= unit that usually combines a tuner with an amplifier and various in/out connectors. Audio/Video receivers may also contain audio processing functions to allow multi-channel audio such as Dolby Atmos, Dolby Digital, DTS, and DTS:X.


In terms of video resolution is defined by how much detail an image holds. The higher the resolution, the more detailed the image. In terms of HD, standardized formats are 1920 x 1080i, 1280x720p, and 1920 x 1080p. When talking about 4k, UHD, or Ultra HD, the standardized format is 3840 x 2160 pixels as defined by the ITU (International Telecommunication Union. 8K UHD is commonly defined as 7680 × 4320 resolution.

RGB (Red, Green, Blue)

The combination of the colors red, green and blue produce an image.

SDTV (Standard Definition Television)

A format of DTV that is approximately the equivalent of the NTSC (or PAL) systems that exist today. Can be defined in resolutions of 480i (576i for PAL).


A subwoofer is a speaker that is designed to reproduce low bass frequencies. These low frequencies are defined as being below 80Hz. In audio descriptions, the subwoofer channels are the first number after a period. So, in 5.1 the “1” describes one discreet subwoofer channel.

S-VHS (Super VHS)

An improved version of the VHS technology introduced in 1987.

S-Video (Separated Video)

This is an encoded signal that separates the luminance (brightness) and chrominance (color) of a signal to improve image quality. The quality using S-Video is much better than composite because it doesn’t require a comb filter to separate the signals.


Equal to one trillion bytes (-1,000,000,000,000).


Lucasfilm Ltd. Created this standard for home theatre equipment which is intended to give you the highest quality home theatre experience. Levels include THX Select, Ultra, and Ultra 2.

Timecode (TC)

Standard format for recording time information on videotape. Each frame is given a unique number that consists of Hours:Minutes:Seconds:Frames.

Title Safe

This is the area of the screen that defines a title safe area in which there is a guarantee that the information will be seen on any television format.


A speaker driver designed to reproduce high frequencies.

Ultra HD

Refers to TV screens, projectors, or media with the capability of displaying 3840 x 2160 resolution. See (4k)


Refers to TV screens, projectors, or media with the capability of displaying 3840 x 2160 resolution. See (4k)

Universal Remote

A remote control developed which can control several different devises. Standard universal remotes control TV, DVD, VHS, Cable/Satellite and sometimes Audio.

VHS (Video Home System)

Playing and recording device introduced in Japan in 1976 that allowed home audiences to watch and tape movies and programming.


A unit of power or energy.


A speaker designed to reproduce low frequencies. (see Subwoofer)


Imaging model where Y stands for luminance (or brightness). U & V represent chrominance (or color)


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