Home Theater Glossary

Don't Get Lost in the Jargon: the Home Theater Glossary Explains all the Technical Terms in Plain English!

Updated: September 17, 2020

Home theater technology might seem like an endless list of technical gobbledygook and incomprehensible acronyms.

And, that's because it is!

But don't despair, help is at hand. I have compiled this home theater glossary to explain many of the terms that you come across when dealing with home theater.

It's a living document and so I'll try and update it as things change. Or, when I remember something else that hasn't been included...

The idea isn't to have in-depth technical explanations of each point - but to give a simple summary so that you have a quick reference point when you need to refresh your memory.

Or when you are completely lost and have no idea what anything means.

Feel free to bookmark this page and refer to it again.

Home Theater Glossary: old books and a pair of glasses

Quick Navigation

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A | B | C | D | E | F | G | H | I

J | K | L | M | N | O | P | Q | R

S | T | U | V | W | X | Y | Z


1

100Hz
A refresh rate used by modern TVs in areas which use the PAL TV system. An interlaced PAL TV signal has a frame rate of 50Hz. The TV will create a duplicate copy of each field - so the original 50Hz frame rate will double to 100Hz. The idea is a higher refresh rate will appear to have less motion blur and flicker to the human eye. Read more: TV Refresh Rates Explained
120Hz
A refresh rate used by modern TVs in areas that use the NTSC TV system. An interlaced NTSC TV signal has a frame rate of 60Hz. The TV will create a duplicate copy of each field - so the original 60Hz frame rate will double to 120Hz. The idea is a higher refresh rate will appear to have less motion blur and flicker to the human eye. Read more: TV Refresh Rates Explained
1080i
A shorthand description for a type of high-definition picture. Often used to describe the capabilities of flat-screen TVs and other digital video equipment. '1080' refers to the number of vertical pixel lines that make up one frame of the picture. The 'i' tells us the picture is interlaced. Read more: Understanding TV Resolutions
1080p
A shorthand description for a type of high-definition picture - also known as full HD. 1080p used to provide the most detailed picture available with high-definition – until Ultra HD was introduced. Often used to describe the capabilities of flat screen TVs - although it really relates to an image resolution rather than the TV screens native resolution. '1080' refers to the number of vertical pixel lines that make up one frame of the picture. The 'p' tells us the image will be displayed using progressive scan. Read more: Understanding TV Resolutions
1280 x 720
The native resolution of an HD ready flat panel display - or the minimum image resolution of a high-definition picture. It means the display/image has 1280 lines of horizontal pixel information and 720 lines of vertical pixel information. Due to the size and shape of the pixels that make up the screen, some HD ready displays may have a slightly different native resolution e.g. 1366 x 768 or 1024 x 768. In total, this means 921,600 pixels.
16:9
The standard aspect ratio of HDTV. It means the shape of the picture is 16 units across and 9 units down. It is also known as 1.78:1 – which is 16 ÷ 9.
1920 x 1080
The native resolution of a full HD flat panel display - or the image resolution of a full HD picture. It means the display/image has 1920 lines of horizontal pixel information and 1080 lines of vertical pixel information. In total, this means over 2 million pixels – or 2,073,600 to be precise.

2

2160p
A shorthand description for a 4K Ultra HD picture. '2160' refers to the number of vertical pixel lines that make up one frame of the picture. The 'p' tells us the image will be displayed using progressive scan. Read more: Understanding TV Resolutions

3

3840 x 2160
The native resolution of a 4K Ultra HD display - or the image resolution of 4K video for consumer televisions. It means the display/image has 3840 lines of horizontal pixel information and 2160 lines of vertical pixel information. In total, this means over 8.2 million pixels – or 8,294,400 to be precise.

4

4:3
The original standard aspect ratio for television programs. Also known as 1.33:1. It means the shape of the picture is 4 units across and 3 units down. It is becoming much less common as transmissions switch to widescreen. However, many old shows will still show in this aspect ratio as that is how they were filmed.
4030p
A shorthand description for an 8K Ultra HD picture. '4030' refers to the number of vertical pixel lines that make up one frame of the picture. The 'p' tells us the image will be displayed using progressive scan. Read more: Understanding TV Resolutions
4096 x 2160
The professional 4K display resolution that is used in the movie industry. It means that the image has 4096 lines of horizontal pixel information and 2160 lines of vertical pixel information. 4K cameras used for shooting movies record a 7% wider image than the 4K standard used in consumer 4K products. So, the 4096 lines of horizontal resolution in this format are the real reason why this resolution is called 4K. This image size is trimmed to 3840 x 2160 to match the 16:9 aspect ratio used in consumer products.
480i
SDTV picture signal in NTSC regions. '480' is the number of visible vertical lines of information in a frame (525 lines in total). 'i' means the signal is interlaced.
480p
Enhanced definition picture signal. '480' is the number of vertical lines of information in a frame. 'p' means the signal is progressive scan.
4K
A video resolution that is part of the Ultra HD family. Also known as 4K UHD. A 4K image will be recorded using progressive scan and have a minimum resolution of 3840 x 2160 pixels - so 8.3 million pixels with a 16:9 aspect ratio. Read more: Understanding TV Resolutions

5

5.1 Surround Sound
See surround sound.
576i
SDTV picture signal in PAL regions. '576' is the number of visible vertical lines of information in a frame (625 lines in total). 'i' means the signal is interlaced.

6

No entries yet.

7

7.1 Surround Sound
See surround sound.
720p
A shorthand description for a type of high-definition picture. This is the minimum requirement for a picture that can be called high-definition. Often used to describe the capabilities of flat screen TVs. '720' refers to the number of vertical pixel lines that make up one frame of the picture. The 'p' tells us the image will be displayed using progressive scan. Read more: Understanding TV Resolutions
7680 x 4320
The native resolution of an 8K Ultra HD display - or the image resolution of 8K UHD video. It means the display/image has 7680 lines of horizontal pixel information and 4320 lines of vertical pixel information. In total, this means over 33.1 million pixels – or 33,177,600 to be precise.

8

8K
A video resolution that is part of the Ultra HD family. Also known as 8K UHD. An 8K image will be recorded using progressive scan and have a resolution of 7680 x 4320 pixels - so 33.18 million pixels with a 16:9 aspect ratio. Read more: Understanding TV Resolutions

9

No entries yet.

A

Active Subwoofer
A subwoofer that has a built-in amplifier. This type of subwoofer should receive a line-level pre-amp signal (a signal that hasn't been amplified yet) from an AV receiver. The subwoofer then amplifies the audio signal itself and plays it back through the speaker. Active subwoofers commonly have basic volume and equalization controls on the unit to alter the output volume and tone. Most subwoofers designed for home cinema will be active subwoofers. The alternative is a passive subwoofer which is less common.
ALLM
Stands for Auto Low Latency Mode. Part of the HDMI 2.1 specification. When compatible devices are connected, they will automatically switch to their gaming modes. This means that they enable their best low latency settings for gaming. All devices in the chain need to support this.
Aspect Ratio
The aspect ratio tells us the shape of a TV image. The aspect ratio of an image is its width divided by its height. For example, the traditional shape of a television picture is 4:3. This means it is 4 units across and 3 units down. Four divided by three = 1.33. So, the aspect ratio of a 4:3 image is 1.33:1 - or, it is 1.33 times wider than it is long. If you look on the back of a DVD case, it will tell you the aspect ratio of the film on the disc. It may say 4:3 or it may say 1.33:1 - or both! The aspect ratio of a 16:9 HDTV image is 1.78:1. Read more: Blu-ray and DVD Aspect Ratios
AV Amplifier
The same as an AV receiver, except it doesn't have a built-in radio tuner.
AV Receiver
The brain of a modern home cinema system. An AV receiver is an amplifier/processor for surround sound systems and a switcher for multiple input devices. A receiver is used to easily switch between different input sources - such as satellite TV boxes, game consoles and DVD/Blu-ray players. All input devices are connected to the AV receiver - both video and audio connections. The receiver then sends the video signals to the display device e.g. an LED TV - and the audio signals to the speakers. An AV receiver has a built-in radio tuner, which makes it different from an AV amplifier. The receiver will also process a 5.1/7.1 surround sound audio signal and send it out to the connected surround sound speaker system. Read more: How to Choose the Best AV Receivers

B

Backlit LED TV
A type of LED TV. The LED lights are placed in banks behind the screen. Each bank can be switched on and off independently of each other. This is called local dimming and it results in an improved contrast ratio over standard LCD TVs. Read more: Back-lit vs Edge-lit LED TVs
Bipole Speakers
Bipole speakers have two sets of speaker drivers and send the sound from two sides of the speaker cabinet at the same time. They are ideal as surround speakers in a 5.1/7.1 system as they spread the audio better than normal direct-radiating speakers and create a less directional sound. Another alternative is dipole speakers. Read more: Bipole Speaker Positioning
Blu-ray Disc
A Blu-ray disc is an optical storage disc similar to a DVD. Blu-ray is the same size as a CD/DVD but it cannot be played in a conventional CD or DVD player. The advantage of a Blu-ray disc is that it can hold about six times the amount of data compared to a dual-layer DVD. This means a Blu-ray disc can store video and audio in high-resolution formats that wouldn't fit onto a DVD. Therefore, a movie can be watched in 1080p high-definition video and heard with uncompressed multi-channel Dolby TrueHD or DTS-HD Master Audio. You can think of it as high definition DVD if you like. Read more: Introduction to Blu-ray Players
BT.2020
The 10-bit color standard incorporated into the Ultra HD specification. It includes standards for the display resolution, frame rate, bit depth, chroma subsampling and the color gamut. If you use an AV receiver, it will need to support BT.2020 to pass this type of content to your 4K-compatible TV.

C

CCFL
Stands for Cold Cathode Fluorescent Lamp. This is the traditional type of lamp that is used as the backlight in an LCD TV. In some new LCD TVs, this type of lamp is now being replaced by the use of LEDs (light-emitting diodes). These televisions are now referred to as LED TVs.
CEC
Stands for Consumer Electronics Control. A two-way serial bus connection between AV devices that allows them to control each other. This connection is part of the HDMI specification and so this control happens over an HDMI interface. Each manufacturer has a different name for this feature such as BRAVIA Sync (Sony) and Viera Link (Panasonic). Read more: What is HDMI CEC?
Chroma Subsampling
A method used in video encoding to reduce the bandwidth required to transmit video. The chroma (color) information in a video signal is sampled fewer times and then recreated by your TV screen when displayed. The result is a smaller amount of data to transfer but with no loss in image quality when you see it. In 4:2:0, one color is sampled every time, another color half the time, and the final color not at all. This is how video is stored on a Blu-ray disc, for example. With 4:2:2, one color is sampled every time, and the other two colors every other time. In 4:4:4, each red, green, and blue color is sampled every time. Your TV uses an algorithm to build the lossless image from the 4:2:0 data it is sent from your Blu-ray player – but there is less data for your HDMI cable to transfer.
Coaxial
A type of cable used for transmitting various radio, video and audio signals. It has a solid conductor core, a plastic insulation layer, another thin conductive layer and finally an outer insulation layer. A 75-ohm coaxial cable is recommended for a digital audio coaxial connection to ensure the correct transmission of the signal. A coaxial connection for digital audio will use one RCA connector at each end. Read more: Coaxial Digital Audio Connections Explained
Codec
Short for coder-decoder. In terms of home cinema, a codec is a term used to describe various digital compression algorithms such as those used for compressing/decompressing audio on DVD and Blu-ray discs. Therefore, we can refer to the Dolby Digital codec or the DTS 5.1 codec.
Color Depth
Also known as bit depth. Most TVs use the RGB color model to display an image. This is where the color of each pixel is made from varying amounts of red, green, and blue. The color depth for video is the total number of bits used to define each color for every pixel. 8-bit color allows for around 16 million colors. 10-bit color allows for about 1 billion colors. 12-bit color allows for around 68 billion colors. Consumer video typically uses 8-bits for each color – this is used on standard Blu-rays, for example. 4K UHD Blu-ray uses 10-bit color and the extra colors are especially useful for HDR content. The Ultra HD specification also allows for 12-bit color but most TV screens are currently 8 or 10-bit. People often get confused between color depth and chroma subsampling. But they are different things.
Component Video
A common output option on DVD, Blu-ray and other audio-visual equipment. You'll see the red, green, and blue RCA connectors. Component video is an analog video signal that is split into two or more separate signals. This splitting of the signal creates a better image than composite video. RGB and YPbPr component video splits the signal into three parts, and each uses the same type of cable to connect devices – a red, green, and blue RCA cable. Read more: Component Video Cable and Connection Explained
Composite Video
A common output option on audio-visual equipment. Composite video is an analog video signal and is the most basic type of video signal. The quality is not as good as S-Video or component video. It is called composite video as it combines three signals (YUV) and sends them as one. Therefore, a composite video cable only has one port to connect to on each device - the single yellow RCA connection. Read more: Composite Video Cable and Connections Explained
Contrast Ratio
The contrast ratio is the difference between the brightest (white) and darkest (black) color signals that a panel can produce. It is expressed as a ratio and tells us how many times brighter the white is compared to the black level e.g. a contrast ratio of 2000:1 means the white is 2000 times brighter than black. A higher contrast ratio is theoretically better as it means the whites are whiter and the blacks are blacker. This produces a more realistic and detailed image – especially for dark scenes. An OLED TV will often be shown to have an infinite contrast ratio. This is because it has perfect black levels – measured as zero. However, don't get too carried away by the numbers alone. In real-world situations, it can mean very little. A TV that is placed in a bright room won’t display its full contrast ratio as the ambient light will wash out the image. So, the contrast ratio is more important if you watch movies in a dark room. Just be aware that this is something to look out for when comparing different TVs in a store. Can your eyes see a difference between the blacks and whites on different screens? Which looks better to you?
CRT TV
The old style of TV. CRT stands for a cathode-ray tube and this is the technology used to produce a picture on the screen. One problem with using the cathode ray tube to display pictures is they are large, deep, and heavy. Which is why you used to strain your back when you had to move the TV! They are being replaced by flat-screen technologies that can provide thinner and lighter panels e.g. LED and OLED.

D

DAB
Stands for Digital Audio Broadcasting. The standard in many countries for broadcasting digital radio. In North America, HD Radio is used instead.
Dipole Speakers
Dipole speakers have a pair of speaker drivers in the same cabinet, and can, therefore, send the sound in two different directions. They are ideal as surround speakers in a 5.1/7.1 system. The sound in dipole speakers are out of phase (when one side is pushing the other side is pulling), and this creates a very diffuse sound that is difficult to pinpoint. It is important to install this type of speaker in the correct position to get the right effect. Another alternative is bipole speakers, which are more flexible in their positioning. Read more: Dipole Speaker Positioning
De-interlacing
The process of converting an interlaced video signal into a progressive scan signal in order to display it on a fixed-pixel HDTV display. A flat screen display shows images as progressive scan. So any interlaced scan video sources need to be de-interlaced by the TV before they are displayed. This process will be done automatically by the TV. However, some models will do this better than others and so it may be a consideration when you buy a new TV.
DLNA
Stands for Digital Living Network Alliance. A trade organization of over 250 companies. They aim to create a set of standards to make it easier to use and share digital music, video and photos. A 'DLNA-certified' device will be able to share data with other DLNA devices on the same network. A standard setup would have a DLNA server that stores the digital media - like a PC or NAS drive. Then, DLNA clients will be able to 'see' the server on the network and be able to playback the files. A client might be a TV, laptop or an AV receiver. Many brands use a version of DLNA for sharing content around a home network – but they often use their own name in menus and manuals. So you may not see it called DLNA when you are setting up your device.
DLP
Short for Digital Light Processing. A video technology developed by Texas Instruments and used in various display systems. This system creates an image by projecting light onto a matrix of small mirrors. Widely used in the manufacture of front projectors - both for the home and in professional cinemas - and sometimes used in rear-projection TVs.
Dolby Atmos
An object-based surround sound format that creates a 3D sound field using height speakers. Rather than using traditional surround sound channels – front left, front right, center, surround left, surround right, and LFE - a Dolby Atmos mix uses up to 128 audio objects. A 10-channel 7.1.2 bed is used to create a mix that will play on any standard 5.1 or 7.1 system. Then, for systems which support Dolby Atmos, a further 118 objects can be placed around the sound field. Read more: Understanding Surround Sound Formats
Dolby Pro Logic II
An audio signal processing technology developed by Dolby. It creates a 5.1 surround sound mix from a standard 2-channel stereo soundtrack. Pro Logic II is a replacement for the original Pro Logic system and is found on many devices such as AV receivers and game consoles. It has been replaced in newer AV receivers by Dolby Surround.
Dolby Pro Logic IIx
Similar to Dolby Pro Logic II, except it will create a 6.1 or 7.1 surround sound mix from either stereo or 5.1 soundtracks.
Dolby Pro Logic IIz
An improvement on Dolby Pro Logic IIx. This version adds a new height dimension to surround sound. For Dolby Pro Logic IIz you should add two speakers above the usual front left and right speakers to create an even more realistic feel to certain sound effects - especially things like wind and rain. These height speakers can be added to a 5.1 system to create 7.1 (with front height speakers instead of back left and right) - or to a 7.1 system to create a 9.1 system. Obviously, the AV receiver will need to support these speaker configurations for this to be available.
Dolby Surround
An upmixing algorithm that is found on many AV receivers. It can upmix any type of stereo or surround soundtrack to match the speaker layout that you have in your room. So it will upmix a stereo soundtrack to use your 5.1 surround sound system. Or, it will upmix a 5.1 soundtrack so that you hear audio in your Dolby Atmos height speakers too. It is a newer version of Dolby Pro Logic II/IIx/IIz. Due to licensing restrictions, you may only be able to use it on Dolby audio soundtracks. Confusingly, Dolby’s original surround sound decoding format - from 1982 - was also called Dolby Surround. This is the new upmixing version released in 2014. Read more: Understanding AV Receiver Listening Modes
Dolby TrueHD
A multi-channel audio format developed by Dolby and used on Blu-ray discs. Dolby TrueHD uses lossless compression - meaning the audio data is compressed to fit on the disc, but what you hear is the uncompressed audio i.e. you hear the audio exactly as it was on the studio master tapes. You get a wide dynamic range, deep bass, and a sparkling top end. It's fab! However, you won’t get much benefit unless you have a pretty good sound system. It competes with DTS-HD Master Audio on a Blu-ray disc. You may get either format - or both.
Dolby Vision
A variation of HDR developed by Dolby. The main advantage over standard HDR is that it can transmit scene-by-scene data to the TV screen on how it should display. It can also adjust to the capabilities of each TV. Dolby Vision can be added via a firmware update, so you may find your current hardware can be updated.
DTS-HD Master Audio
A multi-channel audio format developed by Digital Theater System (DTS) and used on Blu-ray discs. DTS-HD Master Audio uses lossless compression - meaning the audio data is compressed to fit on the disc - but what you hear is the uncompressed audio i.e. you hear the audio exactly as it was on the studio master tapes. You get a wide dynamic range, deep bass, and a sparkling top end. It's great – but you will need a better-than-average sound system to hear the difference. It competes with Dolby TrueHD on a Blu-ray disc. You may get either format - or both. Read more: Understanding Surround Sound Formats
DTS:X
An object-based surround sound audio format developed by DTS. Much like Dolby Atmos, a DTS:X soundtrack can create a 3D sound field using a combination of standard surround sound speakers and height speakers. A DTS:X soundtrack will adjust to the speaker layout in your room. So you can experience DTS:X audio from a range of speaker layouts. You just need to make sure that your AV receiver can decode DTS:X soundtracks. Read more: Understanding Surround Sound Formats
DTS Neo:6
An audio signal processing technology developed by Digital Theater System (DTS). It creates a 5.1 or 6.1 surround sound mix from a standard 2-channel stereo soundtrack. It is found on many devices such as AV receivers and games consoles and gives a better experience for those people with a surround sound system.
DTS Neural:X
An upmixing processing mode that is found in some AV receivers. Developed by DTS, this upmixing mode will play any type of soundtrack around your surround sound speaker system. Stereo audio will play across a 5.1 or 7.1 layout. A 5.1 mix will upmix to 7.1 or a speaker system with height speakers. It is the DTS equivalent of Dolby Surround. Due to licensing restrictions, you may only be able to use it on DTS audio soundtracks. Read more: Understanding AV Receiver Listening Modes
DVD Audio
A digital audio format designed for DVD. Compared to a CD, the higher disc space of a DVD allows the storage and playback of higher quality audio. DVD-Audio allows high-resolution stereo audio tracks up to 192 kHz/24-bit, and 5.1 surround sound up to 96kHz/24-bit resolution.
DVI
Stands for Digital Visual Interface. An interface that transmits uncompressed digital video data - but can also transmit analog video data like a VGA connection. Mainly used with flat screen LCD computer monitors and digital projectors - but is sometimes found on other devices. On a modern flat screen TV and Blu-ray player, you will usually get an HDMI connection, not DVI. Read more: DVI Connector and Cable Explained
Dynamic HDR
A version of HDR that can change the metadata on a frame-by-frame basis. Standard HDR sets a fixed level of brightness and color range for a complete movie or TV show. Dynamic HDR can set a different brightness and color gamut for each scene. Technologies that use dynamic HDR are Dolby Vision and HDR10+.

E

Edge-lit LED TV
A type of LED TV. The LED lights behind the screen are arranged around the perimeter. This type of design allows the screen to be made very thin and enables lower power consumption. Read more: Back-lit vs Edge-lit LED TVs
EDTV
Stands for Enhanced Definition Television. In short, better than SDTV but not as good as HDTV. EDTV has the same number of lines of vertical information per frame as SDTV - the difference is it uses progressive scan rather than interlaced scan. So, an EDTV signal can be called 480p or 576p (depending on where you live in the world). Even though there is the same amount of video information as an SDTV signal, the progressive scan will produce a sharper image as it reduces the artifacts produced by interlacing.

F

Flat Screen TV
Also known as a flat panel TV. A flat-screen TV is thinner and lighter than the traditional style of TV - the CRT. A flat-screen TV will only be a few inches thick which makes it easier to locate in your room - and can even be hung on a wall. They come in a range of sizes from about 10 inches up to a whopping 70 inches plus. Currently, the most common types of flat screen technology are LED and OLED. Older versions that have been discontinued are LCD and plasma.
Frame/Frame Rate
A frame is each unique image, or snapshot, that a video/film camera takes while it records something. The frame rate is the number of frames that this camera takes in one second. If enough frames are taken per second, then any movement in the image will be smooth and natural when seen by the human eye. A movie is traditionally shot on film at 24 frames per second. Video uses different frame rates around the world. In the UK and most of Europe, it is 50 Hz - 25 frames per second/50 fields per second. In North America and Japan, it is 30 frames per second/60 fields per second. Higher frame rates of 50/60Hz might sometimes be used for special broadcasts like sports events where the increased frame rate can help fast-moving action. Read more: Video Frames Rates vs TV Refresh Rates

G

No entries yet.

H

HD Ready
A TV is 'HD ready' if it can accept and display at least the minimum standard for an HD signal. Therefore, this can mean 720p, 1080i or 1080p. The minimum requirement is that the TV can show video with 720 vertical lines and with a widescreen aspect ratio In some countries, the term also requires the picture to be received via analog component or digital connections (DVI or HDMI) - which is pretty much a given with any modern display.
HD Ready 1080p
A TV can be labeled 'HD ready 1080p' if it can meet certain standards when displaying an HD signal. It will exceed the standards for an 'HD ready' TV. It must have a minimum native resolution of 1920 x 1080 pixels (1080 vertical lines at a 16:9 aspect ratio), display the image without distortion (1 pixel for each pixel in the source image), and be enabled for HDCP.
HD DVD
Stands for High-Definition/Density DVD. Developed by Toshiba, this optical disc format for high-density data storage was similar to Blu-ray. The ability to store far more data than a traditional DVD made it ideal for use with high-definition video and audio. It was discontinued in 2008 when the major content manufacturers withdrew their support and chose to go with Blu-ray technology.
HDCP
Stands for High-bandwidth Digital Content Protection. A form of copy protection for digital video and audio content and included in the specification of HDMI 2.0. When devices are connected using an HDMI interface - e.g. your Blu-ray player sends a movie to your LED TV via an HDMI cable - the digital information that is sent can be encrypted. Both the devices (the Blu-ray and the LED TV) talk to each other via the HDMI connection and agree if they are both HDCP compatible. When they decide they are, the Blu-ray will send the movie to the TV. This will happen transparently without your knowledge. A device that isn't HDCP compatible won't be able to receive the digital signal and will have to make do with an analog signal instead. This is to stop people from making a perfect digital copy of the video/audio. For Ultra HD, a device needs to be a minimum of HDCP 2.2 compliant. If your Ultra HD Blu-ray player and your 4K TV support HDCP 2.2, but your AV receiver doesn’t, then the 4K content won’t pass-through the AV receiver.
HDMI
Stands for High-Definition Multimedia Interface. An interface that transmits digital audio and video signals. This type of connection is becoming the standard way to connect modern audio-visual devices. If you are buying a new TV or Blu-ray/DVD player then it should have at least one of these. If you can, this is the connection to use rather than component or SCART connections. One HDMI cable allows the transmission of all digital video signals (including high-definition), and up to 8 channels of uncompressed digital audio (including Dolby TrueHD and DTS-HD Master Audio - with HDMI 1.3). Therefore, you have fewer cables running around the back of your TV - which can only be a good thing! Read more: Understanding the HDMI Connector and Cable
HDMI ARC/eARC
ARC stands for Audio Return Channel. On a TV, AV receiver or soundbar, some HDMI ports may be labeled as ARC. This means that you can send audio from the TV back to the AV receiver or soundbar. Both your TV and receiver/soundbar HDMI ports need to support this for it to work. This can simplify your connections. It can mean that you don't need to connect a separate optical cable if you want to hear the audio that is generated within the TV e.g. from the Netflix or Amazon Prime Video app. This is also useful if your TV doesn't have a digital audio out. eARC (Enhanced Audio Return Channel) is a new version that also supports sending higher bitrate audio like Dolby TrueHD/DTS-HD Master Audio and Dolby Atmos.
HDR
Stands for High Dynamic Range. A technique that increases the dynamic range of an image. Darker blacks. Brighter whites. More colors. Result? The picture will be more life-like. Your AV receiver will need to support HDR to pass this type of content from your HDR-compatible Blu-ray player to your HDR-compatible TV. There are different versions of HDR such as HDR10, HDR10+, Hybrid Log-Gamma and Dolby Vision. Your complete hardware chain will need to support a particular version to use it.
HDR10
An open-source format of HDR supported by several hardware manufacturers. Currently the most common version available on sources and displays.
HDR10+
An updated version of HDR10. Like Dolby Vision, it supports dynamic metadata which can change the brightness and color range for each scene or frame. It is becoming more common in some manufacturer's products.
HDTV
Stands for High-Definition Television. HDTV provides images at a much higher resolution than the previous standards of SDTV and EDTV. To be called a high-definition picture, each frame of a video signal must have a minimum of 720 vertical lines of information with progressive scan or 1080 vertical lines of information with interlaced scan. Therefore, 720p or 1080i are both high-definition signals - as well as the big daddy - 1080p (also known as full HD). The picture should also have a 16:9 aspect ratio (widescreen).
High-Definition Television
See HDTV
Home Cinema
See Home Theater
Home Theater
A term used in North America to describe a high-end home entertainment system. A basic home theater system would usually refer to a large flat screen tv or projector to display the image - and a separate amplifier and speakers for the sound. The sound system is often surround sound. It is more commonly known as home cinema – or home theatre - in Europe.
Hybrid Log-Gamma
Known-as HLG for short. A variation of HDR that was developed by the BBC and NHK in Japan. It is designed to be used by broadcasters for transmitting HDR pictures.

I

Image Resolution
The resolution of a TV image is defined by the number of pixels that make up the image. It can be calculated by the number of lines of vertical pixel data of the image multiplied by the aspect ratio of the image. For example, for HDTV the standard aspect ratio is 1.78 (16:9), and the minimum number of vertical pixel lines per frame is 720. Therefore, 720 (vertical lines) x 1.78 (aspect ratio) = 1280 (horizontal lines). So, the resolution of this 720p image is said to be 1280 x 720 – or 921,600 pixels. The resolution of an image received by your TV can vary depending on the source. This is not the same as the native resolution of the TV screen - which is fixed. Read more: Understanding TV Resolutions
IR
Stands for infrared. A type of electromagnetic radiation that is commonly used to send control signals to household electronic devices using a remote control. Infrared remote controls need 'line-of-sight' with the device they are controlling i.e. they won't work through walls or doors.
Interlaced Video
Interlaced video is a method of doubling the frame rate of video without increasing the bandwidth. An old CRT TV displays an interlaced picture by building each image frame in two separate passes down the screen. First, it fills the odd lines - 1, 3, 5, 7, etc. Then it goes back to the top and fills in the even lines - 2, 4, 6, 8, etc. After these two passes, it will have 'drawn' one frame of an image. Each pass is known as a field. It then goes back and 'draws' frame two – and 3 – and 4 etc. This is the traditional method used by PAL and NTSC TV signals. This technique produces an image that can appear to flicker and lack sharpness. The modern alternative is to use progressive scan. New flat screen TVs aren’t able to handle interlaced video as effectively as older CRT televsions. Therefore, for any interlaced video sources, modern AV products perform a process of deinterlacing.

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LCD TV
A type of flat screen TV. LCD stands for liquid crystal display. An LCD screen is made up of small pixels filled with liquid crystal - and a backlight. The intensity of light in each pixel can be varied by applying an electrical signal which changes the molecular structure of the liquid crystal. Each pixel is divided into three sub-pixels (red, green and blue) by using a color filter - and by varying the intensity of light in each - different colors can be created. By constantly changing the intensity and color in each pixel, a TV picture can be formed. This technology is also used to produce other types of display - such as computer monitors and projectors.
LCoS
Stands for Liquid Crystal On Silicon. A projection technology used in some types of video projectors. It can often be found in rear-projection TVs. It is similar to DLP technology, but the light is reflected off a silicon chip coated with liquid crystals rather than mirrors.
LED TV
A type of flat screen TV similar to a traditional LCD TV. The difference is the backlight in an LED TV is provided by light-emitting diodes (LEDs), as opposed to a CCFL in the LCD TV. However, they both have LCD screens. Confusingly, in the beginning, some manufacturers referred to TVs with LCD screens and LED backlights as LED TVs - and some still called them LCD TVs. Everyone uses the term LED TV now. Read more: How to Pick the Best Flat Screen TV For You
LFE
Stands for Low-Frequency Effects. The LFE is an optional low frequency (below 120 Hz) audio track that can be part of a 5.1/7.1 audio soundtrack. It adds extra bass information in addition to the normal bass within a soundtrack. If you are using an AV receiver, the LFE track is usually sent to a connected subwoofer. However, if you don’t have a subwoofer installed, then the AV receiver can send the LFE track to full-range speakers instead. Read more: How to Connect a Subwoofer
Line Level
A term used to describe the strength of an audio signal. It is expressed as decibels against a reference voltage. Most audio-visual devices output their audio at line level. This signal then needs to be amplified before it can be heard on a speaker. This is why we need to connect a CD or DVD player to a power amplifier first - rather than directly to a speaker. It is not a fixed amount and can vary depending on the equipment. Generally, consumer audio devices output line level at -10 dBV. Whereas professional audio products output a higher level of +4 dBu.
LPCM
Stands for Linear Pulse Code Modulation. A method of digitally encoding/decoding audio data. It is a standard method of encoding audio on CD, DVD and Blu-ray discs.

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Native Resolution
When talking about LCD or plasma displays, the native resolution is the physical size of a TV screen - measured by the number of pixels. This can also be called the pixel dimension. The native resolution of a screen is expressed by stating the number of horizontal pixels by the number of vertical pixels. i.e. a screen that is said to have a native resolution of 1920 x 1080 will have 1920 pixels across the screen, and 1080 pixels down the screen. Generally speaking, the more pixels there are (higher resolution), the sharper the image will be. The native resolution of a display is fixed. Note: this is not the same as the image resolution.
NTSC
Stands for National Television System Committee. The NTSC system is used to encode analog TV transmissions in some parts of the world - mainly in the Americas and Japan. The term is often used to describe a 480i picture (525 lines and 60Hz refresh rate).

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OLED TV
A type of flat screen TV that uses a different display technology than an LED TV. OLED stands for organic light-emitting diode. An OLED has an organic layer that emits light when it is fed an electric current. Due to the way this technology works, these TVs can be very thin and light as there is no backlight. Other benefits are low power requirements, a wide viewing angle and high contrast ratios. They are widely regarded to have the best picture quality currently available. Read more: How to Pick the Best Flat Screen TV For You
Optical Audio Connection
Also known as a TOSLINK connection. A method for transferring digital audio signals between devices. Commonly found on consumer electronic products such as DVD players and games consoles. The audio signal is converted into light and transferred via a cable made from optical fiber. Supports stereo audio and Dolby Digital/DTS 5.1 surround sound audio signals. Read more: Understanding the Optical Digital Audio Cable and Connection
Overscan
Historically, standard-definition TVs were difficult to build accurately enough so that we could guarantee how much of a TV image they would show. Therefore, these televisions used a technique called overscan which zoomed in the image slightly to make sure there was a clean edge around the picture on the screen, all the possible screen area was used for the image, and that no transmission signals and other artifacts were visible. Program makers made sure that they kept all the important action within a 'safe action area', therefore ensuring nobody would miss anything important. However, by using overscan we are losing some of the picture. On a modern HDTV or projector, this overscan feature can often be switched on or off - but not always. It is often recommended to have overscan switched on for standard definition pictures - but switched off for high-definition and UHD pictures. Ultimately it comes down to personal preference.

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PAL
Stands for Phase Alternating Line. The PAL system is used to encode analog TV transmissions in some parts of the world - mainly in Europe and Asia. The term is often used to describe a 576i picture (625 lines and 50Hz refresh rate).
Passive Subwoofer
A subwoofer with no built-in amplifier. This type of subwoofer should receive an amplified signal from an AV receiver/amplifier. The subwoofer is just a housing for the speaker. Generally, passive subwoofers won't have inbuilt volume and tone controls, as this will be done by the amplifier before sending the signal to the subwoofer. Most subwoofers designed for home cinema will be active subwoofers.
Pixel
Short for picture element. A TV screen is made up of a grid of very small dots, squares or rectangles. Each one of these is called a pixel. These pixels can each be made to display a different color at different intensities. A picture on the screen is made from all these small pixels working together to create a large image. If you get very close to your TV, you may be able to see the individual pixels at work. The total number of pixels that make up your TV screen is known as the native resolution.
Plasma TV
A type of flat screen TV. A plasma screen is made up of small phosphor-covered pixels filled with gas. When fed with an electrical signal, the gas and the phosphor interact to create colors. These colors can be controlled to produce a TV image. Clever huh! Plasma TVs used to offer the best TV picture quality but have now been discontinued by all manufacturers.
Progressive Scan
Your TV displays a progressive scan picture by building each image frame one line at a time down the screen i.e. each frame is drawn in one pass. This produces a very sharp and 'flicker-free' picture. The traditional method for displaying TV pictures is by interlaced scan - where each frame is drawn in two passes. Most modern DVD and Blu-ray players will be able to display the image using progressive scan. Some TV transmissions still use interlaced scan.

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QFT
Stands for Quick Frame Transport. Part of the HDMI 2.1 specification. QFT allows the source device to send video frames to the TV as soon as they are produced - rather than wait until the display device is ready for it. This reduces latency when gaming. All devices in the chain need to support this.
QLED TV
A type of LED technology developed by Samsung. They are built using quantum dot technology – hence the name QLED. QLED TVs have a several advantages over standard LED TVs such as a wider color range, increased brightness and wider viewing angles. However, they are also more expensive. Read more: How to Pick the Best Flat Screen TV For You
QMS
Stands for Quick Media Switching. Part of the HDMI 2.1 specification. QMS removes any delay before content is displayed. For example, you may get a temporary black screen when you switch from one video source to another – especially if you are switching video resolutions or frame rates. QMS stops this black screen from happening. All devices in the chain need to support this.

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RF
Stands for radio-frequency. Used by some remote controls to send control signals to home cinema equipment. In the home, many remote controls use infrared to transmit a control signal. However, some devices use RF remote controls which have the advantage of a greater range and the ability to work through walls and other hard surfaces.
RCA Plug
Also known as a phono plug. A common connection for audio/video cables and commonly found as input/output connectors on DVD players and TVs etc. These connections are usually colored red and white for analog stereo audio signals, yellow for analog composite video signals and red/green/blue for analog component video signals. They are also used for coaxial digital audio connections. Read more: Understanding the RCA Plug and Stereo Cables
Rear Projection Television
Also known as an RPT. A type of large screen TV that creates an image by using a small projector behind the screen. This used to be the main method of producing large screen TVs but has been overtaken by LCD and plasma TVs in the last few years. The advantage of this system is that projectors can produce excellent images - however, these systems tend to be rather bulky compared to LCD and plasma flat screen TVs. Traditionally CRT projectors were used in RPTs, but more recently the projectors used are either DLP, LCD or LCoS.
Refresh Rate
The refresh rate of a TV is the number of times per second the picture is 'redrawn'. The quicker a picture is redrawn; any motion will appear smoother to the human eye and it will have less flicker. This figure will be slightly different around the world due to technical differences. In a PAL region, an interlaced TV picture has a frame rate of 25 frames per second - and each frame is drawn in two passes. Therefore, the refresh rate is said to be 50Hz (25 x 2). In North America the frame rate is 29.97 frames per second - so the standard refresh rate is 59.94Hz (29.97 x 2). These refresh rates originated from using interlaced scan images - but they were kept as standard when progressive scan images started to be used. Some newer TVs have increased their refresh rates to 100/120Hz. Some claim even higher refresh rates by using digital signal processing. Read more: Understanding TV Refresh Rates
RMS
Stands for Root Mean Square. A statistical measure of something that varies over time. It is used with amplifiers to get a meaningful value for the power output in watts. The RMS values of voltage and watts are multiplied to get an average value of power. It is important to work with an average power value, rather than a peak value, as this tells us more about how the amplifier will perform in the real world. Read more: AV Receiver & Amplifier Power Ratings Explained

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SACD
Stands for Super Audio Compact Disc. A high-resolution audio format developed by Sony and Philips and designed to improve the audio quality of a traditional CD. SACD is a high-density disc like a DVD, and with a much higher sampling rate than a traditional CD. This results in recordings with a wider frequency response and a larger dynamic range. It also supports multi-channel audio as well as stereo.
SCART
A 21-pin connector used to connect audio-visual equipment. The 21 pins allow a SCART connector to transmit analog audio and video signals through the same cable. Mostly used for interconnecting TVs, DVD players and VCRs. A standard analog connection in Europe, but rarely used in North America. Read more: SCART Connections and Cables
SDR
Stands for Standard Dynamic Range. SDR video doesn't have a large dynamic range like HDR video. Similarly, an SDR TV cannot display the increased brightness, contrast ratio and color gamut required to display HDR video
SDTV
Stands for Standard Definition Television. SDTV is any TV transmission with a lower resolution than Enhanced Definition Television (EDTV) or High Definition Television (HDTV). Depending on where you live, each frame of a standard definition video signal has either 480 (North America) or 576 (Europe) visible vertical lines of information. Therefore, you may see an SDTV transmission described as 480i (480 lines, interlaced) or 576i (576 lines, interlaced). EDTV and HDTV produce a sharper picture than SDTV.
Soundbar
A bar with multiple speakers that is designed to be placed along the front edge of a TV screen. The idea is to replace the TV speakers and get a better sound without installing a more complex AV receiver and surround speaker setup. The soundbar will often use audio processing techniques to imitate the effect of surround sound, without needing extra speakers around the room. It is usually an active speaker, which means it can be connected directly to the audio output of a TV. Read more: The Best Soundbars for Your TV and Home Theater
Speaker Sensitivity
Also known as speaker efficiency. A speaker is sent a fixed level of power (watts), and the resulting sound level is measured to give the efficiency of that speaker. A less efficient speaker will require more power to sound as loud as a more efficient speaker. Speaker sensitivity can range from about 85db (inefficient) to about 100db (efficient). Read more: Understanding Speaker Sensitivity and Efficiency
Stereoscopy
This refers to any technique that records 3-dimensional visual information. These techniques allow the creation of 3D TV images that have the illusion of depth. The basic idea is that a slightly different version of an image is delivered to each eye, and the brain then creates one 3D image.
SUHD
A term used by Samsung to label their high-end 4K LED TVs. Although the name might suggest a higher resolution TV - it doesn't mean anything in terms of UHD. The resolution of the screen is the same as any other 4K TV - 3840 x 2160.
Super UHD
A term used by LG to label their high-end 4K LED TVs. As with SUHD, these TVs are a standard 4K resolution. It refers to a technology that is supposed to improve the colors.
Surround Sound
The reproduction of audio using a multi-channel system. Most of the audio we hear from TV or radio is stereo i.e. the audio is produced to sound good from two speakers in front of you. Surround sound is used in cinema and at home to add a sense of space and direction to the audio. For example, a 5.1 surround sound system uses six speakers. Front left and right (which is the equivalent of your stereo speakers), front center (for dialogue), surround left and right (it's behind you!) and a subwoofer (for bass). A 7.1 surround sound system has two more speakers at the back. Read more: Guide to Setting Up Surround Sound
Subwoofer
A speaker designed to reproduce low bass frequencies. It is often just called a sub. A subwoofer is usually connected to an AV receiver as part of a surround sound speaker system. But, you can also just use one with a stereo amplifier for listening to music. If you have a speaker dedicated to reproducing just the low-end frequencies - or LFE track - you can get a much better bass performance in your room. Your surround speakers may also sound better as they don’t have to try and reproduce the very low-end. This is the one that annoys the neighbors! Read more: How to Connect a Subwoofer
S-Video
A type of component analog video. The video signal is split into two separate parts and is usually connected with a 4-pin mini-DIN cable. S-Video gives you better quality than composite video, but not as good as component video. Read more: S-Video Cable and Connectors Explained

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See optical audio connection.
Transducer
A device that turns one type of energy into another. A loudspeaker is an electroacoustic transducer as it turns electrical energy into sound.
Tuner
In audio-visual technology, a tuner is a device that receives RF (radio-frequency) transmissions. These various frequencies are then converted to a fixed frequency for output. In the case of a radio tuner, it will be able to tune to the frequencies of audio radio transmissions (FM/AM or DAB). Once received, this signal is then passed to an amplifier/speaker configuration to make the radio signal audible. A TV tuner will be able to tune to the frequencies of TV transmissions and convert these to sound and picture. You can get analog tuners for receiving analog transmissions - or these days, a digital tuner is becoming more common to receive digital transmissions.
Tweeter
A loudspeaker designed to reproduce high frequencies - usually in the region of 2 kHz to 20 kHz. A typical bookshelf speaker will have two speaker drivers - a tweeter for the high frequencies, and a woofer for the low frequencies.

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Ultra HD
A new standard of high-resolution video that has more detail than high-definition video. Ultra HD video includes 4K and 8K video. Also known as 4K, 8K, Ultra High Definition, Ultra HD 4K, Ultra HD 8K, UHDTV, SUHD and many more. An increase in pixel density is not the only improvement in UHD video. The standard also allows for an increased dynamic range (darker blacks and whiter whites) and a wider color gamut (more colors).
Upconverting
Changing a video signal from one type to another - or to be precise, from a 'lower quality' video signal to a 'higher quality' video signal. For example, if we have a DVD player connected to an AV receiver with an analog component connection, but we want the AV receiver to output to the display via HDMI. In this case, the AV receiver will need to upconvert the analog component input signal into a digital HDMI output signal. The AV receiver would also need to upconvert if the input is S-Video and the required output is component video. Cheaper AV receivers might not allow for any conversion of video types. The more expensive models should have more options.
UPnP
Stands for Universal Plug and Play. A set of network protocols that allows devices on a home network to share data between each other. In terms of home entertainment, this means that a display device like a TV can display pictures or play movies that are stored elsewhere on the network - such as on a computer or NAS (Networked Attached Storage). It is easily confused with DLNA. The DLNA certification standard uses parts of the UPnP protocol - but it places stricter limits on the types of media files it supports.
Upscaling
Increasing the resolution of a low-resolution video signal to a higher resolution. A video scaler is used to convert video signals from one resolution to another. For instance, a DVD player can play an SD movie (480 lines NTSC, 576 lines PAL) and upscale this image to 720 (or 1080) vertical lines to match the resolution of an HD display. This technique can make standard DVDs look much better on a high-definition TV or projector. In this example, the video scaling can be done by the DVD player or the TV/projector - and the best results will depend on which device has the best video scaler. Often the TV will have a better scaler because its primary purpose is to display video. This process is sometimes referred to as 'upconverting' - but this shouldn't be confused with upconverting! Who said this stuff was easy? :-)

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VESA
Stands for Video Electronics Standards Association. An association formed in 1989 by several video display manufacturers. They aimed to set certain standards within the industry to allow common features between devices. For example, VESA compliant hole patterns define standard hole sizes on TV wall mounts and the rear of flat-panel TVs. Read more: Guide to the Best TV Wall Mounts: Reviews and Buying Guide
VGA Connector
A connection that transmits analog video signals. This port is usually found on devices as a 15 pin D-type connection. It is used mainly on computers and projectors - but they are still provided on some flat panel screens for the connection of laptops. Read more: VGA Connector and Cable
VRR
Stands for Variable Refresh Rate. Part of the HDMI 2.1 specification. A screen that supports VRR can synchronize its refresh rate with the output of a computer graphics card. This is particularly useful for gamers. It means there is no conflict between the refresh rate of the game you are playing and the screen that you are playing the game on. The result is a smooth gaming experience with no screen tearing. It can also reduce power consumption. Examples are NVIDIA G-SYNC and AMD FreeSync. Both the graphics card and screen will need to support the same version of VRR.

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Wide Color Gamut
A color gamut refers to the number of different colors a device can show. This device might be a TV or a projector. Over the years, there have been different color gamut standards for TVs. These standards have gradually evolved with the technology e.g. the introduction of high-definition and UHD TV. The 4K Ultra HD specification introduced a new standard called BT.2020. Part of this new standard included the display of more colors. This improved color standard is often referred to as the wide color gamut.
Widescreen
A widescreen image has an aspect ratio that is wider and shorter than the original standard of 4:3 (1.33:1) aspect ratio. Typically, we mean a 16:9 (1.78:1) aspect ratio when we talk about widescreen, as this is the standard size for flat screen TVs. However, films are traditionally shot with an even wider image size such as 1.85:1 or 2.39:1. This is why we get black bars at the top and bottom of a film on our 16:9 TV - because the original film was shot with a wider aspect ratio than our TV can show. Read more: TV aspect ratios explained
Woofer
A loudspeaker designed to reproduce low frequencies - usually in the region of 40 Hz to 1 kHz. A typical bookshelf speaker may have two speaker drivers - a woofer for the low frequencies, and a tweeter for the high frequencies.

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