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2017-02-13 09:15 admin 人关注

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

H — - See "Horizontal sync."
H.264 (MPEG-4 AVC) - Block-oriented motion-compensation-based codec standard developed by the ITU-T Video Coding Experts Group (VCEG) together with the ISO/IEC Moving Picture Experts Group (MPEG). It is the product of a partnership effort known as the Joint Video Team (JVT). H.264 is used in such applications as Blu-ray Disc, videos from YouTube and the iTunes Store, DVB broadcast, direct-broadcast satellite television service, cable television services, and real-time videoconferencing.
H.264 Encoding - A standard for video compression equivalent to MPEG-4 Part 10 or MPEG-4 AVC – Advanced Video Coding. H.264 was created to provide video quality suitable for high definition applications at bit rates lower than that utilized in MPEG-2, the compression standard used in DVD ing.
H.320 - ITU-T H.320 is a family of standards developed for video teleconferencing systems using ISDN. It references H.261 (for video); G.711, G.722, and G.728 (for audio); H.221, H.230, H.231, H.233, H.234, H.242, and H.243 (for control). The standard allows a system from one manufacturer to talk to a system from another manufacturer, just as two different brands of FAX machines can talk to each other.
H.323 - ITU standard allowing audio, video, and data to be transmitted by way of the Internet Protocol (LAN/WAN). It is the umbrella standard defining multiple codes, call control, and channel setup specifications. Basically, videoconferencing over IP.
Half duplex - Data or audio transmission that can occur in two directions over a single line, but only one direction at a time.
Halogen-free (LSFOH) - Low Smoke and Fumes Zero Halogen. Refers to the material used in cable insulation that emits reduced amounts of hazardous smoke and toxic fumes in the event of a fire. Certain countries, such as in the UK, may require LSFOH cable insulation.
Handshake - In communications, the moment when the transmitting and receiving devices identify themselves to each other.
Harmonics (in music: overtones) - Multiples of an original frequency that add to and modify the original frequency. A pure sine wave is free of harmonics. When harmonics occur in electronic signals, it adds distortion to the original signal, causing undesirable results.
HD connector - A high-density D connector having its pins arranged close together, sometimes in three rows instead of two rows. Example: a 15-pin VGA connector (HD) vs. a Mac connector (D).
HDCP – High-bandwidth Digital Content Protection - A digital rights management scheme developed by Intel to prevent the copying of digital video and audio content. HDCP is mandatory for the HDMI interface, optional for DVI. HDCP defines three basic system components: source, sink, and repeater.

Sources send content to the display. Sources can be set-top boxes, Blu-ray Disc players, computer-graphics cards, and so forth. A source can have only one HDCP transmitter. 

Sinks decrypt the content so it can be viewed. Sink is typically used to describe a flat panel display, television, or projector. Sinks can have one or more HDCP receivers. 

Repeaters sit between Sources and Sinks. They accept content, decrypt it, then re-encrypt and transmit. Internally, a Repeater may provide signal processing, such as scaling, splitting out audio for use in an analog audio playback system, or splitting the input data stream for simultaneous viewing on multiple displays. Switchers, matrix switchers, and distribution amplifiers are all examples of Repeaters.
HDMI – High-Definition Multimedia Interface - An interface for the digital transmission of uncompressed high definition video, multi-channel audio, and control signals, over a single cable. HDMI is the de facto standard for consumer level video sources and displays.
HD-SDI - The high-definition version of SDI specified in SMPTE-292M. This signal standard transmits audio and video with 10 bit depth and 4:2:2 color quantization over a single coaxial cable with a data rate of 1.485 Gbit/second. Multiple video resolutions exist including progressive 1280x720 and interlaced 1920x1080 resolution. Up to 32 audio signals are carried in the ancillary data.
HDTV - High Definition Television. HDTV refers to a complete product/system with the following minimum performance attributes: a receiver that receives ATSC terrestrial digital transmissions and decodes all ATSC Table 3 video formats; a display scanning format with active vertical scanning lines of 720 progressive (720p), 1080 interlaced (1080i), or higher; aspect ratio capabilities for displaying a 16:9 image; receives and reproduces, and/or outputs Dolby Digital audio.
Hertz (Hz) - A unit of frequency; describing the number cycles per second. 1Hz = 1 cycle/second…1MHz = 1 Million cycles/second
High fidelity - Hi fi, accurate, and faithful reproduction of the original. Absence of distortion or enhancements.
High impedance - Hi Z or high Z. A relative term that is different for each application. In video, when the signal is not terminated it has a Hi Z load. Hi Z is typically 800 to 10k ohms or greater.
High pass filter - A circuit that discriminates between high and low frequencies and allows only the high frequencies to pass. Also called a “low cut filter.”
High-Definition Video - Refers to any video system of higher resolution than standarddefinition (SD) video, and most commonly involves display resolutions of 1280×720 pixels (720p) or 1920×1080 pixels (1080i/1080p).
Hooking - See "Bending."
Hop - In a packet-switching network, a hop is the trip a data packet takes from one router or intermediate point to another in the network.
Hop Count - On the Internet (or a network that uses TCP/IP), the number of hops a packet has taken toward its destination.
Horizontal blanking - After making a scan line (left-to-right), the electron beam in a CRT retraces (returns) to the left side of the screen to begin the next line. During retrace time, it is not putting picture information on the screen, so the beam is turned off, or blanked. About 83% of each horizontal cycle is spent writing the line, while 17% is spent retracing the beam to the left before starting the next line. Also see "Blanking."
Horizontal Cabling - Telecommunications cabling used to cover a floor area. It extends from the horizontal cross-connect in the telecommunications room to a local access outlet.
Horizontal centering control - Adjusting the horizontal centering control shifts the displayed image left or right on the display screen. Also called “horizontal shift.”
Horizontal Cross-Connect – HC - A patch panel or LAN – Local Area Network panel, used to cross-connect horizontal cables to other cabling within a building or facility.
Horizontal double images - A video problem when the display is split down the middle with two identical but squeezed images displayed on each side of the screen.
Horizontal filtering - In some Extron scan converters and other products, this is a feature that controls the sampling of the horizontal plane, thereby affecting the sharpness or smoothness of the scan-converted picture.
Horizontal rate - Horizontal scanning frequency. The number of complete horizontal lines (trace and retrace) scanned per second. Measured in kHz, the NTSC standard is 15.75 kHz.
Horizontal resolution - The number of vertical lines that can be perceived in a video device.
Horizontal sync - The pulses that control the horizontal scanning of the electron beam in a video device. On connector panels, “H” identifies the connector for horizontal sync, and “H/HV” means it is also used for combined or “composite” horizontal and vertical sync (RGBS).
Hot Plug/Hot Plug Detect - Describes a feature of DVI, HDMI, USB, and other digital technologies which allows a host device, such as a computer, to detect the presence of a new device without intervention by the user. Hot Plug technology allows a new device to be added to a system while it’s still connected to a power source. Once the new device is connected, the Hot Plug Detect circuit, or HPD, senses the new device and tells the rest of the system that the device is ready to either send or receive a data stream.
Hot spot - Commonly seen on high-gain screens and screens designed for slide or movie projection, a hot spot is a circular area where the image is brighter than the rest of the screen. The hot spot is always located along the line of sight, and “moves” with the line of sight.
Hot-swap - The ability to change electronic components, such as circuit boards or peripheral devices, without removing power from the device.
House sync - See "Blackburst."
HTML - Hypertext Markup Language. A formatting computer language used to create web pages.
HTTP - HyperText Transfer Protocol. A Web protocol based on TCP/IP that is used to retrieve hypertext objects from remote Web pages.
Hub - A shared transmission media to which devices on a network are interfaced. Ethernet hubs have mostly given way to Ethernet switches.
Hue - (1) Color value or saturation, as opposed to brightness or intensity. (2) Tint control – Hue is the parameter of color that allows us to distinguish between colors. The hue, or tint control, adjusts the amount of color displayed.
Huffman Coding - A method of entropy encoding used in lossless data compression where the most frequently occurring values use the shortest codes.
Hum - The coupling of an unwanted frequency into other electrical signals. In audio, hum can be heard; in video, it can appear as waves or bars in the picture. Often it is an audible disturbance caused by the power supply, or an improper ground.
Hum bar(s) - Interference in the form of a horizontal bar moving vertically on the display screen. Hum bars can be caused by ground loops.
Humbucker - A transformer used to isolate video signals caused by interference from hum bars or moiré.

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