Confused about all of those terms?
Glossary of Terms
The 5.1-channel sound system specified in the Standard for Digital-HDTV. Also known as "Dolby Digital," AC-3 delivers CD-quality digital audio and provides five full-bandwidth channels for front left, front right, center, surround left and surround right speakers, plus an LFE (low frequency effect) subwoofer, for a total of 5.1 channels.
Advanced Television Systems Committee (ATSC)
The ATSC is the committee responsible for developing and establishing Digital-HDTV Standards; as well as all (18) formats of Digital TV.
Analog to digital conversion (or converter). Used at transmission end of broadcast.
The highest resolution signal that a display device (TV or monitor) can accept.
Caution: Consumers should be aware however, that although a particular device (Digital-HDTV) is able to receive the resolution, it may not be capable of displaying it.
Analog TV is the NTSC Standard for traditional television broadcasts. Analog signals vary continuously, representing fluctuations in color and brightness.
Unwanted visible effects in the picture created by disturbances in the transmission or image processing, such as 'edge crawl' or 'hanging dots' in analog pictures, or 'pixelation' in digital pictures.
Refers to the width of a picture relative to its height. If an NTSC picture is 4 feet wide, it will be 3 feet high; thus it has a 4:3 aspect ratio. HDTV has a 16:9 aspect ratio.
See Advanced Television Systems Committee.
"Advanced Television" is an earlier term used to describe the development and advance applications of digital television, now simply referred to as DTV.
A range of frequencies used to transmit information such as picture and sound. For TV broadcasters, the FCC has allocated 6Mhz for each channel. For DTV, the maximum bit rate possible within the bandwidth is 19.4 Mbps, which is one HDTV channel. SDTV has a lower bit rate, therefore the bandwidth can accommodate more than one channel.
Measured as "bits per second," and used to express the rate at which data is transmitted or processed. The higher the bit rate, the more data that is processed and, typically, the higher the picture resolution.
A 6 MHz (bandwidth) section of broadcasting spectrum allocated for one analog NTSC transmission.
Component (HD) Video Connection
The output of a high definition video device (such as an HDTV set-top box), or the input of an HDTV receiver or monitor, comprised of (3) primary-color signals: red, green, and blue - each on a separate wire. The combination of these three signals convey all necessary picture information. In consumer video products, these (3) separate component signals refer to: Luminance (Y) - for Light; and two Chroma (Color) signals (Pb - blue) and (Pr - red). HDTV-Component cables and connections are commonly labeled: Y/Pb/Pr.
An analog, encoded video signal (such as NTSC) that includes vertical and horizontal synchronizing information. Since both luminance (brightness) and chrominance (color) signals are encoded together, only a single connection wire is needed (i.e. RCA cables).
A method of electronically reducing the number of bits required to store or transmit data within a specified time or space. The video industry uses several types of compression methods but the method adopted for DTV is called "MPEG2." Four full-range channels of programming and data can be compressed into the same space required by a single analog channel.
Conversion of digital to analog signals. The device is also referred to as DAC (D/A converter). In order for conventional television technology to display digitally transmitted TV data, the data must be decoded first and then converted back to an analog signal.
Abbreviation of "Digital Broadcast Satellite" - refers to digital TV transmissions via satellite. Digital Television (DTV)
Refers to all formats of digital television, including high definition television (HDTV), and standard definition television (SDTV). Also referred to as ATV (Advanced TV).
DLP - Digital light processing. - A microdisplay technology invented by Texas Instruments, DLP is based on a digital micromirror device (DMD), a chip with millions of hinged, microscopic mirrors attached, each of which corresponds to a single pixel in the projected image. Red, green, and blue light filtered through a color wheel is directed alternately onto the DMD, which switches on and off up to 5,000 times a second. The reflected light is directed through a lens and onto a screen, creating an image. High-end HDTV projectors use a three-chip solution, with separate DMD's for green, red, and blue, and forego the color wheel.
Dolby Digital - Six-channel digital audio standard that is part of the U.S. digital television standard; also called AC-3 or Digital 5.1. The channels consist of front left, front right, front center, surround or rear left, surround or rear right, and a separate subwoofer (the .1).
Downconvert - In DTV, the conversion from a higher-resolution input signal number to a lower one. For example, some DTV receivers can be set to downconvert an HDTV 1080i signal to a standard 480i signal that any TV can display.
DTCP - Digital Transmission Copy Protection. HDTV copy-protection scheme more commonly called 5C.
DTLA - Digital Transmission Licensing Administrator. The licensing organization for the 5C DTCP HDTV copy-protection technology.
Digital Theater Systems sound. Discrete 5.1 channel surround system similar but not the same as Dolby Digital. Dolby Digital is the DTV standard, but DTS competes with it on DVD and in the movie theaters.
DTV - Digital television. Generic term that refers to all digital television formats, including high-definition television (HDTV) and standard-definition television (SDTV).
DVI — Digital Visual Interface. This is a high-bandwidth video connection that carries digitized RGB picture information and can support copy-protection methods. The DVI specification allows for the presentation device and display device to agree on an optimal picture size and resolution to ensure the highest quality picture automatically.
D-VHS- Digital-VHS. Version of VHS (Video Home System) videocassette standard capable of recording HDTV via a FireWire connection; D-VHS decks are made by JVC and Mitsubishi.
DVR - Digital video recorder. A television recorder such as Replay and TiVo that uses a hard drive, an EPG (Electronic program guide), and internal processing to drastically simplify programmed recording and playback of recorded programs. A DVR vastly increases recording time compared to VCRs or DVD-recording decks; often enables smart programming, in which the device records an entire series or programming defined by keywords, genre, or personnel; and offers pause control over "live" broadcasts. Also called personal video recorder (PVR) or hard disk video recorder.
Electronic program guide. An on-screen display of channels and program data.
The number of times per second that a signal fluctuates. The international unit for frequency is the hertz (Hz). One thousand hertz equals 1 KHz (kilohertz). One million hertz equals 1 MHz (megahertz). One billion hertz equals 1 GHz (gigahertz). Television is broadcast in frequencies ranging from 54 MHz to 216 MHz (VHF) and 470 MHz to 806 MHz (UHF)
High Definition Television (HDTV)
The generally agreed upon definition of HDTV is approximately twice the vertical and horizontal picture resolution of today's NTSC TV, which essentially makes the picture twice as sharp. HDTV also has a screen ratio of 16:9 as compared with most of today's TV screens, which have a screen ratio of 4:3. HDTV offers reduced motion artifacts (i.e. ghosting, dot crawl), and offers 5.1 independent channels of CD-quality stereo surround sound, (also referred to as AC-3).
HDCP - High-bandwidth Digital Content Protection. Copy-protection scheme developed by Intel to be used in conjunction with DVI and HDMI connections.
HDMI - High-Definition Multimedia Interface. USB-like digital video connectivity standard designed as a successor to DVI; can transmit both uncompressed digital audio and video signals; protected by HDCP digital copy protection.
HD-DVD - High-definition digital video disc. Several formats have been proposed for these high-capacity DVD's, including Blu-ray.
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.
Interactive television: An anticipated use of television with interactive content and enhancements, enabling the viewer to interact with the program. Interactive television, in theory, would enhance the entertainment experience by providing access to additional information; combining normal TV viewing with the interactivity of a personal computer.
In a television display, interlaced scanning refers to the process of re-assembling a picture from a series of electrical (video) signals. The "standard" NTSC system uses 525 scanning lines to create a picture (frame). The frame/picture is made up of two fields: The first field has 262.5 odd lines (1,3,5...) and the second field has 262.5 even lines (2,4,6...). The odd lines are scanned (or painted on the screen) in 1/60th of a second and the even lines follow in the next 1/60th of a second. This presents an entire frame/picture of 525 lines in 1/30th of a second.
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.
ISDN: Integrated Services Digital Network. Enables transmission of data at high speed over the a telephone network. ISDN varies from a Basic Rate of 64 Kbits/sec up to a Primary Rate of 2 Mbps; referred to as (ISDN-30) since it comprises 30 Basic Rate channels.
Liquid Crystal Display — An LCD television or monitor uses liquid crystals that act as "shutters" within the television screen. An LCD television has thousands of small light sources at the rear of the display. A layer of cells containing the liquid crystals is placed between the light sources and the display screen. When the liquid crystal cells are electrified with current, the crystals align and block any light from shining through, or scatter allowing the light to shine through to the screen. LCD monitors typically only display video signals in a progressive scan format. LCD monitors do not use phosphors and are not susceptible to screen burn.
A method, through special circuitry, to modify an NTSC interlaced picture to create an effect similar to a progressively scanned picture. The first field of 262.5 odd-numbered lines is stored in digital memory and combined with the even-numbered lines. Then all 525 lines are scanned in 1/30th of a second. The result is improved detail enhancement from an NTSC source.
Letterbox Mode — A method of presenting widescreen images on a standard screen television. In order to preserve the aspect ratio of the original video content, the picture is scaled down so that it fits the available width of the television screen. Since the picture will not fill the screen vertically, dark bars are displayed above and below the picture.
Lossy compression: Reducing the total data rate by discarding data that is not critical. Both video and audio for DTV transmission use lossy compression.
Luminance: (Light or Brightness) In video signals the component that includes information about its brightness.
Megabyte: One million bytes (actually 1,048,576); one thousand kilobytes.
Modem: Modulator/demodulator. A device that transforms a typical two-level computer signal into a form suitable for transmission over a telephone line. Also does the reverse--transforms an encoded signal on a telephone line into a two-level computer signal.
MPEG: Compression standards for moving images advanced by the “Motion Pictures Expert Group;” the international group of industry experts that set standards for compression of video and audio. MPEG-2 is the basis for ATSC digital television transmission.
MPEG-2: Designed to cover a wide range of requirements from "VHS quality" to HDTV, using a series of algorithms and image resolution levels. MPEG-2 is the compression used by the ATSC and DVB standards.
NTSC: National television system committee. The organization that developed the analog television standard currently in use in the U.S., Canada, and Japan. Now generally used to refer to that standard. The NTSC standard combines blue, red, and green signals modulated as an AM signal with an FM signal for audio.
PAL: Phase Alternate Line. The television broadcast standard in Europe and parts of Asia; (excluding France and Eastern Europe, where SECAM is the standard). PAL signals have 25 frames per second, and so are incompatible with NTSC TV. The PAL Standard transmits (625) lines of resolution, nearly (20%) more than the U.S. NTSC Standard of (525 lines).
Pan and Scan: A method used to crop the picture frame of the original source material produced in a "wide-screen" format, (any format wider than NTSC-analog's 4:3 aspect ratio) so it will fit a conventional (4:3) TV set. By "panning" the focus is kept 'centered' on the original image, in such a way as to follow the on-screen action. This can mean loss of critical detail, resulting in the scene being viewed entirely different from what the director intended.
Parallel cable: A multi-conductor cable carrying simultaneous transmission of digital data bits.
Parallel data: Transmission of data bits, in groups, along a collection of wires (called a bus). A parallel bus may accommodate transmission of one 8-, 16-, or 32-bit byte at a time.
Parallel digital: A digital video interface which uses twisted pair wiring and 25-pin D connectors to convey the bits of a digital video signal in parallel. There are various component and composite parallel digital video formats.
PCM: Pulse code modulation. Sounds are reproduced by modulating the playback rate and amplitude of the sampled digital pulses. This allows PCM sound to be reproduced with varying pitch and amplitude.
Pillarbox: The effect of displaying a traditional (4:3 aspect ratio) image on a widescreen (16:9) monitor. In order to preserve the aspect ratio of the original video content, the picture is scaled so that it fits the television screen, without distorting the image. This allows the picture to fill the height of the screen, but since the picture will not fill the screen horizontally, dark bars are displayed on both the left and right sides of the picture.
Pixel: A shortened version of "Picture cell" or "Picture element." Digital TV Pixels are rectangular-shaped, while HDTV Pixels are virtually square- shaped and significantly smaller in size. This allows High-Definition pictures to contain many more horizontal and vertical colored-dots than standard definition pictures.
Progressive Scan: In Progressive Scanning all the horizontal scan lines are scanned on to the screen at one time. The Digital TV and HDTV Standards accept both Interlaced Scan and Progressive Scan broadcast and display methods. Progressive Scan has long been used in Computer Monitors.
Protocol: Set of syntax rules defining exchange of data including items such as timing, format, sequencing, error checking, etc.
PSIP: Program and System Information Protocol.
A part of the ATSC digital television specification that enables a DTV receiver to identify program information from the station and use it to create easy-to-recognize electronic program guides for the viewer at home. The PSIP generator inserts data related to channel selection and electronic program guides into the ATSC MPEG transport stream.
Plasma Display — A Plasma TV Display uses hundreds-of-thousands of miniature, embedded cells to produce a picture. Each cell equals one pixel, (picture element) and has three sub-cells. The three sub-cells are filled with a plasma gas which will 'glow' red, blue, or green (depending on the phosphor coating) when charged electrically. Light from the three "RGB" sub-cells combines to form a one colored pixel on the screen.
Development of Plasma Display Technology is ongoing; with specific areas of concern remaining. Plasma Displays use phosphor coated screens, placing them at high risk of screen 'burn-in'. Plasma displays are not able to reproduce the color black; various shades of gray are the best that can be achieved - this can negatively affect picture quality. The plasma pixel-cells deteriorate over time causing the picture quality to diminish (fade)
Resolution: A measurement of the finest (smallest) detail that is visible, or can be resolved, in a video image. TV Resolutions may be expressed as "number of pixels" in an image; or more commonly, "As Total Number of (horizontally scanned) Lines used to create the image.
While a TV's Resolution can be influenced by the number of pixels in the image, it is important to note that the pixel numbers do not define ultimate resolution; ONLY the resolution of that part of the equipment.
Many other variables must be taken into account - such as, the quality of lenses, display tubes, film process and film scanners, etc. used to produce the image on the screen - as well as what measurement-methods are used.
Standard Digital TV Resolutions:
- 480i - The picture is 704x480 pixels, sent at 60 interlaced frames per second (30 complete frames per second).
note: NTSC-Analog TV resolution is 480-i
- 480p - The picture is 704x480 pixels, sent at 60 complete frames per second.
- 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.
Return Loss: The ratio of signal power transmitted into a system, to the power reflected or returned. This is like an echo that is reflected back by impedance changes in the system.
Variation in impedance from the source results in some returned signal. Cabling systems lack perfect impedance structure and matching, and have a measurable return loss.
At every connection, the potential exists that the impedance will change, resulting in part of the signal being reflected back to the source. Each impedance change contributes to signal loss (attenuation) and directly causes return loss.
RGB: The abbreviation for red, green and blue signals, the primary colors of light (and television). Cameras and telecines have red, blue and green receptors, the TV screen has red, green and blue phosphors illuminated by red, green and blue guns. Much of the picture monitoring in a production center is in RGB. RGB is digitized with 4:4:4 sampling which occupies 50 percent more data than 4:2:2.
SECAM (Système Electronique Couleur Avec Mémoire) is a signal format used in video equipment in France and the former Soviet Union. It is incompatible with PAL and NTSC formats.
Set-top Box, "STB" (also: Decoder, Receiver, Tuner)
A unit similar to today's cable boxes, which is capable of receiving and decoding DTV broadcasts. A DTV 'Certified' STB can receive all (18) ATSC DTV formats, (including HDTV) and provide a displayable picture.
A range of frequencies available for over-the-air transmission.
Standard Definition Television (SDTV)
SDTV refers to DIGITAL transmissions with 480-line resolution, either interlaced or progressive scanned formats. SDTV offers significant improvement over today's conventional NTSC picture resolution, similar to comparing DVD quality to VHS, primarily because the digital transmission eliminates snow and ghosts, common with the current NTSC analog format. However, SDTV does not come close to HDTV in both visual and audio quality.
Separated video. An encoded video signal which separates the brightness from color data. S-video can greatly improve the picture when connecting TVs to any high quality video source such as digital broadcast satellite (DBS) and DVD's.
Ultra high frequency, the range used by TV channels 14 through 69.
The term used to describe the conversion of a lower apparent resolution to a higher number, such as "up-converting" 720p to 1080i. This is a misnomer, though, since to accomplish this, the horizontal scanning frequency is actually lowered from 45kHz to 33.75kHz. Resolution quality is not improved by this method.
Very high frequency, the range used by TV channels 2 through 13.
Y/Pb/Pr - Designation for HDTV Component Type Connections
Advanced method for interconnecting decoded video data. Generally used where a digital TV signal source is used. Preferred connection for High Definition TV signals; enables superior quality in transmitted picture. The video signal is separated into its component parts of brightness and color differentials.
Y/U/V or Y/Cr/Cb
Y/Cr/Cb designates a "Component" type Digital TV connector/cable.
The separate components of the video signal (Luminance - Light; and Chroma - Color) are kept separated by using a 3-Wire cable. One wire for "Y"- designates Light or Brightness; one wire is "Cr" - Red; and the last wire is "Cb"- Blue.