poynton@vector.Sun.COM (Charles A. Poynton) (03/07/90)
TN32--High-Definition Television (HDTV) and Advanced Television (ATV) Glossary (c) 90/03/03 Charles A. Poynton Sun Microsystems, Inc. 525-line, 625-line Television Terms Scanning Standard. The parameters associated with raster scanning of a pickup device or a display device, or the associated signal in a channel or a recording device. A scanning standard is denoted by its total line count, field rate and interlace ratio (e.g. 525/59.94/2:1 or 625/50/2:1). Colour Standard. The parameters associated with transmission of colour information, for example RGB, YCbCr or MAC component colour standards or NTSC, PAL or SECAM composite colour standards. 525/59.94/2:1. A scanning standard used primarily in North America and Japan, having 525 total lines per frame (of which approximately 484 contain picture information), a field rate of 59.94 Hz and interlace. Without the "/2:1" notation, interlace is implicit. A raster notation such as 525/59.94 does not specify colour coding; colour in 525/59.94 systems is commonly conveyed in the studio using either RGB or YCbCr components and encoded for transmission using the composite NTSC method. Known internationally as CCIR System M. Often colloquially referred to as 525/60; often incorrectly called NTSC (which properly refers to a colour standard, not a scanning standard). 625/50/2:1. A scanning standard used primarily in Europe and Asia, having 625 total lines per frame (of which 576 contain picture information), a field rate of 50 Hz and interlace. Without the "/2:1" notation, interlace is implicit. A raster notation such as 625/50 does not specify colour coding; colour in 625/50 systems is commonly conveyed in the studio using RGB or YCbCr components and distributed by satellite using the MAC system, or distributed by terrestrial VHF/UHF television using the composite PAL method (although France, the USSR and certain other countries use SECAM). Often incorrectly called PAL or SECAM (which properly refer to colour standards). NTSC (National Television Systems Committee). (1) The group that in 1941 established 525-line, 60.00 Hz field rate, 2:1 interlaced monochrome television in the United States. Now properly referred to as NTSC-I. (2) The group, more properly referred to as NTSC-II, that in 1953 established 525-line 59.94 Hz field rate, 2:1 interlaced, composite colour television signals in the United States. (3) A method of composite colour encoding based on quadrature modulation of B-Y and R-Y colour difference signals onto a colour subcarrier and adding the resulting chroma signal to luminance. Used only in 525/59.94 systems, with a subcarrier frequency of 455/2 times the horizontal line rate, i.e. about 3.579545 MHz. (4) Often used incorrectly to denote 525/59.94 scanning. PAL, Phase Alternate Line. A composite colour standard similar to NTSC, except that the R-Y-axis subcarrier reference signal inverts in phase at the horizontal line rate. Commonly used in 625/50 systems with a subcarrier frequency of 4.43361875 MHz, but also used in 625/50 systems with a subcarrier of 3.58205625 MHz in the PAL-N system (e.g. Argentina); and with 525/59.94 scanning and a subcarrier frequency of 3.575612 MHz in the PAL-M system (e.g. Brazil). Often used incorrectly to denote 625/50 scanning. SECAM, Sequential Couleur avec Memoire. A composite colour standard based on line-alternate B-Y and R-Y colour difference signals, frequency modulated onto a colour subcarrier. In use only with 625/50 scanning (e.g. France, USSR). Component Colour. A video system that conveys three colour component signals independently. Examples are RGB, YCbCr and MAC. Composite Colour. A video system that uses the spectral interleaving (frequency interleaving) technique to encode (combine) luminance and colour information into a single signal. The three colour components are simultaneously present in the composite signal. Examples are NTSC, PAL and SECAM. S-video, S-connector, YC3.58, YC4.43. An interface that conveys luminance and quadrature modulated chrominance as two separate signals on a specific four- pin mini-DIN connector. There are only two types of S-video: YC3.58, which has a 525/59.94 raster and chrominance modulated as in NTSC and YC4.43, which has a 625/50 raster and chrominance modulated as in PAL. S-video is a form of component video, in that the three components are conveyed independently (although the colour difference components have limited bandwidth). MAC, Multiplexed Analog Component. A colour standard that transmits three colour components, usually in YCbCr form, in time-compressed serial analog form. Used primarily with 625/50 scanning. 2:1 Interlace. A scanning standard in which alternate raster lines of a frame are displaced vertically by the scanning line pitch and displaced temporally by half the frame time, to form an odd field and an even field. Also called 2:1 Interlace. Examples are 525/59.94/2:1, 625/50/2:1, 1125/60.00/2:1. Systems with high order interlace have been proposed but none have been introduced in practice, so interlace implies 2:1 interlace. Progressive. A video signal in which successive scan lines in each complete frame are vertically and temporally adjacent. Also called 1:1 Interlace, Sequential, Non-interlaced, Pro-scan. Examples of proposed progressive systems are 525/59.94/1:1 and 1250/25/1:1. Improved, Extended, Advanced, High-Definition Television Terms IDTV, Improved Definition Television. A television system that offers picture quality substantially improved over conventional receivers, for signals originated in standard 525-line or 625-line format, by processing that involves the use of field store and/or frame store (memory) techniques at the receiver. One example is the use of field or frame memory to implement de-interlacing at the receiver in order to reduce inter-line twitter compared to that of an interlaced display. IDTV techniques are implemented entirely at the receiver and involve no change to picture origination equipment and no change to emission standards. EDTV, Extended [or Enhanced] Definition Television. A television system that offers picture quality substantially improved over conventional 525-line or 625-line receivers, by employing techniques at the transmitter and at the receiver that are transparent to (and cause no visible quality degradation to) existing 525-line or 625-line receivers. One example of EDTV is the improved separation of luminance and colour components by pre-combing the signals prior to transmission, using techniques that have been suggested by Faroudja, Central Dynamics and Dr William Glenn; these techniques reduce or eliminate NTSC artifacts such as dot crawl and hanging dots. Another example of EDTV is the use of progressive scanning at the camera, interlaced transmission and reconstruction of a progressive display at the receiver to reduce or eliminate interlace artifacts, as in the Faroudja SuperNTSC system. EDTV systems require changes in picture origination equipment, but are completely compliant with current emission regulations. Picture Aspect Ratio. The ratio of picture width to picture height. Usually abbreviated to Aspect Ratio. Current 525-line and 625-line scanning standards have a picture aspect ratio of exactly 4:3. HDTV is defined to have 16:9 aspect ratio. Letter-box. A television system that limits the recording or transmission of useful picture information to about three-quarters of the available vertical picture height of the distribution format (e.g. 525-line), in order to offer program material that has a wide picture aspect ratio. Wide-screen. A television system that offers a picture aspect ratio substantially wider than 4:3, using the full vertical picture area afforded by the distribution signal format (e.g. 525-line). Emission regulation changes are required for wide-screen terrestrial (UHF/VHF) TV transmission. Wide-screen may or may not be combined with EDTV; wide-screen is inherent in ATV and HDTV. ATV, Advanced Television. A system that distributes wide-screen television signals with resolution substantially improved over 525-line and 625-line systems. Terrestrial ATV broadcasting (VHF/UHF) would require substantial changes to current emission regulations. There is general acknowledgement that any ATV distribution system should offer at least stereo (two channel) audio, of CD quality. HDTV, High-Definition Television. A television system with approximately twice the horizontal and twice the vertical resolution of current 525-line and 625-line systems, component colour coding (e.g. RGB or YCbCr), a picture aspect ratio of 16:9 and a frame rate of at least 24 Hz. Production, Exchange, Distribution Terms HDTV Production. The original creation and editing of HDTV program material. SMPTE 240M. An HDTV production standard with 1125/60.00/2:1 scanning. HDTV Exchange. The interchange of HDTV program material among production, distribution and transmission organizations. Editing at the exchange stage is limited to insertion of segments such as commercials and lengthening or shortening the duration of program material up to 5 percent. ATV Distribution. The distribution of ATV program material to the ultimate viewing audience. Distribution may be by physical media such as videotape or videodisc; or by transmission (see below). ATV Transmission. The distribution of ATV program material to the ultimate viewing audience through RF media such as terrestrial VHF/UHF broadcasting, cable television (CATV) or direct broadcast satellite (DBS). ATV Transmission Terms Channel-compatible ATV. A system for transmitting ATV through VHF/UHF or CATV media whose RF spectrum assignment conforms to the six megahertz RF channels of current television transmission. According to FCC Docket 87-268, terrestrial VHF/UHF ATV transmission in the United States is constrained to be channel-compatible with 6 MHz channels. Channel-compatibility does not necessarily require single-channel transmission. Receiver-compatible ATV. An ATV transmission system that provides ATV program material, possibly with reduced aspect ratio, to current 525-line or 625-line receivers. According to FCC Docket 87-268, ATV transmissions in the United States are constrained to be receiver-compatible. Receiver-compatibility can be obtained by augmentation-channel techniques or by simulcasting. Augmentation ATV. An ATV transmission system that transmits an augmentation signal that is intimately associated with a main channel signal conformant to current broadcast standards. The two signals can be combined in an ATV receiver to recreate a complete ATV signal. Augmentation systems provide receiver-compatibility by default. No 625-line country is currently planning to use an augmentation channel approach for ATV. In-Band Augmentation ATV. An ATV transmission system that alters the 525-line or 625-line broadcasting standard by the addition of an augmentation signal within the RF channel bandwidth of the current standard. Such systems necessarily degrade reception of current signals. Sarnoff ACTV is an example of an in-band augmentation ATV system. Out-of-Band Augmentation ATV. A system that transmits an augmentation signal in an RF channel outside the main channel. The NYIT VISTA system is an example of an out-of-band augmentation system. Side Panels. In a wide-screen augmentation system, those portions of the width of a wide aspect ratio picture that are not conveyed in the 4:3 aspect ratio main channel. It is a technical challenge in an augmentation system to avoid visible seams between side panels and the main picture. Self-contained ATV. A system that transmits a complete ATV signal in its own RF channel. A self-contained ATV system is channel-compatible if it transmits the ATV signal within a 6 MHz channel and receiver-compatible if it employs simulcasting. An example of a self-contained, non-channel-compatible system is NHK MUSE-9. Sometimes misleadingly called incompatible. Simulcast ATV. A system that transmits a self-contained ATV signal and achieves receiver-compatibility by simultaneously transmitting the same program material, possibly with reduced aspect ratio, in a separate 525/59.94 or 625/50 channel. Zenith SC-HDTV is an example of such a system that in this case is optimized to exploit a currently-unused VHF/UHF taboo channel to convey the self-contained ATV signal. Sometimes confused with Incompatible ATV. Compatible ATV. An ATV transmission system that is intimately related in some manner to current broadcast. Although it is a self-contained ATV system, Zenith SC-HDTV is called compatible because of its use of a frame rate of 59.94 Hz, its line rate of three times current 525/59.94 and the relationship of its RF channel utilization with NTSC. MUSE. A family of transmission standards for ATV that has been developed by NHK (Japanese Broadcasting Network). MUSE Hardware has been demonstrated for the 1125/60 system; other MUSE variants have been proposed. Digital HDTV Terms CIF, Common Image Format. The standardization of the structure of the samples that represent the picture information of a single frame in digital HDTV, independent of frame rate and sync/blanking structure. CDR, Common Data Rate. The standardization of a single data rate for digital HDTV, independent of the choice of image format, frame rate and sync/blanking structure. CFR, Common Frame Rate. The standardization of a single frame rate for digital HDTV. Sample Aspect Ratio. The ratio of horizontal sample pitch to vertical sample pitch. A sample aspect ratio of unity achieves square pixels. "Square Pixels". A colloquial expression derived from computer graphics: a sample aspect ratio of precisely unity. Orthogonal Sampling. Sampling a digital HDTV picture using samples placed on a regular two-dimensional spatial array or three-dimensional spatio-temporal array. Offset Sampling. Sampling a digital HDTV picture with an array of samples where alternate rows of samples are displaced by half of the pitch of the samples along that axis. Offset sampling may be applied to any combination of the horizontal/vertical/temporal sampling axes of a video signal. Also called Quincunx sampling. Offset sampling in the vertical/temporal plane is more commonly called interlace. -----