poynton@vector.Sun.COM (Charles A. Poynton) (08/11/89)
Here's a contribution that may unravel some of the confusion surrounding HDTV, ATV. IDTV, EDTV, and so on. The most important point is that HDTV relates to production and exchange of programs, and has immediate relevance to computer graphics. Advanced television (ATV) concerns the delivery of entertainment programming to consumers, and has very little to do with computing. To me it is ludicrous to suggest that is strategically important for the U.S. to resurrect domestic colour television receiver manufacturing. Even more ridiculous is the suggestion (by George Gilder in Fortune) that the U.S. can, in a year or two, leapfrog current [Japanese] HDTV technology. Let's get on with exploiting HDTV technology in computing, where we've ALREADY got a vital and profitable industry! (Or should I say, WHILE we've still got it?) The preceeding was my opinion. What follows is fact. C. p.s. 1250/24, 2048-by-1152, 74.25 MHz. Dare to be square! ----- Charles A. Poynton Sun Microsystems Inc. <poynton@sun.com> 2550 Garcia Avenue, MS 8-04 415-336-7846 Mountain View, CA 94043 "Japan has no laws against damage to its flag, but it has strict laws forbidding the burning of foreign flags lest this give offense to the country in question." -- The Economist, July 1, 1989, p. 19. ----- High Definition Television (HDTV) and Advanced Television (ATV) Glossary Charles A. Poynton, Sun Microsystems, Inc. TN32 89/08/07 18:26 525-LINE, 625-LINE TELEVISION TERMS 525/59.94/2:1. A raster scanning standard used primarily in North America and Japan, having 525 total lines (of which approximately 483 contain picture information), a field rate of 59.94 Hz, and interlace. Without the "/2:1" notation, interlace is implicit. Colour in 525/59.94 systems is commonly encoded using the NTSC method. Often colloquially referred to as 525/60, and often incorrectly denoted NTSC. 625/50/2:1. A raster scanning standard used primarily in Europe and Asia, having 625 total lines (of which 575 contain picture information), a field rate of 50 Hz, and interlace. Without the "/2:1" notation, interlace is implicit. Colour in 625/50 systems is usually encoded using the PAL method (although France, the USSR, and certain other countries use SECAM). Often incorrectly denoted PAL or SECAM. NTSC, National Television Systems Committee. (1) The group which in 1953 established 525-line, 2:1 interlaced, 59.94 Hz field rate, composite colour television signals in the U.S. More properly referred to as NTSC-II. [The original NTSC, now properly referred to as NTSC-I, established 525-line, 2:1 interlaced, 60.00 Hz field rate monochrome television in the U.S. in 1943.] (2) A method of composite colour encoding based on quadrature modulation of U and V colour difference signals onto a colour subcarrier. Used only in 525/59.94 systems, with a subcarrier frequency of about 3.579455 MHz. PAL, Phase Alternate Line. A method of composite colour encoding similar to NTSC, except that the phase of the V-axis colour difference signal inverts at the horizontal line rate. Commonly used in 625/50 systems with a subcarrier frequency of about 4.433618 MHz, but also used with a subcarrier of about 3.579455 MHz in the PAL-N system (e.g. Argentina), and with 525/59.94 scanning and a subcarrier frequency of about 3.575611 MHz in the PAL-M system (e.g. Brazil). SECAM, Sequential Couleur avec Memoire. A method of composite colour encoding using line-alternate U and V colour difference signals, frequency modulated onto a subcarrier. Used only in 625/50 systems (e.g. France, USSR). Component. A video system which conveys colour using three separate signals. Examples are RGB, YUV, MAC. Composite. A video system which uses the spectral interleaving (or frequency interleaving) technique to encode (combine) luminance and colour information into a single signal. Examples are NTSC, PAL, SECAM. S-video, S-connector, YC3.58, YC4.43. An interface which conveys luminance, and quadrature modulated chrominance, as two separate signals on a specific 4-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 completely separable. MAC, Multiplexed Analog Component. A video system which transmits three colour components, usually YUV, in time-compressed serial analog form. Interlace. A video signal in which alternate raster lines of a frame are separated into two fields displaced in time by half the frame time. Also called 2:1 Interlace. Examples are 525/59.94/2:1, 625/50/2:1, 1125/60.00/2:1. Progressive. A video signal in which all scan lines of a complete frame are closely related in time. Also called 1:1 Interlace, Sequential, Non-interlaced, Pro-scan. Examples are 525/59.94/1:1, 1250/24/1:1. IMPROVED, EXTENDED, ADVANCED, HIGH DEFINITION TELEVISION TERMS IDTV, Improved Definition Television. A television system which offers picture quality substantially improved over conventional receivers, for signals originated in standard 525-line or 625-line format, by processing which 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, 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 Definition Television. A television system which offers picture quality substantially improved over conventional 525-line or 625-line receivers, by employing techniques at the transmitter and at the receiver which are transparent to (and cause no visible quality degradation to) existing 525-line or 625-line receivers. Examples are improved luminance/colour separation made possible by pre-combing the transmitted signals such as has been suggested by Faroudja, Central Dynamics, and Dr William Glenn, in order to reduce or eliminate NTSC artifacts such as dot crawl and hanging dots. Another example 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 systems both have a picture aspect ratio of 4:3. Letter-box. A television system which 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 which has a wide aspect ratio. Wide-screen. A television system which 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 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 which 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 system which has approximately twice the horizontal and vertical resolution of current 525-line and 625-line television, a frame rate of at least 24 Hz, component colour coding (e.g. RGB or YUV), and a picture aspect ratio of 16:9. PRODUCTION, EXCHANGE, DISTRIBUTION TERMS HDTV Production. The original creation and editing of HDTV program material. 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%. 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 which has carrier-frequency assignments conformant to current 525-line or 625-line television transmission. According to FCC Docket 87-268, terrestrial VHF/UHF ATV transmissions in the U.S. are 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 which 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 U.S. are constrained to be receiver-compatible. Receiver-compatibility can be accomplished by single-channel ATV, augmentation-channel ATV, or simulcasting. Single-channel ATV. An ATV transmission system which alters the 525-line or 625-line broadcasting standard by the addition of augmentation signals within the channel bandwidth of the current standard. Such systems may degrade reception of current signals. Sarnoff ACTV-I is an example of a single-channel ATV system. Augmentation-channel ATV. An ATV transmission system which transmits an augmentation signal associated with a main channel 525/59.94 or 625/50 signal, in order that signals from both channels can be combined in an ATV receiver to form an ATV signal. Augmentation-channel systems provide receiver-compatibility by default. Augmentation channels of 3 MHz and 6 MHz have been proposed for the U.S. Examples of augmentation-channel ATV systems are N.A. Philips HDS-NA, and NYIT VISTA. Sarnoff ACTV-II is an example of a hybrid single- channel/augmentation-channel system, because it transmits augmentation information in both the main NTSC channel and a separate augmentation channel. Simulcast ATV. A system which transmits a complete ATV signal within an RF channel of the same bandwidth as current 525-line or 625-line broadcasts, and which achieves receiver-compatibility through simulcast of the same program material, possibly with reduced aspect ratio, in a separate standard channel. Zenith SC-TV is an example of such a system, which in this case is optimized to exploit a currently-unused VHF/UHF taboo channel to convey an entire ATV signal. Sometimes confused with Incompatible ATV. Incompatible ATV. A system which transmits a complete ATV signal in a format not intimately related to existing broadcast standards. An example of an incompatible system is NHK MUSE-9. An incompatible ATV system is channel-compatible if it transmits the ATV signal within a 6 MHz channel. An incompatible ATV system is receiver-compatible if it employs simulcast of the same program material, possibly with reduced aspect ratio, in a separate NTSC channel. DIGITAL HDTV TERMS CIF, Common Image Format. The standardization of the structure of the samples which represent picture information 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, applicable to two or more different frame rates. 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. Orthogonal sampling. Sampling a digital HDTV picture with an array of samples placed on a regular two-dimensional 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. -----
poynton@vector.Sun.COM (Charles A. Poynton) (08/12/89)
A correspondent writes: >> 1250/24, 2048-by-1152, 74.25 MHz. Dare to be square! > I don't understand how 1250 becomes 2048-by-1152, and what the active > elements stuff is about and how 1250/24 becomes 74.25 MHz. Well, briefly, you get to pick five numbers and the rest fall out of the wash. The best numbers to work with are sample rate, total and picture samples per line, and total and picture lines per frame. The best numbers to publish comprise that set, except publish frame rate instead of total samples per line. Total samples per line needs to be roughly 15% more than picture samples to accommodate horizontal scanning, Total lines per frame needs to be roughly 4% more than picture lines per frame to accommodate vertical scanning. Frame rate just falls out as sample rate, divided by total samples per line, divided by total lines per frame. So in my proposal, total samples per line would be 2475, about 20% greater than 2048, but you can derive the 2475 from the five numbers I gave. You really need to see the trademark Poynton raster diagram to make this all clear. How much can I do with ASCII text ... 74.25 MHz 2475 +---------------------------------------+ | V blank | | +-------------------------------+ | | 2048 | | | | | | | 1250 | H | 1152 picture | | blank | | | | (16:9 aspect ratio) | | | | | | | +-------+-------------------------------+ Video monitors are usually specified by horizontal line rate (easily derived as sampling frequency divided by total samples per line), and frame rate. Unfortunately many frame buffers (whoops, graphics cards) specify some rounded versions of H and V rates, and it's a real nuisance to work backwards to try to figure what the real parameters are. My 1250/24, 2048-by-1152, 74.25 MHz HDTV proposal is, briefly, - use 1250 total lines and 1152 picture lines, as in current Eu95 proposals, to appeal to the Europeans; - use the proposed Japanese [and semi-recommended SMPTE 240M] sampling frequency of 74.25 MHz; - use 2048 samples per picture width and square pixels to appeal to the computer industry; - use 24 Hz to be fully conformable to film, for the Hollywood production community and to utilize current film libraries which will be the source of 90% of the initial ATV programming, with ABSOLUTELY NO temporal artifacts; - accomplish down-conversion to current broadcast standards in exactly the way it is done today from film, that is, 3-2 pulldown 0.1% slow for 525/59.94 and 2-2 pulldown 4% fast for 625/50, with artifacts identical to those seen in today's film transfers; and - display at 72 Hz to satisfy even the most flicker-sensitive, Euro-gonomic, high-ambient viewers, including computer workstation users. Of course a 2048-by-1152 monitor at 72 Hz is quite a way off, so this should mollify the U.S. broadcasters, who are concerned that an early entry into ATV could cost them a lot of money. Don't laugh about this being a political compromise. This is serious business! C. ----- Charles A. Poynton Sun Microsystems Inc. <poynton@sun.com> 2550 Garcia Avenue, MS 8-04 415-336-7846 Mountain View, CA 94043 "As at the ski resorts where girls go looking for husbands, and husbands go looking for girls, the situation is not as symmetrical as it might seem at first." -- attributed to Alan Kay -----
twhlai@watdragon.waterloo.edu (Tony Lai) (08/14/89)
In article <120919@sun.Eng.Sun.COM> poynton@vector.Sun.COM (Charles A. Poynton) writes: >Incompatible ATV. A system which transmits a complete ATV signal in a >format not intimately related to existing broadcast standards. An >example of an incompatible system is NHK MUSE-9. This is rather trivial, but I think you are thinking of MUSE-E, which is the incompatible system that NHK will transmit. I think MUSE-9 is an augmentation-channel system.