[[ Square sampling for HDTV This is a historical document dating from March 1989 wherein I attempted - successfully, as it turned out - to convince the video standards community to adopt square sampling, and in particular 1920x1080 image format, for HDTV. ]] This is a plea for contributions which could convince the HDTV standards community to adopt square pixels for 1125-line HDTV. The current proposal calls for pixels that are 4% narrower than they are high. This fact is of little significance for traditional television but I believe it would severely limit the appeal of the standard to commercial, industrial, scientific, and medical applications, and in particular to computer graphics. Attached to this note is a letter which outlines the state of the 1125-line standards discussions, and presents names and addresses of committee chairmen and such. There is precious little participation in this effort from the computer community, and the television industry recognizes no particular advantage to square pixels. This document recommends a course of action for those of you who would like to contribute. The second posting (TN21) is my current view of HDTV in general. The Europeans have scuttled the adoption of a single international standard and have proposed their own 1250-line standard, and the U.S. television networks are muddying the waters with their 1050-line proposal (for which no hardware exists). Consumer and especially terrestrial broadcast HDTV is a long way off in America. However, the parameters of an 1125-line system for Production HDTV were adopted in the U.S. as ANSI/SMPTE 240M a few weeks ago, commercial 1125-line hardware is abundant (albeit expensive), and industrial and commercial application of this system is imminent. Colour pre-press equipment exploiting 1125-line HDTV display technology is already in the field. Discussions are currently underway to establish the standard "digital representation" of the 1125-line system. The parameters currently favoured are based on a picture with 1035 lines of 1920 pixels, and a picture aspect ratio of 16:9, giving pixels which are 4% narrower than they are high. The third posting (TN28) is a detailed description of the pixel aspect ratio issue, and the choices available for the adoption of square pixels. A 4% reduction of the proposed sampling frequency, or any of a number of other parameter changes, would make the pixels square. Warning: this one is tough slogging for anyone not intimate with television standards. Technical contributions would be most effective; for example, issues of fonts, image processing, anti-aliased rendering, filter and transform algorithms, raster file exchange, input devices (scanners, CCDs), output devices (hard copy, plasma, LCD), window system issues, etc. I'm especially looking for technical contributions from some of the large organizations who have recently announced various HDTV initiatives, for example, IBM, H-P, DEC, Apple, AT&T, MIT, and Tektronix. Organizations such as these have much to gain from the convergence of HDTV and computer graphics, but have been surprisingly absent from the standards discussions. This is a rather liberal use of net bandwidth, but if you wade through this set of documents you will be very well informed regarding HDTV. If you make a short contribution describing why square pixels are desirable, we stand a chance of adopting an HDTV standard which promises to unify the heretofore disparate fields of television and computer graphics. Thanks. Charles A. Poynton Sun Microsystems, Inc. ----- Charles A. Poynton Sun Microsystems, Inc. 2550 Garcia Avenue, MS 8-04 Mountain View, CA 94043 415-336-7846 89.03.10 The basic analog parameters of the 1125-line HDTV system have been accepted internationally (as Annex II of CCIR Report 801-2), and in the U.S. as the recently-adopted ANSI/SMPTE 240M. Standardization of the digital representation of this system is proceeding rapidly. Although it seems that European obstructionism has prevented the 1125-line system from being adopted as a single worldwide standard for HDTV, it is clear that all users of 1125-line HDTV will conform to a common standard. There is a once-in-a-lifetime opportunity to base this standard on a sampling structure which has exactly equal horizontal and vertical sample spacing, which I believe will greatly benefit both the television industry and other industries (in particular, computer graphics), by facilitating the design of hardware and software, and the exchange of images. The parameters contained in CCIR Report 801-1 and ANSI/SMPTE 240M do not specify a sampling frequency. The Japanese manufacturers' Broadcast Television Association (BTA) have recommended a sampling frequency (74.25 MHz) which produces a sample aspect ratio of 120:115, only 4% off- square. There are great benefits in having exactly square pixels, and an alternate proposed sample rate which is just 4% lower (70.875 MHz) achieves precisely square pixels. The Society of Motion Picture and Television Engineers (SMPTE) is accredited by the American National Standards Institute (ANSI) to develop national standards for studio television, and also to recommend to the U.S. State Department the position to be taken by the U.S. in international standards development. The U.S. Advanced Television Systems Committee, ATSC, also contributes to this process. The SMPTE Working Group on High Definition Electronic Production (WGHDEP), has formed the Ad-Hoc Group on Digital Representation of 1125- line HDTV (AHG-DR1125). There has been some discussion within the WGHDEP and the AHG-DR1125 regarding the square-pixel issue, but the various SMPTE groups have representation that is essentially only from the broadcast industry, which does not view square pixels as being important for their particular application. In the absence of any contribution from other industries, the current proposals will almost certainly be adopted. The feeling at the various SMPTE standards committees is that if industries other than television do not contribute to the standardization process, then the work will be done without them, and they can take or leave the result. The international standardization for HDTV is proceeding through Study Group 11 of the CCIR (International Radio Consultative Committee). The chairman of the U.S. National Study Group to the CCIR is Bernie L. Dickens. The chairman of Canadian National Study Group 11 is Ken P. Davies. These groups are fundamental to the international standards process, and the individuals have influence within SMPTE, but the international process lags the national work and this particular issue is likely to be a fait accompli before the CCIR study groups have had a chance to consider it. If you would like to make your views known, then I would suggest a short letter to Dick Stumpf, the chairman of the Working Group on High Definition Electronic Production (WGHDEP). Copies could optionally be sent to the other individuals listed below. The next meeting of the WGHDEP is on April 5 in Los Angeles, and the AHG-DR1125 meets on April 29 in Las Vegas, immediately prior to the National Association of Broadcasting (NAB) convention. I am a member of both committees, and I will convey to the committees any e-mail replies which I receive regarding this issue. A large volume of replies from the net might make the committee sit up and take notice, but e-mail contributions will carry less weight than a written submission to the committee. Please review these documents, distribute them to anyone that you think may have comments, suggestions, or influence, and let your views be known! Charles A. Poynton ----- HDTV STANDARDIZATION -- NAMES AND ADDRESSES SMPTE COMMITTEES Richard J. Stumpf, Chairman SMPTE WHGDEP Vice-President R&D, Universal Studios 100 Universal Plaza Universal City, CA 91608 818-777-3198 Hugo Gaggioni, Chairman SMPTE AHG-DR1125, Sony Advanced Systems 1600 Queen Anne Road Teaneck, NJ 07666 201-833-5715, fax 201-833-9321 Keith Field, Chairman SMPTE AHG-HDSS C.B.C. Engineering Headquarters 7925 Cote St. Luc Road Montreal, Quebec H4W 1R5 Canada 514-485-5570 SMPTE HEADQUARTERS Stanley N. Baron, SMPTE Engineering Vice-President NBC 30 Rockefeller Plaza (1600W) New York, NY 10112 212-664-7557 Barry C. Detwiler, Television Engineer SMPTE 595 West Hartsdale Avenue White Plains, NY 10607 914-761-1100, fax 914-761-3115 Sherwin H. Becker, Director of Engineering SMPTE, 595 West Hartsdale Avenue White Plains, NY 10607 914-761-1100, fax 914-761-3115 CCIR STUDY GROUPS Bernard L. Dickens, Chairman USNSG-11 C.B.S 555 West 57th Street New York, NY 10019 212-975-2003 Ken P. Davies, Chairman CNSG-11 C.B.C. Engineering Headquarters 7925 Cote St. Luc Road Montreal Quebec H4W 1R5 Canada 514-485-5474 ATSC Dr. Robert Hopkins, Executive Director A.T.S.C 1771 N Street N.W. Washington, DC 20036 202-429-5345 -----