Decades ago the NTSC National Television Standards Committee developed a television that could work for then-current 1940's tube-type electronics technology, but it foresaw far greater possibilities ... color in 1951, found itself a niche in the '50's design methodology, and promised yet greater ... but today's 1980-90's HDTV proposals appear to have gone awry, supplementing further advance thinking with mere multi-programmability - compatibility with everything: efficiency with nothing.
The difference is that the future of NTSC still exists - and we ought consider what NTSC really was, and is, and is to be.
Basically NTSC defined a transformation between a broadcastable time-linear signal and a viewable 2-D motion-display [2.5D] of reasonable proportions approximating the picture 'desirability' and 4:3 [horizontal:vertical] aspect ratio of common-theatre 16mm film. But as technology has advanced, the theoretic-possibility has more rapidly furthered ... we could, but don't have wavelet processing implemented - it is available as praxi-theory. We still don't have stereo'eyes'ed processing and viewing that's 2D compatible. We still don't have wide-screen 2:1 aspect [now common in theatres, or wider cinerama] ... understand: space is 4pi radians and the horizon is 2pi radians: verticle height averages 4pi/2pi=2 for pi:1 aspect - or, for sitting steady with foreward view only space is 2pi and the horizon is pi, and eyes yield about 75% vertical height [limited by brows and cheeks], about pi:1.5, or that is, simply 2:1 aspect. [The tradition of 16:9 was based on generalizing HDTV to best-fit the proportioned average of all known aspects previously used, by film historians who thereby know aspects, but neglected your basic linear measure distribution rule of throwing-away the two extremes - curious also, 16:9 = 4:3 squared]
[We may also giggle over the new-generation of technolog'ers who dote on elliptical frames - when we consider that the horizon may be flat, or curved, irregular, or just [easily] tilted - a simple rectangle is a better assured view than an ellipse of an ellipse]The original NTSC concept was 6MHz with 1.25Mhz vestigial, and FM at 4.5Mhz [over video carrier at said 1.25MHz] ... the original intent was that FM, being a constant amplitude, could be instantaneously subtracted from the luminance [except for its audio-modulated very narrow quadrature] for almost 4.75MHz picture. [The technology then-available was not even PLL-ready but they foresaw better] When color came along it was set between 2.3-3.0MHz and 4.2MHz, with its carrier at 3.579545MHz - still without best-fit PLL's.
We may note further that the vestigial-side-band chosen by NTSC was itself a deep-compromise, for they could have chosen full-band luminance, and then decoded the quadrature carrier as more [double] pixels - but that would have required double the receiver demodulator electronics, and that in the era before digital technology and integrated [micro] circuitry. But, we can [consider] pick-up the effort, compatibly, and extend it now: we might take the symmetric band around the carrier as 4.75MHz+4.75MHz = 9.5MHz, with the quadrature representing those 'in-between' pixels as either, double the resolution, or as, the binocular view [compatible with sexichrome - that is, 6 colors = 3 colors for each of 2 eyes - recall that B&W Black&White was also called monochrome, one color, typically white] ... since the 'stereo-eyes-ed' image consists of two views spatially displaced, the resolution is effectually mostly doubled, as well as 3D [3.5D in motion] - if single-eye image-frames were resolved to time-alternate sub-pixels, this would be very-near doubled - this is different from one picture with 'Z-depth' sent as an additional modulation: thus there are options yet to consider ... it's just more compatible with the current technology to consider this continuity of design-methodology.
This DDTV 'double-vision' is also naturally wide-screen proportioned - the interleaved horizontal pixel placement allows up to 4x [range] free-stretching without loss of fine-resolution: in fact the natural stretch is root-three, horizontal:vertical, because that makes for equilateral triangular placement of pixels: optimal viewing pixel density.
I've suggested that the current standards for NTSC and HDTV be made/kept more compatible - the time base be digital near 18MHz, 5x color-carrier, and FM 1/4, and add stereo 'Z-depth' inside the vestigial zone [alternating-phase quadrature for stability] by adding video-low-frequency reduplicated into the quadrature to retain some compatibility for the oldest TV receivers until they quit altogether. My System 18/3,4,5 [band, FM, color] offers a digital time-base closely approximating these parameters - compatible with NTSC, and with receivers in operation today. The horizontal retrace interval can be reduced to a few pixels, with digital 'parity' check - we can extract more from what everyone uses: multiprogrammability is then, just an add-on.
For the near-future digital HDTV, I think also we can have signal-compatibility, that gets most of the picture through the NTSC receivers - there are digital coding schemes that retain a portion of the original signal, and then the lower bits may be the noncompatible codes.
[Further details (below) discuss half-pixel edge-combing and treble-thread-gemming: smoothing and sharpening]
[America seems to have forgotten not what it had possessed, but what had been foreseen ... Yesterday's done: Let's not waste the perception we've attained: This insight and its method is part-and-parcel to our future in space-navigation: our design methods must always illumine the right answer, fitting specification as well as future development and previously discerned possibility: we must have not merely the art, but the science of upgrades]
ITEM by item, NTSC can be improved directly: some without cost to the consumer. And some improvements (can) apply to HDTV. HDTV is, as yet per the cartel's proposals, a distortion, by certain reasoning.
1.a. UN-KELL TV. Current picture definition presumes direct fidelity - unrehearsed imagery. The contrary fact is that edge-combing the image can restore 100% (double) of the resolution lost in the kell-factor (both horizontally and vertically). Think of un-kelling as, combing one's hair so-as to align each strand onto the pixel centers: this can be done fairly inexpensively in the camera iconoscope and image processing electronics, and requires no change in any receiver. The effect is an immediate (100%) sharpening of the image on top-quality receivers: Where the closest strands blurred across adjacent pixels, the combed strands appear distinctly spaced. The average combing adjustment of hairs is a quarter pixel width - maximum, a half - with no degradation visible at proper viewing recess. The cost is for doubling the camera's resolution, and for the un-kell-processor.
1.c. HDTV's bonus factor disappears against this improvement of NTSC, because the proposals have gone for DCT-processing: a giant-step requiring upgrading entire systems, cameras, processors, and receivers, but accomplishing nothing more than un-kelling. The advantage of numeric signal coding is nice but (as yet) incompatible.
2. CLAIMS for HDTV's bigger, better picture have been spurious: the pioneering features of new technology have been idly neglected for filibustering marketing tactics: promises of more talk and less agony.
2.a. ASPECT (ratio) is proffered at a humorous 16:9 - somebody squared NTSC's 4:3 for fun - more precise than one can feel: 7:4 and 9:5 are within 2%, and either is simpler to write and remember.
Aspect (ratio) should reflect the viewing proportions. We live on a plane (plane to the horizons), and except for traversing a chasm, we rarely look down or up for reading or examining significant details: usually there's only the ground and the sky (or floor and ceiling) below and above; and dramatic actors (and sports heroes) array and move most expertly on that plane. On this mathematically simple basis we should more appreciate either a full-turning view of 360deg horizontal and 115deg (average) vertical, or a full-face (non-turning) view of 180deg horizontal and 86deg (average) vertical. The ratio of angle in a circle to solid angle in a viewing sphere is 2pi:4pi, so, average height is 4pi/2pi=2, and the aspect is pi:1. The eyes scope maximally about 180deg horizontally and 135deg vertically, for an aspect ratio of pi:1.5.)
Again, small percentages are not felt: the aspect ratio should be no less than 2:1, and no more than 3:1. The shape is not crucial - though some argue for elliptical aesthetics, the excess in the corners of a rectangle do not contribute much to width or to height; and an ellipse tilted slightly left and right tends to fill a rectangle.
2.b.i. The focal-center position should be frame-by-frame selectable under processor control (with directorial emphasis up to override: such as in "gauze shots"), in six detentes from, detailed middle with coarse wings, to coarse middle with detailed wings ... plus flat; plus a compatible mode, flat over NTSC's 4:3 midrange, with extended wings.
2.c. STEREO-EYES-ING television has been virtually ignored by all but psychedelics, yet numerous technologies exist for producing a 3-D or binocular image: flood-focusing (in the near future) has focus as well as 3-D view, sexichrome (six colors viewed three-per-eye through white 3-D safety goggles) interchanges with HDTV, and, the mundane synchro-shutter-glasses, or even a stereo-eyes-ed SITMAN. An NTSC raster-contour-scan z-depth-carrier needs only to occupy the 1.25MHz vestigial zone.
2.d. COMPATIBILITY, as an objective, is often over-specified: compatibility with NTSC's black-and-white can allow, freeing-up luminance signal space by compressing the horizontal sync-pulse, extremely. (But color needs that very stable timebase).
Also, I'd really like to encourage definition of near-compatible digital signal, in lieu of QAM, so that present TV receivers can discern the picture (albeit without the quality of NTSC) ... as 'communications' is a significant portion of TeleVision. [3/2/96]
Encouragement must be given and received, for continuing the research into signal pre-processing, technology up-grading, and striving for compatibility. [3/2/96]
© 1995-98 Mr. Raymond Kenneth Petry
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