The first part of this paper discusses the requirements that must be met by a new television broadcasting system to maximize its acceptability to the various stakeholders, including broadcasters, equipment manufacturers, program producers, regulatory authorities, and viewers. The most important performance factors are efficient use of over-the-air spectrum, coverage versus quality, cost, interoperability, and the existence of a practical transition scenario. It is concluded that all receivers need not have the same peformance, and that low-cost receivers must be available for noncritical locations in the home. If this variation in price and performance is made possible by appropriate system design, then interoperability is facilitated and nondisruptive improvement over time is made possible, as desired by the Federal Communications Commission. In the second part of the paper, techniques that may permit meeting these requirements are discussed. These include joint multiresolution source and channel coding, multicarrier modulation, and hybrid analog/digital coding and transmission. The analog transform coefficients are subjected to spread-spectrum processing, and coded orthogonal frequency-division multiplex (COFDM) is applied to the complex hybrid symbols to be transmitted through the channel. Various methods of equalization and of improving noise, interference, and multipath rejection are compared. Finally, an example is given of a system that meets the various requirements by making use of a number of the techniques discussed. The system provides extended coverage, albeit at lower quality than currently proposed all-digital systems, and equal or higher quality than such systems in much of their service area. It also features self-optimization at each receiver depending on signal quality and receiver characteristics, and facilitates the design of receivers of lower cost and performance for less-critical applications.>

This paper describes a new HDTV system that applies joint multiresolution (MR) source and channel coding to efficiently use the available radio spectrum. Hybrid analog/digital MR channel modulation provides the benefits of digital source coding and the more efficient spectrum usage of analog transmission. Nonuniform spacing of the digital signaling levels provides MR delivery of the digital components while spread-spectrum processing permits MR delivery of the analog components. Error correction coding and OFDM channel modulation deliver the MR service in widely varying channel conditions. Simulation results demonstrate performance in various regions of the service area.>

A scalable source coder was designed for a hybrid HDTV terrestrial broadcasting system. The hybrid combination of analog and digital methods allows for both high video compression ratios and efficient utilization of the available channel capacity. Efficient channel utilization enables closer receivers to decode high quality video, and allows further receivers to decode natural looking, though lower quality video. The system uses joint source/channel coding to deliver different video components with degrees of integrity reflecting their perceptual importance. Motivation is given for hybrid transmission and analog/digital coding methods. Details of the scalable source coder are provided with a description of its key features, which include pyramid filtering and hybrid video coding. Furthermore, fundamental differences between conventional digital video compression schemes and the proposed scalable hybrid approach are highlighted. Finally, frames of video produced by a computer simulation of the hybrid HDTV system are shown, demonstrating the feasibility of such a system.>

The transformation of image signals between the continuous domain of the real world and the discrete domain of modern data processing can have a significant effect on quality and efficiency. Analysis based on perceptual rather than mathematical considerations has been carried out. A series of experiments based on the analysis has shown that substantial improvement over usual techniques can be achieved by the use of a cascade of a presharpening filter combined with Gaussian presampling and interpolation filters. The resulting ``sharpened Gaussian'' filter, although not exactly circularly symmetrical, gives a high degree of isotropy. Each element in the cascade is separable, so that computational efficiency is high. A favorable tradeoff is achieved among sharpness, smoothness, and the effects of aliasing. Subjective testing, in comparison with other commonly used filters, has shown the clear superiority of this filter.

The two-channel picture coding system previously reported is improved by adaptive companding and extended to component color coding. The basic system divides the spectrum into lowand high-frequency spatial components. The former are coarsely sampled and finely quantized, while the latter are finely sampled and coarsely quantized using a companded, randomized quantizer. The adaptive version uses a companding factor, larger than one, which multiplies the highs before coding and divides the result after decoding. This substantially raises the signal-to-noise ratio, which is calculated for both the adaptive and nonadaptive cases and confirmed by computer simulation. The color version uses an achromatic highs channel as in the basic monochrome system, plus a three-color lows channel coded in a perceptually uniform color space. With 3.5-4.3 bits/pel for 512 × 512 monochrome and color still images, the nonstatistical version produces images free of visible defects under normal viewing conditions. Projections are made for system parameters capable of achieving the very high quality now being proposed for production component coding systems, but with substantial reduction in channel capacity.

The two-channel system previously reported has been implemented in hardware using system parameters appropriate to consumer television. The basic system divides the spectrum into lowand high-frequency spatial components. The lows are coarsely sampled and finely quantized and the highs finely sampled and coarsely quantized using a companded, randomized quantizer. The purpose of this experiment was to demonstrate the potential of the system for low-cost practical application, to study the effect of the character of the randomizing noise, and to ascertain that there were no deleterious effects due to interlace, motion, or input noise. Theoretical noise calculations were qualitatively confirmed.

A computer-based system for automated engraving of gravure cylinders has been developed and is now used in a normal production environment. Either fully composed pages or individual page components are scanned and stored on a large disk. In the case of fully composed pages, an operator uses a TV display to segment the page image into line and tone areas. The image is then coded by a software process and is ready for subsequent engraving. Prior to the scanning of page components, the operator uses a tablet in order to demark both cropping locations and to specify the location of the components on the final page image. The scanned components are then assembled and coded by a single software process. The encoding process reduces the data storage requirement by a factor of two without any apparent loss of quality. Data are retrieved from disk storage, buffered, decoded, transmitted to a special formatter, and used to drive a Helio Klischograph,® which engraves the cylinder in approximately one hour. Completely arbitrary imposition (the arrangement of pages on the gravure cylinder) is accomplished at the time of engraving. Provision is made for the arbitrary intermixture of computer-processed pages and conventional engraving by means of Cronapaquesgi mounted on the companion scanning machine. The motivation for this development was to reduce the cost and time required for the production of gravure cylinders.

A device has been built for the rapid, automatic measurement of the third order probability density of video signals. Special cathode ray tubes are used to perform a 64-level amplitude analysis on each signal. A triple coincidence is formed among the three analyzer outputs, the number of occurrences in a frame interval being stored in an 8 Mc counter. These numbers are recorded on magnetic tape which then becomes the input to an electronic computer. The computer calculates the conditional entropy, i.e., the information generated by one of the signals when the other two are known. Examples are presented of second and third order distributions, and of entropies calculated for a variety of scenes.