Video production systems employing an interlaced scanning format have been proposed, one example being an 1125 line, 30 frames/second 2:1 interlaced system developed by the Japan Broadcasting Company, NHK. Interlace advantageously provides an increase in the large-area flicker frequency at no increase in bandwidth but at the cost of well known interlace "artifacts" which are particularly troublesome where moving images are concerned.
High definition production systems employing a progressive (non-interlaced) format have been proposed which avoid the problems of motion characteristic of interlaced systems and use to advantage the progressive scan characteristic of "pixel adjacency". In a progressive-scan system, vertically adjacent pixels are nearly simultaneous in time hence frames can be processed as complete pictures providing advantages in nearly all post-production processes (e.g., image manipulation and special effects, aperature correction and MTF enhancement, spatial filtering, editing, slow-motion, standards conversion, etc.).
A number of scanning formats have been proposed for use in progressively scanned HDTV production systems. For example, a 1575 line, 24 frame per second, non-interlaced, variable aspect ratio (1.33:1 to 2.35:1) system is described by Bluth et al. in U.S. Pat. No. 3,617,626 entitled "High-Definition Color Picture Editing and Recording System". Such a low frame rate may be expected to provide poor temporal resolution. Non-interlaced systems having higher frame rates (and lower line rates) have been suggested. As an example, the signal parameters of an 800 line per field, 60 field per second system are described in "A Proposed `Strawman` HDTV Origination Standard" by W. Fagot and K. Powers in a contribution to the ATSC Technology Group on HDTV dated Oct. 15, 1984. The "picture structure" of the proposed standard is as follows: 800 lines, 726 active lines, 60 FPS, 1:1 interlace, 5.33:3 (i.e., 1.77:1) aspect ratio and a luminance bandwidth of 29 MHz. The proposed digital encoding standard comprises: 72 MHz sampling rate (luma), 1500 samples per line and 1290 samples per active line.
The foregoing 800/60/1:1 system has many advantages in a production system. Motion artifacts are eliminated by the progressive (non-interlaced) scanning. The temporal resolution is superior to the interlaced 1125 line NHK system and the spatial resolution is also subjectively superior taking into account the loss of resolution due to the so-called "interlace factor" (i.e., the multiplier that must be applied to the number of lines in an interlaced system in addition to the Kell factor in determining the effective resolution of an interlaced system). The interlace factor is, typically, in the range of 0.6 to 0.65 which indicates that the subjective sharpness of the 1125/30/2:1 system is roughly equivalent to that of a progressively scanned system with 35-40 percent fewer lines.
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USPTO Backgrounds