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|5768469||Apparatus for coding and decoding a digital video signal having duplicate pictures and frames with fields originating from different film source frames||1998-06-16||Yagasaki et al.||386/109|
|5754248||Universal video disc record and playback employing motion signals for high quality playback of non-film sources||1998-05-19||Faroudja||386/123|
|5742351||Device for encoding sequences of frames constituted by film-type images and video-type images, and corresponding decoding device||1998-04-21||Guede||348/459|
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|5608464||Digital video effects generator||1997-03-04||Woodham||348/441|
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This application is a continuation-in-part of U.S. patent application Ser. No. 08/050,861, filed Apr. 21, 1993.
This invention relates generally to video production, photographic image processing, and computer graphics design, and, more particularly, to a multi-format video production system capable of professional quality editing and manipulation of images intended for television and other applications, including HDTV programs.
As the number of television channels available through various program delivery methods (cable TV, home video, broadcast, etc.) continues to proliferate, the demand for programming, particularly high-quality HDTV-format programming, presents special challenges, both technical and financial, to program producers. While the price of professional editing and image manipulation equipment continues to increase, due to the high cost of research and development and other factors, general-purpose hardware, including personal computers, can produce remarkable effects at a cost well within the reach of non-professionals, even novices. As a result, the distinction between these two classifications of equipment has become less well defined.
The parent to this application, for example, describes a video production system which integrates equipment supplied by various manufacturers, enabling a consumer to produce and edit video material using an enhanced personal computer. An adapter unit interfaced to each camera in use with the system connects to a camera interface module, and each camera interface module, in turn, feeds a computer interface unit. These computer interface units communicate with a personal computer over a standard interconnect, allowing an operator to control the various cameras while viewing individual video programs which appear in separate “windows” on the computer monitor.
This related invention solves many of the problems associated with combining commercially available hardware to create an economical personal-computer-based system capable of very high quality audio/video production. However, the variety of available and planned program standards and delivery methods places further demands on video production equipment, including the editing and manipulation of images not only from a variety of sources, but in differing pixel formats, frame rates, and so forth. Although general-purpose PC-based equipment may never allow professional-style rendering of images at full resolution in real-time, each new generation of microprocessors enables progressively faster, higher-resolution applications. In addition, as the price of memory circuits and other data storage hardware continues to fall, the capacity of such devices has risen dramatically, thereby improving the prospects for enhancing PC-based image manipulation systems for such applications.
In terms of dedicated equipment, attention has traditionally focused on the development of two kinds of professional image-manipulation systems: those intended for the highest quality levels to support film effects, and those intended for television broadcast to provide “full 35 mm theatrical film quality,” within the realities and economics of present broadcasting systems. Conventional thinking holds that 35 mm theatrical film quality is equivalent to 1200 or more lines of resolution, whereas camera negatives present 2500 or more lines. As a result, image formats under consideration have been directed towards video systems having 2500 or more scan lines for high-level production (such as the Kodak “Electronic Intermediate” system described by Hunt et al.), with hierarchies of production, HDTV broadcast, and NTSC and PAL compatible standards which are derived by down-converting these formats. Several techniques have been described, including those of Bretyl (“3×NTSC ‘Leapfrog’ Production Standard for HDTV”, SMPTE Journal, March 1989), Demos (“An Example Hierarchy of Formats for HDTV”, SMPTE Journal, September 1992), and Lim (“A Proposal for an HDTV/ATV Standard with Multiple Transmission Formats”, SMPTE Journal, August 1993). Most proposals employ progressive scanning, although interlace is considered an acceptable alternative as part of an evolutionary process. In particular, Demos addresses the important issue of compatibility to computer-graphics-compatible formats, although he begins with an 1152-line format, and only considers progressive scanning. And, as pointed out by Thorpe et al., progressive scanning also has drawbacks, and as shown by Kaiser et al. (“Resolution Requirements for HDTV Based Upon the Performance of 35 mm Motion-Picture Films for Theatrical Viewing”, SMPTE Journal, June 1985), even 35 mm theatrical film quality is a misnomer since the realities of mechanical projection systems restrict the typical screen display to less than 700 TV lines/picture height.
Current technology directions in computers and image processing should allow production equipment based upon fewer than 1200 scan lines, with picture expansions to create a hierarchy of upward-converted formats for theatrical projection, film effects, and film recording. In addition general-purpose hardware enhancements should be capable of addressing the economic aspects of production, a subject not considered in detail by any of the available references.
The present invention takes advantage of general-purpose hardware where possible to provide an economical multi-format video production system. In the preferred embodiment, specialized graphics processing capabilities are included in a high-performance personal computer or workstation, enabling the user to edit and manipulate an input video program and produce an output version of the program in a final format which may have a different frame rate, pixel dimensions, or both. An internal production format is chosen which provides the greatest compatibility with existing and planned formats associated with standard and widescreen television, high-definition television, and film. For compatibility with film, the frame rate of the internal production format is preferably 24 fps. Images are re-sized by the system to larger or smaller dimensions so as to fill the particular needs of individual applications, and frame rates are adapted by inter-frame interpolation or by traditional schemes, including “3:2 pull-down” for 24-to-30 fps conversions, or by manipulating the frame rate itself for 24 to 25 fps for a PAL-compatible display. The enhancement to a general-purpose platform preferably takes the form of a graphics processor connected to receive a video signal in an input format. The processor comprises a plurality of interface units, including a standard/widescreen interface unit operative to convert the video program in the input format into an output signal representative of a standard/widescreen formatted image, and output the signal to an attached display device. A high-definition television interface unit is operative to convert the video program in the input format into an output signal representative of an HDTV-formatted image, and output the signal to the display device. A centralized controller in operative communication with the video program input, the graphics processor, and an operator interface, enables commands entered by an operator to cause the graphics processor to perform one or more of the conversions using the television interfaces. The present invention thus encourages production at relatively low pixel dimensions to make use of lower-cost general-purpose hardware and to maintain high signal-to-noise, then subsequently expands the result into a higher-format final program. This is in contrast to competing approaches, which recommend operating at higher resolution, then down-sizing, if necessary, to less expensive formats which has led to the high-cost, dedicated hardware, the need for which the present invention seeks to eliminate.
The present invention builds upon and extends certain of the concepts introduced in the parent to this application, “Personal-Computer-Based Video Production System.” Ser. No. 08/050,861 filed Apr. 21, 1993. The system described in that application allows an operator to control equipment supplied by various manufacturers at a centralized personal computer to produce, edit and record a video program. Each camera to be used with the system described in this previously filed application feeds a signal to the personal computer through a custom adapter unit, cable and camera interface module the latter containing cable compensation and gain circuitry. The interface modules feed a common video switcher, audio mixer and display means, all of which may be provided by a variety of sources, including different manufacturers. In the preferred embodiment, the display is the monitor of a programmed personal computer, and computer interface modules connected between each camera interface module and the computer allow video images generated by the cameras to appear in different windows on the computer monitor. Control signals entered at the computer are routed to the cameras in order to control their functioning.
The present invention is primarily concerned with a different but related aspect of facilitating professional quality audio/video production; namely, the conversion of disparate graphics or television formats, including requisite frame-rate conversions, to establish an interrelated family of aspect ratios, resolutions, and frame rates, while remaining compatible with available and future graphics/TV formats. These formats include images of pixel dimensions capable of being displayed on currently available multi-scan computer monitors, and custom hardware will be described whereby frames of higher pixel-count beyond the capabilities of these monitors may be viewed. Images are re-sized by the system to larger or smaller dimensions so as to fill the particular needs of individual applications, and frame rates are adapted by inter-frame interpolation or by traditional schemes such as using “3:2 pull-down” (for 24 to 30 frame-per-second film-to-NTSC conversions) or by speeding up the frame rate itself (as for 24 to 25 fps for PAL television display). The resizing operations may involve preservation of the image aspect ratio, or may change the aspect ratio by “cropping” certain areas, by performing non-linear transformations, such as “squeezing” the picture, or by changing the vision center for “panning,” “scanning” and so forth. Inasmuch as film is often referred to as “the universal format,” primarily because 35-mm film equipment is standardized and used throughout the world, the preferred internal or “production” frame rate is preferably 24 fps. This selection also has an additional benefit, in that the 24 fps rate allows the implementation of cameras having greater sensitivity than at 30 fps, which is even more critical in systems using progressive scanning, for which the rate will be 48 fields per second vs. 60 fields per second in some other proposed systems.
The image dimensions chosen allow the use of conventional CCD-type cameras, but the use of digital processing directly through the entire signal chain is preferred, and this is implemented by replacing the typical analog RGB processing circuitry with fully digital circuitry. Production effects may be conducted in whatever image size is appropriate, and then re-sized for recording. Images are recorded by writing the digital data to storage devices employing removable hard-disk drives, disk drives with removable media, optical or magneto-optical based drives, or tape-based drives, preferably in compressed-data form. As data rates for image processing and reading-from or writing-to disk drives increase, many processes that currently require several seconds will soon become attainable in real-time, which will eliminate the need to record film frames at slower rates. Other production effects, such as slow-motion or fast-motion may be incorporated, and it is only the frame rates of these effects that are limited in any way by the technology of the day. In particular, techniques such as non-linear-editing, animation, and special-effects will benefit from the implementation of this system. In terms of audio, the data rate requirements are largely a function of sound quality. The audio signals may be handled separately, as in an “interlocked” or synchronized system for production, or the audio data may be interleaved within the video data stream. The method selected will depend on the type of production manipulations desired, and by the limitations of the current technology.
Although a wide variety of video formats and apparatus configurations are applicable to the present invention, the system will be described in terms of the alternatives most compatible with currently available equipment and methods.
An alternative embodiment of the invention is shown in FIG.
Another embodiment of the invention is depicted in FIG.
A further alternative embodiment of the invention is shown in FIG.
Currently available CCD elements for PAL/HDTV dual-use cameras provide 600,000 pixels, typically as arrays of 1024×592 or similar dimensions. By modifying the camera circuitry, the optical and CCD-driver circuitry may be adapted for use by the present invention, thereby allowing for economical implementation of the preferred configuration.
Conventional CCD-element cameras of the type described above produce images of over 800 TV Lines horizontal Luminance (Y) resolution, with a sensitivity of 2,000 lux at f8, and with a signal-to-noise ratio of 62 dB. However, typical HDTV cameras, at 1,000 TV Lines resolution and with similar sensitivity, produce an image with only a 54 dB signal-to-noise ratio, due to the constraints of the wideband analog amplifiers and the smaller physical size of the CCD-pixel-elements. By employing the more conventional CCD-elements in the camera systems of this invention, and by relying upon the computer to create the HDTV-type image by image re-sizing, the improved signal-to-noise ratio is retained. In the practical implementation of cameras conforming to this new design approach, there will be less of a need for extensive lighting provisions, which in turn, means less demand upon the power generators in remote productions, and for AC-power in studio applications.
In practice, the implementation of this design using three 600,000-element CCDs and the commonly employed technique of the spatial-shift for the green CCD-element (as described below) will produce Y/R-Y/B-Y signals with 800 TV lines of resolution, and will provide a luminance bandwidth of 15 MHz and a Chrominance bandwidth of 7.5 MHz. The RGB video signal outputs will provide a full 15 MHz bandwidth for each channel, and the camera will be suitable for the conventional/widescreen application described herein. However, for HDTV production, a higher performance level is desired. Accordingly, the system of
A more economical alternative implementation of the camera system is shown in FIG.
In CCD-based cameras, it is a common technique to increase the apparent resolution by mounting the red and blue CCD-elements in registration, but offsetting the green CCD-element by one-half pixel width horizontally. In this case, picture information is in-phase, but spurious information due to aliasing is out-of-phase. When the three color signals are mixed, the picture information is intact, but most of the alias information will be canceled out. This technique will evidently be less effective when objects are of solid colors, so it is still the usual practice to include low-pass optical filters mounted on each CCD-element to suppress the alias information. In addition, this technique cannot be applied to computer-based graphics, in which the pixel images for each color are always in registration. However, in general-use video, the result of the application of this spatial-shift offset is to raise the apparent luminance (Y) horizontal resolution to approximately 800 television lines.
The availability of hard-disk drives of progressively higher capacity and data transmission rates is allowing successively longer and higher resolution image displays in real-time. At the previously cited data rates, wide-screen frames would require 486 MB/min, so that currently available 10 GB disk drives will store more than 21 minutes of video. When the anticipated 100 GB disk drives (2.5-inch or 3.5-inch disks using Co-Cr, barium ferrite, or other high-density recording magnetic materials) become available, these units will store 210 minutes, or 3½ hours of video. For this application, a data storage unit
A key aspect of the system is the versatility of the graphics processor shown generally as
A standard/widescreen video interface
The management of 25 fps (PAL-type) output signals in a system configured for 24 fps production applications presents technical issues which must be addressed, however. Simple playback of signals to produce PAL output is not a serious problem, since any stored video images may be replayed at any frame rate desired, and filmed material displayed at 25 fps is not objectionable. Indeed, this is the standard method for performing film-to-tape transfers used PAL- and SECAM-television countries. However, it is not practical to produce both PAL and NTSC signals concurrently from a single source running at 24 fps. Simultaneous output of both NTSC and film-rate images is performed by exploiting the 3:2 field-interleaving approach: 5×24=2×60; that is, two film frames are spread over five video fields. This makes it possible to concurrently produce film images at 24 fps and video images at 30 fps. The difference between 30 fps and the exact 29.97 fps rate of NTSC may be palliated by slightly modifying the system frame rate to 23.976 fps. This is not noticeable in normal film projection, and is an acceptable deviation from the normal film rate. However, if the system frame rate is adjusted to 25 fps to produce PAL or SECAM output, there is no convenient technique to produce 30 fps NTSC concurrently, unless multiple-frame storage with motion-interpolation is employed, which tends to create udesirable artifacts in the image produced. Commercial standards-converters are available to perform this function, however, from companies such as Snell & Wilcox. This system is primarily directed towards production of video-based film and high-definition TV images, for which 24 fps and 30 fps, respectively, are the established frame rate for film and the proposed frame rate for HDTV (in NTSC-countries). The conversion to 25 fps is performed without difficulties in any application in which there is no requirement for the simultaneous production of images at other frame rates. Using this approach, the adjustment of frame rates for playback of the images by the system is sufficient for all of the normal production applications.
An HDTV video interface
The third section of the graphics processor
Several additional features of this system are disclosed in FIG.
It is important to note that although
Alternative implementations may employ different frame size (in pixels), aspect ratios, or frame rates, and these variations should be considered to be within the scope of the invention.
The output of processor