EP0997039A4

EP0997039A4 - Multi-format audio/video production system with frame-rate conversion

Info

Publication number: EP0997039A4
Application number: EP96904562A
Authority: EP
Inventors: Kinya Washino; Barry H Schwab
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-04-21
Filing date: 1996-01-23
Publication date: 2000-05-03
Also published as: WO1997027704A1; EP0997039A1; USRE38079E1

Abstract

A program input may be translated into any of various graphics or television formats, and stored as compressed images, using any of several commercially available methods. While being processed, the images (e.g. 180) may be re-sized (182, 184) to produce a desired aspect ratio or dimensions using conventional techniques, such as interpolation, and signals within the video data stream optionally may be used to control 'pan-scan' operations at a receiving end, in case this end does not have the same aspect ratio as the source signal. Frame rate conversion to and from conventional formats is performed by using the techniques employed for well known film-to-NTSC and film-to-PAL transfers, or by inter-frame interpolation. By judicious selection of the optimal digitizing parameters, the system allows a user to establish an inter-related family of aspect ratios, resolutions, and frame rates, and yet remain compatible with currently available and planned formats.

Description

MULTI-FORMATAUDIO/VIDEO PRODUCTION SYSTEMWITH FRAME-RATE CONVERSION

Field of the Invention 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

Background of the Invention 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 nas become less well defined Although general-purpose PC-based equipment may never allow professional-style rendering of images at full resolution m 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 as projected in theaters 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, with hierarchies of production, HDTV broadcast, and NTSC and PAL compatible standards which are derived by down-converting these formats. Most proposals employ progressive scanning, although interlace is considered an acceptable alternative as part of an evolutionary process. Another important issue of compatibility to computer-graphics-compatible formats.

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. Summary of the Invention 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 compa ibility with existing and planned formats associated with standard and widescreen television, high-defmition 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- rame interpolation or by traditional schemes, including "3 2 pull-down" for 24-to-30 fps conversions, or by manipulating the frame rate itself using a program storage facility with asynchronous reading and writing capabilities

The invention 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-defmition television interface unit is operative to convert the video program m 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 .

Brief Description of the Drawings FIGURES 1A-1D show the preferred and alternative image aspect ratios in pixels;

FIGURE 2 shows a functional diagram for disk- based video recording;

FIGURE 3 shows the components comprising the multi-format audio/video production system;

FIGURE 4 is a block diagram of an alternative embodiment of video program storage means incorporating asynchronous reading and writing capabilities to carry out frame- ate conversions;

FIGURE 5 shows the inter-relatlonship of the multi-format audio/video production system to many of the various existing and planned video formats,- and FIGURE 6 shows the implementation of a complete television production system, including signals provided by broadcast sources, satellite receivers, and data-network interfaces .

Detailed Description of the Preferred Embodiment The present invention is primarily concerned with the conversion of disparate graphics or television formats, including requisite frame-rate conversions, to establish an inter-related 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 re¬ sizing 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-fro 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 . Figure IA illustrates one example of a compatible system of image sizes and pixel dimensions. The selected frame rate is preferably 24 per second (2:1 interlaced) , for compatibility with film elements; the selected picture dimension in pixels is preferably 1024 x 576 (0.5625 Mpxl) , for compatibility with the 16:9 "wide- screen" aspect ratio anticipated for all HDTV systems, and the conventional 4:3 aspect ratio used for PAL systems [768 x 576 (0.421875 Mpxl)] . All implementations preferably rely on square pixels, though other pixel shapes may be used. Re-sizing (using the well known, sophisticated sampling techniques available in many image-manipulation software packages or, alternatively, using hardware circuitry described herein below) to 2048 x 1152 (2.25 Mpxl) provides an image suitable for HDTV displays or even theatrical projection systems, and a further re-sizing to 4096 x 2304 (9.0 Mpxl) is appropriate for even the most demanding production effects. Images may be data compressed 5:1 for 16:9 "wide-screen" TV frames, or 10:1 for HDTV; the data files may then be stored on conventional disk drives, requiring only approximately 8.1 MB/sec for wide-screen frames in RGB, and only 16.1 MB/sec for HDTV frames in RGB. An alternative embodiment of the invention is shown m Figure IB. In this case, the user would follow a technique commonly used in film production, in which the film is exposed as a 4:3 aspect ratio image When projected as a wide-screen format image, the upper and lower areas of the frame may be blocked by an aperture plate, so that the image shows the desired aspect ratio

(typically 1.85 1 or 1.66.1) . If the original image format were recorded at 24 frames per second, with a 4 3 ratio and with a dimension m pixels of 1024 x 768, all image manipulations would preserve these dimensions Complete compatibility with the existing formats would result, with

NTSC and PAL images produced directly from these images by re-scaling, and the aforementioned wide-screen images would be provided by excluding 96 rows of pixels from the top of the image and 96 rows of pixels from the oottom of the image, resulting in the 1024 x 576 image size as disclosed above The data content of each of these frames would be

0 75 Mpxlε, and the data storage requirements disclosed above would be affected accordingly

Another embodiment of the invention is depicted m Figure IC In this alternative, the system would follow the image dimensions suggested in several proposed digital HDTV formats under consideration by the Advanced Television Study Committee of the Federal Communications Commission The format to be adopted is expected to assume a wide- screen image having dimensions of 1280 x 720 pixels Using these image dimensions (but at 24 fps with 2 1 interlace) , compatibility with the existing formats would be available, with NTSC and PAL images derived from this frame size by excluding 160 columns of pixels from each side of the image, thereby resulting in an image having a dimension m pixels of 960 x 720. This new image would then be re- scaled to produce images having pixel dimensions of 640 x 480 for NTSC, or 768 x 576 for PAL; the corresponding wide-screen formats would be 854 x 480 and 1024 x 576, respectively In this case, an image having a dimension in pixels of 1280 x 720 would contain 0.87890625 Mpxl, with 1,000 TV lines of resolution; furthermore, the systems under evaluation by the ATSC of the FCC also assume a decimation of the two chrominance signals, w th detail of only 640 x 360 pixels retained. The data storage requirements disclosed above would be affected accordingly The development path to 24 fps with progressive scanning is both well-defined and practical, as is the use of the previously described methods to produce images having a dimension in pixels of 2048 x 1152

A further alternative embodiment of the invention is shown m Figure ID. As with the system described with reference to Figure IB, the user follows the tecnnique commonly used in film production, wherein the film is exposed as a 4:3 aspect ratio image When pro ected as a wide-screen format image, the upper and lower areas of the frame area again blocked by an aperture plate, so that the image shows the desired aspect ratio (typically 1.85-1 or 1.66:1) For an original image format recorded at 24 frames per second, with 4:3 ratio and with pixel dimensions of 1280 x 960, all image manipulations preserve these dimensions. Complete compatibility with the existing formats results, w th NTSC and PAL images produced directly from these images by rescaling, and the aforementioned wide-screen images are provided by excluding 120 rows of pixels from the top of the image and 120 rows of pixels from the bottom of the image, thereby resulting in the 1280 x 720 image size as described above. The data content of each of these frames is 0.87890625 Mpxls, and the data storage requirements disclosed above are affected accordingly.

In each of the cases described herein above, a positioning or image centering signal may be included within the data stream, so as to allow the inclusion of information which may be utilized by the receiving unit or display monitor to perform a "pan/scan" operation, and thereby to optimize the display of a signal having a different aspect ratio than that of the display unit. For example, a program transmitted in a wide-screen forma would include information indicating the changing position of the image center, so that a conventional (4:3 aspect ratio) display unit would automatically pan to the proper location. For the display of the credits or special panoramic views, the monitor optionally could be switched to a full "letter-box" display, or the image could be centered and rescaled to include information corresponding to an intermediate situation, such as halfway between full- height (with cropped sides) and letter-box (full-width, but with blank spaces above and below the image on the display) . This positioning/rescaling information would be determined under operator control (as is typical for pan/scan operations when performing film transfers to video) so as to maintain the artistic values of the original material, within the limitations of the intended display format.

Conventional CCD-element cameras produce images

RECTIFIED SHEET {RULE 91) 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 m the camera systems of this invention, and by relying upon the computer to create the HDTV- ype image by image re-sizmg, 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 m remote productions, and for AC-power m studio applications.

In CCD-based cameras, it is also 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 m-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 n 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 program duration and higher resolution image displays in real-time At the previously cited data rates, wide-screen frames would require 486 MB/mm, 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-mch disks using Co-Cr, barium ferrite, or other high-density recording magnetic materials) become available, these units will store 210 minutes, or 3 1/2 hours of video For this application, a data storage unit is provided to facilitate editing and production activities, and it is anticipated that these units would be employed m much the same way as video cassettes are currently used m Betaca and other electronic news gathering vENG) cameras and n video productions This data storage unit may be implemented by use of a magnetic, optical, or magneto-optical disk drive with removable storage media, or by a removable disk-drive unit, such as those based on the PCMCIA standards Although PCMCIA media are 1 8-ιnches in dimension, alternative removable media storage units are not restricted to this limit, and could employ larger media, such as 2 5-inch or 3 5-inch disks this, in turn, will lead to longer duration program data storage, or could be applied to lower ratios of data compression or higher- pixel -count images within the limits of the same size media .

Figure 2 shows the functional diagram for the storage-device-based digital recorder employed m the video camera, or separately in editing and production facilities. As shown, a removable hard disk drive 70 is interfaced through a bus controller 72,- m practice, alternative methods of storage such as optical or magneto-optical drives could be used, based on various interface bus standards such as SCSI-2 or PCMCIA. This disk drive system currently achieves data transfer rates of 20 MB/sec, and higher rates on these or other data storage devices, such as high-capacity removable memory modules, is anticipated The microprocessor 74 controls the 64-bit or wider data bus 80, which integrates the various components Currently available microprocessors include the Alpha 21064 by Digital Equipment Corporation, or the MIPS R4400 by MIPS Technologies, Inc.; future implementations would rely on the already announced P6 by Intel Corp or the PowerPC 620, which is capable of sustained data transfer rates of 100 MB/sec. Up to 256 MB of ROM, shown at 76, is anticipated for operation, as is 256 MB or more of RAM, shown at 78. Current PC-based video production systems are equipped with at least 64 MB of RAM, to allow sophisticated editing effects. The graphics processor 82 represents dedicated hardware that performs the various manipulations required to process the input video signals 84 and the output video signals 86; although shown using an RGB format, either the inputs or outputs could be configured m alternative formats, such as Y/R-Y/B-Y, YIQ, YUV or other commonly used alternatives. In particular, while a software-based implementa ion of the processor 82 is possible, a hardware- based implementation is preferred, with the system employing a compression ratio of 5 1 for the conventional/widescreen signals ("NTSC/PAL/Widescreen") , and a 10:1 compression ratio for HDTV signals (2048 x 1152, as described herein above) An example of one of the many available options for this data compression is the currently available Motion-JPEG system Image re-sizing may alternatively be performed by dedicated microprocessors, such as the gm865Xl or gm833X3 by Genesis Microchip, Inc Audio signals may be included within the data stream, as proposed m the several systems for digital television transmission already under evaluation by the Federal Communications Commission, or by one of the methods available for integrating audio and video signals used in multi-media recording schemes, such as the Microsoft " AVI" (Audio/Video Interleave) file format As an alternative, an independent system for recording audio signals may be implemented, either by employing separate digital recording provisions controlled by the same system and electronics, or by implementing completely separate equipment external to the camera system described herein above

Figure 3 shows the components that comprise a multi-format audio/video production system As m the case of the computer disk-based recording system of Figure 2, an interface bus controller 106 provides access to a variety of storage devices, preferably including an internal hard- disk drive 100, a tape-back-up drive 102, and a hard-disk drive with removable media or a removable hard-disk drive 104 The interface bus standards implemented could include, among others, SCSI-2 or PCMCIA Data is transmitted to and from these devices under control of microprocessor 110 Currently, data bus 108 would operate as shown as 64-bits wide, employing microprocessors such as those suggested for the computer-disk-based video recorder of Figure 3; as higher-powered microprocessors become available, such as the PowerPC 620, the data bus may be widened to accommodate 128 bits, and the use of multiple parallel processors may be employed, with the anticipated goal of 1,000 MIPS per processor Up to 256 MB of ROM 112 is anticipated to support the requisite software, and at least 1,024 MB of RAM 114 will allow for the sophisticated image manipulations, inter-frame interpolation, and intra- frame interpolation necessary for sophisticated production effects, and for conversions between the various image formats A key aspect of the system is the versatility of the graphics processor shown generally as 116 Eventually, dedicated hardware will allow the best performance for such operations as image manipulations ana re-scaling out it is not a requirement of the system that ι_ assume these functions Three separate sections are employed to process the three classif cations of signals Although the video input and output signals described herein below are shown, by example, as RGB, any alternative format for video signals, such as Y/R-Y/B-Y, YIQ, YUV, or other alternatives may be employed as part of the preferred embodiment One possible physical implementation would be to create a separate circuit board for each of the sections as described below, and manufacture these boards so as to be compatible with existing or future PC-based electrical and physical interconnect standards

A standard/ idescreen video interface 120, intended to operate within the 1024 x 576 or 1024 x 768 image sizes, accepts digital RGB signals for processing and produces digital RGB outputs m these formats, as shown generally at 122. Conventional internal circuitry comprising D/A converters and associated analog amplifiers are employed to convert the internal images to a second set of outputs, including analog RGB signals and composite video signals. These outputs may optionally be supplied to either a conventional multi-scan computer video monitor or a conventional video monitor having input provisions for

RGB signals (not shown) . A third set of outputs supplies analog Y/C video signals. The graphics processor may be configured to accept or output these signals m the standard NTSC, PAL, or SECAM formats, and may additionally be utilized in other formats as employed in medical imaging or other specialized applications, or for any desired format for computer graphics applications Conversion of these 24 frame-per-second images to the 30 fps (actually,

29.97 fps) NTSC and 25 fps PAL formats may be performed m a similar manner to that used for scanned film materials, that is to NTSC by using the conventional 3:2 "pull-down" field-sequence, or to PAL by running the images at the higher 25 fps rate. For other HDTV frame rates, aspect ratios, and line rates, mtra-frame and inter-frame interpolation and image conversions may be performed by employing comparable techniques well known in the art of computer graphics and television.

An HDTV video interface 124, intended to operate within the 2048 x 1152 or 2048 x 1536 image sizes (with re-sizing as necessary) , accepts digital RGB (or alternative) signals for processing and produces digital outputs in the same image format, as shown generally at 126. As is the case for the Standard/Widescreen interface 120, conventional internal circuitry comprising D/A converters and associated analog amplifiers are employed to convert the internal images to a second set of outputs, for analog RGB signals and composite video signals.

The third section of the graphics processor 116 shown in Figure 3 is the film output video interface 128, which comprises a special set of video outputs 130 intended for use with devices such as laser film recorders. These outputs are preferably configured to provide a 4096 x 2304 or 4096 x 3072 image size from the image sizes employed internally, using re-sizing techniques discussed herein as necessary for the format conversions. Although 24 fps is the standard frame rate for film, some productions employ 30 fps, especially when used with NTSC materials, and these alternative frame rates, as well as alternative image sizes, are anticipated as suitable applications of the invention. Several additional features of this system are disclosed in Figure 3. The graphics processor includes a special output 132 for use with a color printer. In order to produce the highest quality prints from the screen display it is necessary to adjust the printer resolution to match the image resolution, and this is automatically optimized by the graphics processor for the various image sizes produced by the system. In addition, provisions are included for an image scanner 134, which may be implemented as a still image scanner or a film scanner, thereby enabling optical images to be integrated into the system. An optional audio processor 136 includes provisions for accepting audio signals in either analog or digital form, and outputting signals in either analog or digital form, as shown in the area generally designated as 138 For materials including audio intermixed with the video signals as described herein above, these signals are routed to the audio processor for editing effects and to provide an interface to other equipment

It is important to note that although Figure 3 shows only one set of each type of signal inputs, the system is capable of handling signals simultaneously from a plurality of sources and in a variety of formats Depending on the performance level desired and the image sizes and frame rates of the signals, the system may be implemented with multiple hard disk units and bus controllers, and multiple graphics processors thereby allowing integration of any combination of live camera signals, prerecorded materials, and scanned images Improved data compression schemes and advances in hardware speed will allow progressively higher frame rates and image sizes to be manipulated in real-time

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 in PAL- and SECAM-television countries Simultaneous output of both NTSC and film-rate images may be performed by exploiting the 3 2 field-interleaving approach 5 x 24 = 2 x 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 _n~,„-,_ΛΛ 97/27704

- 19 -

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.

The management of 25 fps (PAL-type) output signals in a system configured for 24 fps production applications (or vice versa) presents technical issues which must be addressed, however. One alternative for facilitating these and other frame-rate conversions is explained with reference to Figure 4. A digital program signal 404 is provided to a signal compression circuit 408; if the input program signal is provided in analog form 402, then it is first processed by A/D converter 406 to be placed in digital form. The signal compressor 408 processes the input program signal so as to reduce the effective data rate, utilizing any of the commonly implemented data compression schemes, such as JPEG, MPEG-1, MPEG-2, etc. well known in the art. As an alternative, the digital program signal 404 may be provided in data- compressed form. At this point, the digital program signal is provided to data bus 410. By way of example, several digital storage units, designated as "storage means A" 412 and "storage means B" 414, are included for storing the digital program signals presented on data bus 410, under management by controller 418. The two storage means 412 and 414 may be used in alternating fashion, with one storing the source signal until it reaches its full capacity. At this point, the other storage means would continue storing the program signal until it, too, reached its full capacity. The maximum program storage capacity for the program signals will be determined by various factors, such as the input program signal frame rate, the frame dimensions in pixels, the data compression rate, the total number and capacities of the storage means, and so forth. When the available storage capacity has been filled, this data storage scheme automatically will result in previously-recorded signals being overwritten; as additional storage means are added, the capacity for time- delay and frame rate conversion is increased, and there is no requirement that all storage means be of the same type, or of the same capacity. In practice, the storage means would be implemented using any of the commonly available storage techniques, including, for example, magnetic disks, optical or magneto-optical discs, or semiconductor memory. When it is desired to begin playback of the program signal, signal processor 416, under management by controller 418 and through user interface 420, retrieves the stored program signals from the various storage means provided, and performs any signal conversions required. For example, if the input program signals were provided at a 25 fps rate (corresponding to a 625-line broadcast system) , the signal processor would perform image resizing and inter-frame interpolation to convert the signal to 30 fps (corresponding to a 525-line broadcast system) . Other conversions (such as color encoding system conversion from PAL-for at to NTSC, etc., or frame dimension or aspect- ratio conversion) will be performed as necessary. The output of the signal processor is then available in digital form as 422, or may be processed further, into analog form 426 by D/A converter 424. In practice, a separate data bus (not shown) may be provided for output signals, and/or the storage means may be implemented by way of dual-access technology, such as dual-port RAM utilized for video- display applications, or multiple-head-access disk or disc storage units, which may be configured to provide simultaneous random-access read and write capabilities. Where single-head storage means are implemented, suitable input buffer and output buffer provisions are included, to allow time for physical repositioning of the record/play head. In utilizing program storage means including synchronous recording and reprogram capabilities of the types just described, if it is known that a program will be stored in its entirety before the commencement of playback, that is, with no overlap existing between the input and output signal streams, it typically will be most efficient to perform any desired frame conversion on the program either before or after initial storage, depending upon which stored format would result in the least amount of required memory. For example, of the program is input at a rate of 24 frames per second, it probably will be most efficient to bring such program in and store it at that rate, and perform a conversion to higher frame rates upon output. In addition, in situations where a program is recorded in its entirety prior to conversion into a particular output format, it is most efficient to store the program on a tape-based format, given the reduced cost, on a per-bit basis, of tape-based storage. Of course, disk storage may also be used, and may become more practical as storage capacities continue to increase. If it is known that a program is to be output at a different frame rate while it is being input or stored, it is most preferable to use disk storage and to perform the frame rate conversion on an ongoing basis, using one of the techniques described above In this case, the high-capacity video storage means, in effect, assumes the role of a large video buffer providing the fastest practical access time Again, other memory means (types) may be used, including all solid-state and semiconductor types, depending upon economic considerations, and so forth

In some applications, a more sophisticated conversion scheme is required For example, in frame rate conversion systems of conventional design, if an input program signal having a 24 fps rate format is to be displayed at a 25 fps rate, it is customary to simply speed up the source signal playback so as to provide the signals at a 25 fps rate This is the procedure utilized for performing 24-fps-fllm-mateπal transfer for 25 fps PAL- format use However, implementation of this method requires that the user of the output signal must have control over the source-signal playback In a wide-area distribution system (such as direct-broadcast-satellite distribution) this is not possible While a source signal distributed at 24 fps readily could be converted to 30 fps (utilizing the familiar "3-2-pull-down" technique) , the conversion to 25 fps is not as easily performed, due to the complexity and expense of processing circuitry required for inter-frame interpolation over a 24-frame sequence However, utilizing the system disclosed in Figure 4, the conversion is straightforward If, for example, a 24 fps program lasting 120 minutes is transmitted in this format, there are a total of 172,800 (120 x 60 x 24) frames of information, display of this program m speeded-up fashion at 25 fps would mean that the input frame rate falls behind the output frame rate by one frame per second, or a total of 7,200 frames during the course of the program At a 24 fps transmission rate, this corresponds to 300 seconds transmission time; in other words, for the input program (at 24 fps) and the output program (at 25 fps) to _find together, the input process would have to commence 300 seconds before the output process begins In order to perform this process, then, it is necessary for the storage means to have the capacity to retain 300 seconds of program material, in effect serving as a signal buffer As an example, for the systems disclosed herein (in which the compressed- ata rates vary from 8 1 MB/sec (for standard TV formats) to 16 2 MB/see (for HDTV formats) it is necessary to store as much as 4 7 GBytes of data, which is readily available by way of multiple disks or discs utilizing conventional storage technology

A similar situation arises in the case of a 25 fps signal to be displayed at 24 fps, or some other data rate readily provided by conversion from 24 fps (such as 30 fps) In this case, the source signal is provided at a higher frame rate than the output signal, so that a viewer watching a program from the onset of the transmission would fall behind the source signal rate, and the storage means would be required to hold frames of the program to be displayed at a time after the source signal arrival time, in the case of the 120 minute program described above, the viewing of the source program would conclude 300 seconds after the source signal itself had concluded, and comparable calculations are applied for the storage means The conversion of frame rates from 30 fos to 24 fps or to 25 fps is more complicated, because some form of inter-frame interpolation is required. In one case, a multi-frame storage facility would allow this type of interpolation to be performed in a relatively conventional manner, as typically is utilized in NTSC- o-PAL conversions (30 fps to 25 fps) . At this point, a 25 fps to 24 fps conversion could be performed, in accordance with the methods and apparatus described herein above.

An alternative method to carry out this frame rate conversion is to perform, in effect, the reverse of the "3:2 pull-down" procedure. If one were to select every fifth field and delete it from the signal sequence, the resultant ratio of 5:4 of the remaining fields would result in the desired conversion of 30 fps to 24 fps. In this case, it is necessary to re-interlace the image signal, by reversing the field identity (i.e., from odd to even, or from even to odd) of each of the four following fields, so that the signal stream continues to alternate between odd and even fields. The next four fields would be retained, then the fifth field deleted, and the next four again would have their field identity reversed. This pattern would be continued throughout the program. If the original source material were from 24 fps (for example, film) , then if the repeated fields (i.e., the "3" field of the 3:2 sequence) were identified at the time of conversion, then the removal of these fields would simply return the material to its original form. If the desired conversion is to be from 30 fps to 25 fps, then an equivalent procedure would be performed using the storage-based frame-conversion method described herein above, or, alternatively, every sixth field could be deleted, in accordance with the method described for 30 fps to 24 fps. Depending on the original source material frame rate and intermediate conversions, the user would select the method likely to present the least amount of image impairment . In these applications, the presence of the storage means allows the viewer to control the presentation of a program, utilizing a user interface 820 to control the playback delay and other characteristics of the signal while it is being stored or thereafter. In practice, a wide range of alternatives for input frame rates and output frame rate conversions are made available through this system.

Figure 5 shows the inter-relationship of the various film and video formats compatible with the invention, though not intended to be inclusive of all possible implementations. In typical operations, the multi-format audio/video production system 162 would receive film-based elements 160 and combine them with locally produced materials already in the preferred internal format of 24 frames-per-second . In practice, materials may be converted from any other format including video at any frame rate or standard. After the production effects have been performed, the output signals may be configured for any use required, including, but not limited to, HDTV at 30 fps shown as 164, NTSC/widescreen at 30 fps shown as 166, PAL-SECAM/widescreen at 25 fps shown as 170, or HDTV at 25 fps shown as 172. In addition, output signals at 24 fps are available for use in a film-recording unit 168. Figure 6 shows an implementation involving one possible choice for image sizes, aspect ratios, and frame rates to provide a universal television production system. As shown, signals are provided from any of several sources, including conventional broadcast signals 210, satellite receivers 212, and interfaces to a high bandwidth data network 214. These signals would be provided to the digital tuner 218 and an appropriate adapter unit 220 for the data network or "information superhighway" before being supplied to the decompression processor 222. The processor 222 provides any necessary data de-compression and signal conditioning for the various signal sources, and preferably is implemented as a plug-in circuit board for a general- purpose computer, though the digital tuner 218 and the adapter 220 optionally may be included as part of the existing hardware. The output of processor 222 is provided to the internal data bus 226. The system microprocessor 228 controls the data bus, and is provided with 16 to 64 MB of RAM 230 and up to 64 Mb of ROM 232. This microprocessor could be implemented using one of the units previously described, such as the PowerPC 604 or PowerPC 620. A hard disk drive controller 234 provides access to various storage means, including, for example, an internal hard disk drive unit 236, a removable hard disk drive unit 238, or a tape drive 240; these storage units also enable the PC to function as a video recorder, as described above. A graphic processor 242, comprising dedicated hardware which optionally be implemented as a separate plug-in circuit board, performs the image manipulations required to convert between the various frame sizes (in pixels) , aspect ratios, and frame rates. This graphics processor uses 16 to 32 MB of DRAM, and 2 to 8 MB of VRAM, depending on the type of

RECTIFIED SHEET <RULE 91 display output desired For frame size of 1280 x 720 with an aspect ratio 16.9, the lower range of DRAM and VRAM will be sufficient, but for a frame size of 2048 x 1152 the higher range of DRAM and VRAM is required In general, the 1280 x 720 size is sufficient for conventional "multi-sync" computer display screens up to 20 inches, and the 2048 x 1152 size is appropriate for conventional "multi-sync" computer display screens up to 35 inches Analog video outputs 244 are available for these various display units Usmg this system, various formats may be displayed, including (for 25 fps, shown by speeding up 24 fps signals) 768 x 576 PAL/SECAM, 1024 x 576 wide-screen, and 2048 x 1152 HDTV, and (for 30 fps, shown by utilizing the well- known "3 2 pull-down" technique, and for 29 97 fps, shown by a slight slow-down in 30 fps signals) 640 x 480 NTSC and 854 x 480 wide-screen and 1280 x 720 USA and 1920 x 1080 NHK (Japan) HDTV While most NTSC monitors will synchronize to a 30 fps signal, possibly requiring that the color subcamer frequency be adjusted, many PAL and SECAM monitors will not accept a 24 fps signal In this case, more sophisticated frame-rate conversion techniques, sucn as those described herein above, may be required for viewing live broadcasts, since the 24 fps input signal rate cannot keep pace with the 25 fps display rate However, in practice t is anticipated that future television sets will incorporate "multi-sync" designs that eliminate this potential problem

Having described the invention, we claim

Claims

1. A multi-format audio/video production system adapted for use with a display device, comprising- means to receive an input signal representative of an audio/video program in one of a plurality of display formats,- a graphics processor connected to receive the audio/video program and convert the display format of the program into an intermediate production format, the graphics processor including: (a) a standard/widescreen interface unit operative to convert the video program in the production format into an output signal representative of a standard/widescreen formatted program, and (b) a high-definition television (HDTV) interface unit operative to convert the video program in the production format into an output signal representative of an HDTV-formatted program; high-capacity video storage means,- an operator interface,- and a controller in operative communication with the means to receive the input signal, the graphics processor, the high-capacity video storage means and the operator interface, whereby commands entered by an operator through the interface cause the following functions to be performed:

(a) the conversion of an audio/video program into the production format, (b) storage of a program in the production format in the high-capacity video storage means, (c) the conversion of a program in the production format into a standard/widescreen program, either directly from the means to receive the input signal or from the high- capacity video storage means, and

(d) the conversion of a program in the production format into an HDTV program, either directly from the means to receive an input signal or from the high-capacity video storage means.

2. The multi-format audio/video production system of claim 1, the graphics processor further including a film output video interface, the controller further being operative, in response to a command entered by an operator, to convert the video program in the input format into an output signal for photographic production, either directly from the means to receive the input signal or from the high-capacity video storage means.

3. The multi-format audio/video production system of claim 1, including input and output signals compatible with any of the following standard formats: RGB, YIQ, YUV, and Y/R-Y/B-Y.

4. The multi-format audio/video production system of claim 1, including input and output signals compatible with a video standard utilizing separate luminance and chrominance component video signals.

5. The multi-format audio/video production system of claim 1, wherein the means to receive an input signal representative of a video program includes a digital video camera.

6. The multi-format audio/video production system of claim 1 wherein the means to receive a video program includes a removable high-capacity magnetic storage medium.

7. The multi-format audio/video production system of claim 1 wherein, in the event that a change aspect ratio results from any of the format conversions, the controller further is operative to cause the change in aspect ratio to be visibly evident on the display device.

8. The multi-format audio/video production system of claim 1, further including means for controlling pan/scan operations with respect to the video portion of the input signal .

9. The multi-format audio/video production system of claim 1 wherein the means to convert the production format into one or more of the output formats includes interpolation means to expand the number of pixels associated with the production format.

10. The multi-format audio/video production system of claim 1, wherein the high-capacity video storage means includes asynchronous program recording and reproducing capabilities to perform a frame rate conversion on the program. 11. A multi-format audio/video production system forming part of a general-purpose computer platform having a user input and color display, the system comprising: means to receive an input video program in one of a plurality of input formats,- high-capacity video storage means; means to convert the input program into a 24 frames-per-second (fps) production format, if not already in such a format, for storage within the high-capacity video storage means and for review on the color display,- and means to convert the production format into one or more of the following output formats, either directly from the input or from the storage means: NTSC at 30 fps,

PAL/SECAM at 25 fps, HDTV at 25 fps, HDTV at 30 fps, and film-compatible video at 24 fps.

12. The multi-format audio/video production system of claim 11 wherein the means to convert the production format into one or more of the output formats includes interpolation means to expand the number of pixels associated with the production format.

13. The multi-format audio/video production system of claim 11 wherein the high-capacity video storage means includes asynchronous program recording and reproducing capabilities to provide a program in an output format having a desired frame rate. 14. The multi-format audio/video production system of claim 11 wherein tne asynchronous program recording and reproducing capabilities are used to increase the frame rate from the 24 fps production format frame rate to a 25 fps output frame rate.

15. In an enhanced personal computer having a color monitor, the method of producing a video program, comprising the steps of : receiving an input video program, converting the input video program into a production format having a predetermined frame rate and image dimension in pixels; providing high-capacity video storage means,- storing the program n the production format in the high-capacity video storage means,- displaying the video program on the color monitor using the predetermined frame rate and image dimensions in pixels, including cropped versions of the program, with the extent of the cropping being visually evident on the monitor,- accessing the program in the production format from the high-capacity video storage means and manipulating the video program to create a desired edited version of the program in an output format, including an output format having a frame rate and image dimensions in pixels different from that of the production format, and outputting the desired edited version of the program in the output format .

16 The method of claim 15, including the step of providing high-capacity video storage means with asynchronous program recording and reproducing capabilities, and wherein the step of manipulating the video program to create a desired edited version of the program in a final format includes using the asynchronous program recording and reproducing capabilities to convert the frame rate of a program in the production format.

17. The method of claim 15, wherein the step of manipulating the video program to create a desired edited version of the program in a final format includes the step of interpolating to produce an edited version of the program in a final format having pixel dimensions greater than that of the production format.

18. The method of claim 15, further including the step of controlling pan/scan operations relative to a received input video program.