APPARATUS AND METHOD FOR VIDEO BROADCASTING

Abstract: This invention discloses an apparatus for replacing a portion of each of a sequence of existing images with a new image, the apparatus comprises a frame grabber operative to grab a sequence of frames respectively representing the sequence of existing images, a localizer operative to detect at least one site within each existing image at which the new image is to be incorporated, a perspective transformer operative to detect the perspective at which the site is imaged and a transmitter operative to transmit to each of a plurality of remote locations, for each frame the existing image represented in the frame, the coordinates of the site, and the perspective at which the site is imaged.

Description: APPARATUS AND METHOD FOR VIDEO BROADCASTING FIELD OF THE INVENTION The present invention relates to video broad¬ casting systems. BACKGROUND OF THE INVENTION International sports events or other spectacles generally draw the interest and attention of spectators in many countries. For example, the Olympics, Superbowl, World Cup, major basketball and soccer games and auto races fit into this category. Such events are generally broadcast live by video to a large international audi¬ ence. The locale in which these events take place, such as stadiums or courts, provide advertising space all around in the form of signs, posters or other displays on fences and billboards, and in fact on any unoccupied space suitably located, including sections of the playing field. Due to the nature of the displays, which are mostly in the form of printed matter, they are not changed too frequently and remain at least for a day, or a series or a whole season, and are directed mostly at local audiences. In cases where two teams from different countries play each other, the advertisements are occa¬ sionally arranged so that one side of the stadium con¬ tains advertisements directed to audiences in one coun¬ try, while the other side has advertisements directed to the spectators in the other country. The video cameras in these instances film the event from opposite sides of the stadium for their re¬ spective audiences. This of course is logistically complicated and limits the angle from which the events can be seen in either of the countries represented in the game. Another limitation to present methods of adver¬ tising is the stringent safety requirements for position¬ ing the billboards, so as not to interfere with the game, nor disturb the view of the spectators in the stadium, nor pose a danger to the players. The displays must not be too close to the actual field of action, so as not to distract the players. A most serious drawback of the present system for advertising at major world sports events is the fact that although the event is televised live throughout the world, the actual physical advertisements in the stadium, because of their broad international exposure, can only cater to products having a world market. Local advertisers can only make use of such world-class televised events by locally superimposing messages on the TV screen, or by interrupting the real time of the event. Another drawback of the existing system is that over long time periods, due to the scanning of the TV camera, the signs appear too blurred to be read by the TV viewers. On many other occasions, only part of the sign is visible to the TV viewers and the sign cannot be read. In some applications, the requirement for computer resources is very high, on the order of magni¬ tude of 100 BOPS (Billion Operations Per Second) . To achieve this level of performance, multiple processing is employed. Many parallel-processing systems of different sizes and configurations have been developed. As the size, hardware complexity, and programming diversi¬ ty of parallel systems continue to evolve, the range of alternatives for implementing a parallel task on these systems grows. There exist 2 types of models of parallelism: SIMD (Single Instruction Multi- pie Data) machines and MIMD (Multiple Instruction Multi¬ ple Data) machines. Fig. 1A is a schematic diagram of a conventional SIMD machine. SIMD machines contain multiple processors connect¬ ed to their own memory. The PE (processing element) is a processor/memory pair. The control unit broadcasts instructions to processors. All active PEs execute the same instruction synchronously in lockstep on their own data. All machines run a single program and a single control thread (process) . Various SIMD devices have been developed in academic institutions including the AMT DAP, CLIP-4, Connection Machine, Maspar MP-1 and MPP. The MIMD machine schematically illustrated in Fig. IB, has multiple processors connected to their own memory. The PE is a processor/memory pair. Each PE has its own instructions. PE' s execute local pro¬ grams on local data. All machines run multiple dif¬ ferent programs and multiple threads of control. Examples of MIMD devices are: BBN Butterfly, Cedar, CM- 5, IBM RP3, Intel Cube, Ncube, NYU Ultracom- puter. Systems which have been built to accommodate mixed MIMD/SIMD machines are the PASM in Purdure Univer¬ sity, and Opsila. Descriptions of parallel computer architec¬ ture in connection with image processing can be found in the following publications: Siegal H.J. Interconnection Networks for Large- Scale Parallel Processing Theory and Case Studies, Second Edition, McGraw-Hill, New York 1990. The following publications describe parallel solutions for image processing including MIMD and/or SIMD: 1) U.S. Patent 5,212,777 to Balmer et al describes a single MIMD chip, and does not describe in any detail a multi-chip configuration architecture. 2) Great Britain Patent No. 2250362, to Mitsubishi, describes a homogeneous system architecture based on exploiting relative simple processing elements which do not provide sufficient flexibility for graphics and video processing. 3) U.S. 4,873,626 to Gifford describes rigid selection of SIMD mode in a general case of MIMD programming mode. An I/O block for real time video processing is not de¬ scribed. 4) Published European Application 564847 (93104154) to IBM describes a system which is not intended for general purpose image processing. The system has only a single or dual processor array. The following publication, the disclosure of which is incorporated herein by reference, describes Gaussian edge detection: J.F. Canny, "A computational approach to edge detection", IEEE Trans. Pattern Analysis and Machine Intelligence, Vol. 8, pp. 679-698, November, 1986. PCT Patent Application No. WO 95/10919 titled "A method and Apparatus for Detecting, Identifying and Incorporating Advertisements in a Video" assigned to the present applicant. SUMMARY OF THE INVENTION The present invention relates to methods and apparatus for processing and controlling image proc¬ essing using an improved parallel architecture machine for image processing and graphics. The present invention seeks to provide an improved hardware architec¬ ture which is particularly suited for parallel video and graphics processing. Hardware parallel processors are commonly used in academic research and some commercial companies for solving image processing and vision tasks. The need for real-time in processing a video signal has prompted use of replicate hardware to allow concurrent execu¬ tion. Due to the need for concurrent execution, or parallel processing, sequential processing methods may be reformulated to use parallelism. The present invention seeks to provide an improved video broadcasting system in which an adver¬ tisement or other frame portion within a video sequence is replaced such that information identifying the coordi¬ nates of the advertisement site, the perspective at which the site is imaged, and the pixel data of occluding objects are transmitted to a remote location together with the video sequence itself. At the remote location, a replacing advertisement or other image is stored which may be specific to that location. The replacing adver¬ tisement is incorporated into the received video sequence at the appropriate site, with the appropriate scale and perspective, and properly overlaid with the occluding objects. The present invention relates to a reconfigura- ble parallel processing architecture machine and a new way for self-controlling the machine. The machine is a multiprocessor system which is capable of mixed-mode parallelism. It can operate in either SIMD or MIMD mode parallelism and can dynamically switch between modes. In addition, it can be partitioned into inde¬ pendent or communicating submachines, the architec¬ tures of which are similar to that of the original machine. Furthermore, the system uses a flexible multistage crossbar interconnection network between its processors. Furthermore, it enables any data which is to be broadcast (such as video digitized data) to be distributed to any set of processors in a controlled manner without blocking the operation of any part of the machine. Considerable variation can be accom- odated as to the number of processors, the type of proto¬ cols, and the interconnection structure. The mapping of processing routines onto the architecture shown and described herein is done using semi-automatic tools that enable simulating and run¬ ning the processing routine on the invented machine. The processing routines were developed using the mixed-mode parallelism. In the illustrated embodiment, multiple TI MVP 320C80 chips form an adaptable extendible architecture that enables the user to extend to any number of MVP's (multimedia video processors) . Each MVP is a 3 billion instruction machine MIMD/SIMD VLSI chip. Each MVP is connected to its own memory blocks and connected to other MVP's by an interconnection network based on a crossbar network. It is appreciated that the PE (processing element) forming part of the invention described herein need not be the TI MVP and that this specific implementa¬ tion is given only by way of example. Preferably, all processors are identical in flexibility, so that a set of PE's may be selected without considering whether the task is SIMD in nature or MIMD in nature. There is thus provided in accordance with a preferred embodiment of the present invention apparatus for replacing a portion of each of a sequence of existing images with a new image, the apparatus including a frame grabber operative to grab a sequence of frames respec¬ tively representing the sequence of existing images, a localizer operative to detect at least one site within each existing image at which the new image is to be incorporated, a perspective transformer operative to detect the perspective at which the site is imaged, and a transmitter operative to transmit to each of a plurali¬ ty of remote locations, for each frame the existing image represented in the frame, the coordinates of the site, and the perspective at which the site is imaged. There is further provided in accordance with a preferred embodiment of the present invention a method for replacing a portion of each of a sequence of existing images with a new image, the method including providing a new image, receiving from a remote transmitter, for each frame in a sequence of frames an existing image repre¬ sented in the frame, coordinates of a site within the existing image at which the new image is to be incorpo¬ rated, and a perspective transformation representing the perspective at which the site is imaged, applying the perspective transformation to the new image and texture mapping the transformed new image into each existing image at the site. Additionally in accordance with a preferred embodiment of the present invention the site includes a background site and the apparatus includes an occlusion analyzer operative to identify foreground objects which at least partially occlude the background site wherein the transmitter also transmits, for each frame, an occlu- sion map of the background site. Further in accordance with a preferred embodi¬ ment of the present invention the method includes re¬ ceiving from the remote transmitter an occlusion map of the background site and the texture mapping includes texture mapping the transformed new image into each existing image only at non-occluded locations within the site. Still further in accordance with a preferred embodiment of the present invention the new image in¬ cludes an advertisement. Also in accordance with a preferred embodiment of the present invention each existing image includes an advertisement. Additionally in accordance with a preferred embodiment of the present invention the apparatus in¬ cludes an existing image memory operative to store an existing image and the localizer includes an image iden¬ tifier operative to compare the site to the stored exist¬ ing image and the transmitter is also operative to trans¬ mit, for each site, a label identifying the existing image found at the site. Further in accordance with a preferred embodi¬ ment of the present invention the method includes re¬ ceiving from the remote transmitter a label identifying the existing image found at the site, and selecting the new image according to the label. There is further provided in accordance with a preferred embodiment of the present invention real-time video image processing apparatus operative to import and process video data from a video data source in real time, the apparatus including a first plurality of video data input/output devices, a second plurality of interconnect¬ ed MIMD devices each including an array of MIMD units and at least one interconnecting bus, at least one broadcast¬ ing bus interconnecting the first plurality of video data input/output devices and at least some of the second plurality of interconnected MIMD devices defining at least one broadcasting channel from the video data input/output devices to the MIMD devices, at least one communication bus interconnecting at least some of the second plurality of interconnected MIMD devices. Additionally in accordance with a preferred embodiment of the present invention the at least one broadcasting bus includes a plurality of broadcasting busses . There is also provided in accordance with a preferred embodiment of the present invention a method for controlling pipelined performance of a multi-step task by real-time video image processing apparatus, the method including providing a first plurality of video data input/output devices, a second plurality of inter¬ connected MIMD devices each including an array of MIMD units and at least one interconnecting bus, at least one broadcasting bus interconnecting the first plurality of video data input/output devices and at least some of the second plurality of interconnected MIMD devices defining at least one broadcasting channel from the video data input/output devices to the MIMD devices, at least one communication bus interconnecting at least some of the second plurality of interconnected MIMD devices, and a library of image processing primitives, receiving a user-selected sequence including at least some of the image processing primitives in the library, constructing a pipeline to carry out the user-selected sequence which efficiently utilizes available resources, controlling the pipelined performance of the user-selected sequence. Still further in accordance with a preferred embodiment of the present invention the method includes selecting a further pipeline depth in accordance with intermediate results. There is yet further pro¬ vided in accordance with a preferred embodiment of the present invention system control provided by a hierar¬ chical distributed program entity provided on each PE. Functional management of the system is carried out on a system-selected number of PEs. The control software preferably includes the following functional components: a. a real-time executive, which is a library of low level tools which combine and encapsulate the follow¬ ing three basic parts: i. The mechanism of transferring data and control between PEs; ii. Arbitration; and iii. Support of various control structures such as semaphores and messages; and b. a job planner, also termed herein a system task scheduler, which is operative to adapt system configura¬ tion and job distribution between PEs in order to facili¬ tate data flow, for example by pipeline distribution of tasks between PEs. BRIEF DESCRIPTION OF THE DRAWINGS AND APPENDICES The present invention will be understood and appreciated from the following detailed description, taken in conjunction with the drawings and appendices in which: Fig. 1A is a prior art simplified block diagram of a conventional SIMD device; Fig. IB is a prior art simplified block diagram of a conventional MIMD device; Fig. 2 is a simplified block diagram of video broadcasting apparatus constructed and operative in accordance with a preferred embodiment of the present invention; Fig. 3 is a simplified block diagram of the parallel processor and controller of Fig. 2; Fig. 4 is a simplified flowchart of a preferred method of operation of the parallel processor and con¬ troller of Fig. 2, when only a single advertisement site is to be identified and only a single advertisement is to be incorporated at that site; Fig. 5 is a simplified flowchart of a preferred method of operation of the parallel processor and con¬ troller of Fig. 2, when a plurality of advertisement sites is to be identified and a corresponding plurality of advertisements, which may or may not differ in con¬ tent, is to be incorporated at those sites; Fig. 6 is a simplified flowchart of a pre¬ ferred method for performing the segmentation step of Figs. 4 and 5; Fig. 7 is a simplified flowchart of a pre¬ ferred model matching method for performing the adver¬ tisement content identification step of Figs. 4 and 5; Fig. 8 is a simplified flowchart of a pre¬ ferred method for performing the localization step of Figs. 4 and 5; Fig. 9 is a simplified flowchart of a pre¬ ferred method for performing the tracking step of Figs. 4 and 5; Fig. 10 is a simplified flowchart of a pre¬ ferred method for performing the occlusion analysis step of Figs. 4 and 5; Fig. 11 is a simplified flowchart of a pre¬ ferred method of operation for the advertisement incorpo¬ ration controller of Fig. 2; Fig. 12 is a simplified flowchart of a pre¬ ferred method for detecting and tracking moving objects of central interest; Fig. 13 is a high-level schematic block diagram of a sample real-time implementation of the parallel processor and controller of Fig. 2 including 10 boards (also termed herein "multi-MVP blocks" or MMB's) of which 9 are identical (MMB1 - MMB9) and the tenth, the input- output MMB (MMBO), also termed herein "MIOB" or "multi- mput/output block", is typically different and imple¬ ments the field grabber and frame buffer of Fig. 2; Fig. 14 is a schematic block diagram of an individual one of the 9 identical MMB's (multi MVP boards) of Fig. 13, the individual MMB including 9 iden¬ tical SMB's (single MVP blocks) of which one serves as a master and 8 serve as slaves with optional software based reconfiguration; Fig. 15 is a schematic block diagram of an individual one of the SMB's of Fig. 14; and Fig. 16 is a schematic block diagram of the input-output MMB, MMBO of Fig. 13; DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Fig. 2 is a simplified block diagram of video broadcasting apparatus constructed and operative in accordance with a preferred embodiment of the present invention. The apparatus of Fig. 2 includes an advertise¬ ment processing center 90 typically located in physical proximity to the video capturing equipment and a plural¬ ity of remote broadcasting stations 94 of which only one is shown. The scene being telecasted, such as a sports event, includes at least one location on which a new image, such as an advertisement, is to be superimposed. The advertisement processing center preferably generates and transmits to each remote broadcasting station 94 all information needed to superimpose a new image onto the advertisement, such as the location of the site at which the advertisement is to appear, its scale, the perspec¬ tive at which the site is imaged and the locations of foreground objects occluding the site. At each remote station 94, the new advertisements to be incorporated are stored and these advertisement are easily incorporated into the arriving video frames, using the information generated by the advertisement processing center 90. A particular advantage of the apparatus of Fig. 2 is that the function of analysis of the existing video frames is separated from the function of incorporating the new advertisement into the frame. The information employed to superimpose new images onto the advertisement is generated only once and is then employed by all of the broadcasting stations to facilitate incorporation of the new advertisement into the frame. The advertisement processing center 90 includes a video input source 100, such as a video camera, video cassette, broadcast, video disk, or cable transmission, which is connected, via a suitable connector, with a field grabber 110, preferably, or alternatively with a frame grabber. Henceforth, use of the term "field grab¬ ber" is intended to include frame grabbers. The field grabber 110 provides grabbed and digitized fields to a parallel processor and controller 120, (described in more detail below with reference to Fig. 3) which automatically detects, identifies, and localizes a given advertisement in the field of view, and is preferably associated, via a frame buffer 124, with a video display 130 which provides an interactive indica¬ tion to a user of advertisement site detection operations of the system. Preferably a light pen 140 is associated with the video display 130 or alternatively the video display 130 comprises a touch screen. According to an alternative embodiment of the present invention, the system receives an indication from a user of the presence in the field of view of one or more advertisements to be replaced and of the location/s thereof. The user input may, for example, be provided by means of a light pen 140. The indication provided by the user may comprise a single indication of an interior location of the advertisement, such as the approximate center of the advertisement or may comprise two or four indications of two opposite vertices or all four ver¬ tices, respectively, of an advertisement to be replaced. Optionally, the user also provides an indica¬ tion of the contents of the advertisement. For example, a menu of captions identifying advertisements to be re¬ placed, may be provided on the video display 130 adjacent or overlaying a display of the playing field and the user can employ the light pen to identify the appropriate caption. An advertisement images and advertisement arrangement database 150 is preferably provided which may be stored in any suitable type of memory such as computer memory or secondary memory, such as a hard disk. The advertisement image and arrangement database 150 stores an indication of the arrangement of a plurality of adver¬ tisements to be replaced, if the arrangement is known ahead of time. Typically, the indication of the arrange¬ ment does not include an indication of the location of each advertisement relative to the playing field, but instead includes an indication of the order in which the advertisements to be replaced will be arranged in the field. For example, a sequence of 20 side-by-side adver¬ tisements may be arranged around three sides of a playing field. The database 150 may then include an indication of the sequence in which the advertisements are arranged. The database 150 also preferably stores images of the advertisements to be replaced so that these can be recognized. Advertisement images in the database 150 may be provided by field grabber 110 or from any suitable adver¬ tisement image source 160, such as but not limited to an image generating unit such as an image processing work¬ station, a scanner or other color reading device, any type of storage device, such as a hard disk, a CD ROM driver, or a communication link to any of the above. The output of parallel processor and controller 120, also termed herein "the auxiliary output", com¬ prises, for each frame, an indication of the locations at which advertisements are to be incorporated, an indica¬ tion of the perspective at which each advertisement is to be incorporated and an indication of the locations of foreground objects, if any, occluding each advertisement. The auxiliary output may alternatively comprise the scale, location and perspective transformation parameters of other identified landmarks in the video image. The video and auxiliary output of the system may be provided via a suitable connector to suitable equipment for providing satellite or other transmission 95 to a remote broadcasting station 94. Any suitable video broadcasting technology may be employed, such as via satellites, via RF transmission or via cable optics systems. The volume of the auxiliary information regard¬ ing the video original, is small relative to the video original itself. The auxiliary information may be sent on the audio channel or alternatively may be sent on a separate channel but synchronized to the channel over which the video original is being sent by means of a common time code. Alternatively, the bandwidth of the link may be slightly increased so as to enable the auxil¬ iary information and the video original to be sent on the same video channel. The broadcasting station 94 includes conven¬ tional broadcasting equipment (not shown) for wireless or cable transmission to viewers and, additionally, an advertisement incorporation controller 164 accessing an advertisement image source 166. The image source 166 may comprise a hard disk storing a plurality of advertisement images, typically still images, to be incorporated into the image of the playing field, either replacing an existing advertisement or in a location not presently occupied by an advertisement. The advertisement incorporation controller 164 is operative to receive the video frames and the auxil¬ iary information from the advertisement processing center 90 and to incorporate the advertisement image or images of image source 166 into the appropriate locations in each video frame, at the appropriate perspectives and with the appropriate portions thereof removed such that occlusion of the original location by a foreground object is maintained for the incorporated advertisement image. Optionally, a predetermined advertisement incorporation schedule is followed such that different advertisements are incorporated at the same location, each for a prede¬ termined length of time within the game or upon a prede¬ termined occurrence within the game, such as a goal. A preferred method of operation for controller 164 is described below with reference to Fig. 11. Fig. 3 is a simplified block diagram of the parallel processor and controller 120 of Fig. 2. The parallel processor/controller 120 preferably includes an advertisement site detection/content identification unit 170, a plurality of parallel tracking modules 180, an occlusion analysis unit 190, and a controller 210. The advertisement site detection/content iden¬ tification unit 170 of Fig. 3 may be implemented based on a suitable plurality of suitable image processing boards. A specially designed coprocessor is preferably added to these boards to perform the segmentation task. The image processing boards are programmed based on the advertise¬ ment site detection and content identification methods of Figs. 6 and 7. Each of parallel tracking modules 180 may be implemented based on one or more image processing boards. The image processing boards are programmed for parallel operation based on the tracking method of Fig. 9. The occlusion analysis unit 190 may also be based on one or more multi-DSP (Digital Signal Processing) boards, programmed based on the occlu¬ sion analysis of Fig. 10. Controller 210 may, for example, comprise a Silicon Graphics Indy Workstation, programmed based on the control method of Figs. 4 - 5. Fig. 4 is a simplified flowchart of a preferred method of operation of the parallel processor and con¬ troller 120 of Fig. 2, when only a single advertisement site is to be identified. Fig. 5 is a simplified flowchart of a preferred method of operation of the parallel processor and con¬ troller 120 of Fig. 2, when a plurality of advertisement sites is to be identified. The method of Fig. 5 typically includes the following steps, which are similar to the steps of Fig. 4 which are therefore not described separately for brevity: STEP 290: A digitized video field is received from the field grabber 110 of Fig. 2. STEP 300: A decision is made as to whether or not at least one advertisement in the current field was also present in the previous field (and televised by the same camera) . If so, the current field is termed a "consecutive" field and the segmentation, content identi¬ fication and localization steps 320, 330 and 340 prefera¬ bly are replaced only by a tracking step 310. If not, the current field is termed a "new" field. If the field is a "consecutive" field, the plurality of advertisements is tracked (step 310), based on at least one advertisement which was present in a previous field, since the present field is a "consecu¬ tive" field. If the field is a "new" field, the advertise¬ ment site at which an advertisement is to be incorporated is identified in steps 320, 330 and 340. A loop is per¬ formed for each advertisement from among the plurality of advertisements to be processed. Preferably, the segmenta¬ tion and content identification steps 320 and 330 are performed only for the first advertisement processed. In step 320, a pair of generally parallel lines is typically detected and the image of the field is segmented. Specifically, the portion of the field located within the two detected parallel lines, which typically correspond to the top and bottom boundaries of a sequence of advertisements, is segmented from the remaining por¬ tion of the field. Typically, the segmentation step 320 is opera¬ tive to segment advertisements regardless of: the zoom state of the imaging camera lens, the location of the advertisement in the field of view (video field) , the angular orientation of the imaging camera relative to the ground and the location of the TV camera. The segmentation step 320 is typically opera¬ tive to identify an empty or occupied advertisement site, such as but not limited to any of the following, sepa¬ rately or in any combination: a. Geometrical attributes of the advertisement's boundary such as substantially parallel top and bottom boundaries or such as four vertices arranged in a sub¬ stantially rectangular configuration; b. A color or a combination of colors or a color pattern, which is known in advance to be present in the advertisement image. c. The spatial frequencies band of the advertise¬ ment image, which is typically known in advance. Typical¬ ly, the known spatial frequencies band is normalized by the height of the advertisement which may, for example, be derived by computing the distance between a pair of detected horizontal lines which are known to be the top and bottom boundaries of the advertisement sequence. In step 330, the content of the portion between the two substantially parallel lines is matched to a stored representation of an advertisement to be replaced. Steps 320 and 330 allow advertisement sites to be identified and the content thereof to be matched to a stored model thereof, even if cuts (transitions, typical¬ ly abrupt, between the outputs of a plurality of cameras which are simultaneously imaging the sports event) occur during the sports event. Typically, at each cut, steps 320 and 330 are performed so as to identify the adver¬ tisement within the first few fields of the cut. Until the next cut occurs, the identified advertisement is typically tracked (step 310) . In step 340, the advertisement is localized at subpixel accuracy. Finally, for each advertisement, occlusion analysis is performed (step 350) . According to an alternative embodiment of the present invention, the segmentation and advertisement content identification steps 320 and 330 respectively may be omitted if physical landmarks identifying the loca¬ tions of advertisements to be replaced whose contents is known in advance, are positioned and captured ahead of time in the playing field. Fig. 6 is a simplified flowchart of a pre¬ ferred method for performing the segmentation step 320 of Figs. 4 and 5. The method of Fig. 6 preferably includes the following steps: STEP 380: A new field is received and the resolution thereof is preferably reduced since the forgo¬ ing steps may be performed adequately at a lower resolu¬ tion, for example, a low pass filter may be employed to reduce a 750 x 500 pixel field to 128 x 128 pixels. STEP 390: Optionally, the low resolution image is smoothed, e.g. by median filtering or low pass filter¬ ing, so as to remove information irrelevant to the task of searching for long or substantially horizontal lines. STEP 400: Edges and lines are detected, using any suitable edge detection method such as the Canny method, described by J.F. Canny in "A computational approach to edge detection", IEEE Trans. Pattern Analysis and Machine Intelligence, Vol. 8, pp. 679-698, November, 1986. STEP 404: The edges detected in step 400 are thinned and components thereof are connected using con¬ ventional techniques of connectivity analysis. The edges are thresholded so as to discard edges having too small a gradient. STEP 408: The edges detected in steps 400 and 404 are compared pairwise so as to find strips, i.e. pairs of parallel or almost parallel lines which are relatively long. If there are no such pairs, the method terminates. STEP 412: Find the spatial frequency spectrum within each strip and reject strips whose spatial fre¬ quency contents are incompatible with the spatial fre¬ quency band expected for advertisements. Typically, the rejection criterion is such that more than one strip, such as 3 or 4 strips, remain. STEP 416: Rank the remaining strips and select the highest ranking strip. The rank assigned to a strip depends on the probability that the strip includes adver¬ tisements. For example, the strip in the lowest location in the upper half of the field is given higher rank than strips above it, because the strips above it are more likely to be images of portions of the stadium. The lowest located strip is more likely to be the advertise¬ ments which are typically positioned below the stadium. Strips adjacent the bottom of the field are given low rank because the advertisements would only be imaged toward the bottom of the video field if the play¬ ing field is not being shown at all, which is unlikely. Fig. 7 is a simplified flowchart of a preferred model matching method for performing the adver¬ tisement content identification step 330 of Figs. 4 and 5. Alternatively, advertisement content identification may be provided by a user, as described above with refer¬ ence to Fig. 2. The method of Fig. 7 is preferably performed in low resolution, as described above with reference to step 380 of Fig. 6. The method of Fig. 7 preferably includes the following steps: STEP 420: The forgoing steps 424, 430, 436, 440, 444 and 452 are performed for each almost parallel strip identified in segmentation step 320 of Figs 4 and 5. STEP 424: The distance and angle between the two lines of each strip is computed and the scale and approximate perspective at which the strip was imaged is determined therefrom. STEP 430: During set-up, each advertisement model is divided into a plurality of windows. Steps 436, 440 and 444 are performed for each window of each adver¬ tisement model. For example, if there are 5 models each partitioned into 6 windows, this step is performed 30 times. STEP 436: A one-dimensional similarity search is carried out for the suitably scaled current model window k, along the current almost parallel strip. Typi¬ cally, a cross-correlation function may be computed for each pixel along the current strip. STEP 440: The cross-correlation function values obtained in step 436 are thresholded. For example, values exceeding 0.6 may be assigned the value 1 (correlation) whereas values under 0.6 may be assigned the value 0 (no correlation). The l's are weighted, depending on the "significance" of their corresponding windows. The "significance" of each window is preferably determined during set-up such that windows containing more informa¬ tion are more "significant" than windows containing little information. STEP 444: At this stage, weighted thresholded cross-correlation function values have been computed which represent the results of matching the contents of each position along the strip (e.g. of each of a plurali¬ ty of windows along the strip which are spaced at a distance of a single pixel) to each window of each model advertisement known to occur within the strip. The weighted thresholded cross-correlation function values are accumulated per all windows composing a model sign or a model strip. STEP 452: A decision is made as to the approxi- mate location of the sequence of advertising models, within the strip. It is appreciated that, once the loca¬ tion of one advertisement model has been determined, the locations of the other advertisement models in the same sequence are also determined, knowing the scale and approximate perspective of the imaged strip. Fig. 8 is a simplified flowchart of a pre¬ ferred method for performing the precise localization step 340 of Figs. 4 and 5. In Fig. 8, the advertisement model which was approximately localized by the method of Fig. 7, is localized with subpixel accuracy. Accurate localization is typically performed only for new fields. For "consecutive" fields, the advertisement's location is preferably measured by video tracking. The method of Fig. 8 preferably includes the following steps: STEP 460: From Fig. 7, the following informa¬ tion is available per advertisement detected: one loca¬ tion within the advertisement, such as one vertex there¬ of, the advertisement scale height in the image and its approximate perspective. This information is employed to compute the four vertices of each detected advertisement STEP 464: A perspective transformation is computed which describes how to "transform" the typically rectangular model into the detected advertisement area which is typically non-rectangular due to its pose rela¬ tive to the imaging camera. STEP 468: The contents of each of a plurality of model tracking windows to which the model is divided during set up, is mapped into the video field, using the perspective transformation computed in step 464. STEP 470: Steps 472 and 476 are performed for each of the model tracking windows. STEP 472: The current model tracking window is translated through a search area defined in the video field. For each position of the model tracking window within the search area, a similarity error function (like cross-correlation or absolute sum of differences) is computed. Typically, the model tracking window has 8 x 8 or 16 x 16 different positions within the search area. STEP 476: The minimum similarity error function for the current model tracking window is found. Prefera¬ bly, the minimum is found at subpixel accuracy, e.g. by fitting a two-dimensional parabola to the similarity error function generated in step 472 and computing the minimum of the parabola. This minimum corresponds to the best position, at "subpixel accuracy", for the current model tracking window within the video field. If (STEP 480) the similarity error function minima are high for all tracking windows, i.e. none of the tracking windows can be well matched to the video field, then (STEP 482) processing of the current frame is terminated and the method of Fig. 4, from step 320 on¬ ward, is performed on the following frame. STEP 484: Tracking windows which have a high similarity error function minimum are rejected. Typical¬ ly, approximately 30 tracking windows remain. STEP 488 is a stopping criterion determining whether or not to perform another iteration of localiza¬ tion by matching tracking windows. Typically, if the tracking windows' centers are found to converge, relative to the centers identified in the last iteration, the process is terminated. Otherwise, the method returns to step 464. STEP 490: Once the tracking window locations have converged, the perspective transformation between the image's advertisement and its model is recomputed. Fig. 9 is a simplified flowchart of a pre¬ ferred method for performing the tracking step 310 of Figs. 4 and 5. The method of Fig. 9 preferably includes the following steps: STEP 492: A perspective transformation is performed on the model tracking windows and the contents thereof are mapped into the video field. This step em¬ ploys the system's knowledge of the location of the advertisement in the previous field and, preferably, predicted scanning speed of the camera imaging the sports event. STEP 496: Steps 498 and 500, which may be similar to steps 472 and 476, respectively, of Fig. 8, are performed for each model tracking window. STEPS 508 and 512 may be similar to steps 488 and 490 of Fig. 8. STEP 510: If the window center locations do not yet converge, step 492 is redone, however, this time, the texture mapping is based upon the perspective transforma¬ tion of the previous iteration. STEP 520: The coefficients of the perspective transformation are preferably temporally smoothed, since, due to the smoothness of the camera's scanning action, it can be assumed that discontinuities are noise. Fig. 10 is a simplified flowchart of a pre¬ ferred method for performing the occlusion analysis step 350 of Figs. 4 and 5. The method of Fig. 10 preferably includes the following steps: STEP 530: The advertisement image in the video field is subtracted from its perspective transformed model, as computed in step 512 of Fig. 9 or, for a new field, in step 490 of Fig. 8. STEP 534: Preferably, the identity of the advertisement image and the stored advertisement is verified by inspecting the difference values computed in step 530. If the advertisement image and the stored advertisement are not identical, the current field is not processed any further. Instead, the next field is proc¬ essed, starting from step 320 of Fig. 5. STEP 538: The internal edge effects are fil¬ tered out of the difference image computed in step 530 since internal edges are assumed to be artifacts. STEP 542: Large non-black areas in the differ¬ ence image are defined to be areas of occlusion. STEP 546: The occlusion map is preferably temporally smoothed since the process of occlusion may be assumed to be continuous. Fig. 11 is a simplified flowchart of a pre¬ ferred method for performing the advertisement incorpora¬ tion step 164 of Fig. 2. The method of Fig. 11 preferably includes the following steps: STEP 560: The resolution of the replacing advertisement model, i.e. the advertisement in memory, is adjusted to correspond to the resolution in which the advertisement to be replaced was imaged. Typically, a single advertisement model is stored in several different resolutions. STEP 570: The replacing advertisement is trans¬ formed and texture mapped into the video field pose, using tri-lmear interpolation methods. This step typi¬ cally is based on the results of step 512 of Fig. 9 or, for a new field, on the results of step 490 of Fig. 8 relayed to the incorporation unit 94 via the transmission link. STEP 580: Aliasing effects are eliminated. STEP 584: The replacing pixels are keyed in according to an occlusion map. The values of the replac¬ ing pixels may either completely replace the existing values, or may be combined with the existing values, as by a weighted average. For example, the second alterna¬ tive may be used for edge pixels whereas the first alter¬ native may be used for middle pixels. The applicability of the apparatus and methods described above are not limited to the detection, track¬ ing and replacement or enhancement of advertisements. The disclosed apparatus and methods may, for example, be used to detect and track moving objects of central interest, as shown in Fig. 12, such as focal athletes and such as balls, rackets, clubs and other sports equipment. The images of these moving objects may then be modified by adding a "trail" including an advertisement such as the logo of a manufacturer. Fig. 13 is a high-level schematic block diagram of a sample real-time implementation of the parallel processor and controller of Fig. 2 including 10 boards (MMB's) of which 9 are identical (MMB1 - MMB9) 600 and the tenth, the input-output MMB (MMBO) 601, is typically different and implements the field grabber and frame buffer of Fig. 2. Fig. 14 is a schematic block diagram of an individual one of the 9 identical MMB's (multi MVP boards) of Fig. 13, the individual MMB including 9 iden¬ tical SMB's (single MVP blocks) of which one serves as a master and 8 serve as dynamically reconfigurable slaves. Fig. 15 is a schematic block diagram of an individual one of the SMB's of Fig. 14. Fig. 16 is a schematic block diagram of the input-output MMB, MMBO of Fig. 13. The machine vision methods provided by the present invention employs a tremendous amount of and variety of parallelism. There are three processing levels in vision: low (sensory), intermediate (symbolic), and high (knowl¬ edge-based) . In addition to the vision task, the present invention provides for synthesis of a newly created image. A combination of image processing and computer graphics operations are employed. A particular feature of the apparatus shown and described herein is the capabili¬ ty to perform real time video image processing (vision) operations as well as graphics operations in which the image is modified as by adding an artificially created image thereto. For example, a complex texture mapping operation is performed in which a newly computed true perspective texture mapped sign replaces an existing sign in the image. In vision, a typical sensor comprises a camera with resolution of, for example, 720 by 560 pixels each represented by 3 color components: Red, Green and Blue. A plurality of blocks of the image are typically processed in parallel. The images from the video source tend to stream steadily into the machine which preferably requires pipeline parallelism. The present invention allows multiple sensor data to be exploited, thus provid¬ ing yet another potential source of parallelism. The system shown and described herein extracts many features from a given image or set of images, such as lines, regions, texture patches, and motion parameters. These processes are preferably carried . out in parallel. The system shown and described herein is opera¬ tive to add or replace a recognized object within an image in a video sequence, to/with newly created 3D objects projected to the image plane with the right perspective, lighting and blur effect. The system shown and described herein includes three main blocks of hardware: a. A processing block which includes a plurality of PE's (processing elements) each preferably comprising an MVP TI chip with memory and a data exchanging module operative to exchange data with the other PE's. b. An input/output module which inputs and out¬ puts a plurality of video signals to and from the proc¬ essing block. c. Interconnection blocks that are embedded in each PE block and each module card, and enable the exchange of data by means of crossbar switches and enabling hardware to broadcast any type of data from one PE to any set of PEs. The three levels of vision (low, intermedi¬ ate, and high) and graphics are handled on the same PE which may be implemented by the TI MVP chip. Each TI MVP chip is VLSI, structured with several individual processors all having communication links to several memories. A crossbar switch is used to establish the processor memory links. Each processor is operative to execute the same instruction at the same time (SIMD mode) or different instructions at the same time (MIMD mode) . The present invention provides an effective way of using multiple TI chips based on hierarchical archi¬ tecture. In particular, each board contains one master MVP, and each set of boards includes a System Manager MVP chip, thus providing the possibility of reconfiguration of hardware and software, depending on a particular application. Fig. 13 is an overview of a preferred archi¬ tecture. The system is contained in a box or a set of boxes each containing a number of identical boards, also termed herein "MMB's" (Multiple MVP block). The system has a communication channel between nine PEs, one of which is used as a master for the other eight. Any of the PE's can be used for any type of processing. Each of the PE's is configured on an SMB (Single MVP block) which contains a full environment for 1 MVP together with memory and communication means for the crossbar block. All the SMBs on each board are interconnected by a crossbar, which provides at least 4 concurrently different channels between the PEs as well as the ability to broadcast any set of data blocks between one PE (TI-MVP) to a set of other PEs. Each communication channel is connected on¬ board to shared memory. The system is preferably opera¬ tive to transfer a raw video signal from the video I/O block to all the PEs without interfering with operation of each of the PE's. Fig. 14 is a simplified block diagram of an individual MMB. As shown, each MMB includes: 1) A video bus control block 608 which receives video data from the video I/O block in real time and broadcasts it to any of the slaves on the board. The video bus control block 608 is controlled by the SMB #9 (606) . 2) A plurality of SMBs (PEs) 604 and 606, such as 9 SMB's in the illustrated embodiment. Each SMB contains a PE and has two buses 622 and 624 (Fig. 15) of which one is a slave bus 624 and the other is a master bus 622. Each of the buses is connected to a different memory block so that data can move through the slave bus and through the master bus concurrently. 3) CBT - (Crossbar transceivers) also termed herein Crossbar switches 610 which, via the master SMB (PE) 606, provide flexible channel selection. The CBT 610 includes the master bus 622 (Fig. 15). The channel is then arbitrated and the CBT 610 reconfigured such that only a set of SMBs 604 is connected. Thereby, communi¬ cation between any of the SMBs 604 may be either point to point or as a broadcast operation. One CBT is connect¬ ed to each SMB which allows the master bus to be connect¬ ed to one of the four communication channels 611, 612, 613 and 614. When one SMB wishes to connect to a set of other SMBs, it arbitrates for a free channel. When the SMB receives the free channel, it acknowledges this to the master SMB 606 and then sends the required data packets from itself to all the other SMBs. The CBTs preferably share memory, one of the shared block 615 with shared memory block 600. The SMB's can also communicate between them¬ selves via the master processor which uses the master bus to provide communication between the SMBs. After a connection is formed, one PE may be selected by the master to broadcast a block of data to the members in the channel. Alternatively, any of the SMBs may send a packet serially over the network. Fig. 15 is a block diagram of an individual SMB. Each of the PE - MVP chips 620 is flexible enough to accommodate substantially any type of image proc¬ essing and graphics processing. The control method shown and described herein includes a real time executive which facilitates flexibility such that a single process may be run on several MVPs on the same MMB and/or on more than one MMBs. For each SMB, there is one MVP that includes four 32 bits PE integer processors and one 32 bits MP RISC (Reduced Instruction Set Computer) processor, in¬ cluding a floating processor. Each MVP enables opera¬ tion of up to 60 concurrent RISC operations per cycle (3 billion operations per second) and 100 MFLOPS RISC. One box containing 200 MVPs may perform 600 billion operations per second and 20 billion floating operations per second. Fig. 16 is a block diagram of the I/O 601 of Fig. 13 staging module which permits one or more sen¬ sors to input images into a video buffer 640. The buffer 640 can hold several frames for each sensor in a pipeline and broadcast any set of them to any set of MMBs. The input video connects to a block 632 which transfers the video to the global bus through a global connector 633. The output video from the system is transferred through an output block 634 which translates digital video in the system to standard CCIR 601 Dl signals. A LAN (Local Area Network) connect block 636 enables con¬ trol of the system from any host external computer, such as computer 642 (Fig. 13) through a LAN (Local Area Network) connection 638. The system is reconfigura¬ ble in its pipeline depth. In other words, each MMB according to its task in the process stores the required number of images. In the embodiment shown and described herein, a pipeline depth of 6 is required. The block can sustain full resolution broadcast video signals at 30 frames per second on NTSC (US Video Standard) or 25 frames with PAL (European Video Standard) signalling. The operation may be performed either at field level or at frame level. System control is provided by a hierarchical distributed program entity provided on each PE. Function¬ al management of the system is carried out on a system- selected number of PEs. The control software preferably includes the following functional components: a. a real-time executive, which is a library of low level tools which combine and encapsulate the follow¬ ing three basic parts: l. The mechanism of transferring data and control between PEs; li. Arbitration; and in. Support of various control structures such as semaphores and messages; and b. a ob planner, also termed herein a system task scheduler, which is operative to adapt system configura¬ tion and job distribution between PEs in order to facili¬ tate data flow, for example by pipeline distribution of tasks between PEs. In advertisement replacement applications, the job planner selects, according to the location of and other attributes of objects in the current image, a sequence of macro operations. Each macro operation itself comprises a sequence of the low-level tools in the li¬ brary. The job planner also dynamically assigns a specif¬ ic PE to execute certain macro operations. For example, the number of players occluding a sign or a portion of a sign and the total occluded area may each affect the distribution of tasks between PE's. In contrast, a hard- ware system is less adaptive and therefore less effec¬ tive. It is appreciated that the architecture shown and described herein may be extended to an almost unlim¬ ited extent. It is appreciated that the software components of the present invention may, if desired, be implemented in ROM (read-only memory) form or be loaded into RAM (random access memory) . The software components may, generally, be implemented in hardware, if desired, using conventional techniques. It is appreciated that various features of the invention which are, for clarity, described in the con¬ texts of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, de¬ scribed in the context of a single embodiment may also be provided separately or in any suitable subcombination. It will be appreciated by those skilled in the art that the invention is not limited to what has been shown and described hereinabove. Rather, the scope of the invention is defined solely by the claims which follow:

Claims: C L A I M S 1. Apparatus for replacing a portion of each of a sequence of existing images with a new image, the appara¬ tus comprising: a frame grabber operative to grab a sequence of frames respectively representing the sequence of existing images; a localizer operative to detect at least one site within each existing image at which the new image is to be incorporated; a perspective transformer operative to detect the perspective at which the site is imaged; and a transmitter operative to transmit to each of a plurality of remote locations, for each frame: the existing image represented in the frame, the coordinates of the site, and the perspective at which the site is imaged. 2. A method for replacing a portion of each of a sequence of existing images with a new image, the method comprising: providing a new image; receiving from a remote transmitter, for each frame in a sequence of frames: an existing image represented in the frame, coordinates of a site within the existing image at which the new image is to be incorporated; and a perspective transformation representing the perspective at which the site is imaged; applying the perspective transformation to the new image and texture mapping the transformed new image into each existing image at the site. 3. Apparatus according to claim 1 wherein the site comprises a background site and the apparatus also comprises an occlusion analyzer operative to identify foreground objects which at least partially occlude the background site wherein the transmitter also transmits, for each frame, an occlusion map of the background site. 4. A method according to claim 2 and also compris¬ ing receiving from the remote transmitter an occlusion map of the background site and wherein said texture mapping comprises texture mapping the transformed new image into each existing image only at non-occluded locations within said site. 5. Apparatus according to claim 1 or claim 3 wherein the new image comprises an advertisement. 6. Apparatus according to claim 1 or claim 3 wherein each existing image also comprises an advertise¬ ment. 7. Apparatus according to any of claims 1, 3, 5 or 6 and also comprising an existing image memory operative to store an existing image and wherein the localizer comprises an image identifier operative to compare the site to the stored existing image and wherein the trans¬ mitter is also operative to transmit, for each site, a label identifying the existing image found at the site. 8. A method according to claim 2 or claim 4 and also comprising: receiving from the remote transmitter a label identif y ing the existing image found at the site; and selecting the new image according to said label. 9. Apparatus as claimed in claim 1 in which the localizer comprises: multiple video data input/output devices and multiple interconnected MIMD devices each including an array of SMB units and at least one interconnecting bus; and at least one broadcasting bus for interconnect¬ ing the video data input/output devices with selected ones of the SMB devices. 10. Apparatus according to claim 9 comprising a memory containing a library of image processing primi¬ tives, means for receiving a selected sequence including at least some of the image processing primitives in the library, a pipeline to carry out the selected sequence which efficiently utilizes available resources, and means for controlling pipelined performance of the selected sequence. 11. Real-time video image processing apparatus operative to import and process video data from a video data source in real time, the apparatus including: a first plurality of video data input/output devices; a second plurality of interconnected MIMD devices each including an array of MIMD units and at least one interconnecting bus; at least one broadcasting bus interconnecting the first plurality of video data input/output devices and at least some of the second plurality of intercon¬ nected MIMD devices defining at least one broadcasting channel from the video data input/output devices to the MIJ'D devices; and at least one communication bus interconnecting at least some of the second plurality of interconnected MIMD devices. 12. Apparatus according to claim 11 wherein the at least one broadcasting bus includes a plurality of broad¬ casting busses. 13. A method for controlling pipelined performance of a multi-step task by real-time video image processing apparatus, the method including: providing a first plurality of video data input/output devices, a second plurality of interconnect¬ ed MIMD devices each including an array of MIMD units and at least one interconnecting bus, at least one broadcast¬ ing bus interconnecting the first plurality of video data input/output devices and at least some of the second plurality of interconnected MIMD devices defining at least one broadcasting channel from the video data input/output devices to the MIMD devices, at least one communication bus interconnecting at least some of the second plurality of interconnected MIMD devices, and a library of image processing primitives, and receiving a user-selected sequence including at least some of the image processing primitives in the library, constructing a pipeline to carry out the user- selected sequence which efficiently utilizes available resources, and controlling the pipelined performance of the user-selected sequence. 14. A method according to claim 13 and also includ¬ ing selecting a further pipeline depth in accordance with intermediate results. 15. Apparatus according to claim 12 wherein func¬ tional management of the system is carried out on a system-selected number of PE's using control software which preferably includes: a real-time executive comprising a library of low level tools which combine and encapsulate basic parts; and a job planner which is operative to adapt system configuration and job distribution between PEs in order to facilitate data flow. 16. Apparatus according to claim 15 wherein the basic parts comprise: a mechanism of transferring data and control between PEs; arbitration apparatus; and control structure support means. 17. Apparatus according to claim 15 or claim 16 wherein data flow is facilitated by pipeline distribution of tasks between PEs.

Inventors: SHARIR AVI, TAMIR MICHAEL, SHARIR, AVI, TAMIR, MICHAEL
Applicants: ORAD INC, SHARIR AVI, TAMIR MICHAEL, ORAD, INC., SHARIR, AVI, TAMIR, MICHAEL
Application year: 1995
Main classification: H04N7
IPC codes: H04H1, H04H7, H04H60, H04N5