Abstract:
A digital film scanner interface obtains digital image data produced by projecting a motion picture film frame onto a sensor. The image data is transferred from the sensor to a Digital Signal Processor (“DSP”) block. The DSP block processes the image data to, for example, minify, magnify, enhance colors, or correct for errors in the image data. The DSP block comprises four DSPs. One of the DSPs receives the image data from the sensor and controls the flow of the image data to the other three DSPs. The processing tasks can then be distributed to the DSPs based on availability. Alternatively, the digital signal processing tasks can be allocated such that each DSP processes one color component of image data. After the image data is processed, it is transferred over a bus to a long term storage device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of image scanners, and more specifically to the field of motion picture digitizer interfaces. 
     2. Background Art 
     Film scanners have been developed to digitize films for storage and processing in a digital form. Storing motion picture images in a digital form has many advantages over storing motion picture images using film. These advantages include the fact that digital images can be readily duplicated with no loss of image quality, digital images can be readily enhanced by computers, digital films can be stored indefinitely, and digital films can be distributed electronically. 
     Typically a digital film scanner digitizes a film frame using a light source which exposes a film frame and projects an image. The projected image passes through a lens and onto a sensor. The sensor then converts the image into data for storage. Generally a film frame image is exposed by several colored light sources. For example, an image may be first exposed by a red light source, then a green light source, then a blue light source. Some digital film scanners use a sensor as large or larger than the projected image. Other digital film scanners use a sensor smaller than the projected image. 
     A line-array sensor is a sensor having a width smaller than the width of projected film frame images. This requires the projected images to be moved across the line-array sensor to expose the entire projected image to the sensor. One way to scan a film frame using a line-array sensor is to move a lens so as to move the projected image across the sensor. The height of the projected image at the sensor is smaller than or equal to the height of the sensor. Therefore, to expose the line-array sensor to the entire projected image requires only that the projected image move perpendicular to the line-array sensor. The lens moves along an axis parallel to the plane of the film gate, and perpendicular to the direction of film transport. Moving the lens in this manner moves the projected image across the vertical face of the sensor, and thereby exposes the sensor to the entire projected image, one line at a time. This type of scanning sub-system is described in more detail in the co-pending application “METHOD AND APPARATUS FOR SCANNING AN IMAGE USING A MOVING LENS SYSTEM,” David DiFrancesco, Ser. No. 08/664,266, filed Jun. 11, 1996, and assigned to the assignee of this application. 
     A variety of motion generating means may be used to move the lens in a moving lens scanner. For example, a cam connected to the lens via a spring mounted base can be used to move the lens. In one type of cam driven scanner a motor rotates the cam, causing the lens to make a full cycle of movement with each complete rotation of the cam. The horizontal scanning movement of the lens allows the sensor to only have to cover the generally shorter vertical axis of the film frame. The lens may expose the sensor to a full frame in each direction of its motion. Scanning images during both directions of the lens movement maximizes efficiency by avoiding having the sensor wait for the lens to return. Alternatively, an image may be scanned as the lens moves in one direction only, with a wait period following each scan for the lens to return to the start position. The scanning speed is generally limited by the speed of the sensor. To obtain full resolution from a sensor requires that the sensor be exposed to a threshold number of photons. 
     An alternative to using a moving lens is to use a moving mirror system to scan projected images across the sensor, as is known by those of ordinary skill in the art. An example of a scanner that uses a moving mirror system to scan projected images across a sensor is described in U.S. Pat. No. 4,330,793, entitled “ELECTRONIC SCANNING OF SUPER-8 FILMS FOR REPRODUCTION ON A T.V. VIEWING UNIT,” the disclosure of which is hereby incorporated by reference. The tilting mirror system is very similar to that used in galvanometric systems, although slight structural modifications may be necessary with regard to the magnetic system thereof. Such systems provide the precise controllability of deflection required by the scanner. 
     Image scanner references include: 
     In U.S. Pat. No. 5,249,056 Foung et al. describe an apparatus for generating video signals from a photographic image previously recorded on film (a cine video system) which includes a film transport mechanism, an image projector, a video pickup system which receives the image and generates a video signal which represents it, and an output circuit which produces a resultant output video signal. The system performs rudimentary image processing techniques including black and white contrast enhancement. The system may process the data as the data is read out of frame memory. The system may then display this data on a video monitor at a rate of up to 30 film frames per second. 
     In U.S. Pat. No. 4,205,337 Millward describes an apparatus for producing motion picture film by scanning the film horizontally at a scanning station while transporting the film continuously past the scanning station with means for accommodating different film sizes, transport speeds, and film format by changing the frequency of the horizontal scan while performing a predetermined number of horizontal line scans in respect of each frame of the film, The line scan signals are stored in a memory, and the memory is read to produce a plurality of television picture fields at a different frequency from that at which scanning takes place. The frequency at which the television picture fields are generated is higher than that at which the line scan is effected so that the two are made temporally compatible by repeating certain television fields in order to “fill-in” for spare time. 
     In U.S. Pat. No. 4,729,015 Wagensonner describes a system for making positive copies from diapositives. Diapositives are copied on negative photosensitive paper in an apparatus wherein the positive is electronically scanned, line-by-line, and the density signals thereby obtained are electronically inverted prior to influencing the beam of a CRT or laser which is used to reproduce the image of the positive on paper, either line-by-line or point-by-point. The inversion of signals renders it possible to scan the high-transmissivity portions of the positives with a narrow beam, i.e., with a high degree of resolution. 
     Typically, motion picture film digitizers digitize a series of film frames, store that data on a magnetic tape or a collection of hard drives, and then later perform image processing operations. Digital signal processing operations that often must be performed by motion picture film digitizers include: filtering, color correction, minification, and magnification. This two step process is used because the interface between the projected image sensor and the processor is too slow to perform the required image processing of the high resolution color images as they are digitized. Thus, a higher speed interface and image processor are needed to perform the complex image processing required for high resolution color motion picture film digitization. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a digital film scanner interface. The interface obtains digital image data produced by projecting a motion picture film frame onto a sensor. The image data is transferred from the sensor to a Digital Signal Processor (“DSP”) block. The DSP block processes the image data to, for example, minify, magnify, enhance colors, or correct for errors in the image data. After the image data is processed, it is transferred over a bus to a long term storage device. 
     The DSP block comprises four DSPs. Commands can originate from a user interface. The commands are converted by the film scanner interface into an internal representation and executed by the DSP block. One of the DSPs receives the image data from the sensor and controls the flow of the image data to the other three DSPs. The processing tasks are modular to afford flexibility in how the tasks are distributed. The processing tasks can be distributed to the DSPs based on availability. Alternatively, the digital signal processing tasks can be allocated such that each DSP processes one color component of image data. A single task can be performed on two different physical DSPs using dedicated channel connections between the DSPs. This architecture can provide image processing speeds that exceed the speed that a sensor provides image data. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a block diagram of a film scanning apparatus. 
     FIG. 2 illustrates a block diagram of a film scanner interface of the present invention. 
     FIG. 3 illustrates a block diagram of the digital signal processor card configuration in one embodiment of the present invention. 
     FIG. 4 illustrates a block diagram of the front end and digital signal processor block of the present invention. 
     FIG. 5 illustrates a flow chart of the process of digitizing a film frame. 
     FIG. 6 illustrates a flow chart of the process of executing a digital signal processing command. 
     FIG. 7 illustrates a block diagram of the software operations performed by the digital signal processor block. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to a film scanner interface. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without these specific details. In other instances, well-known features have not been described in detail in order not to unnecessarily obscure the present invention. 
     FIG. 1 illustrates a system level overview of a film scanner of the present invention. Element  104  is a light source. In one embodiment, element  104  is an integrating sphere with four strobe or flash lamps. One flash lamp has a red filter attached to it, one flash lamp has a green filter attached to it, and two flash lamps have blue filters attached to them. This type of light source is described in more detail in the co-pending application “METHOD AND APPARATUS FOR DIGITIZING FILMS USING A STROBOSCOPIC SCANNING SYSTEM,” David DiFrancesco, Ser. No. 08/651,164, filed May 17, 1996, and assigned to the assignee of this application, the disclosure of which is hereby incorporated by reference. Other light sources may be used including continuous wave xenon or halogen lamps, as is well known by those of ordinary skill in the art. Element  106  represents a film transport. For example, a “BELL &amp; HOWELL”™ brand film shuttle mechanism as may be used in the motion picture industry. Element  108  represents a light sensor. In one embodiment, element  108  is a “PHOTOMETRICS”™ CCD camera which contains a CCD array (not shown). 
     Alternative sensors may also be used including non-CCD sensors, or a CCD line array. Element  110  represents the film scanner&#39;s interface and control systems, as described in detail below. 
     During operation of film scanning apparatus  100 , light source  104  projects an image of a film frame provided by film transport  106 . The projected image exposes sensor  108 , and the image data is transferred from sensor  108  to film scanner interface  110  for processing and storage. In one embodiment sensor  108  is at least as large as the projected image, so that the entire projected image can be digitized simultaneously. Alternatively a line-array sensor may be used for sensor  108 , and the projected image may be moved across sensor  108  to expose the entire projected image to the sensor. 
     In one embodiment, flash lamp light source  104  comprises four flash lamps, a red flash lamp, a green flash lamp, and two blue flash lamps. Two blue flash lamps are used because the blue filters are denser than the green and red filters. For example, in one embodiment about 1% of the energy of the lamp is transmitted through the blue filter, compared to about 10-12% for the red filter, and higher for the green. Thus, the two blue flash lamps are used to transmit a sufficient amount of blue light through the blue filter to avoid having the blue light exposure time be unacceptably longer than the exposure time for the green and red light sources. 
     In one embodiment, controller  208 , shown in FIG. 2, sends a pulse to a flash lamp in light source  104 . The flash lamp then continues to flash for a predetermined time based on the time required for sensor  108  to saturate as determined in a calibration procedure. A sensor saturates when it obtains a predetermined resolution level of image data. Controller  208  also controls the frequency of the flash lamps. In an alternative embodiment, controller  208  is programmed to deliver a predetermined number of pulses to each flash lamp to trigger the flash lamp to flash, for example, between 1 and 255. A control program executed by controller  208  controls the number of pulses sent to each flash lamp, where the number is determined so as to ensure that the flash lamp provides adequate exposure to sensor  108 . 
     FIG. 2 illustrates a preferred embodiment of the element  110  film scanner interface and control systems. Element  201  is a Central Processing Unit (“CPU”) card. In one embodiment, element  201  is a “THEMIS”™ 10 MP CPU card, this is a 6 U size VME bus card. The preferred configuration of the card includes: 32 megabytes memory, a single 75 MHz “SUN”™ “SPARC II”™processor with cache, an SBus video card for display video, and two RS232 ports. One of these RS232 ports is coupled to sensor  108 . Element  205  is a storage medium, coupled to CPU card  201 . In one embodiment, element  205  is a plurality of hard disk drives coupled to CPU card  201  by a SCSI bus. CPU card  201  is also coupled through interface  206  to a user network, for example, an ethernet connection. CPU card  201  is further coupled to VME bus backplane  225 . CPU card  201  is coupled via VME bus  225  to Input/Output (I/O)  212 , Memory element  213 , and Digital Signal Processor (DSP) block  214 . 
     Element  212  is an I/O card, for example, a “GREEN SPRING”™ VME/IP interface card. “GREEN SPRING”™ VME/IP interface cards provide an interface for up to four Industry Packs (IP) cards to VME bus  225 . Element  209  is a controller for film transport  106  and other ancillary devices. Controller  209  controls these devices through an optically isolated relay panel. Element  208  is a light source controller. In this embodiment, element  209  is an IP card, and element  208  is a specifically designed IP sized card to control flash lamps in light source  104 . Controller  208  includes registers to store the flash lamp frequency, start pulses, stop pulses, and generate interrupts when the flash lamp exposure is complete. Element  208  is coupled to I/O card  212 . 
     Element  213  is a memory means. In one embodiment, element  213  is a “RAMIX”™ RM-140B Memory card with 64 megabytes of dual-ported memory. Element  214  is a DSP block. In one embodiment DSP block  214  comprises a set of two “SPECTRUM”™ VME DSP carrier boards. Each VME board contains two DSP processors, for example, “TEXAS INSTRUMENTS”™ TMS320C40 DSP block  214  is described in greater detail with respect to FIGS. 4 and 5. 
     Element  210  is an interface between sensor  108  and DSP block  214 . In one embodiment, element  210  is a specially designed interface to attach to a buffered COMM port on the “SPECTRUM”™ VME DSP carrier boards in DSP block  214 . The maximum data rate on a buffered COMM port is about 15 megabytes/second (Mb/sec.). The maximum data rate from one embodiment “PHOTOMETRICS”™ CCD camera is 2 Mb/sec. The fact that the COMM port data rate is substantially higher than the CCD data rate will allow the scanner interface system to be used with future faster sensors. 
     In operation, CPU card  201  is the central controller for the film scanning system. CPU card  201  runs an operating system (“OS”), which in one embodiment is the “SOLARIS”™ OS. CPU card  201  controls the operation of sensor  108  through RS232 port  207 . CPU card  201  controls I/O card  212 , Memory  213 , and DSP block  214  via VME bus  225 . Image data is stored in storage medium  205 . Interface  206  is used to transfer image data to users. 
     Memory  213  may be accessed by either VME bus  225  or VSB bus  226 . In one embodiment, VSB bus  226  moves processed data out of DSP block  214  to Memory  213 . Image data then moves from memory  213  across VME bus  225  to CPU card  201  for final processing and storage in storage medium  205 . Memory  213  acts as both a large buffer for image data between DSP block  214  and CPU card  201 , and as a fast means for transferring data from DSP block  214 . Data rates out of DSP block  214  are about 2 Mb/sec. on VME bus  225  and are about 15 Mb/sec. on VSB bus  226 . 
     To turn on a flash lamp, light source controller  208  sends a pulse to the flash lamp. The green and red light sources each have a dedicated channel connection to light source controller  108 , and a third channel connects controller  108  to both of the blue flash lamps. Alternatively, a dedicated channel may be used for each of the blue flash lamps. 
     FIG. 3 illustrates one embodiment VME carrier board configuration. Elements  310  and  320  are VME carrier boards. VME carrier boards  310  and  320  are components of DSP block  214  shown in FIG.  2 . Each carrier board  310  and  320  provides support for four single sized DSP cards or two double-sized DSP cards. Carrier boards  310  and  320  contain COMM ports that connect the four DSP card sites on the board, as well as COMM ports that are routed to the edge of the card to provide connections to other carrier boards or I/O devices. DSP 0   312 , DSP 1   314 , DSP 2   322 , and DSP 3   324  are DSP cards plugged into VME carrier boards  310  and  320 . DSP 0   312  is the only DSP directly coupled to VSB bus  226 . DSP 0   312 , DSP 1   314 , DSP 2   322 , and DSP 3   324  are all coupled to VME bus  225 . The coupling between the DSPs is described in greater detail in FIG.  4 . 
     FIG. 4 illustrates DSP logical connections in one embodiment of the present invention. The COMM port interconnects between the DSP processors are elements  450 ,  452 ,  454 ,  456 ,  458  and  460 . The four DSPs are arranged in a star network, so that each DSP is directly connected to every other DSP and all the DSPs can communicate together. The COMM port interconnects operate at 20 Mb/sec. for intra-board transfers. Element  420  is a buffered inter-board COMM port interconnect. Element  422  couples DSP 0   312  to VSB PIM card  410 . VSB PIM card  410  is an interface to VSB bus  226 . Elements  424 ,  426 ,  428  and  430  are COMM port links which connect each DSP to VME bus  225 . 
     DSP 0   312  is the only DSP which has an interface to sensor  108 . DSP 0   312  is also the only DSP with an interface to VSB bus  226 . DSP 0   312  is coupled to CPU card  201  via VME bus  225 . In one embodiment DSP 0   312  is a “TEXAS INSTRUMENTS”™ TMS320C40 with a 50 MHz clock speed, and 12 Megabyte of zero wait state EDRAM. In one embodiment DSP 1   314 , DSP 2   322 , and DSP 3   324  are “TEXAS INSTRUMENTS”™ TMS320C40 with 40 MHz clock speed and 32 megabyte of one wait state DRAM. In one embodiment the 32 megabytes of memory is enough for one and half frames of image data. 
     In operation, DSP 0   312  manages image data created by sensor  108 . DSP 0   312  distributes image data among DSP 1   314 , DSP 2   322 , and DSP 3   324  via the intra-board COMM ports  450 ,  452 ,  454 ,  456 ,  458  and  460 . In this embodiment DSP 0   312  is a control DSP, and DSP 1   314 , DSP 2   322 , and DSP 3   324  are task DSPs. DSP 0   312  also communicates with CPU card  201  to provide input for the control of light source  104 , sensor  108 , and film transport  106 . In one embodiment, each DSP processes data created by one of the color component light sources in light source  104 . For example, in one embodiment, DSP 1   314  processes red data, DSP 2   322  processes green data, and DSP 3   324  processes blue data. Each DSP 0  signals DSP 0   312  when it completes processing a group of data. The DSP 0  then sends the processed data through the dedicated channel to VSB bus  226  and to CPU card  201  for storage in storage element  205 . DSP 0   312  controls the transfer of data from each DSP to VSB bus  226 . An alternative method, is to divide the image into geometric regions and process the data in groups representing each region. The operation of the DSPs is described in greater detail below. 
     COMM port links  424 ,  426 ,  428 , and  430  which link the DSPs to VME bus  225  are used for a variety of functions including: testing the DSPs, loading and executing DSP programs, and generating interrupts. Interface  210  transfers data to DSP 0   312  for processing through interconnect  420 . Element  422  couples DSP 0   312  to VSB PIM card  410 . 
     FIG. 7 illustrates the operation of the DSP block  214  software. The components illustrated in the DSPs in FIG. 7 represent software tasks, in contrast to FIG. 4 which illustrates a block diagram of the DSP hardware. An overview of the process of executing commands is illustrated in FIG.  6 . Commands relating to digital signal processing may originate from the user interface task. 
     The text strings are transferred from the user interface to command interpreter  762  via VME bus  225 . Command interpreter  762  parses the text string commands, checks the syntax, and ultimately compiles each command into an internal representation that is readable by dispatcher  764 . Command interpreter  762  outputs the internal representation of the commands to a queue to make command interpreter  762  available to process another command or provide status information to CPU  201 . 
     This approach provides a natural way to implement scripting and simplifies debugging of both the user interface and the DSP software. Command interpreter  762  converts general text string commands into DSP driver level code. Using text string commands also allows script files to be written as simple text files to perform frequently used DSP tasks. 
     Dispatcher  764  removes commands from the queue and runs the appropriate tasks to complete the commands. Each command can comprise more than one task. Dispatcher  764  runs commands by connecting the composite tasks together. The tasks can be executed by the task DSPs  314 ,  322  and  324 , or by the root DSP  312 . Dispatcher  764  also coordinates execution of the tasks. Dispatcher  764  connects tasks via channels. A single command may be executed by a single DSP, or by several DSPs working in parallel. Each DSP processor has a dedicated channel connecting it to each of the other DSP processors. These dedicated channels can only accommodate communication between one pair of tasks at a time. Wire channel router  770  is a software function that arbitrates the dedicated channels between the DSPs. Dispatcher  764  monitors the active tasks and along with wire channel router  770  ensures that only one pair of active tasks communicate over a dedicated channel at a time. Dispatcher  764  may place commands in a temporary waiting state when the resources to execute the commands are not available. 
     The tasks are highly modular. Tasks are generally all similar in that they take image data from an input channel, perform an operation on the image data, and then send the results to the output channel. The task code is independent of which DSP the task is executed on, and is also independent of where the data is received from or sent to. Examples of tasks include minification, sharpening, and image compression. There are some special tasks such as the “camera interface” that do not have an input channel. The “camera interface” task receives image data from sensor  108 . Another special task is the “VSB” task. The “VSB” task transfers image data from the DSP block  214  to the CPU  201  via either VME bus  225  or VSB bus  226 . 
     Dispatcher  764  uses a standard method to allocate input and output channels to tasks to allow task pairs to communicate. The modular approach to establishing communication channels allows the same communication code to be used in all of the tasks, thereby simplifying the development of new tasks. 
     The DSP run-time environment includes a micro-kernel. The microkernel provides inter-task communication channels. The inter-task communication channels provide an abstraction that allows tasks to be on the same or two different physical DSPs without requiring any changes to the tasks. Tasks are run as time-sliced threads. 
     This modular task based architecture provides the advantage of facilitating the addition of new processing options without modifying existing tasks. Further, the modular nature of the tasks effectively uses the parallel processing capability of the DSP hardware architecture by distributing different tasks to different DSPs for concurrent execution. 
     FIG. 5 illustrates at a high level one embodiment of how the film scanner interface obtains and processes image data. In step  512 , light source controller  208  signals the red flash lamp in light source  104  to start flashing at the frequency stored in a register in light source controller  208 , for example 30 Hz. In one embodiment, all of the flash lamps flash at the same frequency. In an alternative embodiment, the flash lamp frequency of each lamp is independent of the other flash lamps. Each flash of the red flash lamp in one embodiment produces four joules of light. In each sensor exposure cycle, the red flash lamp flashes for a predetermined time. The duration of the flashing cycle is determined by a calibration procedure in which the amount of time required to expose sensor  108  to a predetermined amount of light for a given image is measured. For example, according to one embodiment of the invention a CCD array sensor saturation level is twelve bits logarithmic, on a scale of 0 to 4096. After the exposure period, in step  516  sensor  108  transfers the red image data from the radiation sensitive element in sensor  108  to shift registers in sensor  108 . Sensor  108  then transfers the data from the sensor  108  shift registers to interface  210 . The data is transferred immediately after each color is finished. The data out of the camera is essentially a raster. Sensor  108  transfers data along a 16 bit wide connection. Control information is transferred along with the image data, including pixel clock, valid line, and valid frame signals. Interface  210  converts the data from the 16 bit wide format in which sensor  108  transfers it, to an 8 bit wide format for transfer to DSP 0   312 . DSP 0   312  distributes the image data to an available DSP or a DSP dedicated to processing that color of data, either DSP 1   314 , DSP 2   322 , or DSP 3   324 . When the selected DSP finishes processing the data, it signals DSP 0   312 . The data is then transferred via VSB bus  226  to CPU card  201  and ultimately to storage medium  205 . 
     While the red color data is being processed, in step  520  light source controller  208  signals the green flash lamp to begin to flash. In one embodiment, the green flash lamp flashes for a predetermined time. As with the red flash lamp, each flash of the green flash lamp produces four joules of light. In step  526  the green color data is transferred from the radiation sensitive element in sensor  108  to shift registers in sensor  108 . The green color data is then transferred to DSP 0   312 . As with the red data, DSP 0   312  distributes the green data to an available DSP or alternatively to a DSP dedicated to processing green data. When the dedicated DSP finishes processing the data, it signals DSP 0   312 . The data is then transferred via VSB bus  226  to CPU card  201  and ultimately to storage medium  205 . 
     At step  528 , while the green color data is being processed, light source controller  208  signals the two blue flash lamps to begin to flash. The blue flash lamps are flashed simultaneously. Each flash of one of the blue flash lamps in this embodiment produces up to four joules of light. After the blue flash lamps flash for a predetermined time required to expose sensor  108 , the blue color data is transferred from the radiation sensitive element in sensor  108  to shift registers in sensor  108 . In step  532 , the blue color data is then transferred to DSP 0   312 , and distributed for processing as described for the red and green data. 
     Each cycle of exposing the CCD array with the red, green, and blue color components is a “scan.” One embodiment performs three scans, one each for the red, green, and blue component light sources, to digitize the image of each film frame. The duration of each color scan is determined using a calibration procedure which measures the amount of each light component required to saturate sensor  108 . In one embodiment sensor  108  is a 2 k×3 k CCD pixel array. Therefore, each scan generates six million pixels of color data. As described above, when the CCD array is fully saturated each pixel comprises twelve bits of information. When the proper amount of light has been delivered, the image data is transferred from sensor  108  to DSP block  214 . In one embodiment, the image data is transferred from sensor  108  to DSP 0   312  at a rate of two million pixels per second. Thus, it takes three seconds to transfer the color data corresponding to each strobe lamp color from a 2 k×3 k CCD array to DSP 0   312 . 
     The following provides a summary of the timing sequence for exposing sensor  108  to each color component light source and transferring the image data from sensor  108  to DSP 0   312 . The red light source exposes the frame image on sensor  108  for approximately one second. To transfer the red color data from sensor  108  to DSP 0   312  takes three seconds. As DSP 0   312  receives the red data, it simultaneously transfers the red data to a DSP dedicated to processing red data, at a rate of 20 Mb/sec. After sensor  108  transfers the red data, there is then approximately one second of green light exposure to sensor  108 , simultaneous with the DSP processing of the red color data. This is followed by three seconds to transfer the green color data to DSP 0   312 . After sensor  108  transfers the green data, there is then approximately one second of blue light exposure to sensor  108 , followed by three seconds to transfer the blue color data to DSP 0   312 . Thus, a total of twelve seconds are spent in order to capture and pass all color data from a single film frame to DSP 0   312 . 
     DSP block  214  can perform many different image processing operations including filtering, color correction, minification, magnification, correction for sensor defects, and rotation. Minification is a critical application because for many scanner applications the bandwidth of the back-end image processing system will be limited and therefore the per-frame image data size must be reduced to be processed by the back-end system. 
     As described above in one embodiment, DSP 1   314 , DSP 2   322 , and DSP 3   324  are each dedicated to processing a particular color of data. An alternative approach, is to use a pipeline approach whereby each DSP performs a process. For example, DSP 1   314  minifies the image data, DSP 2   322  corrects the color of the image data, and DSP 3   324  normalizes the image data. When a color component of image data has been fully processed it is transferred back to DSP 0   312 . DSP 0   312  then transfers it to CPU card  201 . Software control of DSP 0   312  and CPU card  201  are tightly coupled because of the extensive inter-relationship between the transfer of data to and from DSP 0   312  and the control of the light source  104  and sensor  108 . 
     Thus a method and apparatus for a film scanner interface have been described. Although the present invention has been described with respect to certain specific embodiments, it will be clear to those skilled in the art that the inventive features of the present invention are applicable to other embodiments as well, all of which are intended to fall within the scope of the present invention.