Abstract:
A method of embedding a security mark or code on a film during the printing process is provided. The security mark or code includes unique print identification information that can be tracked to determine sources of piracy. The security code is incorporated to the film print in the form of a shift in the light exposure (e.g., color density) of pre-selected frames within pre-selected zone of pre-selected scenes. By shifting the color density and thereby marking a particular zone within a scene, these markings can be used to place a unique print ID onto the film print. This embedded security code (e.g., print ID) will be virtually undetectable to the viewer and film pirates; yet will enable the identification of the film source in the event of piracy.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application 60/576,264 filed Jun. 2, 2004, the entire contents of which is incorporated herein by reference. 

   TECHNICAL FIELD 
   The present invention relates to the printing of motion picture film. More particularly, the present invention relates to the application of security codes to film during film printing. 
   BACKGROUND ART 
   The process of printing a motion picture film entails projecting light of varying intensity onto unexposed film stock. In the course of printing a motion picture film, a security code or other type of identifier is often printed onto the film in an effort to uniquely identify each print that is made. The identification of the print enables the motion picture studio that produced the film to track the location of the various film prints, which aids in fighting piracy. In the event piracy occurs, the security code on the pirated film will assist in the identification of the source of the pirated film. In this respect, the code can, among other things, uniquely identify a theater that received the film print for public viewing. Thus, these identifying security codes can provide a studio with information relating to the theater from which the piracy occurred. From such information, the studio can track the piracy patterns and develop and implement theft controls. 
   One known technique for adding such security codes is the Cap Code technique, which applies a unique pattern of codes to each print. The pattern of codes is repeated every twenty feet (20′) or so throughout each reel of the film. However, this approach appears to have lost its viability due to the increase in compression employed during film making and recording. In addition, this security technique can incur certain disadvantages. For example, the cap code technique has a limit of approximately 2000 unique dot combinations. Further, the image rarely survives capture and compression. Further, and all of the dots added as codes are required in order to decode the print number. In other words, it is not possible to decode a partial pattern. 
   Recent trends in technology have enabled film pirates to discover the use of such security codes on the film prints. Thus, such pirates constantly attempt to thwart such security codes and subsequent identification of the film source by eliminating them from the reproduced copies. 
   Thus, a need exists to provide security codes on a film during printing that are undetectable to pirates, and that do not impair the image quality and hence, the viewing experience of viewers. Furthermore, a need exists to provide security codes on film prints that not only uniquely identify each print, but also survive capture and compression to 150 k. Additionally, a need exists to minimize the security code required on the print, as well as to make such codes invisible to the viewing audience and to facilitate decoding, thereby allowing the use of such codes as evidence of piracy. 
   BRIEF SUMMARY OF THE INVENTION 
   In accordance with one aspect of the invention, a security code is embedded in a motion picture film during the film printing process. The method for providing a security code on a motion picture film during film printing commences by exposing the film to light, for example, to red, green and blue light directed at the film. A security code is generated by identifying at least one location on the motion picture film which will have a shift in light density, and controlling the exposure of the light during the printing process to impart the shift in the light density at the at least one location. 
   According to another aspect of the invention, a method for embedding at least one security code on a motion picture film during film printing commences by obtaining security code information from an external source, the security code information including film location information for placement of the security code. The security code information is provided to a light valve controller connected to a film printing apparatus. The film position is determined during printing, and the light valve controller is controlled to vary the light exposure at the film location intended for placement of the security code. 
   Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings wherein like reference numerals denote similar components throughout the views: 
       FIG. 1  depicts a schematic view of four exemplary scenes on a length of motion picture film, each scene subdivided into forty-two zones; 
       FIG. 2  is an enlarged view of a portion of one of the scenes depicted in  FIG. 1 , and shows a shift in density to create a security code according to an aspect of the invention; 
       FIG. 3  is a diagrammatic representation of an exemplary security code printed on a motion picture film according to an aspect of the invention; 
       FIG. 4  is a schematic diagram of a light valve system according to another aspect of the invention; and 
       FIG. 5  is a flow diagram of the method for printing a security code on the film. 
   

   DETAILED DESCRIPTION 
   In accordance with an aspect of the invention, a security code can be applied to a film print by creating density shifts in the printing process. By way of example,  FIG. 1  shows four separate length of a single motion picture film  10 , each separate length containing one of four scenes, identified as scene one, scene two, scene three and scene four, respectively. Each scene is subdivided into 42 zones. 
     FIG. 2  shows an enlarged portion of the first eight frames of scene one, identified as frames  1 - 8 , respectively. In accordance with the present principles, a shift in density is applied in the printing of the film to a plurality of consecutive frames in a designated grouping of frames within a scene. This density shift from a normal density identifies the location of the security code. The locations of the density shifts determine the actual security code embedded within the film print. In the illustrated embodiment of  FIG. 2 , the density shift occurs in the first three frames (i.e., Frames  1 - 3 ) in scene one. 
   By varying the light density during film printing (such as by varying the color level, grayscale, etc) on some predetermined number of frames within at least one zone in each of a number of scenes, it is possible to obtain thousands of possible security code permutations. For purposes of this discussion, the example of varying the color density is used to describe the embedding method of the present invention. Those of skill in the art will recognize that other perceivable changes in the exposure (e.g., perceived light) in pre-designated locations on the film are also within the scope and spirit of the invention. The use of “density shift” and “changes in the perceived light” exposure are interchangeably used herein. 
   In the example shown in the Figures, by varying the color density on frames within one zone in each of three scenes, each scene having 42 zones (0-41), it is possible to obtain 42 3  or 74,088 unique combinations of scenes and zones for providing a unique security code for the film print. In other words, the shift in color density identifies a numerical value corresponding to the zone within a particular scene. The scene four in the present example can be used as a checksum to confirm the coding applied to scene one, scene two and scene three. 
     FIG. 3  shows an example, where four scenes are shown (i.e., scene one through scene four), with each scene having 42 zones. Each zone consists of a number of frames. In this example, the security code, to be implemented is 8, 1, and 12 (with a check sum of 21). Thus, for scene one, the 8 th  zone is shown shaded (shading represents shift in perceived light or in color density), for scene two, the 1 st  zone is shaded, etc. These shadings are shown for purposes of illustration. These density shifts, identify the zone number of the respective scene and in combination with the other density shifts of the other scenes, provide each film with the unique print identification used to track and identify the theater or other destination for the film print. Scene four is used as the checksum indicator and includes the density shift in zone 21 (i.e., 8+1+12=21). 
   With the system of the present invention, the proposed code can be implemented into a film print at 4 different scenes, where those 4 scenes can be anywhere in each reel. This makes the embedded security code virtually undetectable to the pirates. 
   Some of the advantages of present method of embedding the security code into the film print include: 1) a small amount of film is required to embed the code (i.e., 21 feet per density shift, x four scenes, thus entire film is not required to decode the embedded code); 2) the scene selection is independent of the code to be embedded and could be but need not be customer based; 3) unique coding (e.g., bar codes) can be printed on each reel; 4) a tracking database can be easily maintained for all security codes; 5) any pirated material can be decoded and the source of the piracy (i.e., the destination to which the original film print was sent) can be identified using the embedded security code; 6) only a small number of actual frames are marked over the entire file; and 7) decoding can occur at up to 150 k Divx compression (e.g., the embedding the code over three frames enables compression methods keep to the different video information, but the density shift doesn&#39;t occur not long enough to become objectionable or even noticeable). 
     FIG. 4  shows a block diagram of a film printing apparatus  40  using the security coding method of the present invention to print a security code on a motion picture film print. The film printing apparatus  40  includes a printer  42  having a light source  41 , and a light valve controller  50 . The printer  42  includes blue ( 44 ), green ( 46 ) and red ( 48 ) light valves that control the amount of the blue, green and red light, respectively, applied from the light source  41  to the film during the printing (exposure) process. The film  60  has an unexposed stock  62  that is passed by the printing head  58  of the printer  42  and accumulated on an exposed reel  64 . 
   In accordance with one embodiment, the light valve controller  50  receives the desired security coding information for a particular film printing from a computer device  66 , either directly, or through a network, such as local area network (LAN)  68 . As explained above, this coding information typically includes: the scene #, zone # and frame or frames where the code is to be embedded, while also providing information as to which color or colors (e.g., red, green or blue) require variation to achieve the desired color density shift for the code printing. Those of skill in the art will recognize that the color density of one or more of the red, green and blue colors can be made at any one of the security code printing locations. Which color or colors will depend on the particular scene and frame, and can be selected on the basis of the least possible variation in the frame during actual viewing. 
   The light valve controller  50  obtains the film position information from a sensor  52  and based on the received position information of the film  62 , the controller outputs red, green and blue command signals  54   a ,  54   b  and  54   c  to the printing apparatus  42 . The command signals  54   a ,  54   b  and  54   c  control the respective red ( 48 ), green ( 46 ) and blue ( 44 ) light valves to control the amount of red light  49 , green light  47  and blue light  45  that ultimately arrives at the printer head where it is recombined and exposed ( 58 ) onto the film  60  during printing. 
   By varying the light exposure (e.g., color density) at the selected locations (i.e., scene # and zone #), the codes can not only be embedded and hidden within the actual film, but will also not interfere with the viewing and/or compression of the film during processing. Since the security code is effectively a number code that is printed on the film using the zone numbers within more than one scene, subsequent identification of the code and the source of the film print become easy. 
   According to an embodiment of the invention, decoding of the embedded code (i.e., print number) can occur, even in the presence of partial density shift information. For example, the availability of any three of the four scenes permits decoding of the print identifier using any three scenes number since the last scene constitutes a sum of the others. If less than three scenes are available, additional detective methods for decoding can be employed. For example, if only two scenes are available, then the print number is one of only 42 possibilities. Such information can be sufficient to determine a single print number if all print numbers had the same missing code due to a limited release of prints. Other factors such as sound track language and known print defects can also play a part in decoding. 
     FIG. 5  shows an a flow chart illustrating the steps of an exemplary method  100  for printing a security code on a film during printing according to an aspect of the invention. Initially, the security code is obtained or generated during step  102  for use as a Print identifier on the film undergoing printing. The light valve controller  50  of  FIG. 4  receives the Security code during step  104  of  FIG. 5 . As explained above, when printing begins, the light valve controller  50  receives the film position information at all times via sensor  52  of  FIG. 4 . Once the correct film position has been determined during step  106 , the light valve controller  50  of  FIG. 4  changes the perceived light at the desired film position during step  108  of  FIG. 5 . This process continues until completion of film printing. 
   While there have been shown, described and pointed out fundamental novel features of the invention as applied to preferred embodiments thereof, it will be understood that various omissions, substitutions and changes in the form and details of the methods described and devices illustrated, and in their operation, can be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps, which perform substantially the same function in substantially the same way to achieve the same results, are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention can be incorporated in any other disclosed, described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.