Method for presenting improved motion image sequences

A method for the presentation of digital motion image sequences includes the steps of capturing a digital motion image sequence at a given frame rate; temporally interpolating the digital motion image sequence to a higher frame rate than the given frame rate to produce interpolated digital image frames; and storing the digital motion image sequence and the interpolated digital image frames as extensions to the stored digital image sequence, whereby the stored digital image motion sequence can be presented at the given frame rate or combined with the interpolated digital image frames for display at the higher frame rate.

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for the presentation of digital motion image sequences at a higher frame rate than the original frame rate at which the motion image sequence was captured. This higher rate of presentation produces a smoother and more pleasing viewing experience, particularly for digital image projectors and digital image capture devices. In order to maintain compatibility with other projectors that are not modified as described in the present invention, the interpolated image sequence data is stored in such a way that conventional projectors can ignore the additional data while specially equipped projectors can utilize the data to provide a superior viewing experience. Referring to FIG. 1 an image is captured 10 . The image capture can be done using either a conventional motion picture camera using motion picture film, a video camera, or a digital motion image camera that captures and stores a digital image. In the first two cases, once the image sequence is captured, it is then digitized 12 , for example by scanning the motion picture film, or converting the video signals produced by the video camera to digital image signals. In any case, the image sequence is acquired at a given frame rate, typically 24 frames per second for motion picture film, or 30 frames per second for NTSC standard video. If the original image sequence were to be acquired at a higher frame rate (for example, 48 frames per second) in an attempt to produce a higher quality motion image sequence, the cost of film (or other storage media such as video tape) would be doubled. The cost of manipulating, storing, and transmitting the data would likewise be greatly increased. It is the object of this invention to avoid this additional cost while accruing the benefits of a higher frame rate in presentation. Once the digital image sequence is available, the digital image sequence is temporally interpolated 14 using a digital image interpolation method to produce an image sequence at a higher frame rate. This higher frame rate reduces motion artifacts in the displayed image. The higher frame rate preferentially is an integral multiple of the original frame rate which is easier to calculate and control than non-integral multiples. The interpolation can include known techniques such as frame combination, or more sophisticated techniques relying on motion vector analysis such as that used in the Kodak Cineon System. Not all of the image sequence needs to be interpolated. Only those portions of the image sequence that will benefit from interpolation in the anticipated presentation devices may be interpolated. Portions of the image sequence which will not improve noticeably or which will include objectionable artifacts resulting from the interpolation, may be excluded from interpolation. In contrast, those portions that will benefit from or for which interpolation is desired for artistic or other reasons may be interpolated. The frame rate of portions of the image sequence which are not interpolated may be increased by simple frame replication. Once the image sequence is suitably interpolated 14 , it is stored 16 for example on a conventional digital storage medium such as magnetic tape, magnetic disks, or optical disks. According to the present invention, the originally captured image sequence is stored as a standard computer file format of sequential frames, and the interpolated frames (including any replicated frames) are stored as an extension to the standard computer file. The extension can be implemented using information in file headers or stored separately or otherwise associated with the original image sequence in such a way that the original image sequence without the interpolated frames can be accessed by a standard presentation device. An example of such a storage format is the MPEG format with the interpolated frames stored as file extensions. The interpolated frames may be tagged to indicate their location in the digital image sequence. Alternatively, frame location data may be provided to specify the construction of a higher frame rate sequence from the original sequence and the interpolated frames. The digital image sequence and/or the interpolated frames may be compressed prior to storage to reduce the storage or transmission needs of the system. If the compression involves motion vector analysis, such as the MPEG standard, the interpolation method may utilize the same motion vector information used in the compression. Conversely, if the interpolation method involves motion vector analysis, such as the method employed in the Kodak Cineon System, the compression may utilize the same motion vector information used in the interpolation. It is also possible to store the interpolated frame information as a description of an image rather than the image itself. For example, a motion vector map indicating the changes in position of various elements in an image in the sequence, or a simple code indicating that an image is to be replicated may be stored. Fundamentally, this amounts to a compression of the interpolated image sequence which must be reconstructed by the presentation device. In this way, the computing requirements of the encoding and decoding devices may be traded off. Preferably, the compression method used for the original image frames will be used for the interpolated frames so as to reduce the computational requirements of the presentation device. It may also be useful to compress and store the original image frames before interpolation. Since standard hardware may be available to support standard image compression, it may be cost-effective to first use the available, relatively inexpensive compression devices and then modify the resulting image files, where necessary, to accommodate the interpolated data. Alternatively, a more complex control mechanism may be useful to apply an existing compression device for all the image sequence frames. Once stored, the image sequence may be communicated 18 for example by transmitting the image sequence using telecommunications such as cable, satellite, the internet, etc. Alternatively, no transmission may be desired and the image sequence may be stored 16 in temporary digital storage such as RAM and presented immediately. Upon arrival at a suitable presentation device such as a digital projector, the interpolated digital image sequence is recreated 20 . If the image sequence has not been compressed and the interpolated frames are ignored, the recreation can simply be a matter of reading the stored media or receiving a transmission and displaying the standard digital image file. If the image is compressed, it is first decompressed. If a suitable projector capable of reading the interpolated frames is used, the interpolated frames are inserted into the sequence using the location tags or frame location data associated with the sequence. Once recreated, the digital image sequence is presented to a viewer 22 at the higher frame rate. Alternatively, the original digital image sequence can be compressed using a standard compression technique, and the decompression and interpolation steps can also be implemented within a presentation device. The interpolation method may use existing MPEG standards and compression devices. By first compressing the data, then communicating it to the presentation device, the presentation device may then utilize the MPEG information to create interpolated frames in real-time. This approach, however, requires a much greater computing capability within the presentation device. FIG. 2 illustrates a system that may be used to implement the method of the present invention. In FIG. 2 a conventional motion picture camera 30 exposes film 31 that is developed and then digitized by a scanner 32 to produce a digital image sequence. Alternatively, a digital camera 34 can be used to capture digital image sequences directly with no need for subsequent digitization. The digital image sequence is supplied to a digital computer device 36 which processes the digital image sequence as described above. The digital computer 36 includes a display 35 and an operator interface 39 , with which an art director can view the digital image sequence and select those portions of the sequence which are to be interpolated. The processed digital image sequence is then stored for example on an optical disc 37 or transmitted over a distribution channel 38 . The digital image sequence can be displayed to a viewer on a presentation device such as a digital projector 40 . The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 1 PARTS LIST 10 acquisition step 12 optional digitization step 14 interpolation step 16 store image sequence step 18 communication step 20 recreation step 22 presentation step 30 conventional motion picture camera 31 film 32 scanner 34 digital camera 35 display 36 processor 37 optical disc 38 communication 39 interface 40 presentation