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METHOD AND APPARATUS FOR PRODUCING STILL VIDEO IMAGES USING ELECTRONIC MOTION VIDEO APPARATUS
FIELD OF THE INVENTION
 The present invention relates to digital data devices, and in particular to digital cameras, motion video, and similar devices which electronically capture optical images.
BACKGROUND OF THE INVENTION
 In the latter half of the twentieth century, there began a phenomenon known as the information revolution. While the information revolution is a historical development broader in scope than any one event or machine, no single device has come to represent the information revolution more than the digital electronic computer. The development of computer systems has surely been a revolution. Each year, computer systems grow faster, store more data, and provide more applications to their users.
 The declining prices and expanding capabilities of modem digital technology has caused it to be used in an ever increasing variety of applications. One of these applications has been the capturing of optical images electronically. Optical imaging technology generally uses a digital sensor array, such as a charge-coupled device (CCD) array, having a large number of photo-sensitive elements arranged in a regular pattern, and appropriate supporting hardware which scans the output of the elements and constructs therefrom a digital image. The digital image can then be stored in any digital data storage medium, displayed on a digital display device, printed on paper or other medium, manipulated using editing tools, or transmitted to remote locations using any transmission medium appropriate for digital data.
 Optical imaging has been used in a variety of settings, including fax machines, document scanners, bar code readers, and so forth. In particular, electronic optical imaging is also used as a substitute for older film-based media in high-resolution still and motion picture cameras. Indeed, as electronic optical technology improves in quality and declines in price, many foresee the day when it will completely supplant the older film-based media in these fields.
 A typical electronic camera, whether used for still or motion video, has an on-board digital data processor and is in effect a small, special purpose computer. These cameras are therefore often referred to as "digital" camera, and will be so referred to herein, although in fact data may sometimes be sensed, stored, or temporarily held or transmitted in an analog electronic mode. The optical sensor array used for capturing images can be used for either still or motion video images, provided that appropriate supporting hardware, programming and recording media is available. This fact has been used to advantage in various commercially available video cameras, which also have the optional capability to capture still images. Since a still image is normally saved in a different format than a motion video image, these cameras typically offer the user the option of a motion video or a still video mode. The common optical sensor array is used to capture the image in either case, but the captured image may be saved differently, depending on the operational mode.
 Most digital cameras to date make limited use of digital technologies beyond straightforward optical scanning and recording. Such an approach fails to recognize the vast potential of the information age to provide improved integration of digital technology and enhanced function of digital cameras not yet conceived, a potential which is bounded only by human imagination. In particular, it fails to recognize the potential to obtain relatively high-resolution still images while recording in a relatively low-resolution motion video mode.
SUMMARY OF THE INVENTION
 An electronic video camera apparatus temporarily records and saves motion video in a relatively high-resolution form in a frame aging buffer. While the video frames are saved in high-resolution form, it is possible to extract a relatively high-resolution still image from the buffer. The camera holds the video frames in high-resolution form a limited time, eventually "aging" them out of the buffer or to a lower resolution form as more motion video is captured.
 In the preferred embodiment, the camera apparatus may have several modes of operation, including a motion video mode having standby high-resolution still video capability. The motion video is continuously saved on a motion video medium (such as magnetic tape) in a relatively lowresolution format typical of motion video. The frame aging buffer contains a series of recently captured frames in high-resolution form, and is therefore constantly being overwritten as new frames are captured. For example, the buffer may contain all frames in the last 10 seconds in highresolution form. If, while recording the motion video, an event occurs which the user would like to capture as a high-resolution, still digital photograph, the user activates a saving function before the buffer has been overwritten, e.g., before the 10 second time period has elapsed. The saving function then preserves some or all of the buffer contents in high resolution form. Frames may be preserved, e.g., by disabling further writing to the buffer, or by writing the buffer contents to some other media, such as a flash memory stick. The user may continue to record motion video, and may later review the saved buffer contents and select one or more frames from the saved buffer for preservation as a still digital photograph.
 A method and apparatus described herein provides an enhanced capability to capture still images in highresolution format. Specifically, it allows a user to determine, after the occurrence of an event, that the event is such as should be preserved as a still image. This capability is generally useful for recording events of a momentary and unpredictable nature, when it is not known until after the event that a high-resolution still photograph will be desirable. Examples of such events include critical plays occurring in sports competitions, "cute" happenings in children at play, crimes or surveillance events as part of law enforcement, natural disasters, weather phenomena, and many others.
 The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: