Image analysis – Image compression or coding – Adaptive coding
Reexamination Certificate
2000-03-08
2002-12-17
Couso, Jose L. (Department: 2621)
Image analysis
Image compression or coding
Adaptive coding
Reexamination Certificate
active
06496601
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the fields of data compression, transmission, decompression, storage and display for graphic images such as film, video (television) and other moving picture image sequences. In particular, the present invention relates to systems for compressing and decompressing moving picture image sequences by an asynchronous, non frame-based technique. The system for compressing is reductive, i.e. “lossy”. The “lossiness” is adjustable and can be tailored to suit factors such as available bandwidth, available storage capacity or the complexity of the image.
BACKGROUND OF THE INVENTION
There has been slow progress in uniting the world of video and film with the power of the computer so that motion picture images—especially live video—can be quickly transmitted to users within a computer network. The advent of the computer network has brought forth tremendous communications capability. Where computers were once seen only as whirring number crunchers and processing machines, they are now also seen as potential vehicles for entertainment, advertising, information access and communication. The potential of video technology holds tantalizing opportunities for businesses, entrepreneurs and the public at large. In the workplace, the ordinary PC computer, a fixture on most office desks, could better maximize business resources with video conferencing and other interactive communications that link one worker or working group to another. Intraoffice computer networks could provide training, demonstrations, reports and news through broadcasts using one centralized computer to send live or taped video to workstations within the office or to linked office and customer sites. Previously, live visual communication links were not thought feasible without specialized video or television equipment.
The establishment of the Internet and its World Wide Web has also created demand for increased use of motion pictures in computer applications. Businesses see the Internet's vast network potential as a boon for interactive communications with the public at large. Entrepreneurs have envisioned and have even attempted live, on-line broadcasts of news, concerts and other events; attempts frustrated by the current limitation of real-time computer video technology. Further, as more people communicate via the World Wide Web, there is a natural incentive to create polished information access sites. Internet users come steeped in the heritage of television, movies and other forms of highly produced motion picture entertainment. These users imagine communicating with that same clarity, expediency and visual power and have come to expect such standards.
The potential for such real-time video communications exists, but until this point there has been great difficulty in transmitting motion picture image sequences, live video (television) and previously recorded film and video through the computer. The limitations on computer speed, memory and disk storage have expanded enough to make the storage of digitized film and video clips possible. However, the inordinate amount of data that must be transmitted to display a digitized moving picture sequence on the computer has been one factor preventing the widespread use of video and film in real time applications—especially those in which speed is imperative, like video conferencing, live news feeds and live entertainment broadcasts.
The data problem pertains to the nature of the digital computer and network hardware, the method by which a computer generates images and the processing that is needed to handle the many, many images that make up a motion picture sequence. Since its invention, motion picture technology has followed a process of presenting a rapid sequence of still images to give the impression of motion to the eye. A film is essentially a “flip book” of still camera photographs (i.e. frames) stored on a long strip used for playback through a projector. Current video technology follows the same frame-based concept as film, with some variation. A video camera rapidly collects a sequence of light images by scanning in horizontal movements across a light sensitive device and outputting a stream of “broadcast line” data which describes the image. Typically, a camera scans every other available line on the light sensitive device and alternates between line sets (odd and even) to create two, one-half frame “fields” which, when interlaced, form a full-frame image. Video has typically been recorded by video camera in analog format, but cameras which can record video in digital format are available. To transmit analog video via a computer, each frame or field input to the computer must be converted into a digital format or “digitized” for use. A computer screen is made up of thousands of pixels—programmable light units which can be instantly set and reset to emit light in one of the multitude of colors supported by the computer system. Typical monitors (ranging from 12-21 inches on the diagonal) contain matrices having resolutions of e.g. 640×512, 1,024×820, 1,280×1,024 and 1,600×1,280 pixels organized into rows of pixels stacked upon rows of pixels.
Each pixel in the screen display requires a color assignment from the computer to construct an image. Computer display controllers contain a large memory space, called a bitmap memory, which allocates an amount of memory for each pixel unit on the screen, e.g. 640×512, 1,024×820, 1,280×1,024, etc. (Other screens which process and work on displays in background have the same size can also be defined in the bitmap memory.) The computer drives the monitor and creates images via the bitmap memory, writing pixel color assignments to its memory locations and outputting signals to the monitor based on those assignments. The digitization process creates a set of digital pixel assignments for each frame or field of video input.
During video capture a computer executes an analog-to-digital “AID” conversion process—reading the provided film or video data (using specialized “frame grabber” hardware) and transforming the analog data into a stream of digital color codes, i.e. a bitmap data set for each frame or field of the motion picture. The data size of digital video stream depends upon the resolution at which the video was digitized. Resolution depends upon factors such as: i) frame resolution or frame size; ii) color depth; and iii) frame rate.
Frame resolution, or frame size, is the size in pixels of each digitized frame bitmap. Frame size does not need to be directly related to the monitor resolution in any computer configuration. Thus, while a monitor may have a resolution of 640×512 or 1,024×820, for example, a video can be digitized with a different resolution, such as 320×240. Video following the National Television Standards Committee (NTSC) standard for analog resolution digitizes to frames of 640×480, 320×240, 160×120 or other resolutions. Such video could well be displayed on a computer having a monitor resolution of 1,280×1,024 or other resolution.
Color depth specifies the number of bits used by the digitizer to describe the color setting for each pixel of a digitized frame bitmap. Computer pixel units typically output color following one of several color-generating systems. RGB (Red, Green, Blue) is one system which permits all the colors of an available palette to be expressed as combinations of different amounts of red, green and blue. Red, green and blue light elements or “color channels” are considered primary and can be blended according to color theory principles to form other colors. Electron guns fire beams to activate each of the light elements to different degrees and form colors that make up an image. The pixel assignments written to the bitmap memory control the settings used in the monitor to output colors using the pixels.
Computers vary greatly in the range of colors they can support, the number often depending on the size of the bitmap memory (an expensive item) and the
Aguera-Arcas Blaise
Migdal Alexander A.
Couso Jose L.
Kenyon & Kenyon
Viewpoint Corp.
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