Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Patent
1997-09-22
2000-07-11
Britton, Howard
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
348409, 348415, H04N 712, H04N 1102, H04N 1104
Patent
active
060883944
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a system and method for processing digital images.
In order to store or transmit a sequence of digital images efficiently it is desirable to compress the sequence so that the amount of data constituting the compressed sequence is less than that of the original sequence and to be able to recover the original sequence from the compressed sequence.
Compression can be utilised in, for example, video conferencing systems, video telephones or collaborative working systems. The users of such systems communicate both aurally and visually. The ability to see the other party imparts a more natural and interactive quality to the communication and allows the parties to more confidently evaluate their counter-part. In such systems large amounts of data have to be exchanged to update the images of the parties. Further, a sequence of compressed digital images requires less bandwidth to transmit as compared to a sequence of complete digital images.
Digital image compression also finds application in storing image data on mass storage media, such CD-ROMS or magnetic storage media, to reduce the amount of storage required to record a sequence of digital images.
Contiguous images generated, by image capture apparatus, such as a video camera, during a video conference or derived from a mass storage media are often substantially similar and vary only by small amounts. Accordingly, attempts have been made to use this property to reduce the amount of data which needs to be exchanged to support a video conference or processed to record a sequence of digital images. The reduction is achieved by exchanging or storing, for example, only selective areas of the digital images or eliminating the areas which are, as between contiguous images, constant.
U.S. Pat. No. 4,958,378 discloses a system and method which provides for the updating of a digital image according to differences between successive digital images. During a process of storing data in memory, the data currently stored in the memory is read and compared to data to be written into the same location. If the data is not the same, the discrepancy and location of the same is noted in a separate area of memory to be used for subsequent analysis. By utilising information gathered on the changed pixels, a video display need only update the changed data thereby reducing the amount of data to be manipulated. U.S. Pat. No. 4,958,378 compares all corresponding pixels as between successive images and only updates the preceding image when differences are identified therebetween.
WO 86/03922 discloses a video compression system and method which compares successive images to detect areas that have changed. A reference memory is used such that whenever an area of an image is detected to have changed, a determination is made to determine whether or not the changed picture area corresponds to information stored in a respective location of the reference memory; if the determination is positive, the transmitter outputs a code word instructing the receiver to retrieve image data from its respective reference memory; otherwise the changed picture area is transmitted to the receiver.
EP 0 303 322 A1 discloses a system for transmitting and/or storing data in a digitised form. Successive images, stored in respective memories, are compared and when difference between corresponding locations are identified, the image data of one memory is transmitted to a receiver and also used to update the image stored in the other memory.
One of the factors which determines the speed with which images can be updated is the number of pixels which have to be compared to effect an update.
Accordingly the present invention provides a method for processing a sequence of digital images comprising a current image and a subsequent image, said method comprising the steps of locations stored in said list to identify any locations which correspond to differences between said current image and said subsequent images, to update said current image, comparing.
The speed of processing of the curre
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Britton Howard
Diep Nhon T.
Drumheller Ronald L.
International Business Machines - Corporation
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