United States Patent  8,255,461 Liu ,   et al.  August 28, 2012 

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Efficient transmission of changing images using image caching

Abstract In one embodiment, a display of a source device is shared with one or more viewer devices, e.g., of an online collaborative computing session, and the display is divided into a plurality of identified blocks. In response to changes in the display, the source device determines an outer boundary of an updated region affected by the change, where the updated region defines a plurality of "update blocks" of the identified blocks within the outer boundary. Images within each update block may then be compared to a previous version of the corresponding update block to determine if that individual update block is affected by the change. Any unchanged update blocks may be converted to an easily compressible image, and the source device may then compress and transmit the updated region to the viewer devices, where the transmitted updated region has instructions to use previous versions of unchanged converted update blocks.

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Inventors:  Liu; Guangbing (Sunnyvale, CA), Sheng; Hailei (Fremont, CA), Gu; Jiannong (Sunnyvale, CA)  Assignee: Cisco Technology, Inc. (San Jose, CA)   Appl. No.:  12/399,089 Filed:  March 6, 2009