Browse Prior Art Database

Improved Data Compression Technique for the Transmission of Bitmap Graphics

IP.com Disclosure Number: IPCOM000118453D
Original Publication Date: 1997-Feb-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Fehr, C: AUTHOR [+2]

Abstract

Disclosed is a data compression technique which, for instance, allows multiple users to synchronously work with a single user application (application sharing) in a desktop conferencing system without need to change the application code. The major problem is that the information, particularly bitmaps, to be distributed among the used computer systems in order to achieve the described functionality requires a very high bandwidth of the underlying communication network. Using such a system over low bandwidth wide area networks thus becomes impractical.

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Improved Data Compression Technique for the Transmission of Bitmap
Graphics

      Disclosed is a data compression technique which, for instance,
allows multiple users to synchronously work with a single user
application (application sharing) in a desktop conferencing system
without need to change the application code.  The major problem is
that the information, particularly bitmaps, to be distributed among
the used computer systems in order to achieve the described
functionality requires a very high bandwidth of the underlying
communication network.  Using such a system over low bandwidth wide
area networks thus becomes impractical.

      In a teleconferencing environment, relatively small changes of
application window contents are often observed.  Most changes are
caused by a moved cursor within the presentation window of a text
processor.  Thereupon, for most of the large changes, e.g., those
caused by shifting an entire application window on the desktop, there
exists window sections which are not amended.

      It is, therefore, proposed to apply known delta calculation and
compression algorithms to the transferred bitmap information on both
the sender and the receiver side.  Accordingly, on the receiver side,
the received information is decompressed and subtracted from a
previous data generation.

      The following code example illustrates the proposed technique
in more detail.  The following two bit patterns are presumed:
  Bit pattern of first generation:       001101110110011
  Bit pattern of second generation:      001111110110011

      Both patterns diffe...