Electrical computers and digital processing systems: multicomput – Computer-to-computer data modifying – Compressing/decompressing
Reexamination Certificate
1999-05-19
2001-10-30
Lim, Krisna (Department: 2153)
Electrical computers and digital processing systems: multicomput
Computer-to-computer data modifying
Compressing/decompressing
C348S394100, C348S403100, C707S793000
Reexamination Certificate
active
06311224
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of data compression. More specifically, the present invention relates to the art of dynamically scaling data compression.
2. Background Information
A number of individual lossless and lossy data compression techniques are known in the art. Examples of lossless data compression include Run Length Limited Encoding (RLL), and V.42bis, a standard promulgated by the International Telecommunication Union—Technical Standard Section (ITU-T), whereas examples of lossy data compression include data compression standards promulgated by Moving Picture Engineer Guild (MPEG).
Lossless data compression techniques are known to have been integrated as part of the data communication services offered by a system to all applications, regardless of the nature of the applications, whereas lossy data compression techniques are known to have been integrated as part of device services designed for certain types of applications, e.g. video applications. In the area of data communication, it is also known that some systems supporting multiple data compression techniques are further equipped to negotiate on the specific data compression technique to be employed for a particular data communication session. These negotiations are known to be conducted without regard to the workloads of the respective systems. In other words, there is no attempt to scale the amount of compression to be performed based on the workloads of the communicating systems.
Experience has shown that such ability to dynamically scale the amount of data compression being performed, depending on the workloads of the communicating systems is highly desirable in certain applications, e.g. in the area of network computing. in addition to scalability, experience has also shown that it is desirable to maintain symmetry on the amount of computations required for compression and decompression, as the amount of compression is scaled. In other words, whether it is minimal compression or maximum compression, the amount of computations required for compression and decompression are roughly the same. Furthermore, experience has also shown that it is desirable to exploit certain application characteristics to enhance compression/decompression efficiencies, even for lossless data compression.
In view of these and other desired results, the subject scalable data compression methods and apparatuses are invented.
SUMMARY OF THE INVENTION
An apparatus is provided with operating logic for performing a number of data compression operations, and control logic for dynamically selecting one or more of the data compression operations, and have the selected data compression operation(s) performed on a set of data, in accordance with a set of scaling policies. In one embodiment, the scaling policies include policies that take into account the processing capacity of the apparatus, and the current backlog for processing capacity, and the data compression operations include run length limited encoding of the set of data, differential encoding between current and a preceding set of data, and encoding of data values with cache indices.
In one embodiment, the apparatus is a server serving a number of networked client computing devices, wherein the server is programmed with programming instructions implementing the operating and control logic. The processing capacity is determined using the processor type of the server's processor, and the backlog level is determined using the number of threads waiting for execution.
In one application, the data being compressed are pixel values of display data, the unit of data being analyzed is a line of display data, and the data values cached are the most recently used pixel values.
REFERENCES:
patent: 5621660 (1997-04-01), Chaddha et al.
patent: 5745379 (1998-04-01), Lewis
patent: 5748904 (1998-05-01), Huang et al.
patent: 5764910 (1998-06-01), Shachar
patent: 5768537 (1998-06-01), Butter et al.
patent: 5964842 (1999-10-01), Packard
Blakely , Sokoloff, Taylor & Zafman LLP
Lim Krisna
Network Computing Devices, Inc.
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