Image analysis – Image compression or coding – Contour or chain coding
Reexamination Certificate
1995-04-17
2001-07-10
Patel, Jay (Department: 2723)
Image analysis
Image compression or coding
Contour or chain coding
C348S026000, C356S370000, C382S241000, C382S250000
Reexamination Certificate
active
06259818
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a contour approximation apparatus for use in a video signal encoder; and, more particularly, to a contour approximation apparatus for reconstructing a contour of an object.
DESCRIPTION OF THE PRIOR ART
In digital television systems such as video-telephone, teleconference and high definition television systems, a large amount of digital data is needed to define each video frame signal since a video line signal in the video frame signal comprises a sequence of digital data referred to as pixel values. Since, however, the available frequency bandwidth of a conventional transmission channel is limited, in order to transmit the substantial amount of digital data therethrough, it is inevitable to compress or reduce the volume of data through the use of various data compression techniques, especially, in the case of such low bit-rate video signal encoder as video-telephone and teleconference system.
One of such methods for encoding video signals for a low bit-rate encoding system is the so-called object-oriented analysis-synthesis coding technique(see Michael Hötter, “Object-Oriented Analysis-Synthesis Coding Based on Moving Two-Dimensional Objects”, Signal Processing: Image Communication 2, 409-428(1990)).
According to the object-oriented analysis-synthesis coding technique, an input video image is divided into objects; and three sets of parameters for defining the motion, contour and pixel data of each object are processed through different encoding channels.
Specifically, in processing a contour image of an object, contour information is important for the analysis and synthesis of the object shape. The classical coding method for representing the contour information is the chain coding. The chain coding method, however, requires a substantial amount of bits for the representation thereof although there is no loss in the contour information.
In this regard, there have been proposed several methods to approximate contours such as polygonal approximation and B-spline approximation, etc. One of the disadvantages in the polygonal approximation is the rough representation of the contour image. The B-spline approximation is, on the other hand, capable of representing the contour image more precisely: however, it requires high-order polynomials to reduce approximation errors, thereby increasing the overall computational complexity of the video encoder.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the invention to provide a novel contour approximation apparatus by employing a polygonal approximation and discrete sine transform(DST), thereby providing a representation of an contour image with an increased accuracy and a reduced overall computational complexity.
In accordance with the invention, there is provided a contour approximation apparatus, for use in a video signal encoder, for representing a contour image of an object, which comprises: means for determining a number of vertices on the contour image; means for fitting the contour image with a plurality of line segments to provide a polygonal approximation of the contour image, each of the line segments joining two neighboring vertices; means for providing N sample points for each of the line segments, said N sample points being equi-spaced on each of the line segments; means for calculating an error for each of the N sample points on each of the line segments to produce a set of errors for each of the line segments, each of the errors of the set representing the distance between said each of the N sample points and the contour image; means for converting each set of errors into a set of discrete sine transform coefficients; and means for generating the set of discrete sine transform coefficients into a set of quantized transform coefficients.
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Kim Jin-Hun
Kim Jong-Lak
Anderson Kill & Olick PC
Daewoo Electronics Co. Ltd.
Patel Jay
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