Pulse or digital communications – Bandwidth reduction or expansion
Reexamination Certificate
1998-06-02
2001-07-10
Kelley, Chris (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
C375S240240
Reexamination Certificate
active
06259732
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for encoding interlaced macroblock texture information; and, more particularly, to a method and apparatus for padding interlaced texture information on a reference VOP on a texture macroblock basis in order to perform a motion estimation while using the interlaced coding technique.
DESCRIPTION OF THE PRIOR ART
In digitally televised 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 large amount of digital data therethrough, it is necessary 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 encoders as video-telephone and teleconference systems.
One of such techniques for encoding video signals for a low bit-rate encoding system is the so-called object-oriented analysis-synthesis coding technique, wherein 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.
One example of object-oriented coding scheme is the so-called MPEG(Moving Picture Express Group) phase 4(MPEG-4), which is designed to provide an audio-visual coding standard for allowing content-based interactivity, improved coding efficiency and/or universal accessibility in such applications as low-bit rate communication, interactive multimedia(e.g., games, interactive TV, etc.) and area surveillance(see, for instance, MPEG-4 Video Verification Model Version 7.0, International Organisation for Standardisation, ISO/IEC JTC1/SC29/WG11 MPEG97/N1642, Apr. 1997).
According to the MPEG-4, an input video image is divided into a plurality of video object planes(VOP's), which correspond to entities in a bitstream that a user can access and manipulate. A VOP can be referred to as an object and represented by a bounding rectangle whose width and height may be the smallest multiples of 16 pixels(a macroblock size) surrounding each object so that the encoder may process the input video image on a VOP-by-VOP basis, i.e., an object-by-object basis.
A VOP disclosed in the MPEG-4 includes shape information and texture information for an object therein which are represented by a plurality of macroblocks on the VOP, each of macroblocks having, e.g., 16×16 pixels, wherein the shape information is represented in binary shape signals and the texture information includes luminance and chrominance data.
Since the texture information for two input video images sequentially received has temporal redundancies, it is desirable to reduce the temporal redundancies therein by using a motion estimation and compensation technique in order to efficiently encode the texture information.
In order to perform the motion estimation and compensation, a reference VOP, e.g., a previous VOP, should be padded by a progressive image padding technique, i.e., a conventional repetitive padding technique. In principle, the repetitive padding technique fills the transparent area outside the object of the VOP by repeating boundary pixels of the object, wherein the boundary pixels are located on the contour of the object. It is preferable to perform the repetitive padding technique with respect to the reconstructed shape information. If transparent pixels in a transparent area outside the object can be filled by the repetition of more than one boundary pixel, the average of the repeated values is taken as a padded value. This progressive padding process is generally divided into 3 steps: a horizontal repetitive padding; a vertical repetitive padding and an exterior padding(see, MPEG-4 Video Verification Model Version 7.0)
While the progressive padding process as described above may be used to encode progressive texture information which has a larger spacial correlation between rows on a macroblock basis, the coding efficiency thereof may be low if the motion of an object within a VOP or a frame is considerably large. Therefore, prior to performing the motion estimation and compensation on a field-by-field basis for an interlaced texture information with the fast movement such as a sporting event, horse racing and car racing, an interlaced padding process may be preferable to the progressive padding process, wherein in the interlaced padding process a macroblock is divided into two field blocks and padding is carried out on a field block basis.
However, if all field blocks are padded without considering their correlation between fields, certain field blocks may not be properly padded.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to provide a method and apparatus capable of padding the interlaced texture information considering its correlation between fields.
In accordance with the invention, there is provided a method for encoding interlaced texture information on a texture macroblock basis through a motion estimation between a current VOP and its one or more reference VOP's, wherein each texture macroblock of the current and the reference VOP's has M×N defined or undefined texture pixels, M and N being positive even integers, respectively, the method comprising the steps of:
(a) detecting whether said each texture macroblock of each reference VOP is a boundary block or not, wherein the boundary block has at least one defined texture pixel and at least one undefined texture pixel;
(b) dividing the boundary block into two field blocks, each field block having M/2×N texture pixels;
(c) extrapolating the undefined texture pixels of each field block based on the defined texture pixels thereof to generate an extrapolated boundary block for said two field blocks; and
(d) if the boundary block has an undefined field block and a defined field block, padding the undefined field block based on the defined field block, wherein the undefined field block and the defined field block represent one field block having the undefined texture pixels only and the other field block having at least one defined texture pixel, respectively.
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Daewoo Electronics Co. Ltd.
Kelley Chris
Pennie & Edmonds LLP
Wong Allen
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