Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-08-12
2001-06-05
Le, Vu (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240020, C375S240080, C382S243000
Reexamination Certificate
active
06243418
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for coding a binary shape signal; and, more particularly, to a method and an apparatus for encoding a motion vector of the binary shape signal.
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 such object-oriented coding scheme is the so-called MPEG (Moving Picture Experts 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.
According to 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 have an access to and manipulate. A VOP can be referred to as an object and represented by a bounding rectangle whose width and height may be 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.
A VOP described in MPEG-4 includes shape information and texture information consisting of luminance and chrominance data, wherein the shape information represented in binary shape signals is referred to as an alpha plane. The alpha plane is partitioned into a plurality of binary alpha blocks, wherein each binary alpha block (BAB) has 16×16 binary pixels, each pixel being “binary” in the sense that it can take on only one of two predetermined value. Each of the binary pixels is classified as either a background pixel or an object pixel, wherein the background pixel located outside the object in the alpha plane is used to assign a binary pixel value, e.g., 0, while the object pixel inside the object is used to assign another binary pixel value, e.g., 255.
Each of the binary pixels in the BAB may be encoded by using a conventional bit-map-based shape coding method such as a context-based arithmetic encoding (CAE) discipline. For instance, in an intra mode, all binary pixels of a BAB are encoded by using an intra-CAE discipline to thereby generate an intra coded BAB, wherein a context value for each binary pixel of the BAB in the intra-CAE discipline is calculated by using binary pixel values of a predetermined number, e.g., 10, of binary pixels surrounding said each binary pixel in the BAB. In an inter mode, on the other hand, all binary pixels of a current BAB are encoded by using an inter-CAE discipline to thereby generate an inter encoded BAB, wherein a context value of each binary pixel of the current BAB in the inter-CAE discipline is calculated by using binary pixel values of a predetermined number, e.g., 4, of binary pixels surrounding said each binary pixel in the current BAB and binary values of a predetermined number, e.g., 5, of binary pixels within a bordered motion compensated BAB (see MPEG-4 Video Verification Model Version 7.0, International Organisation for Standardisation, Coding of Moving Pictures And Associated Audio Information, ISO/IEC JTC1/SC29/WG11 MPEG97/N1642, Bristol, April 1997, pp 28-30).
Meanwhile, in the conventional binary shape encoding discipline, a mode signal representing or characterizing a corresponding encoding condition for the BAB is encoded to improve the coding efficiency, thereby generating and then transmitting a corresponding encoded mode signal.
For example, if all of the binary pixels within a BAB are object pixels, instead of encoding the binary pixel values of the object pixels to generate encoded binary pixel values to be transmitted, it will be preferable to encode a mode signal indicating that all of the binary pixels within the BAB are object pixels. By employing the method described above, i.e., by transmitting the corresponding encoded mode signal as binary shape information for the BAB, it is possible to enhance the coding efficiency.
Referring to Table 1, there are 7 number of modes for the binary alpha information of a BAB according to a conventional mode coding discipline, wherein a motion vector difference for shape (MVD) of the BAB is a difference between a motion vector for shape (MV) and a motion vector predictor for shape (MVP); and the MVP is determined by using a conventional motion estimation discipline (see MPEG-4 Video Verification Model Version 7.0, International Organization for Standardization, Coding of Moving Pictures And Associated Audio Information, ISO/IEC JTC1/SC29/WG11 MPEG97/N1642, Bristol, April 1997, pp 20-23).
TABLE 1
Coding Modes
mode
coding condition
0
MVD==0 && no_update
1
MVD!=0 && no_update
2
all_0
3
all_255
4
intra-CAE
5
MVD==0 && inter-CAE
6
MVD!=0 && inter-CAE
Mode 0 represents that an MVD for a current BAB is zero and the current BAB can be represented by a most similar candidate BAB thereof, whereas mode 1 indicates that an MVD for a current BAB has a value other than zero and the current BAB can be represented by a most similar candidate BAB. For the current BAB of mode 0, only the mode signal is encoded; whereas the current BAB of mode 1 is represented by the mode signal and the MVD thereof. In determining “no_update”, a difference BAB is formed by a difference between each pixel of the most similar BAB and a corresponding pixel thereof in a current BAB and it is checked whether an error for any of 4×4 subblocks of 4×4 pixels included in the difference BAB is less than a predetermined threshold, an error of a subblock being, e.g., a sum of absolute pixel values within the subblock. If the error values of all the subblocks are equal to or less than the threshold, the current BAB is declared as of mode 0 or 1 depending on the value of the MVD thereof.
Similarly, if an error for any of the 4×4 subblocks is equal to or less than the threshold when the pixels in the current BAB are all changed to 0, the current BAB is coded as an “all
—
0” mode, i.e., mode 2. If an error for any of the 4×4 subblocks is equal to or less than the threshold when the pixels in the current BAB are all changed to 255, the current BAB is coded as an “all
—
255” mode, i.e., mode 3. For the current BAB of mode 2 or 3, only the mode signal is encoded for the current BAB. When a current BAB does not belong to any one of modes 0 to 3, either “intra-CAE” or “inter-CAE” is employed for the coding of the current BAB, whereas a current BAB of mode 4 is represented by the mode signal and intra-CAE coded BAB data. A current BAB of mode 5 is represented by the mode signal and inter-CAE coded BAB data; and a current BAB of mode 6 is represented by the mode signal, inter-CAE coded BAB data and an MVD.
Conventional binary shape encoding methods employing the conventional mode coding method described above are basically progressive coding methods. Namely, in the conventional binary shape encoding methods, an interlaced coding technique performed by using a field-based motion estimation method has not been u
Daewoo Electronics Co. Ltd.
Le Vu
Pennie & Edmonds LLP
LandOfFree
Method and apparatus for encoding a motion vector of a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for encoding a motion vector of a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for encoding a motion vector of a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2475894