Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-06-18
2001-07-03
Britton, Howard (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C348S699000, C382S243000
Reexamination Certificate
active
06256345
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for coding interlaced shape information; and, more particularly, to a method and apparatus for effectively coding the interlaced shape information by modifying a coding mode of the interlaced shape information based on field_no_update estimation.
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 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.
A VOP described in MPEG-4 includes shape information and texture information having 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 conventionally 16×16 binary pixels. Each of the binary pixels is classified as either a background pixel or an object pixel, wherein the background pixel is located outside the object in the alpha plane and represented by a binary pixel value, e.g., 0, while the object pixel is positioned inside the object and represented by 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) technique and a motion estimation and compensation technique. For instance, in an intra-mode, all binary pixels of a current BAB are encoded by using an intra-CAE technique to thereby generate intra-CAE data, wherein a context value for a binary pixel of the BAB is calculated based on a predetermined number, e.g., 10 of binary pixels around the binary pixel in the BAB. In an inter-mode, all binary pixels of a current BAB are encoded by using an inter CAE technique to thereby generate inter-CAE data, wherein a context value of a binary pixel of the current BAB is calculated based on, e.g., 4 binary pixels surrounding the binary pixel in the current BAB and, e.g., 5 binary pixels in a reference BAB, e.g., 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).
In the conventional binary shape encoding scheme, a BAB_type. for representing or characterizing an encoding type of a BAB is employed to improve the coding efficiency. For example, if all binary pixels within a BAB are object pixels, a BAB_type indicating that all the binary pixels within the BAB are object pixels is encoded and transmitted to a decoder of a receiving end in lieu of pixel data itself. Therefore, it is possible to enhance the coding efficiency by transmitting the BAB_type as the basic binary shape information for the BAB.
TABLE 1
BAB_type
semantics
0
MVDs=0 and no_update
1
MVDs≠0 and no_update
2
transparent (all_0)
3
opaque (all_255)
4
intra_CAE
5
MVDs=0 and inter_CAE
6
MVDs≠0 and inter_CAE
Referring to Table 1, there are illustrated 7 BAB_types for a BAB conventionally employed in the art, wherein a motion vector difference for shape (MVDs) is a difference between a motion vector for shape (MVs) and a motion vector predictor for shape (MVPS) of a BAB. (see MPEG-4 Video Verification Model Version 7.0, supra, pp 20-23).
In Table 1, a BAB_type ‘0’ represents that the MVDs for a BAB is zero and the BAB corresponds to no_update, i.e., the BAB can be replaced by a most similar candidate BAB thereof, whereas a BAB_type ‘1’ describes that the MVDs for a BAB has a value other than zero and the BAB can be replaced by a most similar candidate BAB thereof. A BAB of the BAB_type ‘0’ can be represented by only the BAB_type itself while a BAB of the BAB_type ‘1’ can be represented by both the BAB_type and the MVDs thereof.
A BAB_type ‘2’ represents that a BAB is transparent, i.e., all the binary pixels within the BAB can be treated as background pixels, whereas a BAB_type ‘3’ shows that a BAB is opaque, i.e., all the binary pixels within the BAB can be represented by object pixels. No other data than the BAB_type is required in representing the BAB of the BAB_type ‘2’ or ‘3’.
A BAB_type ‘4’ implies that all the binary pixels within a BAB have been encoded by intra-CAE; a BAB_type ‘5’ denotes that the MVDs is defined as zero and all the binary pixels within a BAB have been encoded by inter-CAE; and a BAB_type ‘6’ signifies that the MVDs has a value other than zero and all the binary pixels within a BAB have been encoded by inter-CAE. A BAB of the BAB_type ‘4’ or ‘5’ is represented by the BAB_type ‘4’ or ‘5’ followed by the intra-CAE or the inter-CAE data. A BAB of the BAB_type ‘6’ requires the MVDs and the inter-CAE data in addition to the BAB_type itself.
Referring to
FIG. 1
, there is illustrated a conventional apparatus for adaptively encoding interlaced shape information of a VOP on a frame BAB basis and a field BAB basis, wherein a frame BAB includes M×N pixels therein and can be divided into a top and a bottom field BAB's, each having M/2×N pixels, M being an even positive integer and N being a positive integer. Typically, M and N have a value of 16 and the top and the bottom field BAB's are constituted by odd and even rows of pixels of the frame BAB, respectively. The interlaced shape information of a VOP is inputted to a frame detection circuit
10
on the frame BAB basis. The frame detection circuit
10
examines whether a current frame BAB having, e.g., 16×16 binary pixels can be treated as either transparent or opaque. Typically, if an error generated when the pixels within the current frame BAB are replaced with all 0's or all 255's is less than a predetermined threshold, the current frame BAB is determined as transparent or opaque. If the current frame BAB is determined as either transparent or opaque, the BAB_type ‘2’ or ‘3’ is provided to a transmitter(not shown) via a multiplexor (MUX)
60
and the encoding process of the current frame BAB is terminated.
If the current frame BAB is neither transparent nor opaque, the interlaced shape information of the current frame BAB is provided to an encoding_type decision circuit
20
and a switch
30
. The enco
Britton Howard
Daewoo Electronics Co. Ltd.
Pennie & Edmonds LLP
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