Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-06-02
2001-10-30
Kelley, Chris (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06310916
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for coding a video signal; and, more particularly, to a method and an apparatus for effectively encoding texture information of the video signal by determining a coding type of the texture information based on the texture information and its corresponding shape information.
DESCRIPTION OF THE PRIOR ART
In digital video systems such as video-telephone and teleconference systems, a large amount of digital data is needed to define each video signal since the video 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 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 an 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 schemes 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 a 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 Organization for Standardization, Coding of Moving Pictures and Associated Audio Information, ISO/IEC JTC1/SC29/WG11 MPEG97/N1642, Bristol, April 1997).
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 access and manipulate. A VOP can be 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 processes the input video image on a VOP-by-VOP basis.
A VOP disclosed in 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 the macroblocks having, e.g., 16×16 pixels. Each of the macroblocks on the VOP can be classified into one of a background, a boundary and an object macroblocks. The background macroblock contains only background pixels located outside an object in the VOP; the boundary macroblock includes at least one background pixel and at least one object pixel located inside the object; and the object macroblock has only object pixels. The shape information is encoded by using, e.g., a context-based arithmetic encoding (CAE) technique on a macroblock basis and the texture information is encoded through the use of conventional encoding techniques such as DCT (discrete cosine transform), quantization and VLC (variable length coding) techniques on the macroblock basis. Specifically, the DCT process for transforming the texture information is performed on a DCT-block basis, wherein a macroblock is divided into 4 DCT-blocks of 8×8 pixels.
From the DCT and the quantization processes, one DC component and a multiplicity of AC components are produced for each DCT-block. However, if all values of texture information for a DCT-block are constant, there is no corresponding nonzero AC component for the DCT-block. Therefore, CBPY (coded block pattern type) information has been proposed to represent whether a DCT-block has at least one corresponding non-zerc AC component. To be more specific, if there exists at least one non-zero AC component corresponding to a DCT-block, the CBPY information obtains a bit of, e.g., “1”, and, if otherwise, a bit of, e.g., “0”. Accordingly, a decoding part can tell the existence of non-zero AC components for a corresponding DCT-block by simply detecting the CBPY information transmitted thereto through a transmission channel without any further information for the corresponding DCT-block and before encoded texture information for the corresponding DCT-block is transmitted thereto.
Conventionally, in order to encode the texture information for the VOP, the texture information on each of the macroblocks is processed by adaptively using a progressive and an interlaced coding techniques to thereby enhance the coding efficiency. Therefore, DCT_type information representing a coding condition, i.e., a DCT_type, of the texture information is employed and the DCT_type is determined on the macroblock basis using the texture information. For example, a video signal encoder determines an appropriate DCT_type for a macroblock by comparing a spatial correlation between pixel rows in the macroblock which are re-formed to a progressive or an interlaced type macroblock according to the progressive or the interlaced coding technique. If the progressive coding technique is determined to be more effective, the DCT_type information on the macroblock will have a bit of, e.g., “0”, and, if otherwise, a bit of, e.g., “1”.
After the DCT_type for a macroblock is determined based on the texture information, the CBPY information on the macroblock is obtained from quantized DCT results which are derived by performing the DCT and the quantization processes for the texture information on the macroblock in the determined DCT_type thereof.
For instance, if a macroblock is a background macroblock, its texture information is not encoded and, therefore, its DCT_type and CBPY information are not generated.
If the macroblock is an object macroblock, either the progressive or the interlaced coding technique can be selected based on the texture information on the macroblock and, therefore, the DCT_type information of the object macroblock representing the selected coding technique is produced. Also, the CBPY information of the object macroblock will have 4-bit data, the respective bits corresponding to the respective 4 DCT-blocks within the macroblock, since the object macroblock has 4 non-transparent DCT-blocks, wherein a non-transparent DCT-block has a DCT-block size and contains at least one object pixel to be encoded.
On the other hand, if the macroblock is a boundary macroblock, either the progressive or the interlaced coding technique is also chosen based on the texture information on the macroblock. In addition, the boundary macroblock can include both a transparent DCT-block and a non-transparent DCT-block together, wherein the transparent DCT-block has only background pixels therein and need not be encoded. Consequently, the CBPY information corresponding to the boundary macroblock may have i-bit data, i being a positive integer ranging from 1 to 4, and the respective bits corresponding to the respective non-transparent DCT-blocks in the macroblock.
Referring to
FIGS. 4A
to
4
C, there are provided various examples of boundary macroblocks which are classified into two different types, i.e., a progressive and an interlaced type macroblocks. In the drawings, macroblocks P
1
to P
3
, which represent progressive type macroblocks, respectively, are reformed to interlaced type macroblocks I
1
to I
3
including top- and bottom-field DCT-blocks IT
1
and IB
1
to IT
3
and IB
3
, respectively. Therefore, in the progressive coding technique, the macroblock is encoded based on the progressive type macroblock while it is encoded by using the interlaced type macroblock including the top- and bottom-field DCT-blocks in the interlaced coding technique.
As can be seen in
FIG. 4A
, since both the progressive type macroblock P
1
and its interlaced type macroblock I
1
contain only non-transparent DCT-blocks, the corresponding CBPY informati
Daewoo Electronics Co. Ltd.
Kelley Chris
Pennie & Edmonds LLP
Wong Allen
LandOfFree
Method and apparatus for encoding a video signal 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 video signal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for encoding a video signal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2564885