Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2001-10-11
2004-11-30
Lee, Young (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06826231
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the related Japanese Patent Application No. 2000-312309, filed Oct. 12, 2000, the entire contents of which are incorporated herein by reference.
The present application also contains the subject matter related to concurrently filed U.S. patent applications by Takahashi, et al. entitled “Motion Vector Conversion Method and Conversion A pparatus”, based upon and claims the benefit of priority from the related Japanese Patent Application No. 2000-310836.
The related applications are assigned to the same assignee as the present application.
BACKGROUND OF THE INVENTION
This invention relates to a motion vector conversion method and a motion vector conversion apparatus for use with an image information conversion method and an image information conversion apparatus wherein the MPEG system is used to receive, through a satellite broadcast, a cable TV or network media such as the Internet, or process, on such storage media as an optical or magnetic disk or a flash memory, a bit stream representative of image information compressed by orthogonal transform such as discrete cosine transform and motion compen sation.
In recent years, an apparatus which complies with the MPEG system wherein image information is treated as digital data and compressed by orthogonal transform such as discrete cosine transform and motion compensation maki ng use of the redundancy unique to the image information in order to transmit and store the information with a high efficiency has been and is being popularized in both information distribution of broadcasting stations and so forth and information re cept ion in general homes.
Particularly, the MPEG2 (ISO/IEC 13818-2) is defined as a general purpose image coding system and is a standardized system which covers both interlaced scanned images and progressively scanned images as well as standard resolution images and high resolution images. It is estimated that the MPEG2 is used for a wide variety of applications for professi onal use and for consumer use also in the future. The use of the compression system of MPEG2 can achieve a high compress ion ratio and a good picture quality, for example, for both interlaced scanned images of a standard resolution having 720×480 pixels or interlaced scanned images of a high resolution having 1,920×1,088 pixels at 4 to 8 Mbps by allocating a code rate (bit rate) of 18 to 22 Mbps.
Although MPEG2 is directed principally to high picture duality coding suitable for broadcasting, it is not ready for a lower code rate (bit rate) than that of MPEG1, that is, it is not ready for a coding system of a higher compression ratio. It is considered that the need for such a coding system as just described increases in the future a popularization of portable terminals proceeds. In order to cope with the need, standardization of the MPEG4 coding system has been performed. The standards for the MPEG4 image codi ng system have been approved as international standards as ISO/IEC 14496-2 in December 1998.
Meanwhile, it is requested to convert a bit stream which represents image compression information of MPEG2 coded once for digital broadcasting into another bit stream representative of image compression information of MPEG4 of a lower code rate (bit rate) which is more suitable for processing on a portable terminal or the like.
An example of a related art image information conversion apparatus which satisfies the request is shown in FIG.
1
. Referring to
FIG. 1
, the image information conversion apparatus shown converts a bit stream representative of image compression information of MPEG2 inputted thereto into another bit stream representative of image compression information of MPEG4. In particular, the inputted bit stream representative of image compression information of MPEG2 is decoded by an MPEG2 image information decoding apparatus
1
. The decoded image signal is transmitted to a resolution frame rate conversion apparatus
2
, by which it is converted into an image signal having an arbitrary different resolution and frame rate. The image signal obtained by the conversion is inputted to an MPEG4 image information coding apparatus
3
, by which it is coded into and outputted as a bit stream representative of image compression information of MPEG4.
In the related art image information conversion apparatus, as seen in
FIG. 1
, the image signal decoded in accordance with the MPEG2 decoding system is coded by the MPEG4 image information coding apparatus, and a bit stream representative of image compression information of MPEG4 is outputted. The MPEG2 image information decoding apparatus
1
may be configured such that it performs a decoding process for both horizontal and vertical direction components using all eighth order DCT (discrete cosine transform) coefficients of the bit stream representative of the inputted image compression information of MPEG2. However, the MPEG2 image information decoding apparatus
1
may be configured otherwise such that it performs a decoding process wherein all eighth order coefficients in the vertical direction are used but only four lower frequency ones of eighth order coefficients in the horizontal direction are used (the decoding process is hereinafter referred to as 4×8 down decoding) or another decoding process wherein only four lower frequency ones of eighth order coefficients in both the horizontal direction and the vertical directions are used (the decoding process is hereinafter referred to as 4×4 down decoding) in order to reduce the arithmetic operation amount and the video memory capacity and simplify down sampling processing in the following stage while suppressing the picture quality deterioration to the minimum.
According to such a related art method as described above, when the MPEG4 image information coding apparatus codes an image signal inputted thereto, the arithmetic opera tion processing amount for detecting a motion vector occupies approxima tely 60 to 70% of the total arithmetic operation processing amount. This gives rise to such problems that real time processing of an image becomes difficult, that a time delay occurs and that a large apparatus scale is required.
As a countermeasure for solving such problems as just described, the inventors have proposed an image information conversion apparatus shown in FIG.
2
. Particularly, the inventors have filed the following applications for patent in Japan relating to the image conversion apparatus shown in FIG.
2
.
Japanese Patent Application No. 2000-129002 “Motion Vector Conversion Apparatus and Method”: This application discloses a technique wherein information of each of macro blocks of MPEG2 is used to select a motion vector of MPEG 2 of that one of macro blocks of MPEG2 which exhibits the highest coding efficiency to produce a motion vector of MPEG4.
Japanese Patent Application No. 2000-132915 “Motion Vector Conversion Apparatus and Method”: This application discloses a technique wherein information of each of macro blocks is used to select, based on lengths of motion vectors, a motion vector of MPEG2 of that one of macro blocks of MPEG2 which exhibits the highest coding efficiency to produce a motion vector of MPEG4.
Japanese Patent Application No. 2000-191616 “Motion Vector Conversion Apparatus and Method”: This application discloses a technique wherein information of each of macro blocks is used to produce a P-VOP motion vector for an intra-macro block of MPEG2.
FIGS. 3A and 3B
illustrate a correlation between a motion vector in a bit stream representative of image compression information of MPEG2 and a motion vector in a bit stream representative of image compression information of MPEG4 and particularly show images of a current frame before and after resolution conversion, respectively. When the resolution of an image is converted, a horizontal component of a motion vector from the position in the preceding frame to a position in the current frame after the conversion can be determined from
Sato Kazushi
Suzuki Teruhiko
Takahashi Kuniaki
Kananen Ronald P.
Lee Young
Rader & Fishman & Grauer, PLLC
Sony Corporation
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