Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2000-06-02
2004-02-24
Lee, Young (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06697431
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image signal decoder for decoding a coded image signal and converting to the previous image signal of the coding, and an image signal display system for decoding a coded image signal, converting to the previous image signal of the coding, and displaying the image signal on a display device, and a liquid crystal display (hereinafter, referred to as LCD) is used as the display device.
Examples of the known apparatuses which highly efficiently code or decode image signals are based on the standards such as the ISO/IEC 13818-2 “Coding of Audio, Picture, Multimedia and Hypermedia Information” and ISO/IEC DIS 11172 “Coding of Moving Pictures and Associated Audio ISO/IEC JTC1/SC29 WG11”.
A conventional apparatus for decoding the image signal (hereinafter is referred to as image signal decoder) will be described with reference to FIG.
6
.
FIG. 6
is a block diagram showing the example of the conventional apparatus for decoding the image signal. In
FIG. 6
, the output terminal of a variable length decoding section
601
to which a coded image signal is input is connected to the input terminal of an inverse quantization section
602
. The output terminal of the inverse quantization section
602
is connected to the input terminal of an inverse discrete cosine transform (hereinafter, referred to as DCT) section
603
. The output terminal of the inverse DCT section
603
is connected to the input terminal of a motion compensation section
604
. The output terminal of the motion compensation section
604
is connected to the input terminal of a frame buffer
605
. The output terminal of the frame buffer
605
is connected to the input terminal of the motion compensation section
604
. A decoded image signal is output from the output terminal of the motion compensation section
604
.
Decoding operation of the conventional image signal decoder configured above will be described. The input image signal is image data highly efficiently coded based on the ISO/IEC 13818-2 (hereinafter, referred to as coded data). On the input coded data, variable length decoding is performed by the variable length decoding section
601
. By the variable length decoding, the following pieces of information are extracted: motion vector information for motion compensation; coded image signal coefficient information; time information for playback stored in the header; and header information representative of the coding mode of each frame and the like.
The coefficient information includes quantized coefficient data and quantization scale data used for the quantization. On the coefficient information, inverse quantization is performed by the inverse quantization section
602
, so that the coefficient information is restored to the original DCT coefficient information which was converted into the coefficient information through quantization. On the DCT coefficient information, inverse DCT is performed by the inverse DCT section
603
, so that the DCT coefficient information is converted into the original pixel value information which was converted into the DCT coefficient information through orthogonal transformation.
When the pixel value information is that of a frame on which intra-frame coding is performed (hereinafter, referred to as I frame), the pixel value information is output without undergoing the motion compensation by the motion compensation section
604
. When the pixel value information is that of a frame on which forward predictive coding is performed (hereinafter, referred to as P frame) or of a frame on which bidirectional predictive coding is performed (hereinafter, referred to B frame), the pixel value information undergoes the motion compensation. That is, the converted pixel value information undergoes the motion compensation by the motion compensation section
604
by use of the motion vector information extracted by the variable length decoding section
601
, and are successively output in accordance with the time information for playback. Determining the coding mode of the frame of the pixel value information, which has been, converted by the inverse DCT section
603
(whether the frame is the I frame, the P frame or the B frame) is made based on the header information.
When the pixel value information output from the motion compensation section
604
is that of the I frame or the P frame, it is temporarily stored in the frame buffer
605
so that it is used for the next motion compensation. The frame buffer
605
is capable of storing a maximum of two frames of reference data so that bidirectionally predictive-coded data can be decoded. The frame buffer
605
has a ring buffer configuration in which when the newest frame data is input, it is stored by overwriting the frame data being oldest in time with it.
In this manner, an image signal coded by a hybrid coding method that uses both intra-frame coding and interframe coding is decoded into pixel value information and is output to the display device.
A conventional image signal display system for displaying a decoded image signal on a display device will be described with reference to FIG.
7
and FIG.
8
. This image signal display system is disclosed, for example, in Japanese Laid-open Patent Application No. Hei 10-11021.
FIG. 7
is a block diagram showing the configuration of the conventional image signal display system. In
FIG. 7
, the output terminal of a variable length decoding section
701
to which coded data is input is connected to the input terminal of an inverse quantization section
702
. The output terminal of the inverse quantization section
702
is connected to the input terminal of an inverse DCT section
703
. The output terminal of the inverse DCT section
703
is connected to the input terminal of a motion compensation section
704
. The output terminal of the motion compensation section
704
is connected to a frame buffer
705
, an image analyzation section
706
and an output signal correction section
707
. The output terminal of the frame buffer
705
is connected to the input terminal of the motion compensation section
704
. The output terminal of the image analyzation section
706
is connected to the input terminal of the output signal correction section
707
. An output image signal of the output signal correction section
707
is input to an image display section
708
.
FIG. 8
is a block diagram showing the configuration of the output signal correction section
707
. In
FIG. 8
, the image signal and signal level distribution information described later are input to a level correction section
801
. The output terminal of the level correction section
801
is connected to the input terminal of an RGB conversion section
802
. The output terminal of the RGB conversion section
802
is connected to a gamma correction section
803
.
Next, the operation of the conventional image signal display system will be described with reference to FIG.
7
. On the input coded data, variable length decoding is performed by the variable length decoding section
701
. By the variable length decoding, the following pieces of information are extracted: motion vector information for motion compensation; coded image signal coefficient information; time information for playback stored in the header; and header information representative of the coding mode of each frame and the like.
The coefficient information extracted by the variable length decoding section
701
includes quantized coefficient data and quantization scale data used for the quantization. On the coefficient information, inverse quantization is performed by the inverse quantization section
702
, so that the coefficient information is restored to the original DCT coefficient information which was converted into the coefficient information through quantization.
On the DCT coefficient information restored by the inverse quantization section
702
, inverse DCT is performed by the inverse DCT section
703
, so that the DCT coefficient information is restored to the original pixel value information which wa
Akin Gump Strauss Hauer & Feld L.L.P.
Lee Young
Matsushita Electric - Industrial Co., Ltd.
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