Facsimile and static presentation processing – Facsimile – Auxiliary signal
Reexamination Certificate
1997-08-22
2001-04-17
Nguyen, Anh-Vinh (Department: 2622)
Facsimile and static presentation processing
Facsimile
Auxiliary signal
C358S539000, C358S461000, C348S439100
Reexamination Certificate
active
06219157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image coding apparatus, and more particularly to an image coding apparatus which divides an image into blocks and codes it for each block.
2. Related Background Art
As one of coding methods for highly compressing an image signal while suppressing the deterioration of the image signal (high efficiency coding), a block coding method which divides an image into a plurality of blocks and codes it for each block has been known.
A representative method for coding an image signal in a block is a DCT (Discrete Cosine Transform) coding method.
In the DCT coding method, pixel data in a coding block are converted to DCT coefficient data representing a spatial frequency distribution by the DCT conversion and the DCT conversion coefficients are compressed in accordance with the fineness of the image and a visual characteristic.
The above high efficiency coding method enables the transmission at a low transmission rate but it includes a large affect by a transmission error.
Accordingly, it is necessary to countermeasure against the code error such as an error detection and correction code.
Particularly when the coded data is to be transmitted through an electromagnetic transformation system such as a magnetic recording or a BS communication system, the deterioration of the transmission quality is anticipated and hence the countermeasure for the code error is essential.
FIG. 1
shows a block diagram of an image transmission system by the high efficiency coding. An image signal to be transmitted is applied to an input terminal
10
. An A/D converter
12
digitizes an analog signal from the input terminal
10
and a block forming circuit
14
divides the image data from the A/D converter
12
to coding blocks of 8×8 pixels or 4×4 pixels and outputs them in the order of coding blocks. In
FIG. 2
, one frame of image is divided into blocks of 4×4 pixels.
A high efficiency coding circuit
16
highly efficiently codes the image data of the coding blocks from the block forming circuit
14
for each coding block. Thus, the information quantity is compressed. An error correction coding circuit
18
codes with an error correction function the image data compressed by the high efficiency coding circuit
16
. Namely, it calculates an error detection and correction parity and adds it to the compressed image data. The compressed image data which has been error correction coded by the error correction coding circuit
18
is outputted to a transmission line
20
.
The transmission line
20
may be a wired or wireless communication medium such as an optical fiber, a BS or a microwave, or a recording and reproducing system such as a magnetic tape, a magnetic disk, an optical disk or a semiconductor memory (for example, a digital video tape recorder (VTR) or a digital audio tape recorder (DAT)). The transmission rate may be several tens K bits/sec to several tens M bits/sec although it depends on the information quantity of the original image, the compression rate and the transmission time.
In a receiving station, the data transmitted through the transmission line
20
is temporarily stored in a memory
22
, and an error correction circuit
24
corrects an error in the transmitted data by the error correction parity of the transmission. The data stored in the memory
22
and having the error corrected is supplied to a high efficiency decoding circuit
26
, which expands the compressed image data.
For an encoding block including a transmission error which has not been corrected by the error correction circuit
24
, an interpolation circuit
28
interpolates by replacing it with the data of the encoding block at the same position in the previous frame (or field). The D/A converter
30
converts the output of the interpolation circuit
28
to an analog signal which is supplied to an output terminal
32
.
In the image transmission system shown in
FIG. 1
, it frequently happens that the transmission error created in the transmission line
20
exceeds an error correction ability of the error correction code by the error correction coding circuit
18
. As a result, the interpolation ability of the interpolation circuit
28
significantly affects to the quality of the reproduced image.
In a prior art system, the unit of processing of the interpolation circuit
28
is equal to the encoding block.
Namely, in the prior art interpolation method, the coding block having an incorrectable error is interpolated by using the coding block at the same image position in the immediately previous frame.
Accordingly, when the coding block is considerably large, the unit of processing of the interpolation is large and the effect of interpolation is reduced.
Further, since the interpolating block is spaced in time and space, it may be visually recognized.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image coding apparatus for reducing the deterioration of an image quality by an interpolation process done in decoding image coded data.
In order to achieve the above object, in one preferred embodiment of the present invention, the image coding apparatus comprises division means for dividing an image into a plurality of encoding blocks overlapped to each other, and coding means for coding the encoding blocks divided by the division means, for each block.
Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the appended claims.
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Gohda Makoto
Ishii Yoshiki
Shikakura Akihiro
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Anh-Vinh
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