Electrical computers and digital processing systems: multicomput – Computer-to-computer protocol implementing – Computer-to-computer data framing
Reexamination Certificate
1996-10-09
2003-07-01
Burgess, Glenton B. (Department: 2153)
Electrical computers and digital processing systems: multicomput
Computer-to-computer protocol implementing
Computer-to-computer data framing
C709S247000
Reexamination Certificate
active
06587885
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fixed length cell handling type image communication method as well as a transmission apparatus for fixed length cell handling type image communication and a reception apparatus for fixed length cell handling type image communication, and more particularly to a fixed length cell handling type image communication method as well as a transmission apparatus for fixed length cell handling type image communication and a reception apparatus for fixed length cell handling type image communication suitable for use with image communication which makes use of an ATM network which handles a fixed length cell called ATM (Asynchronous Transfer Mode) cell.
2. Description of the Related Art
FIG. 53
shows in block diagram an example of an image communication system which makes use of an ATM network. Referring to
FIG. 53
, the image communication system shown includes an ATM exchange
101
, a plurality of (two in
FIG. 53
) ATM image communication apparatus
102
, a plurality of (two in
FIG. 53
) cameras
104
for image communication, and a plurality of (two in
FIG. 53
) television sets
105
.
The cameras
104
and the television sets
105
are normally connected to the respective ATM image communication apparatus
102
and accommodated in the ATM exchange
101
via respective user network interfaces (UNIs) including a plurality of channels. However, they may be accommodated directly in the ATM exchange
101
via an ATM image communication section
1012
in the ATM exchange
101
, for example, like a camera
104
′ and a television set
105
′.
In the image communication system constructed in such a manner as described above, an image from each camera
104
(or
104
′) is first subject to required processing such as image compression, conversion into an ATM cell (fixed length cell) and so forth by a corresponding one of the ATM image communication apparatus
102
(or ATM image communication section
1012
) and then sent out as an ATM cell
106
to the ATM exchange
101
. Then, an ATM switch section
1011
of the ATM exchange
101
is switched in response to a portion of a frame format of the ATM cell
106
which represents information of a destination of data so that the data are outputted to the desired transfer destination (in this instance, to one of the television sets
105
and
105
′).
In the following, an image compression process (system), an ATM cell transferring process and so forth of the ATM image communication apparatus
102
or the ATM image communication section
1012
described above will be described in detail.
1. Image Compression Method
1-1. Outline
Generally, a compression method which utilizes a JPEG (Joint Photograph coding Experts Group) algorithm is well known as an image compression method. The JPEG algorithm has been produced as standards for image compression of the international standardization group JPEG.
FIG. 54
shows in block diagram an example of a construction of the ATM image communication apparatus
102
(or ATM image communication section
1012
) which utilizes a JPEG system. Referring to
FIG. 54
, the ATM image communication apparatus
102
shown includes a transmission section
111
and a reception section
112
. The transmission section
111
includes an 8×8 blocking section
113
, a discrete cosine transform section
114
, a quantization section
115
, a quantization table
116
and a JPEG coding section
117
. The reception section
112
includes a JPEG decoding section
121
, a dequantization section
122
, a quantization table
123
, an inverse discrete cosine transform section
124
and an 8×8 deblocking section
125
.
In the transmission section
111
, the 8×8 blocking section
113
performs 8×8 blocking of image information for one field, that is, for image information for one screen. The discrete cosine transform section
114
performs discrete cosine transform (DCT) for extracting frequency components representative of characteristics of fineness of an image for each block of image information blocked by the 8×8 blocking section
113
. It is to be noted that image information generally includes higher frequencies at portions of finer patterns and includes lower frequencies at portions of rougher patterns.
The quantization section
115
performs quantization for each block, for which discrete cosine transform has been performed by the discrete cosine transform section
114
, using the quantization table
116
. Upon such quantization, the compression ratio of image data can be adjusted using a parameter called scaling factor SF. The JPEG coding section
117
performs JPEG coding processing by coding each block quantized by the quantization section
115
and outputs compressed data.
Meanwhile, in the reception section
112
, the JPEG decoding section
121
, dequantization section
122
, quantization table
123
, inverse discrete cosine transform section
124
and 8×8 deblocking section
125
perform processing reverse to that performed by the JPEG coding section
117
, quantization table
116
, quantization section
115
, discrete cosine transform section
114
and 8×8 blocking section
113
described above, respectively. Consequently, the reception section
112
can regenerate original image data from compressed data transmitted thereto as JPEG coded compressed data as described above.
In the ATM image communication apparatus
102
(or ATM image communication section
1012
) having the construction described above, input image data for one field, that is, original image information for one screen, is subject to blocking processing in units of vertical and horizontal 8×8 pixels (8×8 blocking) by the 8×8 blocking section
113
. Further, each block obtained by such blocking is subject to discrete cosine transform by the discrete cosine transform section
114
so that frequency components included in the block are extracted.
Thereafter, each block discrete cosine transformed in this manner is quantized by the quantization section
115
using the quantization table
116
so that the image is compressed. The scaling factor SF is adjusted to adjust the compression ratio then. It is to be noted that, where an input image is the same, generally a decrease of the scaling factor SF decreases the compression ratio and increases the amount of image data after compression, but an increase of the scaling factor SF increases the compression ratio and decreases the amount of image data after compression.
Further, when image compression is performed, generally the amount of data after compression is large with an image of a fine pattern, but is small with an image of a rough pattern. Further, where an image is the same, if the compression ratio is raised to decrease the amount of data after compression by means of the scaling factor SF, then the picture quality after decompression (regeneration) is deteriorated, but if the compression ratio is lowered to increase the amount of data after compression, then the picture quality after regeneration is improved.
Then, each block quantized in such a manner as described above is coded by the JPEG coding section
117
and outputted as JPEG compressed image data.
On the other hand, JPEG image data received by the reception section
112
are subject to processing reverse to that of the transmission section
111
by the JPEG decoding section
121
, dequantization section
122
, quantization table
123
, inverse discrete cosine transform section
124
and 8×8 deblocking section
125
so that original image data are regenerated.
It is to be noted that
FIG. 55
shows an example of a frame format employed in the JPEG system mentioned above. Referring to
FIG. 55
, the JPEG frame format shown includes an SOI (Start Of Image marker), a quantization table
118
, a compressed image data part
119
and an EOI (End Of Image marker). The SOI is a code indicating the beginning of an image data frame, and a fixed value of, for example, “FFD
8
” is placed in the code.
Kawataka Miyuki
Matsumura Naoya
Nakayama Mikio
Takeda Takayuki
Burgess Glenton B.
Fujitsu Limited
Katten Muchin Zavis & Rosenman
Kupstas Tod
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