Image analysis – Image compression or coding
Reexamination Certificate
1998-05-29
2001-06-26
Mancuso, Joseph (Department: 2621)
Image analysis
Image compression or coding
C725S151000
Reexamination Certificate
active
06252990
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a motion image encoder which inputs a plurality of motion image signals, codes the input motion image signals, multiplexes the coded motion image signals, and sends out the multiplexed motion image signals to a plurality of transponders, a motion image decoder which decodes multiplexed motion image signals transmitted via a plurality of transponders, and a readable storage medium storing an encoding or decoding program.
DESCRIPTION OF THE RELATED ART
Now, digital satellite broadcasting is put into practice pursuant to the IS-13818 (MPEG-2) standard of the international standard organization (ISO). An artificial satellite is provided with a plurality of transponders (transmission lines). A transmission ability per one transponder (bit rate) is approximately 30 Mbps. For example, assuming that 6 Mbps as the necessary bit rate required in coding motion image signals to meet image quality is required, 5 motion image signals can be transmitted per one transponder (multiplicity 5), and thus 20 transponders are required for broadcasting 100 motion image signals (100 channels of motion image signals) in digital satellite broadcasting.
Each channel is composed of a variety of programs, and the necessary bit rate changes depending on the contents of the programs. For instance, in a hard motion sports relay broadcast, a bit rate of approximately 10 Mbps is required. If a coding is carried out at approximately 6 Mbps in a similar manner to a usual motion sports relay broadcast, the image quality is degraded. In order to prevent such a problem, it is considered that the multiplicity of the transponders is reduced and the bit rate allocated to each motion image signal is increased. In such a case, when the number of the motion image signals is equal, the number of the transponders must be increased. Alternatively, when the number of the transponders is equal, the number of the motion image signals must be reduced.
In order to solve this problem, a statistical multiple coding has been developed, in which a bit rate allocated to each motion image signal is not fixed, but the sum of the bit rates is fixed.
In
FIG. 1
, there is shown a conventional motion image encoder using the statistical multiple coding. As shown in
FIG. 1
, the motion image encoder comprises two image motion encoder units
132
-
0
and
132
-
1
, in which 10 motion image signals V
0
to V
9
are coded and then multiplexed (5 signals in each image motion encoder unit
132
-
0
or
132
-
1
) to output two multiplexed motion image signals to transponders (not shown) C
0
and C
1
from the image motion encoder units
132
-
0
and
132
-
1
, respectively.
More specifically, the motion image encoder unit
132
-
0
includes 5 coding means
130
-
0
,
130
-
1
,
130
-
2
,
130
-
3
and
130
-
4
for coding the motion image signals V
0
, V
1
, V
2
, V
3
and V
4
to output code strings, and a multiplexer (MUX)
131
-
0
for multiplexing the code strings output from the coding means
130
-
0
,
130
-
1
,
130
-
2
,
130
-
3
and
130
-
4
to send out a multiplexed code string to a transponder C
0
. Similarly, the motion image encoder unit
132
-
1
includes 5 coding means
130
-
5
,
130
-
6
,
130
-
7
,
130
-
8
and
130
-
9
for coding the motion image signals V
5
, V
6
, V
7
, V
8
and V
9
to output code strings, and a multiplexer (MUX)
131
-
1
for multiplexing the code strings output from the coding means
130
-
5
,
130
-
6
,
130
-
7
,
130
-
8
and
130
-
9
to send out a multiplexed code string to a transponder C
1
.
Now, for example, it is assumed that the transmission ability of the transponders C
0
and C
1
are each 30 Mbps, and that the necessary bit rates of the motion image signals V
0
and V
5
are each 10 Mbps and those of the motion image signals V
1
to V
4
and V
6
to V
9
are each 5 Mbps in a certain time period. The sum of the bit rates allocated to the 5 signals VO to V
4
or V
5
to V
9
becomes 30 Mbps which is equal to the transmission ability of the transponder C
0
or C
1
, inviting no image quality degradation. In this manner, in the conventional motion image encoder shown in
FIG. 1
, even when a large bit rate is required for parts of the motion image signals V
0
to V
9
, the sum of the bit rates for the motion image signals V
0
to V
4
is equal to or less than the transmission ability of the transponder C
0
and the sum of the bit rates for the motion image signals V
5
to V
9
is equal to or less than the transmission ability of the transponder C
1
, resulting in preventing the image quality degradation.
However, in this conventional motion image encoder, as described above, the motion image signals V
0
to V
4
are coded in the respective coding means and are then multiplexed in the MUX to output the multiplexed code string to the transponder C
0
, and similarly, the motion image signals V
5
to V
9
are coded in the respective coding means and are then multiplexed in the MUX to output the multiplexed code string to the transponder C
1
. That is, the groups of motion image signals correspond fixedly to the respective transponders. As a result, the transmission ability of a plurality of transponders cannot be sufficiently exploited, and the image quality may be deteriorated.
For instance, it is assumed that the transmission ability of the transponders C
0
and C
1
are each 30 Mbps, and that the necessary bit rates of the motion image signals V
0
and V
1
are each 3 Mbps, those of the motion image signals V
2
to V
4
are each 4 Mbps, those of the motion image signals V
5
and V
6
are each 6 Mbps, and V
7
to V
9
are each 10 Mbps in a certain time period. In the conventional motion image encoder, the motion image signals V
0
to V
4
and V
5
to V
9
are fixedly assigned to the respective transponders C
0
and C
1
, respectively, and the sum of the necessary bit rates for the motion image signals is 18 Mbps or 42 Mbps in the transponder C
0
or C
1
, respectively. The transmission ability of the transponders C
0
and C
1
is each 30 Mbps. In other words, the transponder C
0
has 12 Mbps surplus while the transponder C
1
is 12 Mbps short with the result of the image quality degradation.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a motion image encoder in view of the aforementioned problems of the prior art, which is capable of making an effective use of a plurality of transponders without surplus and shortage in their transmission ability, and preventing image quality degradation.
It is another object of the present invention to provide a motion image decoder for decoding motion image signals coded by the above motion image encoder, which is capable of preventing image quality degradation.
It is a further object of the present invention to provide a readable storage medium storing a program for realizing a motion image encoder and decoder using a computer, the program operating the computer as parts of the motion image encoder and decoder, which is capable of preventing image quality degradation.
In accordance with one aspect of the present invention, there is provided a motion image encoder, in which N-number of motion image signals are coded to produce N-number of code strings and the N-number of code strings are multiplexed to produce M-number of multiplexed code strings to be output to M-number of respective transponders, comprising N-number of coding means for coding N-number of respective motion image signals to produce N-number of code strings; and
multiplexing means for multiplexing the N-number of code strings per M-number of groups corresponding to M-number of transponders to produce M-number of multiplexed code strings, while grouping the N-number of code strings into M-number so that the sum of the necessary bit rates of each group of the motion image signals included in each of the M-number of multiplexed code strings becomes closest to bit rates of the corresponding transponder, and outputting the M-number of multiplexed code strings to the respective transponders.
In thi
Bayat Ali
Mancuso Joseph
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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