Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1999-02-26
2003-09-30
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S537000, C370S538000
Reexamination Certificate
active
06628677
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coding and multiplexing apparatus and method and more particularly, is suitably applied to a transmission system for a digital multichannel broadcasting.
2. Description of the Related Art
Digital multichannel broadcastings using a communication satellite (CS) have been started even in Japan. Moreover, in the near future, a similar service will be provided in broadcasting systems using a broadcasting satellite (BS), and ground waves or cables.
Such digital multichannel broadcasting is performed in such a manner that, in a transmitting side, a video signal of each channel is subjected to a digital compression processing and obtained coded data is transmitted after being multiplexed within a limited band (hereinafter, this is referred to as broadcast bandwidth), for instance, of 30 bps degree.
FIG. 1
shows a structural example of the transmitting side in such the digital multichannel broadcasting system. In such a transmission system
100
, a plurality of coding devices
102
A to
102
N are provided, in which video signals S
101
A to S
101
N are supplied to the coding devices
102
A to
102
N respectively.
Each of the coding devices
102
A to
102
N performs compression coding on the supplied video signal S
101
A to S
101
N, for example, at a peculiar set rate preset based on the moving picture experts group phase
2
(MPEG
2
), and transmits thus obtained coded data D
101
A to D
101
N to a multiplexer
103
. Note that, the set rate for each coding device
102
A to
102
N has been set so that the total of the set rates is within the broadcast bandwidth of the digital multichannel broadcasting.
In the multiplexer
103
, a plurality of buffers
104
A to
104
N provided corresponding to coding devices
102
A to
102
N respectively and a multiplexing control part
105
for controlling read-write of each buffer
104
A to
104
N are included. The coded data D
101
A to D
101
N supplied from coding devices
102
A to
102
N respectively are sequentially fed into the corresponding buffers
104
A to
104
N.
Besides, the multiplexing control part
105
monitors the amount of data in each buffer
104
A to
104
N via a control bus
106
, and evenly reads the coded data D
101
A to D
101
N from respective buffers
104
A to
104
N in time division based on the monitor result.
As a result, these coded data D
101
A to D
101
N, respectively read from respective buffers
104
A to
104
N, are supplied to a transmitting part
108
via a data bus
107
as transmission data D
102
. In the transmitting part
108
, the transmission data D
102
is subjected to a predetermined signal processing, such as quadrature phase shift keying (QPSK) modulation, and then transmitted to a receiving side sequentially via an antenna
109
, a communication satellite not shown in the figure, and the like, as a transmission signal S
102
.
The fixed rate method of coding each of the video signals S
101
A to S
101
N for a plurality of channels at a rate preset for each channel has an advantage that the coded data D
101
A to D
101
N corresponding to the video signals S
101
A to S
101
N can be multiplexed in time division within the broadcast bandwidth without requiring complicated control.
However, the fixed rate method as described above has a problem in that pictures are greatly inferior in quality in complicated pictures or in changing scenes because the video signal A
101
A to A
101
N of each channel is always digital-compressed at a fixed rate.
In addition, the fixed rate method has a problem in that transmission efficiency deteriorates because dummy data has to be added to a picture which needs only a few amount of code in order to keep the output rate constant.
To solve the problems, a statistics multiplexing method has been proposed as another method of coding and multiplexing video signals S
101
A to S
101
N for a plurality of channels.
FIG. 2
in which the same reference numerals are applied to parts corresponding to
FIG. 1
shows a structural example of a transmission system
200
for performing coding and multiplexing in accordance with the statistics multiplexing method. A plurality of coding devices
202
A to
202
N are provided so as to be given video signals S
101
A to S
101
N respectively.
In this case, each of the coding devices
202
A to
202
N is composed of a coding-difficulty detecting parts
212
A to
212
N and a coding part
213
A to
213
N, so as to input the supplied video signal S
101
A to S
101
N to the coding-difficulty detecting part
212
A to
212
N. Then, the coding-difficulty detecting part
212
A to
212
N detects difficulty of coding the supplied video signal S
101
A to S
101
N, and transmits the obtained difficulty information D
210
A to D
210
N to a multiplexer
203
and the video signal S
101
A to S
101
N to the coding part
213
A to
213
N of the next stage.
The multiplexer
203
includes a plurality of buffers
204
A to
204
N respectively corresponding to the coding devices
202
A to
202
N, a multiplexing control part
205
for controlling write-read of each buffer
204
A to
204
N, and a coding control part
215
for controlling the coding parts
213
A to
213
N of the coding devices
202
A to
202
N. The difficulty information D
210
A to
210
N supplied from the coding-difficulty detecting parts
212
A to
212
N of the coding devices
202
A to
202
N are input to the coding control part
215
.
The coding control part
215
decides coding rates for the coding devices
202
A to
202
N based on the respective difficulty information D
210
A to D
210
N so that a video signal S
101
A to S
101
N having larger difficulty can use a wider bandwidth and the total of coding rates is within the broadcast bandwidth for the digital multichannel broadcasting. Then, the coding control part
215
transmits control signals S
210
A to S
210
N based on the derision result to the coding parts
213
A to
213
N of the coding devices
202
A to
202
N respectively.
Thus, the coding parts
213
A to
213
N of the coding device
202
A to
202
N code the respectively-supplied video signals S
101
A to S
101
N at respective coding rates, which are obtained based on the. control signals S
210
A to S
210
N supplied from the coding control part
215
of the multiplexer
203
. Each of the obtained coded data D
201
A to D
201
N is transmitted to the multiplexer
203
.
As a result, the coded data D
201
A to D
201
N, which are output from the coding devices
202
A to
202
N respectively, are fetched to the corresponding buffers
204
A to
204
N of the multiplexer
203
, are evenly read out in time division under the control of multiplexing control part
205
, and then, are transmitted to a transmitting part
108
through a data bus
207
as transmission data D
202
. The transmission data D
202
is subjected to a predetermined signal process in the transmitting part
108
, and then is transmitted to the receiving side sequentially via the antenna
109
, a communication satellite not shown in figure, and the like, as a transmission signal S
202
.
Such the statistics multiplexing method has an advantage in that, as compared with the fixed rate method, transmission efficiency is good and a picture having high difficulty can be transmitted remaining comparatively high quality on the average of picture quality among channels, because dummy data does not have to be added and the coding rate is decided based on the difficulty of a picture for each channel as described above.
However, the statistics multiplexing method has a problem in that simultaneous control of channels is complicated and it is difficult to make the best use of the merit of dynamically controlling bandwidth, in such a case that the same video signal is hierarchical-coded to be broadcasted on plural channels, because the amount of coded data changes depending on a picture.
Further, in the digital multichannel broadcasting, also materials, such as a movie, in which the contents have been already fixed are coded and broadcasted in real time at present. In this case, as one o
Kizou Hassan
Lerner David Littenberg Krumholz & Mentlik LLP
Tsegaye Saba
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