JPS6244458B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system for storing and transmitting facsimile signals using redundancy reduction coding.

In recent years, communication using facsimile has become popular. In particular, facsimile, which uses telephone lines, can be used anywhere in the country, and its range of use is wide. There are various types of facsimile machines that use telephone lines, but CCITT divides facsimile devices into three groups and defines them as follows.

Group 1 Devices that use double-sideband transmission without using any special method to band-compress the transmission signal, and use telephone lines to transmit ISO/A4 signals at a nominal line density of 4 lines/mm.
Transmits legal documents in approximately 6 minutes. This group of devices can be designed to electronically transmit ISO/A4 documents at lower resolutions in 3 to 6 minutes.

Group 2 Using a telephone line, with a nominal linear density of 4 lines/mm,
A device that uses bandwidth compression technology to electronically transmit ISO/A4 documents in about 3 minutes. This band compression includes a combination of encoding, VSB, etc., but does not include processing to suppress the redundancy of the document signal.

Group 3 Equipped with a method to suppress redundancy for the signal before modulation processing, it uses typical ISO/A4
A device that can electronically transmit documents in approximately one minute. This device can also be used for band compression of line signals.

Instead of the usual group 1 equipment, group 2 equipment, etc., they are distinguished into 6-minute machines, 3-minute machines, and 1-minute machines.

Among these, the 6-minute machine is slow in speed, but the equipment price is low and it has the character of being a popular product. In addition, the three-minute machine is gradually establishing itself as a popular product. On the other hand, although the 1-minute device is expensive, it is advantageous for users who use a large amount of communication because it improves transmission efficiency.

Therefore, if a transmission efficiency equivalent to that of a one-minute machine can be obtained using inexpensive equipment, economical communication can be realized. A storage transmission system using redundancy reduction coding achieves exactly this purpose. Furthermore, by storing facsimile signals in the station equipment, various forms of communication such as broadcast communication and proxy communication can be realized.

Conventionally, this type of facsimile signal storage and transmission system accepts multiple lines of facsimile signals from low- and medium-speed machines such as 6-minute machines and 3-minute machines, stores one screen worth of signals in a storage device, and then sequentially encodes them to reduce redundancy. was being transmitted. When transmitting to a terminal, the process is reversed; the transmitted signal is stored or decoded as it is and stored as a signal for one screen, and then the facsimile terminal is called and transmitted.
Here, if the terminals are under the control of the same station device, no transmission is necessary.

Conventionally, this type of facsimile signal storage and transmission system receives facsimile signals for a plurality of lines, stores them for one screen in a plurality of storage devices corresponding to each line, and then sequentially encodes the facsimile signals with reduced redundancy before transmitting them. FIG. 1 is a diagram for explaining one embodiment of this type of conventional system, and as shown in the figure, image signals generated from a plurality of facsimile terminals 1 pass through an exchange 2 and are sent to each line for each screen. The image signal is temporarily accumulated and stored in the image signal storage device 12 corresponding to the image signal. The image signals stored in the image signal storage device 12 are sequentially read out by the signal reading mechanism 5, sequentially encoded with redundancy suppression by the redundancy suppression encoder 6 for each screen, and temporarily stored in the buffer memory 13. After that, it is sent out to the transmission line through the modem 10. However, this type of system requires as many storage devices as there are lines to store image signals for one screen, and has the disadvantage that it requires a large number of storage elements.

The present invention has been made to eliminate the drawbacks of this conventional method. In particular, in front of the redundancy suppression encoder, only a few scanning lines worth of signals are stored, and the signals are encoded and redundancy suppressed. The system stores signals for one screen and uses a redundancy suppressing encoder in common.The drawings will be described in detail below.

FIG. 2 is a diagram for explaining one embodiment of the present invention, in which 1 is a facsimile terminal, 2 is a facsimile terminal;
is an exchange, 3 is a main line memory, 4 is a front line memory, 5 is a signal reading mechanism, 6 is a redundancy suppression encoder, 7 is a signal writing mechanism, 8 is an encoded signal storage device, 9 is a signal sending mechanism, 10 is modem, 11
is the control device.

In FIG. 2, a plurality of facsimile terminals 1
The image signals generated from the main line memory 3 are stored in the main line memory 3 corresponding to each line through the exchange 2 for each scanning line. This main line memory 3 can store image signals for two scanning lines, and is used alternately for writing and reading. These main line memories 3
The image signals stored in the image signals are read out at high speed for each line memory by a signal readout mechanism 5, and are subjected to redundancy suppression encoding processing at high speed by a redundancy suppression encoder 6. In addition, for low-speed terminals, the transmitted image signal is 3 to 9.
For example, in the case of 9 lines/second, one line is transmitted in about 110 milliseconds. Therefore, if the processing time for one line of the redundancy suppressing encoder is, for example, within 5 milliseconds, then 22
Encoding of facsimile signals for lines is possible. At this time, in the redundancy suppression encoding method using the previous line image signal, the previous line image signal stored in the previous line memory 4 is read out at high speed and used for encoding. Further, the output of the main line memory 3 is simultaneously stored in the previous line memory 4 and used for encoding the next line. Note that if the image signal of the previous line is not required in the encoding process, the previous line memory 4 is omitted. The output from the redundancy reduction encoder 6 passes through a signal writing mechanism 7 and is temporarily stored in an encoded signal storage device 8 corresponding to each line. The stored encoded signals are sent to the transmission line through the signal sending mechanism 9 and the modem 10 for each screen when all the coding is completed. Here, a control device 11 operates in the signal reading mechanism 5, signal writing mechanism 7, and signal sending mechanism 9 to perform timing control, encoding completion control, etc.

As a special case in FIG. 2, a plurality of facsimile terminals 1 are directly connected to the main line memory 3,
The exchange 2 can also be omitted.

As explained above, according to the present invention, a main line memory is required, but since a redundancy suppressed coded signal is stored in the image signal storage device, approximately the same amount of redundancy is suppressed, that is, approximately It has the advantage that the number of memory elements can be reduced by one-seventh. Note that even with such a configuration, the advantage that the redundancy suppression encoder can be used in common by a plurality of facsimile terminals is not lost.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an example of a conventional facsimile signal storage and transmission system, and FIG. 2 is a diagram for explaining an embodiment of the present invention. 1... Facsimile terminal, 2... Switchboard, 3
...Main line memory, 4...Previous line memory, 5
... Signal reading mechanism, 6 ... Redundancy suppression encoder, 7 ... Signal writing mechanism, 8 ... Encoded signal storage device, 9 ... Signal sending mechanism, 10 ... Modem, 11 ... Control device.

Claims (1)

[Scope of Claims] 1. A first apparatus for storing image signals transmitted from a plurality of facsimile terminals through a plurality of lines in a line memory corresponding to each line for each scanning line.
means for sequentially reading out image signals in a plurality of line memories stored for each scanning line at high speed, and a single redundancy suppression encoder for reading out the image signals read out at high speed. a third means for encoding and storing the encoded output in a plurality of encoded signal storage devices corresponding to each input line; and a third means for sequentially transmitting signals from each encoded signal storage device to the transmission path for each screen through a modem. and a fourth means for transmitting a facsimile signal. 2 In the method described in claim 1,
When the image signal of the previous line is required for the encoding process, a line memory corresponding to each input line is further added, and the signal of the line memory that has been encoded is stored in the added line memory, and then A facsimile signal storage and transmission method characterized by being used for encoding lines.