JPS6074876A - Picture communication device - Google Patents

Abstract

PURPOSE:To prevent previously the overflow of a buffer memory by providing a device control part to a transmitter to calculate the margin degree of the transmission and reception buffer memories at the reception and transmission sides respectively. CONSTITUTION:A device control part 30 is provided to a picture communication device to receive the main scan number stored in a transmission frame via a transmission buffer memory part 23 and a code transmitting part 24 as well as the end time point for the transmission of a frame with which the transmission is through. Then the part 30 calculates the margin degree of the transmission buffer memory and decides the transmission of a transmission frame. Then a transmission permission signal for the transmission frame is delivered to the part 24. While the information on the code storage quantity of the part 23 is received by the part 30. When the part 23 has no margin for storage, the input of pictures which is given from a picture reader 21 via a band compression part 22 is discontinued. This prevents previously the overflow of the part 23.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image communication device that converts an image into a binary or multi-value image signal, performs band compression processing to remove redundancy, and then transmits the image as a compressed code. It is something.

Conventional configuration and its problems In systems that transmit two-dimensional images to remote locations, such as by facsimile, the original image is scanned at regular intervals in the main scanning direction (direction of arrow 11), as shown in Figure 1. It reads the image, encodes it, and then transmits it to a remote location. The image read in one scan is called a main scanning line 13. This operation can be performed in the sub-scanning direction (
By repeating the process in the direction of arrow 12), the image can be transmitted.

Generally, images have a high degree of redundancy, so if a read image signal is transmitted as it is, the transmission efficiency is poor and a long transmission time is required.

Therefore, the redundancy of the input image signal is removed in units of main scanning lines, and the code is converted into a compressed code with a smaller amount of code than the code of the read image signal. (referred to as compressed transmission).

Furthermore, when transmitting compressed codes, a certain amount of compressed codes are collected to form a packet and transmitted in units of packets (this packet is called a transmission frame).

By configuring a transmission frame and performing code transmission, it becomes easy to configure a transmission error detection code and a transmission error correction code.

When band-compressing an image, the code amount of the generated compression code changes depending on the nature of the image (ie, whether the redundancy is high or low) even if the code amount of the image signal per main scanning line is the same.

Therefore, in an image communication device using band compression, a playback section 21 is provided as shown in FIG.
A transmission puffer memory 23 is provided between the transmitter and the code transmitter 24, and when a certain amount of codes sufficient to constitute a transmission frame is stored in the transmitter puffer memory 23, the codes are transmitted.

Therefore, even in a transmission frame composed of a fixed number of codes, the number of main scanning lines generated when the original image signal is restored is not constant.

On the other hand, since the output speed of the image signal to be recorded in the recording unit 29 is constant, as shown in FIG. 27, it is necessary to temporarily store compressed codes.

Now, the above-mentioned receiving puffer memory 27 has a high compression ratio.
In other words, if a compressed code with a large number of main scanning lines is generated during restoration, it will take a long time until all the compressed codes are output. Also, the compression rate is low on the transmitting device side.
When processing an image with a large amount of compressed codes generated after double compression, many transmission frames are constructed and transmitted in a certain period of time.

Therefore, in the case of an image whose properties change rapidly from a portion with a high compression rate to a portion with a low compression rate, the compressed code stored in the reception puffer memory 27 is being output.

In other words, while a compressed code with a high compression rate is being output, a compressed code with a low compression rate of 4 is input, so the receiving puffer memory 2
7 will overflow.

Conventionally, the following two measures have been taken to prevent this reception puffer memory 270 from overflowing.

■ Make the capacity of the reception puffer memory 27 sufficiently large.

(2) Before the receive puffer memory 270 overflows, the receiving device sends a request to the transmitting device to interrupt the transmission of the transmission frame.

In the former case, if the receiving puffer memory 27 has a capacity equal to the capacity of the image signal, overflow of the receiving puffer memory 27 will not occur.

However, since the amount of code for the image signal is generally large, the size of the receiving puffer memory 27 is large and the cost of the device is high.

On the other hand, in the latter case, the capacity 1j1 of the reception buffer memory 23
Although it is possible to prevent the reception puffer memory 27 from overflowing even if the reception puffer memory 2
7, a means for monitoring the storage capacity is required, a means for transmitting new information to the transmitting station is required in the receiving device, and a means for newly receiving information from the receiving station is required in the transmitting device. This has the disadvantage that the overall scale of the device increases.

In the case of the latter method, a transmission line 25 (wired or wireless) is required to transmit information from the receiving station to the transmitting station, which increases the cost of maintaining the transmission line and requires a communication satellite line. When using a transmission line with a long transmission time, there is a drawback that a transmission frame transmission stop message must be sent to the transmitter while there is sufficient free space in the reception puff 7 memory 27.

OBJECTS OF THE INVENTION The present invention has been made in view of the above problems, and by calculating the amount of code stored in the receiving puffer memory in a transmitting device, it is possible to predict the occurrence of O/<-flow in the receiving puffer memory, and to calculate the amount of code stored in the receiving puffer memory. An object of the present invention is to provide an image communication device that can prevent the reception puffer memory from overflowing by interrupting the transmission of the data.

Structure of the Invention The present invention includes at least a transmission band compression means for performing band compression processing on an image signal to be transmitted to generate a compression code, and a transmission side storage means for temporarily storing the compression code.
a sending side output means for sending out the compressed code temporarily stored in the sending side storage means; a receiving side input means for inputting the compressed code sent from the sending side output means; and a receiving side input means for inputting the compressed code sent from the sending side output means; a receiving side storage means for temporarily storing the compressed code temporarily stored in the receiving side storage means; a receiving side band restoring means for restoring the compressed code temporarily stored in the receiving side storage means into an image signal; and a reproduction means for reproducing the information, and a transmission side control means for controlling the output amount of the transmission system according to the processing capacity of the reception system which is known in advance. , which achieves the above objectives.

Purpose of the example The present invention will be explained below along with examples using the drawings.

FIG. 3 is a block diagram of an image communication device according to an embodiment of the present invention. In the figure, arrows drawn with solid lines indicate the flow of image signals, and arrows drawn with broken lines indicate the flow of control signals.

Now, in FIG. 3, the difference from the transmitting side configuration in FIG. 2 is that a device control section 30 is newly provided.

The device control section 3o, the transmission buffer memory section 23. Receives the main scanning line number stored in each transmission frame and the transmission completion time point of the transmission frame from the code transmission unit 24, calculates the margin of the reception puffer memory 27, makes a decision to transmit the transmission frame, and transmits the transmission frame. A frame transmission permission command is output to the code transmitter 24.

The device control unit 30 also relates to the amount of code stored in the transmitting puffer memory 23 from the transmitting puffer memory 3 .

When information is received and there is no room for storing codes in the transmitting puffer memory 23, the image signal is sent out from the reproducing section 21 via the band compressing section 22 and inputting of the image signal is interrupted in order to prevent the transmitting puffer memory 230 from overflowing. Note that even when the transmission puffer memory 23 overflows, that is, even when transmission frame transmission is interrupted, the reproducing unit 21 reproduces the image signal at a constant cycle, and the band compression unit 22 stores the compressed code in the transmitting puffer memory 23. is being generated.

The operation of the above configuration will be described in detail below.

First, as shown in FIG. 4, the compressed code a is sent to the transmission puffer memory 23 together with a sampling clock b and an enable signal C indicating the main scanning unit of the compressed code.

The operation timings of the signals a, b, and c are shown in FIG. In FIG. 5, the shaded area with respect to the compression code a indicates invalid data.

Now, the compressed code afd is input into the data latch circuit 41 in the transmission puffer memory 23 in synchronization with the sampling clock b. The latched data d is written to the memory 42. When the compressed code for one frame is stored in the memory 42, the compressed code is read out from the memory 42 in synchronization with the transmission lock h sent out from the signal transmitter 24, and the data latch circuit reads out the compressed code from the memory 42. 43 and is output to the signal transmitter 24 as a transmission code g.

On the other hand, the address j of the memory 42 is the write address e
The memory address circuit 44 generates read address 1. The memory address circuit 44 outputs a transmission puff memory overflow occurrence warning signal k to the device control unit 3o when the unused area of the memory becomes less than a certain amount.

When the device control unit 30 receives the warning signal k, it outputs a scanning stop signal q to the image reading device 21. Since the image reading device 21 interrupts image scanning in response to the scanning stop signal q, the image signal r is no longer output to the band compression section 22. Therefore, the input of the compression code to the transmission puffer memory 23 is interrupted.

Since the compression code in the transmission puffer memory 23 decreases each time a transmission frame is transmitted, the unused area of the memory 42 increases, and when it reaches a certain amount, the warning signal is canceled and the scanning stop signal is also canceled. Therefore, the image reading device 21 resumes scanning.

The transmission puffer memory 23 measures the number of main scanning lines included in the compressed code constituting one transmission frame when writing the compressed code, and writes it into the memory 46 for storing the main scanning line number. As is clear from FIG. 6, the enable signal C is turned on every time a compressed code for -main scanning line is input. Therefore, the number of codes constituting one transmission frame is measured using the sampling clock b, and one transmission frame is By counting how many times the enable signal C is turned on during the constituent codes using the counter circuit 46, it is possible to grasp the main scanning line number included in one transmission frame. The main scanning line number m in the transmission frame is temporarily stored in the memory 46 for storing the main scanning line number, and when the transmission frame is output to the signal transmitter 24, it is read out from the memory 46 and is stored as the main scanning line number. It is output to the device control unit 30 as 1.

Further, the signal transmitter 24 outputs a transmission completion signal n to the device controller 30 when the transmission of the transmission frame is completed.

FIG. 6 shows a timing chart showing the control operation of the device control section 300.

As shown in FIG. 6, when the transmission frame transmission permission signal p turns on (time ti), the compressed code g for one transmission frame is transmitted at time t2 in synchronization with the transmission port h. It is output to section 24. At this time, the main scanning line number included in the transmission frame is sent to the device control unit 3o as a signal l.
Output to. After outputting the compression code for one transmission frame,
When time t3 has elapsed, the signal transmitter 24 sends a transmission frame transmission completion signal n to the device controller 3o. The equipment controller 30 calculates the code storage margin of the reception puffer memory section during time t4, and turns on the transmission frame sending permission signal p if the margin is a certain amount or more.

Further, if the margin is less than a certain amount, the transmission frame sending permission signal p is turned off. When the transmission frame sending permission signal p is turned off, the margin of the receiving puffer memory is calculated at fixed time intervals, and when the margin exceeds a certain value, the transmission frame sending permission signal p is turned on (time t9).

Next, the operations performed by the device control section 30 will be explained using the block diagram of the device control section shown in FIG.

First, when a warning signal k indicating that there is no more room to store the compressed code a in the transmission puffer memory 23 is sent, the scanning stop signal generation circuit 73 generates a scanning stop signal q and outputs it to the information reproducing section 21. do. When the warning signal k is canceled, the scanning stop signal generation circuit 73 cancels the output of the scanning stop signal q.

On the other hand, the margin calculation circuit 71, which calculates the margin of the reception puffer memory and generates the transmission frame transmittable signal p, has a transmission delay time ta necessary for the transmission frame to reach the reception device in advance, and the image recording device 29 will last a lifetime. 17rf tp is known when it is necessary to record the image signal of the scanning line (note that the values of td and tp are assumed to be constant).
. It is also assumed that the processing time required for the compressed code to be restored into an image signal by the band restoration section 28 can be ignored when compared with the values of td and tp, since the band restoration process is performed at high speed. ) FIG. 8 shows the flow of operations from when the margin calculation circuit 71 receives the transmission frame transmission completion signal n until it outputs the transmission frame transmission permission signal p.

Upon receiving the transmission frame transmission completion signal n, the margin calculation circuit 71 takes in the main scanning line number l and the time signal S output from the timer circuit 72, and in operation 81 creates the data in Table 1.

Table 1: If the time when transmission of the first transmission frame is completed in Table 1 is 81, the time when the transmission frame arrives at the receiving station is 1ri, and the transmission delay time is td.

It becomes Si+td. Also, if the final main scanning line number included in the same transmission frame is 11, recording starts at time (Sj + tcl), and the time required to record - main scanning line is tp.
Therefore, the time when all the compressed codes included in the first transmission frame are completely recorded reaches S1+td+11×tp. Similarly, since the recording start time is 81+td, the frame output completion time is as shown in Table 1.

Next, in operation 82, it is determined from the data in Table 1 which transmission frame is being output based on the frame arrival time and frame output completion time.

For example, for the sixth transmission frame, 1+Xtp
+S1+td<Ss+td<jbXtp+s++td If there is a relationship such as +S1+td<Ss+td<jbXtp+s++td, the second frame is currently being output, and the compressed codes of up to four transmission frames from the second to the sixth are stored in the reception puffer memory. become. - If the code amount of the transmission frame is V and the reception puff 7 memory capacity is vO, then the reception puff memory margin V is V = Vo - 77X4, and v > 7. If y, it is possible to receive the sixth transmission frame, so the process branches to operation 83. Further, when v<v, it is impossible to receive the sixth transmission frame, so the process branches to operation 84.

In operation 83, the transmission frame transmission permission signal P is turned on and output (the above is the process performed at time t4 in FIG. 6).

Still in operation 84, the transmission frame permission signal P is turned off and output. (This is the process performed at time t8 in FIG. 6.) Then, in the case of operation 84, after a certain period of time has elapsed, in the example in Table 1, the reception buffer memory margin V is calculated again at time S6. , v>v, in operation 83 the transmission frame transmission permission signal P is turned on and output. (This is the process that is performed at time t9 in FIG. 6.) According to the above embodiment, the device control unit 3o is provided on the transmitting side to predict the occurrence of an overflow in the receiving side memory. By interrupting the transmission of transmission frames as necessary, it is possible to prevent the reception buffer memory from overflowing.

The general processing of the above embodiment will be further explained below.

First, the code jl' stored in the receive puffer memory
tvn 1. ) Code t1 input to puffer memory
) and the amount of code output from the receiving puffer memory.

Tsumashi, v: vxN-voU, (1) However, vIN is the code amount of the transmission frame, vOf, which increases by a fixed amount each time the transmission frame is correctly received.
fT is a compression code unit that constitutes a main scanning line that is output every time the image recording device records a scanning line.

If there are compressed codes stored in a transmission frame for n main scanning lines, and if the time it takes for the image recording device to record image signals of scanning lines for a lifetime is tp, then all the compressed codes stored in the transmission frame are output. The time t required for this is t=tpXn.

According to the relationship between equations (1) and (2) above, each time a transmission frame is stored in the reception puffer memory, the amount of code stored in the reception puffer memory is used as shown in Table 2. can.

In the Hikobo 2 table, the time is determined by taking the time when the first transmission frame is written to the receive buffer memory as the origin of time measurement.
This field describes the time each time a transmission frame is written. The frame number is a number assigned sequentially to the received transmission frame, the transmission frame storage main scanning line number indicates the last main scanning line number stored in the transmission frame, and the transmission frame output completion time is the number assigned to the received transmission frame in order. This indicates the time when the compressed code of the main scanning line indicated by the frame storage main scanning line number is completed to be output.

Therefore, by using Table 2, it can be determined in which transmission frame the compressed code stored in the transmission frame is being output at the time the transmission frame is received.

For example, regarding time t5 when the fifth transmission frame is received, if there is a relationship such as L2Xtp<ts<LsXtp (3), the compressed code stored in the third transmission frame is being output and the receiving puffer memory is , compression codes stored in the third to fifth transmission frames at most are stored.

Table 2: The code amount of the transmission frame is V, and the reception puff memory capacity is V.
o, then the free space (unused area) of the receive buffer memory is V, =VO-7,7X3 (4).

If V≧v(5), the sixth transmission frame can be stored.

Note that in the above explanation, the time required for decompressing the compressed code and returning it to the image signal is ignored because it is sufficiently quick.

By performing the above processing on the transmitter side before sending out a transmission frame and interrupting the transmission of the transmission frame when there is no room to store codes in the reception puffer memory, overflow of the reception puffer memory can be prevented.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, it is possible to prevent the reception puffer memory from overflowing with a simple configuration, and there is a circuit for monitoring the reception puffer memory capacity, a circuit for transmitting information from the receiving side to the transmitting side, and a transmission circuit. This eliminates the need for lines, etc., and the scale of the image signal transmission system can be simplified, which is highly effective.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the scanning direction of an image, FIG. 2 is a block diagram of a conventional image communication device using band compression, and FIGS. 3 and 4 are transmissions of an image communication device according to an embodiment of the present invention. System block diagram, Fig. 6 is a timing diagram showing the operation when compressed code is input, Fig. 6 is a timing diagram showing the operation when compressed code is output, Fig. 7 is a block diagram of the device control section, and Fig. 8 is the device. FIG. 3 is a flow diagram showing the operation of the control section. 21... Image reading device, 22... Bandwidth compression unit, 23... Transmission puffer memory unit, 24...
... code transmitter, 26 ... code receiver,
27... Receive puffer memory, 28...
Band restoration unit, 29... Image recording device, 30...
...Device control section, 25...Transmission section.

Claims (3)

[Claims] (1) A transmitting side band compression means that applies band compression processing to an image signal to be transmitted and generates a compressed code; a transmitting side storage means that temporarily stores the compressed code; a transmitting-side output means for transmitting the compressed code transmitted from the transmitting-side output means; a receiving-side input means for inputting the compressed code sent from the transmitting-side output means; and a receiving-side memory for temporarily storing the compressed code input from the receiving-side input means. a receiving side band restoring means for restoring the compressed code temporarily stored in the receiving side storage means into an image signal; and a reproducing means for reproducing the original information from the image signal of the receiving side band restoring means. 1. An image communication apparatus comprising: a transmitting side control means provided on a transmitting side for controlling an output amount of the transmitting system according to a processing capacity of the receiving system which is known in advance. (2) a transmitting side image reading means for reading an image signal to be transmitted; a transmitting side band compression means for performing band compression processing on the image signal read by the transmitting side image reading means to generate a compressed code; and a transmitting side band compression means for generating a compressed code; A transmitting side storage means for temporarily storing the code, a transmitting side output means for transmitting the compressed code temporarily stored in the transmitting side storing means, and a receiving side input means for inputting the compressed code sent from the transmitting side output means. a receiving side storage means for temporarily storing the compressed code inputted from the receiving side input means; a receiving side band restoring means for restoring the compressed code temporarily stored in the receiving side storage means into an image signal; and a reproduction means for reproducing the original information from the image signal of the reception side band restoration means, and a transmission side for controlling the output amount of the transmission system according to the processing capacity of the reception system which is known in advance. An image communication device comprising: a transmitting side control means. (3) The transmitting side control means includes a means for calculating the time during which the receiving station side reproducing means reproduces the image signal, and a means for calculating the compression code generated after performing band compression processing on the image signal in scanning units inputted at regular intervals. When a means for ascertaining the amount of code and an output means on the transmitting side compose a compressed code as a transmission frame for each fixed amount of codes and transmit it without transmission errors using an error correction code, the transmission of the transmission frame is controlled by the means for determining the amount of code. means for stopping and restarting transmission frames in units of transmission frames according to the amount of code and the time of the calculation means; and means for stopping image reading for the sending side image reading means according to the amount of codes of the grasping means and the time of the calculation means. 3. The image communication device according to claim 2, further comprising means for instructing restart.